KWBC Extended FCST Map Discussion

[UNIDATA Local Data Mangement daemon]

189
FXUS02 KWBC 161826
PMDEPD
EXTENDED FORECAST DISCUSSION FOR 19 MAY THRU 21 MAY 1996
HYDROMETEOROLOGICAL PREDICTION CENTER..NCEP..NWS..WASHINGTON DC
2:30 PM EDT THU MAY 16 1996

TODAYS MED RANGE GUIDANCE IS IN FAIRLY GOOD AGRMNT WITH ALL
MODELS FCSTG AN UNSEASONABLY STRONG UPR TROF TO REMAIN ANCHORED
IN THE MEAN OVR THE NERN PAC NR 50N 140W OVER THE NEXT FIVE
DAYS..WHILE ABOVE NORMAL HTS ARE EXPECTED OVR A LARGE PORTION OF
THE ERN U.S. FROM THE MID ATL INTO THE MID MS VALLEY.

THE STRONG JET WHICH HAS BECOME ESTABLISHED ACRS NEARLY ALL OF
THE PAC OCEAN ALONG APPROX 35-40N WL HELP PUSH HT FALLS INTO THE
WRN U.S. THIS PERIOD PRODUCING BELOW NORMAL HTS ACRS ALL OF THE
NWRN QUARTER OF THE NATION EXTENDING AS FAR TO THE SOUTH AS CNTRL
CA. THERE IS SOME TIMING DIFFS WITH THESE HT FALLS WHICH MOVE
INTO CA AND THE GTBASIN ON SUN (DAY 3) WITH THE MORE PROGRESSIVE
MRF FAVORED IN THIS FAST WLY FLOW. PCPN WL GENERALLY BE LIGHT
ACRS THE WRN U.S. ON SUN AND MON (DAY 3 & 4) AS THE ONSHORE FLOW
WL BE WEAK. MORE TIMING DIFFS BY TUE (DAY 5) WITH THE NEXT AREA
OF HT FALLS MOVG IN THE STRONG NERN PAC JET TOWARD THE NRN CA
COAST. AGAIN...THE FASTER MRF WAS FAVORED. MORE UNSEASONABLY
LATE SEASON PCPN IS ON TAP BY EARLY TUE FOR PORTIONS OF NRN AND
CNTRL CA. BELOW NORMAL HTS EXPECTED THRU THE PERIOD OVR A LARGE
PART OF THE WEST WL RESULT IN BELOW TO MUCH BELOW NORM TEMPS FROM
THE NRN ROCKIES THRU THE PAC NW AND INTO THE VALLEYS OF CNTRL CA.

DOWNSTREAM...THE UPR FLOW WL BECOME WSWLY IN THE MEAN DURG THE
MED RANGE PERIOD...WITH A MEAN FRONTAL BNDRY STRETCHING FROM THE
CNTRL PLAINS EWD THRU THE MID MS VALLEY...OH VALLEY AND INTO THE
NRN MID ATL. THESE ABOVE CONDITIONS SHOULD PRODUCE A VERY
ACTIVE MCS/MCC PATTERN ALONG THIS FRONT AS THE WRN HT FALLS MOVE
EAST OF THE ROCKIES. ON SUN AND MON (DAYS 3 & 4) THE LOW LEVEL
CONVERGENCE APPEARS TO BE FOCUSED OVR THE CNTRL PLAINS/MID MS
VALLEY INVOF NE/IA NERN KS AND NRN MO. ALL OF THE MED RANGE
GUIDANCE IS SHOWING WELL DEFINED 1000-500 MB THICKNESS DIFFLUENCE
ACRS THIS REGION INDICATIVE OF THE LOW LEVEL CONVERGENCE.
MCS/MCC ACTIVITY SHOULD FORM IN THE VICINITY OF THIS DIFFLUENT
THICKNESS PATTERN EARLY SUN AND MON MORNINGS AND PROPAGATE ESEWD
AS FAR DOWNSTREAM AS THE OH VALLEY...CNTRL APPALACHIANS AND
POSSIBLY THE MID ATL. BY TUE (DAY 5)...THE FRONTAL BNDRY IS FCST
TO SLIP SWD INTO THE SRN PLAINS WITH THE BEST THICKNESS
DIFFLUENCE OVR NRN OK...NWRN AR...SWRN MO AND SERN KS. ON ALL OF
THESE DAYS THE MRF DOES NOT FCST ANY PCPN NEAR THIS FRONT. GIVEN
THE WELL DEFINED THICKNESS DIFFLUENCE AND THE SHRTWV ALOFT...WE
BELIEVE LOCALLY HEAVY PCPN IS POSSIBLE ACRS THESE REGIONS.

ABOVE NORMAL HTS FARTHER TO THE SOUTH AND EAST WL KEEP TEMPS MUCH
ABOVE NORMAL FROM THE SRN PLAINS...ACRS THE SOUTH AND INTO THE
SRN MID ATL. FARTHER TO THE SOUTH...THE MRF IS AGAIN BRINGING A
LOW NWD FROM THE SWRN CARIBBEAN ACRS WRN CUBA AND INTO THE SERN
GULF BY TUE (DAY 5). THE OTHER MED RANGE MODELS DID NOT INDICATE
ANY TROPICAL SYSTEM MOVG NWD. THE MRF HAS A BIAS OF OVER
FORECASTING TROPICAL SYSTEMS...ESPECIALLY RECENTLY. THE LATEST
AVN CONTS TO FCST A LOW MOVG ALONG THE ERN NICARAGUAN AND
HONDURAN COAST BY SUN MORNING...HOWEVER...WE CONT TO HAVE LOW
CONFIDENCE IN THE MRF/AVN SOLN HERE.

ACRS SERN CAN WE HAVE LOW CONFIDENCE WITH THE MRF SOLN OF
BRINGING THE CLOSED LOW FCST TO MOVE NWD ALONG NEW FOUNDLAND THIS
WEEKEND...BACK TOWARD THE SW ON MON (DAY 4) AND TUE (DAY 5). IT
APPEARS THE MRF IS OVER-EMPHASIZING A SHRTWV ROTATING ARND THIS
TROF WHICH PULLS THE WHOLE TROF BODILY SWWD. WE FAVOR KEEPING
HTS HIGHER ACRS THIS REGION..WITH THE SFC PRESSURES HIGHER ACRS
SERN CAN AND NEW ENGLAND ON BOTH OF THOSE DAYS. TEMPS SHOULD
REMAIN COOL ALONG THE NRN TIER DURG THE MED RANGE PERIOD FROM NEW
ENGLAND THRU THE GTLKS AND INTO THE NRN PLAINS AS THESE LOCATIONS
WL BE TO THE NORTH OF THE ABOVE MENTIONED W-E ORIENTED FRONT WITH
CONSIDERABLE AMTS OF CLOUDINESS.

ORAVEC/FORECAST OPERATIONS BRANCH

[UNIDATA Local Data Mangement daemon]

722
FXUS02 KWBC 181903
PMDEPD
EXTENDED FORECAST DISCUSSION FOR 21 MAY THRU 23 MAY 1996
HYDROMETEOROLOGICAL PREDICTION CENTER..NCEP..NWS..WASHINGTON DC
3:00 PM EDT SAT MAY 18 1996

MEDIUM RANGE MODEL MEANS ARE SHOWING SOME SUBTLE BUT SIGNIFICANT
ENOUGH DIFFERENCES TODAY TO CAUSE MAJOR PROBLEMS WITH FORECAST
CONFIDENCE IN THE DAILIES. THE FAST ZONAL TYPE PACIFIC FLOW
COMING INTO THE NWRN PAC U.S. COAST WILL CONTINUE TO BRING
PROGRESSIVE SHORTWAVE ENERGY INTO THE NW COAST KEEPING IT WET
DURING THE PERIOD. THE FAST RELATIVELY ZONAL FLOW CONTS ACROSS
THE CENTRAL U.S ZONAL WITH HIGH HGTS OVER THE THE SRN TIER OF
STATES. THE ECMWF AND UKMET BECOME MORE AMPLIFIED IN THE PACIFIC
FLOW WHICH TRANSLATES INTO A MORE AMPILIFIED PATTERN OVER THE
U.S. THE MRF MAINTAINS A MORE FLATTER AND PROGRESSIVE MEAN FLOW
PATTERN OVER THE PACIFIC WITH A CORRESPONDING FLATTER PATTERN
OVER LOWER NOAM. WITH THE CURRENT AND PAST FAST PAC FLOW THE MRF
MEAN SOLUTION SEEMS TO BE A BETTER FIT. MODEL MEAN AND DAILY
DETAILS CAN BE FOND IN THE PMDHMD.

