SPC AC 052003
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0303 PM CDT TUE MAY 05 2009
VALID 052000Z - 061200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CAROLINAS WSWWD INTO
THE SRN PLAINS...
...SRN OK/N TX EWD INTO THE ARKLATEX...
CAPPING INVERSION REMAINS IN PLACE ACROSS MUCH OF TX...S OF A WARM
FRONT LYING W-E ACROSS N TX. N OF THE FRONT IN A ZONE OF LOW-LEVEL
WARM ADVECTION...CONVECTION HAS PERSISTED...WITH A BOW ECHO NOW
CROSSING SERN OK.
MEANWHILE...HEATING CONTINUES ACROSS W TX AHEAD OF THE
DRYLINE...WITH A DRYLINE/WARM FRONT INTERSECTION NOW INDICATED NW OF
ABI. CAPPING IS EXPECTED TO HINDER CONVECTIVE DEVELOPMENT TO SOME
DEGREE...THOUGH ISOLATED STORMS SHOULD DEVELOP LATE THIS AFTERNOON
AND EVENING. GIVEN DEGREE OF INSTABILITY AND FAVORABLE
SHEAR...THESE STORMS -- WHICH WILL QUICKLY BECOME SUPERCELLULAR --
WILL BE CAPABLE OF PRODUCING VERY LARGE HAIL.
ADDITIONALLY...LOCALLY-DAMAGING WINDS AND/OR ISOLATED TORNADOES WILL
BE POSSIBLE -- PARTICULARLY NEAR THE WARM FRONT. WITH CAPPING
LIKELY TO LIMIT THE NUMBER OF STORMS...WILL DROP THE MDT RISK THIS
FORECAST BUT MAINTAIN THE PROBABILITY FOR ISOLATED/SIGNIFICANT
SUPERCELLS.
THIS EVENING...AS A SHORT-WAVE TROUGH CROSSES THE REGION...EXPECT
STORMS DEVELOPING OVER N TX TO ORGANIZE INTO ONE OR MORE MCS/BOW
ECHOES -- WHICH SHOULD THEN RIDE ESEWD ALONG THE SURFACE FRONT.
FAVORABLE INSTABILITY AND 40-50 KT WLY MID-LEVEL FLOW SUGGESTS THE
POTENTIAL FOR FAIRLY WIDESPREAD/DAMAGING WINDS ACROSS N TX -- AND
LATER INTO THE ARKLATEX REGION.
...CAROLINAS WSWWD INTO SRN GA/SRN AL/SRN MS...
SHOWERS AND THUNDERSTORMS CONTINUE INVOF A WEAK SURFACE FRONT
EXTENDING WSWWD ACROSS THE SOUTHEAST...AS WELL AS NEAR SMALLER-SCALE
BOUNDARIES WITHIN THE WARM SECTOR. MOIST BOUNDARY LAYER COMBINED
WITH DAYTIME HEATING HAS YIELDED MODERATE DESTABILIZATION...WHICH
COMBINED WITH AMPLE SHEAR HAS YIELDED LOCALLY-ORGANIZED/ISOLATED
SUPERCELL STORMS. LOW-LEVEL SHEAR IS SUPPORTIVE OF AN ISOLATED
TORNADO OR TWO -- PARTICULARLY OVER THE ERN CAROLINAS...BUT
OTHERWISE A MAINLY DIURNAL THREAT FOR HAIL AND/OR LOCALLY-DAMAGING
WINDS IS EXPECTED INTO THE EVENING HOURS.
...ERN MN/NWRN WI...
MARGINAL INSTABILITY HAS EVOLVED ACROSS PARTS OF MN/WI THIS
AFTERNOON...WITH DAYTIME HEATING OF MODESTLY-MOIST AIRMASS BENEATH
MID-LEVEL COLD POOL. A FEW STRONGER CELLS -- CAPABLE OF PRODUCING
MARGINAL HAIL -- WILL BE POSSIBLE ACROSS PARTS OF ERN MN INTO NWRN
WI THIS AFTERNOON...WITHIN LARGER AREA OF CONVECTION E/SE OF THE
CIRCULATION CENTER ALOFT.
..GOSS.. 05/05/2009
.PREV DISCUSSION... /ISSUED 1122 AM CDT TUE MAY 05 2009/
...SRN PLAINS...
PRIMARY CHALLENGE WILL BE TIMING OF INITIATION OF SURFACE BASED
SEVERE THUNDERSTORMS VICINITY OF THE E/W FRONTAL ZONE THAT STRETCHES
FROM NRN LA ACROSS NRN TX TO ERN NM. ONGOING OK STORMS IN RESPONSE
TO ASCENT ON NOSE OF 30-40KT LLJ AND ADVECTION OF ELEVATED
MOISTURE/INSTABILITY. THESE SHOULD REMAIN PRIMARILY HAIL PRODUCERS
DUE TO THEIR ELEVATED NATURE THRU MID AFTERNOON.
