SWODY1
SPC AC 241937
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0237 PM CDT FRI JUN 24 2011
VALID 242000Z - 251200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NORTHEAST
AND MID-ATLANTIC REGION SWD TO NERN NC...
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE NRN AND CENTRAL HIGH
PLAINS SEWD INTO THE SOUTHEAST CONUS...
...PORTIONS OF THE NORTHEAST AND MID-ATLANTIC SWD TO NC...
BROKEN BAND OF STORMS CONTINUES TO DEVELOP FROM THE ERN FRINGE OF
LAKE ONTARIO AND ADJACENT UPSTATE NY SWD INTO NERN NC INVOF THE
SURFACE COLD FRONT...WHILE SCATTERED/WEAKER CONVECTION IS ONGOING
ACROSS THE LOWER GREAT LAKES AND UPPER OH VALLEY REGION.
STORMS FROM SERN NY SWD INTO NC ARE OCCURRING IN A REGION OF
MODERATE INSTABILITY AND SUFFICIENT DEEP-LAYER WIND FIELD TO SUPPORT
A CONTINUATION OF THE SLIGHT RISK FORECAST INTO THIS EVENING.
PRIMARY THREAT REMAINS LOCALLY DAMAGING GUSTS...THOUGH HAIL REACHING
SEVERE LIMITS WILL ALSO BE POSSIBLE WITH A FEW STRONGER CELLS.
...NRN AND CENTRAL HIGH PLAINS...
STORMS CONTINUE TO SLOWLY DEVELOP ACROSS PARTS OF WY AND ADJACENT
NERN CO...AND SHOULD SPREAD EWD WITH TIME INTO THE DESTABILIZING
AIRMASS ACROSS THE HIGH PLAINS. THREATS FOR DAMAGING WINDS AND
LARGE HAIL WILL ACCOMPANY STRONGER STORMS AS THEY EVOLVE THIS
AFTERNOON/EVENING. FOR ADDITION SHORT-TERM INFORMATION...PLEASE
REFER TO SPC SWOMCD #1375.
...MID MO VALLEY SEWD INTO NRN PORTIONS OF THE GULF COAST STATES...
BIGGEST CHANGE TO THE CURRENT FORECAST IS THE ADDITION OF SLIGHT
RISK /15% HAIL AND WIND PROBABILITY/ ACROSS NRN PORTIONS OF THE GULF
COAST STATES AND INTO SRN TN AND THE WRN CAROLINAS. A BAND OF
STRONG/LOCALLY SEVERE STORMS HAS DEVELOPED ACROSS THIS REGION AHEAD
OF A REMNANT MCV NOW CROSSING THE MID MS/TN VALLEY REGION. STORMS
ARE INCREASING WITHIN THE VERY UNSTABLE AIRMASS WHICH HAS DEVELOPED
ACROSS THIS REGION...WITH STEERING FLOW EXPECTED TO CARRY THE
CONVECTION ESEWD/SEWD WITH TIME. WHILE MAGNITUDE OF THE FLOW FIELD
IS NOT PARTICULARLY STRONG...DEGREE OF INSTABILITY IS SUFFICIENT
GIVEN THE AMBIENT FLOW FIELD TO SUPPORT A MORE WIDESPREAD SEVERE
EVENT THAN INITIALLY ANTICIPATED.
..GOSS.. 06/24/2011
.PREV DISCUSSION... /ISSUED 1112 AM CDT FRI JUN 24 2011/
...UPSTATE NY/SWRN NEW ENGLAND INTO ERN NC...
VORTICITY MAXIMUM OVER IND/OH AS OF MID MORNING WILL TRANSLATE EWD
TO OFF THE MID ATLANTIC COAST BY 25/12Z. DCVA IN ADVANCE OF THIS
FEATURE COUPLED WITH CONVERGENCE ALONG EWD-PROGRESSING COLD FRONT
WILL SERVE TO FOCUS SURFACE-BASED TSTM DEVELOPMENT THIS AFTERNOON.