THE FAST PACIFIC FLOW WILL BRING IN A SERIES OF PACIFIC
SHORTWAVES WHICH WILL TRACK EWD IN THE WESTERLIES AND GENERATE
SEVERAL FRONTAL WAVES ALONG THE PERSISTANT WAVY EAST TO WEST
BOUNDARY FROM THE MIDWEST THRU THE OH RIVER VALLEY DURING THE
PERIOD. BY DAY 5 (THU) A DEVELOPING STORM IN THE GULF OF AK WILL
RAISE DOWNSTREAM HGTS OVER THE PAC NW COAST AND ALLOW GREATER
DOWNSTREAM AMPLIFICATION OF SHORTWAVE ENERGY MOVING INTO THE
CENTRAL PLAINS BRINGING AN END TO THE UNSTABLE ZONAL FLOW PATTERN
OVER THE U.S. AND APPEARS TO BE REVERTING TO A WRN RIDGE/ERN TROF
PATTERN. THIS WILL GRADUALLY TEND TO REVERSE THE CURRENT
TEMPERATURE PATTERN OF A COOL WEST AND WARM EAST TOWARD NEXT
WEEKEND.

A MEAN FRONTAL BNDRY WILL STRETCH FROM THE CNTRL PLAINS EWD THRU
THE MID MS VALLEY...OH VALLEY AND INTO THE NRN MID ATL. PACIFIC
SHORTWAVE ENERGY TRAVERSING THE FRONT WILL CONTINUE THE TREND OF
PRODUCING AN ACTIVE MCS/MCC PATTERN AS THE WRN HT FALLS MOVE EAST
OF THE ROCKIES. THE FRONTAL BOUNDARY STRETCHED FROM THE UPPER MID
ATLC WILL MOVE NORTHWARD IN THE EAST AND SAG SOUTHWARD THRU THE
CENTRAL PLAINS AS ONE SHORTWAVE MOVES EAST INTO WRN NY AND OFF
THE UPPER NEW ENG COAST THU. BOTH OVERUNNING RAINFALL AND SOME
STRONG CONVECTIVE ACTIVITY CAN BE EXPECTED NEAR THE FRONT. AS
STRONGER HGT FALLS MOVE INTO THE NRN ROCKIES AND HIGH PLAINS WED
AND THURS A SIGNIFICANT LEE SIDE LOW WILL FORM IN THE NRN HIGH
PLAINS WITH A FAIRLY STRONG COLD FRONT DROPPING THRU THE GREAT
BASIN AND INTO THE SRN ROCKIES. THIS WILL SPREAD OVERUNNING
RAINFALL THRU THE NRN PLAINS AND UPPER MS VALLEY WITH SOME STRONG
CONVECTION OVER THE LOWER MO VALLEY AND SOUTH THRU THE CENTRAL MS
VALLEY.

THE SOUTHEAST WILL SEE A CONTINUED BUILD UP OF THE STRONG BERMUDA
HIGH AS UPPER LEVEL RIDGING CONTS OVER THE AREA PRODUCING SUMMER
LIKE TEMPERTURES.

THE MOST DISCONCERTING FORECAST PROBLEM REMAINS OVER THE ERN GULF
OF MEXICO AND THE SOUTHEAST. THE MRF AND AVN AGAIN TODAY AS THEY
HAVE FOR THE PAST SEVERAL DAYS INSIST ON TROPICAL DEVELOPMENT
NEAR THE GULF OF HONDURAS. BOTH MODELS HAVE BEEN CONSISTANT
TAKING A TROPICAL SYSTEM NORTH INTO THE ERN GULF OF MEXICO AND
INTO THE SERN U.S. THE MRF STILL WANTS TO RAPIDLY TAKE A SYSTEM
NORTH INTO THE ERN GULF AND THEN INTO GA WHERE IT IS INFLUENCED
BY A POLAR TROF IN PLACE OVER THE WRN GULF OF MEXICO. THE MRFX
AGAIN TODAY HAS A SLOWER AND MORE WESTWARD TRACK AS IT BECOMES
INFLUENCED BY THE WESTERN GULF TROF/UPPER LOW WHILE THE
BAROTROPIC EXTENSION OF THE ETA LEAVES THE POLAR TROF IN PLACE
AND TRACKS WHATEVER EXISTS OF THE CARRIBEAN SYSTEM NEWD FROM WRN
CUBA ON TUES TO NEAR NASSAU BY THURS. THEREFORE WE ESSENTIALLY
HAVE 3 MODELS FORECASTING SPRING TROPICAL DEVELOPMENT IN THE
CARRIBEAN AND ERN GULF OF MEXICO. WHILE THERE HAVE ONLY BEEN 14
OF THESE IN THE LAST 110 YEARS IN MAY THERE HAVE BEEN
CONSIDERABLY MORE IN JUNE. WITH THE ATMS ACTING MORE LIKE JUNE IT
IS NOT INCONCIEVABLE FOR SOME DEVELOPMENT TO HAPPEN.
HOWEVER...NEITHER THE ECMWF NOR THE UKMET GENERATE ANY
DEVELOPMENT IN THIS AREA WHILE THE ECMWF DOES DEVELOP A WEAKER
SYSTEM OVER THE NERN GULF ASSOCIATED WITH THE POLAR TROF IN THE
NRN GULF OF MEXICO...A NON TROPICAL SYSTEM. AGAIN TODAY WE HAVE
VERY LIMITED CONFIDENCE IN THE MRF...WITH THE LATEST AVN OFFERING
AN EVEN SCARIER SOLUTION OF A FAST MOVER APPROACHING THE CENTRAL
GULF COAST BY 72 TO 84 HRS. WHILE WE STILL BELIEVE THERE IS A
CONVECTIVE FEEDBACK PROBLEM WITH THESE MODELS OVER DEVELOPING
THIS SYSTEM WE CAN NOT IGNORE THEIR PERSISTANCE AND CONSISTANCY.

MANUAL PROGS REFLECT A MUCH SLOWER AND WEAKER ERN GULF OF MEXICO
SYSTEM MOVING FROM THE SWRN TIP OF CUBA TUES TO THE CENTRAL ERN
GULF THURSDAY. THIS MAY WELL BE TOO SLOW IF ANYTHING DEVELOPS AND
IS PICKED UP AND ACCELERATED TOWARD THE NORTH BY THE POLAR TROF
AND CLOSED UPPER LOW OVER THE WESTERN GULF. SEE LATEST NHC
ADVISORIES.

