DAY 1 CONVECTIVE OUTLOOK
Robert
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1144 AM CDT SAT JUL 18 2015
VALID 181630Z - 191200Z
...THERE IS AN ENH RISK OF SVR TSTMS OVER PARTS OF
IA...IL...IND..SRN WI...AND SRN MI...
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE MID MS
VLY/GRT LKS...
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE CNTRL HIGH
PLNS...
...THERE IS A MRGL RISK OF SVR TSTMS FROM THE MID/UPR MS VLY INTO
THE LWR GRT LKS...
...THERE IS A MRGL RISK OF SVR TSTMS OVER PARTS OF THE
MID-ATLANTIC/NORTHEAST...
...THERE IS A MRGL RISK OF SVR TSTMS OVER THE LWR CO VLY...
...SUMMARY...
SEVERE THUNDERSTORMS WILL BE SCATTERED ESPECIALLY THIS AFTERNOON AND
EVENING OVER PARTS OF THE MIDWEST AND GREAT LAKES...AND OVER THE
CENTRAL HIGH PLAINS. A FEW STRONG STORMS MAY ALSO FORM OVER PARTS OF
FLORIDA...THE MID-ATLANTIC/NORTHEAST...AND THE LOWER COLORADO
VALLEY.
...SYNOPTIC SETUP...
MODERATE TO SEASONABLY STRONG ZONAL FLOW WILL CONTINUE ACROSS THE
NRN TIER...ON POLEWARD SIDE OF ELONGATED RIDGE FROM THE SRN
RCKYS/HIGH PLNS TO THE S ATLANTIC CST. WITHIN THE JET...POTENT
SHORTWAVE IMPULSE NOW ON THE ND/MB BORDER EXPECTED TO DEVOLVE INTO
AN OPEN WAVE AND ACCELERATE E/ENE THROUGH THE PERIOD...REACHING WRN
ONT EARLY TNGT...AND NE ONT BY 12Z SUN. FARTHER S AND W...TRAILING
POSITIVE-TILT TROUGH WILL LINGER OVER THE NRN GRT BASIN...WHILE A
SERIES OF WEAK DISTURBANCES IN REMNANT SUBTROPICAL STREAM MOVE ENE
FROM UT/CO ACROSS THE CNTRL PLNS TO THE MID MS/MID OH VLYS. A
DIFFUSE TROUGH WILL EXIT THE NERN STATES EARLY TNGT.
SFC PATTERN WILL REMAIN COMPLICATED BY OUTFLOW FROM OVERNGT MCSS.
COLD FRONT ASSOCIATED WITH MB/ND TROUGH SHOULD ARC FROM WRN LK
SUPERIOR THROUGH CNTRL IA TO SE CO BY THIS EVE. HOWEVER...THE
ASSOCIATED ZONES OF STRONGEST LOW-LVL CONVERGENCE IN MANY SECTIONS
MAY BE DISPLACED S AND E INTO PARTS OF LWR MI/IND/IL/MO.
...MID/UPR MS VLYS INTO MIDWEST TODAY/TNGT...
12Z RAOB AND CURRENT SFC/SATELLITE DATA SUGGEST A CONDITIONALLY
POTENT SET-UP FOR SVR STORMS OVER PARTS OF SE MN-IA-WI-IL-IND-MI-NRN
MO TODAY INTO TNGT AS SFC HEATING DESTABILIZES REGION IN WAKE OF
OVERNGT STORMS.
THE MOST OBVIOUS FOCUS IN THE NEAR-TERM IS NRN IL/NRN IND/WRN
WI...INVOF TRAILING OUTFLOW BOUNDARY FROM WEAKENING MI MCS.
PARTICULARLY IN SRN WI/IL...COMBINATION OF STEEP MID-LVL LAPSE
RATES...WEAK CIN...RICH MOISTURE...AND MODERATE UNIDIRECTIONAL WLY
FLOW SUGGEST POTENTIAL FOR STRONG/SUSTAINED UPDRAFT DEVELOPMENT THAT
COULD ORGANIZE INTO A FORWARD-PROPAGATING MCS WITH AN ATTENDANT
WIND/HAIL AND ISOLD TORNADO THREAT. COMPLICATING THE
PICTURE...HOWEVER...IS CLOUD DEBRIS ASSOCIATED WITH LINGERING NE MO
MCS. A MORE LIMITED POTENTIAL ALSO EXISTS FOR REJUVENATION OF
STORMS OVER SRN LWR MI/NRN IND/NW OH.
