SPC AC 071733
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1233 PM CDT THU MAY 07 2009
VALID 081200Z - 091200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM OK AND VICINITY EWD INTO
THE MID MS/TN VALLEYS...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS ERN PORTIONS OF NC/SERN
VA...
...SYNOPSIS...
BROAD CYCLONIC FLOW AT MID-LEVELS WILL PREVAIL ACROSS THE CONUS THIS
PERIOD...WITH SEVERAL SMALLER-SCALE FEATURES MOVING THROUGH THE
FAST/GENERALLY WLY FLOW. THE STRONGEST FEATURE -- MOVING ACROSS THE
N CENTRAL CONUS -- WILL DRIVE CYCLOGENESIS OVER THE UPPER MIDWEST.
ELSEWHERE...A SURFACE LOW WILL LINGER OVER TX...WITH A BAROCLINIC
ZONE EXTENDING NEWD TOWARD THE MID MS VALLEY REGION THROUGH THE
PERIOD.
...OK AND VICINITY EWD INTO THE MID MS/TN VALLEY REGION...
ONE OR MORE MCS WILL LIKELY BE ONGOING AT THE START OF THE PERIOD
ACROSS PARTS OF KS/OK AND THE OZARKS -- WHICH SHOULD PERSIST/SHIFT
EWD THROUGH THE DAY IN CONJUNCTION WITH THE VEERING/EWD-MOVING
LOW-LEVEL JET. WITH SOME DESTABILIZATION OF THE MOIST LOW-LEVEL
AIRMASS THROUGH THE DAY AND WITH FAVORABLE SHEAR ACROSS THIS
REGION...THREAT FOR HAIL AND/OR LOCALLY-DAMAGING WINDS WILL LIKELY
ACCOMPANY BOTH THE ONGOING STORMS AND ANY CONVECTIVE REDEVELOPMENT
NEAR ASSOCIATED CONVECTIVE BOUNDARIES.
FARTHER W DURING THE AFTERNOON...DAYTIME HEATING OF THE MOIST
BOUNDARY LAYER BENEATH A PLUME OF VERY STEEP MID-LEVEL LAPSE RATES
WILL RESULT IN VERY STRONG DESTABILIZATION FROM ERN OK SWD INTO NERN
TX...NEAR AND S OF A WARM FRONT EXTENDING FROM A NW TX SURFACE LOW
ENEWD ACROSS OK. ISOLATED STORMS MAY DEVELOP WITHIN THE WARM SECTOR
DURING THE AFTERNOON -- BOTH NEAR THE WARM FRONT AND POSSIBLY INVOF
LEFT-OVER CONVECTIVE BOUNDARIES. HOWEVER...THE LACK OF AN
APPRECIABLE FEATURE ALOFT SUGGESTS THAT CAPPING SHOULD GENERALLY
HINDER CONVECTIVE DEVELOPMENT -- ESPECIALLY S OF THE RED RIVER.
WITH MODERATE/VEERING FLOW ACROSS THIS REGION...SHEAR WILL SUPPORT
SUPERCELLS -- AIDED IN INTENSITY BY THE STRONG INSTABILITY. THUS --
VERY LARGE HAIL WILL BE POSSIBLE WITH ANY STORM WHICH CAN DEVELOP
DURING THE AFTERNOON...ALONG WITH LOCALLY-DAMAGING WINDS.
OVERNIGHT...AN INTENSIFYING LOW-LEVEL JET AND RESULTING INCREASE IN
WARM ADVECTION WILL FUEL MUCH MORE WIDESPREAD -- BUT LIKELY SLIGHTLY
ELEVATED -- STORM DEVELOPMENT ACROSS OK. DEGREE OF INSTABILITY AND
AMPLE SHEAR WILL SUPPORT A CONTINUED SEVERE THREAT THROUGH THE
EVENING AND INTO THE OVERNIGHT HOURS...WITH LARGE HAIL AND DAMAGING
WINDS REMAINING THE PRIMARY SEVERE THREATS. WITH MAIN SEVERE
POTENTIAL LIKELY TO BE SLIGHTLY-ELEVATED AND AFTER DARK...IT APPEARS
THAT SEVERE POTENTIAL WILL REMAIN BELOW MODERATE RISK THRESHOLDS.
...CAROLINAS/VA AND VICINITY...
A SERIES OF SMALL SHORT-WAVE TROUGHS MOVING THROUGH FAST WLY
MID-LEVEL FLOW FIELD WILL RESULT IN ANOTHER DAY OF SHOWERS AND
THUNDERSTORMS ACROSS VA AND THE CAROLINAS AND VICINITY. GIVEN
FAVORABLY-SHEARED/VEERING FLOW WITH HEIGHT AND MODEST
INSTABILITY...THREAT FOR HAIL/DAMAGING WINDS AND PERHAPS AN ISOLATED
TORNADO OR TWO DURING THE AFTERNOON IS EVIDENT -- PARTICULARLY
ACROSS VA/NC AHEAD OF A FEATURE MOVING INTO THE MID-ATLANTIC REGION
LATE IN THE DAY.
...UPPPER MIDWEST...
A STRONG MID-LEVEL TROUGH CROSSING THE NRN PLAINS WILL SUPPORT
SURFACE CYCLOGENESIS/FRONTOGENESIS OVER THE MID MO VALLEY
REGION...WITH THIS SYSTEM THEN SHIFTING ACROSS THE MIDWEST/OH
VALLEY/UPPER GREAT LAKES REGION THROUGH THE END OF THE PERIOD.
WHILE STRENGTHENING MID-LEVEL FLOW WILL RESULT IN DEEP-LAYER SHEAR
BECOMING INCREASINGLY-FAVORABLE FOR SUSTAINING ORGANIZED/SEVERE
CONVECTION...GENERALLY-LIMITED INSTABILITY IS FORECAST ACROSS THE
WARM SECTOR /MIXED-LAYER CAPE GENERALLY NEAR 500 J/KG/. EXPECT
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS TO DEVELOP DURING THE
AFTERNOON NEAR AND AHEAD OF THE DEVELOPING LOW/FRONT. GIVEN THE
DEGREE OF SHEAR...A FEW SEVERE STORMS CAPABLE OF PRODUCING HAIL AND
LOCALLY-DAMAGING WINDS WILL LIKELY EVOLVE...BEFORE AN OVERALL
DECREASE IN CONVECTIVE COVERAGE AND INTENSITY THROUGH THE EVENING.
..GOSS.. 05/07/2009
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NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z
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