Message from discussion KWBC Extended FCST Map Discussion

From: l...@wetterhorn.ucar.edu (UNIDATA Local Data Mangement daemon)
Subject: KWBC Extended FCST Map Discussion
Date: 1996/05/21
Message-ID: <FXUS02KWBC211842@wetterhorn>
X-Deja-AN: 155963155
distribution: usa
organization: National Center for Atmospheric Research/Boulder, CO
newsgroups: ncar.weather


 
404 
FXUS02 KWBC 211842
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