ROSENSTEIN/FORECAST OPERATIONS BRANCH

[UNIDATA Local Data Mangement daemon]

855
FXUS02 KWBC 191817
PMDEPD
EXTENDED FORECAST DISCUSSION FOR 22 MAY THRU 24 MAY 1996
HYDROMETEOROLOGICAL PREDICTION CENTER..NCEP..NWS..WASHINGTON DC
2:15 PM EDT SUN MAY 19 1996

MEDIUM RANGE MODEL MEANS ARE IN BETTER AGREEMENT TODAY THAN YTDA
WITH BOTH THE UKMET AND ECMWF MEANS COMING BACK TO THE MRF
SOLUTION. STRONG HGT RISES ARE OCCURING IN THE DEEP TROF FROM THE
GULF OF AK SOUTHWARD ALONG THE WEST COAST. THIS TROF WILL BE
REPLACED BY FLAT RIDGING OVER THE WEST COAST WHILE HGT FALLS
DRIVE INLAND AND CREATE DOWNSTREAM TROFFING IN THE CENTRAL AND
SRN ROCKIES AND THE HIGH PLAINS. HGTS ARE EXPECTED TO REMAIN
BELOW NORMAL NORTH OF THE MEAN JET PATTERN FROM THE WESTERN
PACIFIC THRU MOST OF CANADA AND THE ARCTIC. HGTS WILL ALSO FALL
OVER THE ERN THIRD OF THE NATION FROM THE CURRENT STRONG UPPER
RIDGE TO MORE OF A FLAT RIDGE WITH HGTS CONTINUING SLIGHTLY ABOVE
NORMAL.

GREATER SHORTWAVE SEPERATION IS NOW EXPECTED IN THE FAST PACIFIC
FLOW WITH ONLY ONE STRONG SHORTWAVE COMING ONSHORE INTO THE NW
PAC COAST EARLY IN THE PERIOD. THIS ONE FOLLOWED BY STRONG
UPSTREAM HGT RISES DROPS SOUTHEASTWARD TOWARD THE CENTRAL ROCKIES
AND CARVES OUT A DEEP AND SLOWLY PROGRESSIVE TROF THRU THE SRN
ROCKIES AND HIGH PLAINS DURING THE PERIOD WITH A SLOW EASTWARD
PROGRESSION INTO A DEEP FULL LATITUDE TROF MOVING INTO ERN STATES
DURING THE 6 TO 10 DAY PEROOD. THIS EFFECTIVELY REVERSES THE
CURRENT WRN TROF/ERN RIDGE PATTERN.

THE CARVING OUT OF THE ROCKIES TROF IS MUCH DEEPER IN TODAYS RUNS
THAN YTDA AND WITH A CLOSING OFF OF THE H500 LOW LATER ON THURS
AND FRI. OVER THE ERN 2/3RDS OF THE NATION THE PERSISTANT
TROUBLESOME BOUNDARY FROM THE MIDWEST THRU THE OH VALLEY AND
UPPER MID ATLC IS FORECAST BY ALL MODELS TO DROP SOUTHWARD AS A
COLD FRONT ON DAYS 4 AND 5 AS STRONGER HIGH PRESSURE BUILDS SEWD
FROM THE NRN CANADIAN PLAINS. THE MRF HAS THE FARTHEST SOUTHWARD
POSTION OF THE FRONT FROM SRN MD TO THE TN VALLEY THU AND INTO SC
AND NRN GA FRI. IN MOST CASES THE MRF SEEMS TO OVERDO COLD
ADVECTION AND ERN FRONTS CAN BE ADJUSTED NORTH (EXCEPT FOR TRUE
BACK DOORS). HOWEVER THE UNUSUALLY LATE SNOW COVER OVER CENTRAL
AND NRN CANADA SEEMS TO HOLD UP ANY AIRMASS MODIFICATION THIS
SPRING AND EVERY FRONT THAT HAS BEEN FORECAST TO DROP INTO THE
EAST AND SOUTH GONE MUCH FARTHER THAN FORECASTERS EXPECT. SO HAVE
GONE WITH THE COLDER DEEPER MRF BY THU AND FRI. THIS WILL LOWER
THE HOT TEMPERATURES OVER THE SERN SEABOARD TO A MORE NORMAL
RANGE.

THE CARVING OUT OF THE DEEP TROF/CLOSED LOW IN THE SRN ROCKIES
THU AND FRI WILL BRING VERY COOL CONDITIONS TO THE ROCKIES AND
HIGH PLAINS WITH A FAIRLY STRONG SFC CYCLOGENESIS OCCURING THU IN
THE SRN HIGH PLAINS. OVERUNNING RAINFALL WILL SPREAD THROUGHOUT
THE PLAINS AND INTO THE UPPER MS VALLEY WITH A BROKEN AREA OF
CONVECTION FROM THE LOWER RED RIVER VALLEY NORTH THRU THE LOWER
MO AND CENTRAL MS VALLEYS.

AGAIN TODAY THE MOST DISTURBING FEATURE WE HAVE TO DEAL WITH IS
THE PERSISTANT AVN/MRF FORECAST OF A TROPICAL SYSTEM DEVELOPING
IN THE GULF OF HONDURAS AND MOVING RAPIDLY NORTHWARD AS IT
BECOMES INFLUENCED BY A DEEP POLAR TROF IN THE WESTERN AND
CENTRAL GULF OF MEXICO. THE AVN AND MRF HAVE BEEN FORECASTING
THIS FOR DAYS WHILE THE ECMWF AND UKMET HAVE HAD A VERY LIMITED
REFLECTION OF ANY DISTURBANCE AT ALL. TODAYS ECMWF DOES LIFT
NORTH A MID LEVEL DISTURBANCE AND A WEAK ASSOCIATED SURFACE LOW
FROM WRN CUBA WED THRU THE FLORIDA STRAITS THU AND INTO THE WRN
BAHAMAS FRI. THIS IS SIMILAR TO YTDAS BARX TRACK. ETA CARRIES A
WEAKER SYSTEM THAN THE MRF AND AVN WHILE NGM STILL DOESNT HAVE A
CLUE. IT STILL APPEARS TO US THAT THE AVN AND MRF GUESS FIELDS
ARE BEING CONTAMINATED BY CONVECTIVE FEEDBACK IN THE LOWER
LATITUDES AND ARE OVERDEVELOPING THIS SYSTEM. THIS IS VERY
APPARENT IN THE LATEST AVN RUN BY TAKING IT TOO FAR WEST WITH THE
WRONG VORT CENTER. THE LATEST GFDL RUN ON THIS SYSTEM IMMEDIATELY
KILLS IT. WE BELIEVE THAT THIS SYSTEM IF IT EXISTS AT ALL WILL BE
CONSIDERABLY WEAKER THAN THE AVN/MRF FORECAST...THE TIMING AND
RAPID ACCLERATION NORTHWARD IS QUITE POSSIBLE AS WHATEVER ENERGY
COMES NORTH IS INFLUENCED BY THE WRN GULF UPPER LOW. ONCE (AND
IF) THE SYSTEM COMES NORTH INTO THE EAST CENTRAL GULF AND UNDER
THE INFLUENCE OF THE POLAR TROF/UPPER LOW THE SYSTEM WILL BE MUCH
MORE OF A HYBRID CROSS OF A BAROCLINIC SYSTEM AND TROPICAL
DISTURBANCE. WE HAVE VERY LOW CONFIDENCE IN THE FORECSTING OF
THIS SYSTEM...WHICH MAY WELL NOT EVEN DEVELOP. BUT THE
PERSISTANT SIGNAL FROM THE AVN AND MRF FORCE US TO AT LEAST CARRY
SOME FEATURE ON THE PROGS. MANUAL PROGS HAVE SLOWED THE POSITION
OF THE MRF SURFACE POSITION WED AND MOVE IT ACROSS NRN FL TO OFF
THE GA/SC COAST THURSDAY. BY LATER THURSDAY AND FRIDAY THE LOW
WILL COME UNDER THE INFLUENCE OF THE COLD FRONT DROPPING
SOUTHWARD ALONG THE ATLC SEABOARD AND BECOME TRULY BAROCLINIC AND
RAPIDLY MOVE TO SEA AS A FRONTAL WAVE. SEE LATEST NHC ADVISORIES.