A GREATER POTENTIAL FOR NEW STORM DEVELOPMENT MAY EXIST ALONG COLD
FRONT FROM SE MN INTO CNTRL IA...WHERE IT APPEARS SOME DEGREE OF
LARGE-SCALE FORCING WILL PERSIST PER SATELLITE...AND SUBSTANTIAL
HEATING WILL OCCUR. WERE A CLUSTER OF STORMS TO EVOLVE IN THIS
REGION...SETUP ALSO WOULD BE FAVORABLE FOR FORWARD-PROPAGATION E/SE
INTO IL AND PERHAPS NRN MO LATER TODAY/TNGT.
FARTHER N...THE STRONGEST FORCING FOR ASCENT WITH MD/ND TROUGH
SHOULD BE CONFINED TO CANADA. BUT AT LEAST GLANCING INFLUENCE OF THE
SYSTEM COULD SUPPORT STRONG TO POSSIBLY SVR STORMS LATER TODAY
THROUGH EARLY TNGT IN AREAS OF ENHANCED HEATING OVER NRN MN/NRN WI
AND UPR MI.
...CNTRL HIGH PLNS THIS AFTN INTO TNGT...
POST-FRONTAL...INCREASINGLY MOIST UPSLOPE FLOW SHOULD PROMOTE SCTD
AFTN/EVE STORMS ALONG THE CO/SE WY FRONT RANGE/FOOTHILLS AS SFC
HEATING BOOSTS MLCAPE TO 1000-2000 J/KG. COUPLED WITH 25-30 KT WSWLY
500 MB FLOW...35-40 KT WSWLY DEEP SHEAR COULD YIELD A FEW SUSTAINED
STORMS/SUPERCELLS WITH SVR WIND/HAIL. SUBSTANTIAL DIRECTIONAL
COMPONENT TO LOW-LVL DIRECTIONAL SHEAR COULD SUPPORT A TORNADO OR
TWO...ALTHOUGH MAGNITUDE OF LOW-LVL SHEAR WILL BE LIMITED BY MODEST
NEAR-SFC FLOW. THE STORMS MAY EVOLVE INTO ONE OR TWO SMALL/WEAKENING
E-MOVING CLUSTERS TNGT.
...CAROLINAS TO NEW ENGLAND THIS AFTN/EVE...
DIFFUSE/FRACTURED...SLOWLY-PROGRESSIVE UPR TROUGH WILL BE
ACCOMPANIED BY POCKETS/BANDS OF MODESTLY-ENHANCED LARGE-SCALE
FORCING FOR ASCENT OVER THE MID-ATLANTIC/NORTHEAST. IN
GENERAL...W/WNW FLOW ALOFT WILL DECREASE WITH SWD EXTENT...WHILE
BUOYANCY AND LOW-LVL HEATING POTENTIAL INCREASE. AT THE
SFC...SEGMENTED LEE TROUGH WILL PERSIST FROM THE HUDSON VLY SSW TO
THE MID-ATLANTIC PIEDMONT. COUPLED WITH WEAK CIN...SETUP COULD
FOSTER DEVELOPMENT OF SCTD AREAS OF STRONG AFTN STORMS...A FEW OF
WHICH COULD YIELD LOCALLY DMGG GUSTS AND...MAINLY OVER ERN NY AND
WRN NEW ENGLAND...MARGINALLY SVR HAIL.
...FL PENINSULA THIS AFTN...
SCTD TO NUMEROUS AFTN/EVE TSTMS SHOULD ONCE AGAIN FOCUS ALONG
OUTFLOW/SEA-BREEZE BOUNDARIES. WARM MID-LVL TEMPERATURES WILL LIMIT
OVERALL STRENGTH OF CONVECTION...BUT PW AOA 2 INCHES AND NELY
HIGH-LVL FLOW MAY SUFFICIENTLY ENHANCE DOWNDRAFT STRENGTH/STORM
VENTING TO YIELD ISOLD LOCALLY DMGG GUSTS.
...SRN GRT BASIN/LWR CO VLY THIS AFTN/EVE...
BELT OF ENHANCED MID/UPR-LVL FLOW ON WRN FLANK OF UPR RIDGE...AND
RECENT INFLOW OF RICHER MOISTURE /PW AOA 1.50 INCHES/ MAY PROMOTE
THE DEVELOPMENT OF AFTN/EVE MULTICELL CLUSTERS WITH ISOLD STG TO SVR
GUSTS. DEVELOPMENT MAY BE MODULATED BY WEAK DISTURBANCES IN THE SWLY
UPR FLOW...ONE OF WHICH ATTM APPEARS TO BE ENTERING SRN CA.
..CORFIDI/MARSH.. 07/18/2015