DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0719 AM CDT THU JUL 26 2012
VALID 261300Z - 271200Z
...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON/EVENING FOR PARTS
OF THE OH VALLEY ACROSS PA TO SRN NEW ENGLAND...
...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK...FROM
OK TO WI...AND EWD TO THE MID ATLANTIC...
...OH VALLEY ACROSS PA TO SRN NEW ENGLAND THROUGH LATE EVENING...
A MIDLEVEL SHORTWAVE TROUGH IS MOVING SEWD OVER NW MN THIS
MORNING...AND THIS WAVE IS PRECEDED BY SEVERAL EMBEDDED SPEED MAXIMA
AND MCV/S THAT WILL TRAVERSE THE OH VALLEY/PA/NY THIS AFTERNOON.
THUNDERSTORM CLUSTERS PERSIST THIS MORNING FROM NRN IL/INDIANA
ACROSS LOWER MI ALONG AND N OF A COMPOSITE OUTFLOW BOUNDARY...AS
WELL AS FARTHER E INTO PA/SRN NY IN A ZONE OF ENHANCED LOW-LEVEL
WAA. THE OVERALL TREND IN THE CONVECTION SHOULD BE CONTINUED
WEAKENING THROUGH THE MORNING...WITH THE OUTFLOW/EFFECTIVE COLD
FRONT EXPECTED TO KEEP MOVING SEWD ACROSS IL/INDIANA/SE LOWER MI.
THE WARM FRONT WILL PROGRESS EWD IN CONJUNCTION WITH A SURFACE LOW
AND DESTABILIZATION WILL OCCUR ACROSS PA/SRN NY/SRN NEW ENGLAND IN
THE WAKE OF THE MORNING CONVECTION.
STRONG INSTABILITY /MLCAPE OF 2500-4000 J PER KG/ AND WEAKENING
CONVECTIVE INHIBITION WILL ALLOW NEW SURFACE-BASED THUNDERSTORM
DEVELOPMENT BY ABOUT 18Z ACROSS CENTRAL INDIANA/OH AND W/NW PA ALONG
THE COLD FRONT AND LINGERING OUTFLOW BOUNDARIES. CONVECTION WILL
THEN GROW QUICKLY INTO MULTIPLE BANDS THROUGH THE AFTERNOON WHILE
SPREADING EWD ACROSS PA TOWARD SE NY AND SRN NEW ENGLAND...AND ESEWD
TOWARD NRN WV/MD...IN THE 21-00Z TIME FRAME. CONVECTIVE MODE WILL
BECOME PREDOMINANTLY LINEAR IN THE FIRST 1-2 HOURS AFTER
INITIATION...WITH BOWING SEGMENTS THE MAIN CONCERN. ADDITIONALLY...
DEEP-LAYER AND LOW-LEVEL SHEAR WILL BE STRONGER NEAR THE WARM FRONT
THIS AFTERNOON ACROSS SE NY AND ADJACENT AREAS...WHERE EMBEDDED
ROTATING STORMS AND A COUPLE OF TORNADOES WILL ALSO BE POSSIBLE.
WIDESPREAD DAMAGING WINDS WILL BE POSSIBLE IN MULTIPLE SWATHS GIVEN
THE STRONG INSTABILITY...STEEP LOW-LEVEL LAPSE RATES...DCAPE IN
EXCESS OF 1000 J/KG...AND 35-45 KT WLY MIDLEVEL FLOW.
...SRN PLAINS TO MID MS VALLEY TODAY...
THE COMPOSITE OUTFLOW BOUNDARY GENERATED BY OVERNIGHT CONVECTION
CONTINUES TO MOVE SEWD INTO CENTRAL OK/MO/IL...JUST NW OF I-44.
THOUGH THE SYNOPTIC COLD FRONT IS LOCATED FARTHER TO THE
NW...LINGERING CLOUDS SUGGEST THAT THE GREATER RISK FOR ISOLATED
SEVERE STORMS WILL BE FOCUSED ALONG THE INITIAL WIND SHIFT AND
DIFFERENTIAL HEATING ZONE. DEEP-LAYER UNIDIRECTIONAL WIND PROFILES
WILL WEAKEN WITH SWWD EXTENT FROM IL TO OK...SUGGESTING THAT
MULTICELL CLUSTERS WILL BE MORE PREVALENT TOWARD IL...AND PULSE-TYPE
STORMS ALONG THE WIND SHIFT INTO OK. MODEST MIDLEVEL LAPSE RATES
AND INVERTED-V PROFILES WILL FAVOR DAMAGING OUTFLOW GUSTS AS THE
PRIMARY SEVERE RISK THIS AFTERNOON/EVENING.
...WI AREA THIS AFTERNOON...
RESIDUAL BOUNDARY LAYER DEWPOINTS IN THE MID-UPPER 60S AND CLEARING
OF CONVECTIVE DEBRIS CLOUDS WILL ALLOW DESTABILIZATION ACROSS
CENTRAL WI BY AFTERNOON. THE DESTABILIZATION WILL COINCIDE WITH THE
PASSAGE OF THE SOMEWHAT DIFFUSE SYNOPTIC COLD FRONT AND THE APPROACH
OF THE BAND OF LOW-MIDLEVEL ASCENT PRECEDING THE SHORTWAVE TROUGH.
GIVEN MLCAPE IN THE 1000-2000 J/KG RANGE AND STRAIGHT HODOGRAPHS
WITH 30-40 KT EFFECTIVE BULK SHEAR...A FEW ORGANIZED STORMS WILL BE
POSSIBLE WITH AN ATTENDANT RISK FOR ISOLATED LARGE HAIL AND DAMAGING
WINDS.
..THOMPSON/MOSIER.. 07/26/2012