ROSENSTEIN/FORECAST OPERATIONS BRANCH

[UNIDATA Local Data Mangement daemon]

007
FXUS02 KWBC 191825

PMDEPD
EXTENDED FORECAST DISCUSSION FOR 22 MAY THRU 24 MAY 1996
HYDROMETEOROLOGICAL PREDICTION CENTER..NCEP..NWS..WASHINGTON DC

2:25 PM EDT SUN MAY 19 1996...CORRECTION TO LAST PARAGRAPH

WRONG VORT CENTER. THE LATEST GFDL TAKES A MUCH WEAKER LOW
NORTHAND THAN NORTHEASTWARD TOWARD THE FL PANHANDLE BY 60 HRS TO
THE EAST OF THE MRF RUN. WE BELIEVE THAT THIS SYSTEM IF IT EXISTS

AT ALL WILL BE CONSIDERABLY WEAKER THAN THE AVN/MRF
FORECAST...THE TIMING AND RAPID ACCLERATION NORTHWARD IS QUITE
POSSIBLE AS WHATEVER ENERGY COMES NORTH IS INFLUENCED BY THE WRN
GULF UPPER LOW. ONCE (AND IF) THE SYSTEM COMES NORTH INTO THE

EASTERN GULF AND UNDER THE INFLUENCE OF THE POLAR TROF/UPPER LOW

THE SYSTEM WILL BE MUCH MORE OF A HYBRID CROSS OF A BAROCLINIC
SYSTEM AND TROPICAL DISTURBANCE. WE HAVE VERY LOW CONFIDENCE IN

THE FORECASTING OF THIS SYSTEM...WHICH MAY WELL NOT EVEN DEVELOP
OR BE A VERY MINOR FEATURE. BUT THE PERSISTANT SIGNAL FROM THE

[UNIDATA Local Data Mangement daemon]

784
FXUS02 KWBC 201830
PMDEPD
EXTENDED FORECAST DISCUSSION FOR 23 MAY THRU 25 MAY 1996
HYDROMETEOROLOGICAL PREDICTION CENTER..NCEP..NWS..WASHINGTON DC
2:30 PM EDT MON MAY 20 1996

MEDIUM RANGE MODEL MEANS GENERALLY AGREE ON THE PATTERN OVER THE
WRN HALF OF NOAM AND THE ERN PACIFIC..SHOWING A DEEPENING CENTRAL
PAC TROF..A BLDG EPAC RIDGE..BLOCKING OVER NW CANADA..AND A
DEEPENING TROF OVER THE GRT BASIN. THE 72 HR FCST FROM THE NEW
AVN RUN VALID FRI AM IS DEEPER/FARTHER S THAN THE MRF WITH THE
NEW WRN TROF..SUGGESTING A SLIGHT WWD CORRECTION TO THE MRF WITH
THE DVLPG CUTOFF UPPER LOW OVER THE GRT BASIN THRU THE MEDIUM
RANGE PERIOD. THE PMDHMD DID NOT REFLECT THIS. THE ECMWF IS BY
ITSELF IN DVLPG A DEEP MEAN TROF OFF THE E COAST WITH A NEG HGT
ANOMALY CENTER OVER MAINE. WHILE NOT SUPPORTED BY ANY OTHER
MEDIUM RANGE GUIDANCE..THE PATTERN COULD TREND TOWARDS THE ECMWF
ALONG THE E COAST SINCE UPSTREAM FEATURES MAY BECOME MORE
AMPLIFIED THAN FCST BY THE MRF.

FALLING HGTS OVER THE ERN STATES OVER THE NEXT COUPLE OF DAYS
WILL ALLOW A COLD FRONT TO BRING COOLER AND DRIER AIR TO MOST OF
THAT REGION. MEANWHILE..AN UPPER TROF WILL BE AMPLIFYING SE OVER
THE WRN STATES WITH A DEEP LEESIDE SFC LOW DVLPG E OF THE CO
ROCKIES BY THU (DAY 3). THIS SCENARIO WILL ALLOW A LARGE AREA OF
CONVECTIVE OVERRUNNING PCPN TO ORGANIZE OVER NRN PORTIONS OF THE
PLAINS AND MS VLY. FARTHER S..IN THE CENTRAL AND SRN PLAINS..THE
GRADUAL WEAKENING OF THE WARM MID-LEVEL CAP MAY ALLOW SCTD TSTMS
TO FORM ALONG THE DRYLINE FROM WRN KS SWD INTO NW TX. SHWRY PCPN
ASSOC WITH COLD AIR ALOFT WILL GRADLY END FROM W TO E ACROSS THE
NW BORDER STATES. MOISTURE FROM A WEAK TROPICAL DISTURBANCE NOW E
OF YUCATAN IS NOT EXPECTED TO MOVE AS FAR INTO THE SERN STATES AS
MRF RH PROGS INDICATED. LEFTOVER MOISTURE FROM THIS MAY ENHANCE
DIURNAL SHWRS OVER FL FRI..AND THE REST OF THE GULF COAST REGION
OVER THE WEEKEND.

BY DAY 4 (FRI) CONTINUED AMPLIFICATION/CLOSING OFF OF THE UPPER
TROF SEWD INTO THE GRT BASIN WILL ALLOW THE MAIN SFC LOW E OF THE
ROCKIES TO SHIFT S INTO NW TX AS SFC PRES FALL NEWD ALONG A FRONT
THRU THE MS VLY. GENERAL PCPN WITH EMBEDDED CONVECTION IS
EXPECTED IN THE NRN PORTIONS OF THE PLAINS/MS VLY..AND IN UPSLOPE
AREAS OF THE NRN ROCKIES. FARTHER S..THE DRYLINE SHOULD BE ACTIVE
IN THE SRN PLAINS AS THE MID-LEVEL CAP WEAKENS FURTHER AND SFC
DEWPOINTS REMAIN HIGH OVER CENTRAL/ERN PORTIONS OF TX/OK. THE
RETURNING WARM FRONT IN THE ERN STATES WILL BE OVERRUN BY
INCREASING GULF INFLOW WITH SOME LOCALLY HVY PCPN TOTALS PSBL IN
THE MIDWEST. DIURNAL CONVECTION WILL INCREASE IN THE WARM HUMID
UNSTABLE AIR ACROSS THE GULF STATES AND FL FROM REMNANTS OF THE
WEAK TROPICAL DISTURBANCE.

BY DAY 5 (SAT) A WAVY COLD FRONT WILL PUSH SLOWLY SEWD INTO THE
CENTRAL AND SRN PLAINS. REPEAT TSTMS MAY GIVE EXCESSIVE RAFL
TOTALS TO A LARGE AREA FROM CENTRAL TX TO THE MIDWEST. DROUGHT-
STRICKEN S CENTRAL TX MAY FINALLY RECEIVE SOME SIGNIFICANT RAFL.
WARM ADVECTION PCPN WILL CONTINUE TO SPREAD INTO THE ERN LAKES
AND NRN APLCNS. WE DID NOT BRING PCPN AS QUICKLY INTO NEW ENG AS
THE MRF SINCE WE ARE TRENDING SOMEWHAT TOWARDS THE ECMWF SFC FCST
OF HIGH SFC PRES OVER THAT AREA. PCPN WILL DECREASE OVER THE NRN
PLAINS AND OVER UPSLOPE PORTIONS OF WY/CO..WITH THE PAC NW DRY
UNDER RIDGING ALOFT.