UPSTREAM S/WV TROUGH CENTRAL ROCKIES WILL SPREAD INCREASING ASCENT
AND SOME MID LEVEL COOLING WHICH COMBINED WITH THE WARM/MOIST
ADVECTION ACROSS THE FRONTAL ZONE WILL PROVIDE A FERTILE ENVIRONMENT
FOR SUPERCELL SEVERE THUNDERSTORM DEVELOPMENT LATER THIS AFTERNOON
AND EVENING. WITH EXTENSIVE LOW CLOUDINESS WITH THE GULF MOISTURE
AND HIGH LEVEL CLOUDINESS SPREADING EWD AHEAD OF THE APPROACHING
TROUGH...ALONG WITH INCONSISTENT MODEL SOLUTIONS...THE PRIMARY
UNCERTAINTY IS WITH THE TIMING OF THE MOST INTENSE SURFACE/NEAR
SURFACE BASED INITIATION. THE DRY LINE WILL MIX EWD TO WCENTRAL TX
S OF E/W FRONTAL ZONE PROVIDING POTENTIAL FOR INITIATION BY LATER
THIS AFTERNOON WITH THE FRONTAL INTERSECTION. WITH MLCAPES CLIMBING
TO AOA 3000 J/KG IN THE WARM SECTOR BY MID AFTERNOON E OF DRY
LINE...ANY NEAR SURFACE BASED STORM WOULD QUICKLY BECOME SEVERE WITH
POTENTIAL FOR VERY LARGE HAIL.
AS LOW LEVEL JET INCREASES BY THIS EVENING SEVERE THUNDERSTORMS
INCLUDING SUPERCELLS WILL BECOME MORE COMMON EWD ALONG AND S OF RED
RIVER VALLEY VICINITY OF FRONTAL CONVERGENCE. IN ADDITION TO VERY
LARGE HAIL...VEERING SHEAR PROFILES WILL BE CONDUCIVE TO VERY LARGE
HODOGRAPHS AND TORNADO POTENTIAL. OVERNIGHT A SEVERE MCS SHOULD
EVOLVE AND TRACK S OF E ACROSS NRN TX POSSIBLY INTO NRN LA BY 12Z
WED. WIND DAMAGE POTENTIAL WOULD INCREASE AS THE MCS DEVELOPS DURING
THE EVENING.
...ERN CAROLINAS...
MOIST/UNSTABLE AND A WEAKLY CAPPED AIR MASS REMAINS ACROSS AREA TO E
OF SRN APPALACHIANS AS A S/WV TROUGH PASSES BY TO THE N.
THUNDERSTORMS ARE ALREADY INCREASING ERN CAROLINAS THIS AM WITHIN AN
UNCAPPED ENVIRONMENT. WITH 30-40KT OF SHEAR AND MLCAPES AOA 2000
J/KG...STRONG/SEVERE STORMS WHICH HAVE DEVELOPED ERN CAROLINAS WILL
INCREASE IN INTENSITY AS THEY MOVE TOWARD THE COAST...WITH POSSIBLE
ENHANCEMENT OF CONVERGENCE WITH THE SEA BREEZE FRONT. AFTERNOON
HEATING SHOULD SUPPORT REDEVELOPMENT OF STORMS AGAIN ERN CAROLINAS.
STORMS WILL EVOLVE INTO SHORT LINE SEGMENTS/BOWS GIVEN THE AVAILABLE
SHEAR WITH BOTH LARGE HAIL AND WIND DAMAGE THE PRIMARY THREAT.
...GULF COAST STATES...
THE MORE DIFFUSE E/W STATIONARY FRONTAL ZONE FROM NRN GA TO CENTRAL
MS WILL BE A FOCUS FOR PRIMARILY A DIURNAL LOWER END SEVERE
POTENTIAL TODAY. WITH SURFACE TEMPS INTO THE 80S AND DEWPOINTS NEAR
70F ALONG AND S OF FRONT...MLCAPES AGAIN WILL BE QUITE UNSTABLE
RANGING UPWARDS TO 3000 J/KG WHERE HEATING IS STRONGEST. GENERALLY
30KT OR LESS OF DEEP LAYER SHEAR SUGGESTS MOST STORMS WILL BE
MULTI-CELLULAR WITH A LARGE HAIL AND ISOLATED DAMAGING WIND THREAT
FROM MID AFTERNOON UNTIL LATER THIS EVENING WHEN BOUNDARY LAYER
STABILIZES.
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