DESPITE THE TENDENCY FOR SLIGHT WARMING ALOFT...DAYTIME HEATING AND
A MOIST BOUNDARY LAYER WITHIN PRE-FRONTAL WARM SECTOR WILL YIELD A
MODERATELY UNSTABLE AND WEAKLY CAPPED ENVIRONMENT WITH MLCAPE
APPROACHING 1500 J/KG. THIS INSTABILITY AXIS WILL COINCIDE WITH A
BELT OF 40-45 KT WSWLY FLOW AT 500 MB...RESULTING IN SUFFICIENT
/35-40 KT/ DEEP-LAYER SHEAR FOR ORGANIZED MULTICELL AND SOME
SUPERCELL STRUCTURES CAPABLE OF DAMAGING WINDS AND HAIL THROUGH THIS
EVENING.
FOR ADDITIONAL NEAR-TERM GUIDANCE ON NRN HALF OF REGION...SEE MCD
1372.
...NRN/CNTRL HIGH PLAINS...
12Z UPPER-AIR ANALYSIS SHOWS A MIDLEVEL THERMAL TROUGH FROM THE NRN
ROCKIES INTO GREAT BASIN WHICH APPEARS TO BE ASSOCIATED WITH
VORTICITY MAXIMA OVER ERN WA AND SRN ID. THESE FEATURES WILL
PROGRESS EWD TODAY WITHIN PREVAILING WSWLY FLOW REGIME.
DOWNSTREAM...A LEE LOW OVER WRN KS COUPLED WITH INVERTED/LEE TROUGH
NWD THROUGH THE WRN DAKOTAS WILL MAINTAIN A LOW-LEVEL MOISTURE AXIS
BENEATH THE NRN EDGE OF THE EML...RESULTING IN MODERATE AFTERNOON
INSTABILITY WITH MLCAPE OF 1500-3000 J/KG.
WEAK HEIGHT FALLS/DYNAMIC FORCING FOR ASCENT ATTENDANT TO
ABOVE-MENTIONED IMPULSES WILL FOSTER SCATTERED TSTMS THIS AFTERNOON
ALONG FAVORED TERRAIN AND INVERTED/LEE TROUGH. ELY/NELY LOW-LEVEL
FLOW VEERING TO WSWLY IN THE MIDLEVELS WILL RESULT IN 40-50+ KT OF
DEEP WLY SHEAR WHICH WILL SUPPORT SUPERCELL DEVELOPMENT. THE
ABSENCE OF STRONGER LOW-LEVEL SHEAR WILL PRECLUDE A MORE ROBUST
TORNADO THREAT. HOWEVER...LARGE HAIL AND DAMAGING WINDS WILL BE
LIKELY WITH THE STORMS AS THEY MOVE/DEVELOP EWD/SEWD LATE THIS
AFTERNOON INTO TONIGHT.
...MID MO INTO LOWER OH VALLEYS...
STRENGTHENING WAA/ISENTROPIC ASCENT AT THE TERMINUS OF A 50+ KT
NOCTURNAL LLJ WILL SERVE TO FOCUS A BAND OF ELEVATED TSTMS OVERNIGHT
ALONG THE ERN EDGE OF THE CAP WHERE MUCAPE WILL APPROACH 2000-3000
J/KG. GIVEN THE PRESENCE OF 40-45 KT OF CLOUD-BEARING
SHEAR...ENVIRONMENT WILL BE SUPPORTIVE OF SEVERE STORMS CAPABLE OF
HAIL AND PERHAPS DAMAGING WIND GUSTS.
...GULF COAST STATES...
DESPITE POOR MIDLEVEL LAPSE RATES /REF. 12Z REGIONAL
SOUNDINGS/...DAYTIME HEATING AND A MOIST BOUNDARY LAYER WILL YIELD
AFTERNOON MLCAPE VALUES OF 1500-2500 J/KG. THE INFLUENCE OF WEAK
MIDLEVEL IMPULSE TRANSLATING SEWD THROUGH THE LOWER MS VALLEY WILL
CONTRIBUTE TO THE DEVELOPMENT OF SCATTERED STRONG TSTMS THIS
AFTERNOON WITHIN PRE-FRONTAL WARM SECTOR. REGION WILL REMAIN
DISPLACED WELL TO THE S OF STRONGER MIDLEVEL FLOW FIELD...RESULTING
IN WEAK VERTICAL SHEAR. NONETHELESS THE PRESENCE OF STEEP LOW-LEVEL
LAPSE RATES AND POTENTIAL FOR DOWNDRAFT ENHANCEMENT DUE TO WATER
LOADING WILL RESULT IN ISOLATED OCCURRENCES OF DAMAGING WIND GUSTS
INTO THIS EVENING.
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