FLOOD/FORECAST OPERATION BRANCH

[UNIDATA Local Data Mangement daemon]

402
FXUS02 KWBC 211841
PMDEPD
EXTENDED FORECAST DISCUSSION FOR 24 MAY THRU 26 MAY 1996
HYDROMETEOROLOGICAL PREDICTION CENTER..NCEP..NWS..WASHINGTON DC
2:40 PM EDT TUE MAY 21 1996

THE LATEST MEDIUM RANGE MODEL GUIDANCE IS IN GENERALLY GOOD
AGREEMENT WITH THE EVOLUTION OF THE PATN THIS PD. THE VRY
FAST...RELATIVELY FLAT MEAN FLOW OVR THE PAC DURG THE WEEKEND IS
IN THE PROCESS OF BUCKLING...WITH A STG TROF DEVELOPING OVR THE
CNTRL PAC INVOF THE DATELINE WHILE A RIDGE STRENGTHENS DOWNSTREAM
BTWN 130-140W. PAC ENERGY LIFTING OVR THIS ERN PAC RIDGE WILL
SPLIT AS IT REACHES THE WRN NOAM COAST...WITH THE MAJORITY DIVING
SEWD AND CARVING OUT AN IMPRESSIVE TROF OVR THE GRT BASIN IN THE
SRN STREAM. THE REMAINING PAC ENERGY WILL LIFT UP AND OVR A STG
RIDGE CNTRD OVR THE NRN NW TERRITORIES. FARTHER EAST...HGTS WILL
BUILD SLIGHTLY IN THE MEAN OVR THE CNTRL AND SERN U.S. DOWNSTREAM
OF THE GRT BASIN TROF. HGT FALLS ARE PROGGED OVR NEW ENGLAND AS
A COMBINATION OF SHORT WAVE ENERGY ROTATING ARND THE NRLY
STATIONARY UPR LOW OVR NRN QUEBEC AND ENERGY PROGRESSING EWD OUT
OF THE WKNG UPR TROF OVR SCNTRL CAN CARVES OUT A BROAD MEAN TROF
OVR THE NERN U.S. AND ADJACENT WRN ATLC.

IN THE DAILIES...THE MODELS ARE IN PRETTY GOOD AGREEMENT ON DAY 3
(FRI). LOW PRESSURE WILL BE ANCHORED OVR THE CNTRL HI PLAINS
DOWNSTREAM OF THE UPR TROF OVR THE CNTRL INTERMTN RGN. STG GULF
INFLOW OUT AHD OF IT WILL SUPPORT POTENTIAL MCS DEVELOPMENT OVR
THE ECNTRL PLAINS/MID-UPR MS VALLEY LATE THU NIGHT/FRI
MORN...WHICH WILL THEN SLIDE ESEWD INTO THE UPR MIDWEST ALG THE
NRLY STATIONARY BNDRY DRAPED ACRS THE RGN. WDSPD LGT-MDT RAINS
WILL BE FOUND ACRS THE NRN/CNTRL HI PLAINS SWWD INTO THE CNTRL
ROCKIES UNDER THE COOL UPR TROF. AMTS MAY BE A BIT HVIER ACRS
UPSLOPE RGNS OF WY/SERN MT...BUT WE FEEL THAT THE MRF IS
SIGNIFICANTLY OVERDONE (AS IT TYPICALLY PREDICTS TOO MUCH UPSLOPE
PCPN). HGT FALLS PUSHING INTO THE PLAINS SHOULD ALLOW THE CAP TO
BREAK E OF THE TRAILING COLD FRONT...WITH SCT-NUMEROUS STG TSTRMS
DEVELOPING ALONG /AHEAD OF THE FRONT LATE FRI AFT/EVENING.

ELSEWHERE...COOL DRY CONDITIONS WILL PREVAIL OVR NEW ENGLAND AND
THE PAC NW. WE ARE SOMEWHAT SKEPTICAL OF THE MRF'S HIGH RHS/PCPN
IN THE CNTRL/ERN GULF. AS HAS BEEN THE CASE RECENTLY...THE MRF
IS OVERDEVELOPING SFC LOW PRESSURE IN THE GULF (A CONVECTIVE
FEEDBACK PROBLEM IN THE MODEL). IT SHEARS SOME OF THE LOW NEWD
ACRS FL (SIMILAR TO THE LATEST SHORT RANGE RUNS) BUT TAKES A
SPURIOUS LOW TWD THE CNTRL GULF COAST EARLY FRI. THIS SYS AND
ITS ASSOCIATED PCPN IS NOT SUPPORTED IN THE NGM/ETA AND HAS BEEN
DISREGARDED.

ON DAY 4 (SAT)...NOT MUCH OVERALL CHANGE IN THE PATN. WE
BELIEVED THAT THE ECMWF WAS A LITTLE TOO STG LIFTING A SHORT WAVE
IMPULSE INTO THE NRN PLAINS...PREFERRING THE WKR MRF. THE COLD
FRONT IN THE CNTRL PLAINS WILL ONLY EDGE EWD...WITH THE TRAILING
PORTION REMAINING NRLY STATIONARY AS LOW PRESSURE RE-DEVELOPS ALG
IT OVR THE SRN HI PLAINS. WDSPD HVY OVERRUNNING CONVECTION AGAIN
IS EXPECTED OVR THE NRN MS VALLEY/UPR MIDWEST AND NRN OH
VALLEY...AS ANOTHER MCS LIKELY TRIGGERS OVR IA/SRN MN LATE
FRI/EARLY SAT. LGTR RAINS MAY XTND AS FAR EWD ALG THE FRONT AS
THE MID-ATLC. SCT POPCORN CONVECTION IS EXPECTED OVR THE SERN
QUARTER OF THE NATION IN THE INCREASINGLY MOIST AIR MASS SOUTH OF
THIS FRONT. ANOTHER ROUND OF HVY TSTRMS IS LIKELY SAT
AFTN/EVENING ALG THE COLD FRONT/DRYLINE XTNDG SWD INTO SWRN TX.
WDSPD MAINLY OROGRAPHIC SHWRS WILL CONT IN THE 4 CORNERS/CNTRL
ROCKIES RGN UNDER THE COOL UPR CYCLONE. NEW ENGLAND AND THE PAC
NW WILL REMAIN DRY AND COOL.

ON SUN (DAY 5)...THE MRF EJECTS A RATHER STG PIECE OF ENERGY FROM
THE LOW OVR THE SWRN STATES AND SUBSEQUENTLY DEVELOPS A DECENT
SFC SYS OVR THE SRN LAKES. THIS SEEMS OVERDONE. SHORT WAVE
ENERGY LIFTING INTO THE MEAN RIDGE PSN DOWNSTREAM SHOULD INSTEAD
WKN/SHEAR OUT...AS PER THE PREFERRED ECMWF SOLN. WE DID
FEEL...HOWEVER...THAT THE ECMWF WAS BRINGING TOO MUCH HIGH
PRESSURE INTO NEW ENGLAND...CREATED IN THE WAKE OF A CLOSED
CYCLONE DRIVING SEWD INTO THE CANADIAN MARITIMES (THE SAME LOW
CURRENTLY PARKED OVR NRN QUEBEC). PREFER HERE A COMPROMISE
MRF/ECMWF SOLN. HVY OVERRUNNING CONVECTION IS EXPECTED OVR THE
LAKES STATES/NRN OH VALLEY...A LITTLE FARTHER NORTH/EAST THAN FRI
AND SAT. MORE STG CONVECTION WILL FIRE ALG THE WAVY TRAILING
COLD FRONT (WHICH HAS NOT MOVED MUCH THRU THE 3 DAY PD).
OROGRAPHIC PCPN WILL BE GRADUALLY DIMINISHING ACRS THE CNTRL
ROCKIES/4 CORNERS AREA AS THE UPR LOW SLOWLY FILLS. A WK FRONT
APPROACHING THE PAC NW MAY BRING LGT SHWRS INTO NWRN WA. SCT
CONVECTION AGAIN EXPECTED IN THE SOUTHEAST...WHILE MAINLY DRY
COOL WX CONTS OVRN NEW ENGLAND.

KLEIN/FORECAST OPERATION BRANCH

[UNIDATA Local Data Mangement daemon]

404
FXUS02 KWBC 211842

[UNIDATA Local Data Mangement daemon]

616
FXUS02 KWBC 221825
PMDEPD
EXTENDED FORECAST DISCUSSION FOR 25 MAY THRU 27 MAY 1996
HYDROMETEOROLOGICAL PREDICTION CENTER..NCEP..NWS..WASHINGTON DC
2:25 PM EDT WED MAY 22 1996

MEDIUM RANGE 5 DAY 500MB MODEL MEANS CENTERED ON 25 MAY CONTINUE
A TREND FOR AMPLIFICATION. THEY FCST A CENTRAL PAC TROF..AN E PAC
RIDGE..A CUTOFF LOW OVER THE GREAT BASIN..A RIDGE OVER THE GULF
STATES AND LOWER OH VLY..AND A DEEPENING TROF OFF THE NEW ENG
COAST AND ADJACENT CANADA. A BLOCKING RIDGE WILL REMAIN IN PLACE
OVER W CENTRAL CANADA AND HELP SUPPORT A COOL SURFACE HIGH
SLIDING SLOWLY ESE FROM S CENTRAL CANADA INTO ERN CANADA. THIS
SURFACE HIGH WILL BE A MAJOR PLAYER IN KEEPING MOSTLY COOL DRY WX
ACROSS THE NRN LAKES INTO NEW ENG.

DURING THE PERIOD..THE CUTOFF UPPER LOW OVER THE SRN GRT BASIN
WILL SET UP A WET PATTERN FOR THE CENTRAL AND NRN PLAINS STATES.
MCS CONVECTIVE CLUSTERS WILL PERIODICALLY FORM IN THE CENTRAL
PLAINS AND MOVE THRU THE MEAN FRONTAL ZONE FROM KS TO THE
CAROLINAS. EXCESSIVE RAINS ARE LIKELY FROM NRN KS/NE EWD THRU THE
MIDWEST AS CONVECTION REPEATS IN THE SAME GENERAL AREAS DAY AFTER
DAY. THESE CONVECTIVE CLUSTERS WILL BE ASSOC WITH WEAK SHORT WV
TROFS ALOFT MOVING AROUND THE NRN PERIPHERY OF THE WARM UPPER
RIDGE OVER THE GULF STATES. IN THE SRN PLAINS..A GRDL WEAKENING
OF MID-LEVEL CAPPING SHOULD ALLOW CONVECTION TO DVLP ALONG AND E
OF THE DRYLINE. THERE WILL BE LOTS OF INSTABILITY SHWR ACTIVITY
OVER THE GREAT BASIN ASSOC WITH COLD AIR ALOFT.

ON DAY 3 (SAT)...HOT HUMID AIR WILL CLASH WITH COOLER CANADIAN
AIR ALONG A FRONTAL BOUNDARY FROM KS TO NC. CONVECTION IS
EXPECTED ALONG AND EITHER SIDE OF THIS FRONTAL BOUNDARY.
EXCESSIVE RAINFALL IS PSBL FROM NRN KS/NRN MO INTO IL WHERE GULF
INFLOW INTERCEPTS THE FRONT AT A FAVORABLE ANGLE FOR LOTS OF
LIFT. MORE SCTD CONVECTION IS LIKELY FROM ERN KY INTO THE
CAROLINAS. VERY SLY UPPER FLOW WILL ALLOW THE DRYLINE TO FIRE
CONVECTION QUITE FAR W IN THE SRN HIGH PLAINS. LOOK FOR SHWRY WX
OVER MUCH OF THE W ESPECIALLY VCNTY OF THE CLOSED UPPER LOW.

ON DAY 4 (SUN)...WX WILL BE MUCH THE SAME AS SAT ALONG THE E-W
FRONTAL ZONE..EXCEPT THAT ACTIVITY WILL SHIFTING FARTHER S INTO
THE PLAINS STATES AS THE COOL CANADIAN HIGH PRESSES SE ACROSS THE
LAKES. HOT AND HUMID WX WILL PREVAIL S OF THE FRONT. PLEASANTLY
COOL AND DRY CONDS ARE DUE OVER NEW ENG. SHWR ACTIVITY WILL TAPER
OFF OVER MOST OF THE W AS THE COLD UPPER LOW SLOWLY STARTS
LIFTING OUT TO THE ENE. HOWEVER..A NEW SHORTWAVE WILL BE ENTERING
THE INTERIOR PAC NW WITH MORE PCPN. ACTIVITY ALONG AND E OF THE
DRYLINE IN THE SRN PLAINS WILL INCREASE IN COVERAGE AND SPREAD
SLOWLY EWD.

ON DAY 5 (MON)...THE FRONTAL ZONE FROM THE CENTRAL PLAINS TO THE
CAROLINAS WILL BEGIN TO RETURN NWD ALONG WITH ITS ASSOC
CONVECTION. SHWRS MAY RE-INTENSIFY OVER THE GRT BASIN IN RESPONSE
TO THE SECOND SHORT WAVE ALOFT. CONTINUED COOL AND DRY OVER NEW
ENG..HOT OVER THE GULF STATES. THE DRYLINE IN THE SRN PLAINS MAY
BEGIN ACTING MORE LIKE A COLD FRONT WITH ORGANIZED CONVECTION
PUSHING WELL EWD INTO OK AND TX.

FLOOD/FORECAST BRANCH

[UNIDATA Local Data Mangement daemon]

140
FXUS02 KWBC 231826
PMDEPD
EXTENDED FORECAST DISCUSSION FOR 26 MAY THRU 28 MAY 1996
HYDROMETEOROLOGICAL PREDICTION CENTER..NCEP..NWS..WASHINGTON DC
2:25 PM EDT THU MAY 23 1996

MEDIUM RANGE 5 DAY 500MB MODEL MEANS CENTERED ON 26 MAY CONTINUE
FCSTG A STRONG E PAC RIDGE..A CUTOFF LOW OVER THE GREAT BASIN..A
POS HGT ANOMALY CENTERED OVER THE OH VLY..AND A DEEPENING TROF
OFF THE NEW ENG COAST AND ADJACENT CANADA. THE MRF/ECMWF ARE
FCSTG A SLIGHTLY MORE PROGRESSIVE PATTERN ACROSS CANADA IN TODAYS
MEAN FCSTS THAN THEY WERE YESTERDAY. THE RIDGE/TROF PATTERN ALOFT
ACROSS CANADA WILL ALLOW A SURFACE HIGH TO SLIDE SLOWLY ESE FROM
S CENTRAL CANADA INTO ERN CANADA..KEEPING COOL DRY WX ACROSS THE
NRN LAKES INTO NEW ENG THRU THE MEMORIAL DAY WEEKEND.

SLY COMPONENTS E OF THE CUTOFF UPPER LOW FORMING OVER THE SRN GRT
BASIN WILL FAVOR A PROLONGED WET PATTERN FOR THE CENTRAL AND NRN
PLAINS STATES. CONVECTIVE CLUSTERS WILL PERIODICALLY FORM IN THE
CENTRAL PLAINS AND MOVE ESE THRU THE MEAN FRONTAL ZONE FROM KS TO
THE CAROLINAS. EXCESSIVE RAINS ARE LIKELY ALONG AND ON THE N SIDE
OF THIS ZONE AS CONVECTION REPEATS IN THE SAME GENERAL AREAS EACH
DAY. FARTHER S..A DRYLINE SHOULD BECOME ACTIVE EACH DAY NOW THRU
SUN..BRINGING SOME DROUGHT RELIEF TO PARCHED AREAS OF W TX. BY
DAYS 4-5 (MON-TUE) THE DRYLINE WILL BEGIN TO PUSH SLOWLY INTO
CENTRAL AND E TX..WITH CONVECTION FIRING UP ALONG AND AHEAD OF
THE BOUNDARY.

ON DAY 3 (SUN)..THE AFOREMENTIONED FRONTAL BOUNDARY FROM SRN KS
TO THE CAROLINAS WILL REMAIN ACTIVE. THE MEMORIAL DAY WEEKEND
WILL CONCLUDE WITH A COOL AND DRY SUN OVER THE GRT LAKES AND NEW
ENG. CONSIDERABLE SHWR ACTIVITY WILL OCCUR OVER THE ERN GRT BASIN
ASSOCIATED WITH COLD AIR ALOFT. THE NEW 72HR AVN WAS A LITTLE
FASTER THAN THE 84 MRF IN ALLOWING THE CLOSED SWRN UPPER LOW TO
LIFT ENE. A NEW SYS ENTERING THE PAC NW WILL BRING ANOTHER
ORGANIZED AREA OF SHWRS TO THE NRN INTERMOUNTAIN REGION. HOT AND
HUMID WX IS DUE FROM E TX ACROSS THE GULF STATES TO FL. A MID-
LEVEL CAP WILL KEEP A LID ON MOST DIURNAL CONVECTION OVER THAT
AREA.

ON DAYS 4-5 (MON-TUE) CONVECTION..WITH SOME LOCALLY HVY RAINS..
WILL CONTINUE ALONG THE E-W FRONTAL ZONE FROM THE CENTRAL PLAINS
TO THE CAROLINAS. THERE WILL BE A TREND FOR PCPN TO SHIFT NWD
INTO THE MIDWEST AND MID ATLC REGIONS TUE AS A COOL SFC HIGH
MOVES ACROSS NEW ENG..WITH A GENERAL WARM ADVECTION PATTERN
ACROSS THE NE QUARTER OF THE COUNTRY. HOT HUMID WX WITH WIDELY
SCTD SHWRS WILL CONTINUE IN THE WARM SECTOR ACROSS THE SE STATES.
MORE GENERAL CONVECTION IS EXPECTED ALONG/AHEAD OF THE COLD FRONT
PUSHING E ACROSS THE SRN PLAINS. THE NEW UPPER TROF DROPPING INTO
THE WRN STATES WILL CAUSE SHWRY WX TO PERSIST OVER HIGHER ELEVS
FROM THE CENTRAL/NRN GRT BASIN EWD TO THE E SLOPES OF THE
CENTRAL/NRN ROCKIES.

FLOOD/FORECAST BRANCH

[UNIDATA Local Data Mangement daemon]

608
FXUS02 KWBC 241840
PMDEPD
EXTENDED FORECAST DISCUSSION FOR 27 MAY THRU 29 MAY 1996
HYDROMETEOROLOGICAL PREDICTION CENTER..NCEP..NWS..WASHINGTON DC
2:40 PM EDT FRI MAY 24 1996

...HVY RAINS TO CONTINUE FOR THE MIDWEST/OH VALLEY INTO EARLY
NEXT WEEK...

THE LATEST MEDIUM RANGE GUIDANCE MAINTAINS A STGLY AMPLIFIED PATN
ACRS THE STATES...WITH LITTLE OVERALL CHANGE IN THE PSNS OF THE
MEAN LARGE-SCALE FEATURES. MAJOR TROFFING WILL CONTINUE TO
PREDOMINATE ACRS THE WRN THIRD OF THE COUNTRY...HOWEVER...THE
MODELS INDICATE THAT THERE IS TREND FOR THIS MEAN TROF TO
GRADUALLY WKN AND BEGIN RETROGRESSING TWD THE COAST BY THE END OF
THE PD. FARTHER DOWNSTREAM...THE MEAN RIDGE WHICH HAS BEEN
BUILDING ACRS THE CNTRL STATES WILL FLATTEN A BIT AS SHORT WAVE
ENERGY EJECTS OUT OF THE TROF IN THE WEST. STG RIDGING WILL
CONTINUE UPSTREAM OF THIS SYSTEM...WITH ALL MODELS AGREEING ON
THE MEAN AXIS OF THE RIDGE (INVOF 140W-145W). ELSEWHERE ...ONE
OF THE MOST PERSISTENT FEATURES OF LATE HAS BEEN A PRONOUNCED
MEAN RIDGE XNTDG FROM SCNTRL CAN NWWD ACRS THE NW TERRITORIES AND
YUKON REGIONS OF CAN. SHORT WAVE ENERGY DIVING DOWN THE FRONT
SIDE OF THIS RIDGE WILL HELP KICK THE POLAR VORTEX CURRENTLY
PARKED E OF HUDSON BAY SEWD...HELPING TO CARVE OUT A POTENT TROF
FROM NRN NEW ENGLAND EWD ACRS THE CANADIAN MARITIMES.

IN THE DAILIES...TODAY'S BIGGEST PROBLEM WAS TRYING TO FCST THE
TRACK OF THE INTENSE LOW CURRENTLY IN THE SWRN STATES. ALL OF
THE MODELS AGREE THAT A STG SHORT WAVE RIDING OVR THE RIDGE IN
THE ERN PAC WILL AMPLIFY AS IT APPROACHES THE PAC NW COAST LATE
SUN NIGHT. THIS SYS IS CLOSE ENUF THAT IT WILL BE ABLE TO KICK
THE LOW OUT OF THE SW. ON DAY 3 (MON)...THERE IS LITTLE
DISAGREEMENT...ALL MODELS LIFT THE SYSTEM INTO THE CNTRL HI
PLAINS AND WKN IT. THE ECMWF IS THE SLOWEST OF THE 3 MODELS
TODAY...AND APPEARS TOO SLOW GIVEN THE LATEST SHORT RANGE
GUIDANCE. ON DAYS 4/5 (TUE/WED) THE MODEL SOLNS DIVERGE. THE
MRF/UKMET TAKE THE LOW UNDERNEATH OF A SHORT WAVE RIDGE IN SCNTRL
CANADA. THIS IS A BIG SWITCH FROM YESTERDAY'S MRF...WHICH HAD
LIFTED IT INTO THE DAKOTAS TUE. THE UKMET TRACKS THE SHORT WAVE
AND ASSOCIATED SFC LOW FARTHER SOUTH AND SOMEWHAT QUICKER THAN
THE MRF...AND SHOWS SOME PHASING WITH NRN STREAM ENERGY ON WED.
THE ECMWF...LIKE YESTERDAY'S MRF...LIFTS THE BULK OF THE ENERGY
INTO THE NRN PLAINS/NRN MS VALLEY TUE. A VRY WK PIECE OF ENERGY
SQUIRTS UNDERNEATH THE RIDGE INTO THE MID ATLC STATES WED.

TELECONNECTIONS ON THE POSITIVE ANOMALY ASSOCIATED WITH THE MEAN
RIDGE IN CNTRL CAN SUPPORT THE MRF/UKMET IDEA OF TAKING THE SYS
EWD UNDERNEATH THE RIDGE. OF THE TWO...WE PREFER THE MORE SRN
SOLN OF THE UKMET. SO FAR IN THIS PATN...THE MRF HAS BEEN
VERIFYING TOO FAR NORTH WITH WAVES ALG THE NRLY STATIONARY FRONT
XTNDG FROM THE CNTRL PLAINS EWD...AS IT KEEPS TRYING TO LOWER
PRESSURES TOO MUCH IN THE COLD AIR NORTH OF THE BNDRY. A NUMBER
OF MRF ENSEMBLE MEMBERS ALSO FAVOR THE UKMET...ESPECIALLY WITH
PHASING BY THE END OF THE PD. SINCE BOTH THE MRF AND UKMET
CHARACTISTICALLY BIAS TWD PHASING...WE HAVE OPTED INSTEAD TO KEEP
THE SFC WAVE WK AND FAST-MOVING.

ANOTHER MAJOR MCS WILL LIKELY DEVELOP LATE SUN/EARLY MON ACRS THE
ECNTRL PLAINS/MID MS VALLEY AS MOIST GULF INFLOW OVERRUNS THE
POTENT SFC BNDRY...AND IS ACCOMPANIED BY STG HGTS FALLS AND
FAVORABLE JET DYNAMICS FROM THE SHORT WAVE LIFTING OUT OF THE
ROCKIES. THE MCS SHOULD THEN TRAVEL ESEWD INTO THE OH VALLEY AS
THE DAY PROGRESSES. STG CONVECTION SHOULD FIRE ALG THE TRAILING
COLD FRONT MON AFTN/EVENING AT LEAST AS FAR SOUTH AS NRN TX AS
HGT FALLS BREAK THE STG MID-LVL CAP. ELSEWHERE ON MON...HIGH
PRESSURE SETTLING INTO NEW ENGLAND WILL PROVIDE COOL AND MAIN DRY
CONDITIONS. IN THE WEST...THE AMPLIFYING SHORT WAVE WILL DRAG A
SFC FRONT ACRS THE NRN INTERMTN RGN. MOISTURE WITH THIS SYS IS
SOMEWHAT LIMITED...BUT THE STG DYNAMICS SHOULD BE ABLE TO SQUEEZE
OUT SOME MDT PCPN AMTS...ESPECIALLY IN FAVORED ORORGRAPHIC RGNS.

ON DAY 4 (TUE)...THE HVIEST OVERRUNNING CONVECTION WILL SHIFT EWD
INTO THE ERN OH VALLEY/MID-ATLC AS THE SFC WAVE SHIFTS EAST. HVY
TSTRMS SHOULD AGAIN FIRE ALG/AHD OF THE TRAILING COLD FRONT AND
EAST OF THE DRYLINE OVR CNTRL TX. SCT TSTRMS ARE POSSIBLE OVR
THE SOUTHEAST AND SRN ATLC COASTAL STATES. DRY...COOL WX WILL
CONTINUE IN NEW ENGLAND. CONDITIONS SHOULD FINALLY DRY OUT ACRS
THE PLAINS. IN THE WEST...GENERALLY PREFER THE MRF/ECMWF
HANDLING OF THE NEXT DEVELOPING UPR LOW...THE UKMET APPEARS TOO
WK AND IS TOO PHASED WITH SHORT WAVE TROFFING MOVING INTO WRN
CAN. THIS SYS WILL BRING WDSPD SHWRS TO MUCH OF THE NWRN QUARTER
OF THE NATION ON TUE. THE HVIEST RAINS WILL PROBABLY BE FOUND IN
THE ERN MT/WY...WHERE UPSLOPE LOW-LVL FLOW COMBINES WITH BROADLY
DIFLUENT FLOW ON THE EAST SIDE OF THE SYS.

ON DAY 5 (WED)...THE SHORT WAVE IN THE OH VALLEY TUE WILL PUSH
OFF THE COAST...WITH OVERRUNNING RAINS ENDING IN THE MID-ATLC/SRN
NEW ENGLAND EARLY IN THE DAY. BROAD UPR DIFLUENCE AND HGT FALLS
WILL SUPPORT WDSPD TSTRM DEVELOPMENT ACRS THE SERN STATES ALG THE
COLD FRONT. MOISTURE RETURNING FROM THE GULF OF MEX WILL OVERRUN
THE TAIL END OF THIS FRONT...WITH ANOTHER ROUND OF CONVECTION
LIKELY BREAKING OUT AGAIN ACRS THE CNTRL PLAINS/LWR MO VALLEY. WK
SHORT WAVE ENERGY EJECTING INTO THE NRN PLAINS OUT OF THE UPR
TROF IN THE WEST WILL BRING SOME SHWRS/POSSIBLE TSTRMS INTO THE
DAKOTAS. SCT MAINLY OROGRAPHIC SHWRS WILL CONT IN THE NRN/CNTRL
INTERMTN WEST UNDER THE UPR TROF.

KLEIN/FORECAST OPERATIONS BRANCH

[UNIDATA Local Data Mangement daemon]

076
FXUS02 KWBC 251838
PMDEPD
EXTENDED FORECAST DISCUSSION FOR 28 MAY THRU 30 MAY 1996
HYDROMETEOROLOGICAL PREDICTION CENTER..NCEP..NWS..WASHINGTON DC
2:45 PM EDT SAT MAY 25 1996

MEDIUM RANGE MODEL MEANS INDICATE AN ALTERATION TO THE CURRENT
SPLIT FLOW PATTERN OVER NOAM. THE WESTERN TROF AND FLAT EASTERN
RIDGE PATTERN IS FORECAST TO EVOLVE MORE INTO A MORE BALANCED
WESTERN TROF/CENTRAL U.S RIDGE AND WEST ATLC TROF PATTERN BY ALL
THREE MODELS. THE SRN STREAM BRANCH REMAINS STRONG AND CONSISTANT
IN THE MEANS AND DAILY RUNS WHILE PROBLEMS STILL OCCUR IN THE NRN
BRANCH. THE ECMWF MEAN IS SIMILAR TO THE MRF TODAY WITH ITS A
FAIRLY AMPLIFIED PATTERN CONSISTING OF A MEAN TROF IN THE GREAT
BASIN...RIDGING THRU THE MS VALLEY AND A WEST ATLC TROF ALONG
65W-60W. THE UKMET MAINATINS A MORE ZONAL FLOW TO THE HIGHER HGTS
ACROSS THE CENTRAL AND SRN TIER OF STATES WITH MORE AMPLIFICATION
OF ITS TROF/RIDGE/TROF CONFIGURATION AT HIGHER LATITUDES.

IN THE DAILIES...TODAYS ECMWF HAS COME AROUND TO YTDAS MRF
SOLUTION OF HAVING MORE AMPLIFICATION OF THE WESTERN ATLC TROF.
THE MRF/ECMWF AND UKMET ARE REASONABLY SIMILAR ON DAYS 3 AND 4
BUT THE FLATTER UKMET RESULTS IN A MORE RAPID PROGRESSION OF
SHORTWAVE ENERGY BY DAY 4 AND DEVELOPS A FASTER AND DEEPER WEST
ATLC LOW BY DAY 5. THE MRF AND MRFX AND LATEST AVN INDICATE THAT
THE SRN STREAM WILL STILL DOMINATE AND EJECTING ENERGY COMING OUT
OF THE SWRN TROF WILL CONT TO UNDERCUT THE RIDGE EARLY IN THE
PERIOD. THE WESTERN TROF WILL RELOAD AS SHORTWAVE ENERGY DROPS
DOWN THE WEST COAST INTO THE MEAN TROF AND DOWNSTEAM RIDGING
BUILDS IN THE PLAINS AND MS VALLEY. THIS RIDGING ALLOWS SHORTWVE
ENERGY DROPPING SEWD FROM ERN CANADA TO CARVE OUT AN ERN
SEABOARD/WEST ATLC TROF.

AT THE SFC...SHORTWAVE ENERGY EJECTING EAST FROM THE SWRN TROF
WILL MOVE EAST ALONG THE PERSISTANT FRONTAL BOUNDARY FROM THE
CENTRAL PLAINS INTO THE OH VALLEY CONTINUING THE COMBINATION OF
OVERUNNING RAINFALL AND MCS DEVELOPMENT AND THREAT OF EXCESSIVE
RAINFALL TUES. IN THE WEST THE CLOSED UPPER LOW AND FRONT
DROPPING INTO THE GREAT BASIN WILL CONTINUE TO GENERATE
INSTABILITY SHOWERS AND KEEP MAX TEMPERATURES WELL BELOW NORMAL.
COOL HIGH PRESSURE WITH ONSHORE FLOW WILL ALSO KEEP THE MID ATLC
AND THE NORTHEAST QUITE COOL.

BY DAY 4 AND DAY 5 (WED AND THURS) A LOW WILL MOVE OFF THE NC
COAST LATE TUES AND RAPIDLY MOVE NEWD WED. THE ERN FRONTAL
BOUNDARY WILL DROP SEWD WELL INTO SC TN AND NRN GA WED AND INTO
NRN FL THURS AS HIGH PRESSURE BUILDS SOUTH INTO THE MID ATLC
COASTAL REGION. MEANWHILE ADDITIONAL SHORTWAVE ENERGY DROPPING
INTO THE WESTERN TROF WILL CONTINUE THE TREND OF SHOWERY AND VERY
COOL CONDITIONS. LOW PRESSURE (MORE OF A THERMAL LOW) IN THE SRN
HIGH PLAINS WILL REMAIN NEARLY STATIONARY ON THE WEST SIDE OF THE
UPPER RIDGE WITH VERY HOT TEMPS RETURNING TO THE DROUGHT STRICKEN
SRN PLAINS WED AND THURS.

ROSENSTEIN/FORECAST OPERATIONS BRANCH