SWODY2
SPC AC 260556
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1156 PM CST WED FEB 25 2009
VALID 271200Z - 281200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE LWR MS VLY INTO THE
SRN APLCNS...
...SYNOPSIS...
BROAD...LOW AMPLITUDE...MULTI-STREAM CYCLONIC FLOW WILL EVOLVE OVER
THE SERN QUARTER OF THE NATION OVER THE NEXT TWO DAYS AS A SERIES OF
DISTURBANCES NOW OVER THE WRN AND N CNTRL U.S. CONTINUE GENERALLY
ESE. BY 12Z FRI/27...LEAD IMPULSE NOW OVER THE DAKOTAS EXPECTED TO
HAVE REACHED MI/IL...WITH ASSOCIATED COLD FRONT TRAILING SW THROUGH
WRN KY/TN AND BECOMING STATIONARY OVER SRN AR/NRN LA AND NE TX.
AS THIS OCCURS...CURRENT SATELLITE DATA SUPPORT GFS AND ECMWF FCSTS
SHOWING THAT A SEPARATE DISTURBANCE WILL EMERGE IN BRANCH OF FLOW
ROUNDING BASE OF STRONG UPR LOW NOW OVER THE PACIFIC NW. AS THIS
FEATURE AND ITS ASSOCIATED UPR DIFLUENCE APPROACH THE SRN PLNS EARLY
SAT/28...IT APPEARS PROBABLE THAT A WAVE WILL EVOLVE OVER STALLED
FRONT IN NRN LA. THIS WAVE SHOULD MOVE ENE TO NEAR BHM BY 12Z SAT.
...LWR MS VLY TO SRN APLCNS...
EXPECT ONGOING CONVECTIVE BAND LINGERING FROM DAY 1 WILL PERSIST
THROUGH AT LEAST LATE MORNING ALONG/AHEAD OF AFOREMENTIONED COLD
FRONT OVER PARTS OF THE TN VLY. SLIGHTLY ELEVATED WAA/MOISTURE
TRANSPORT...AND 40-50 KT CLOUD LAYER SHEAR...SHOULD BE SUFFICIENT
FOR AT LEAST SCTD SUSTAINED/POSSIBLY SVR STORMS. HAIL SHOULD BE THE
MAIN THREAT...WITH WIND POTENTIAL LIKELY REMAINING ISOLD GIVEN
EXPECTED PERSISTENCE OF NEAR-SFC STABLE LAYER.
DURING THE DAY FRI...EXPECT ADDITIONAL DEVELOPMENT WITH SFC HEATING
ALONG OUTFLOW BOUNDARY AND/OR STALLING FRONT ASSOCIATED WITH MORNING
ACTIVITY. A FEW SFC-BASED STORMS WILL BE POSSIBLE.
RESIDUAL/ELEVATED MIXED LAYER WILL MAINTAIN CONSIDERABLE CIN DURING
THIS PERIOD. THIS SHOULD RESULT IN A FAIRLY SHARP SRN AND WRN
CUT-OFF TO THE STORMS. BUT AMPLE /50 KT/ DEEP WLY SHEAR...MOISTURE
/MID 60S F SFC DEWPOINTS/...AND LOW LVL CONVERGENCE SHOULD BE
PRESENT TO SUPPORT SUSTAINED SUPERCELLS. DEEP FORCING FOR ASCENT
WILL...HOWEVER...REMAIN WEAK UNTIL UPR IMPULSE APPROACHES LATE IN
THE DAY.
DEEP UVV AND LOW LVL CONVERGENCE SHOULD INCREASE ACROSS THE LWR MS
VLY E INTO AL AND GA FRI NIGHT/EARLY SAT AS CYCLOGENESIS OCCURS OVER
NRN LA. COMBINATION OF INCREASING ASCENT WITH CONTINUED SFC-BASED
MOISTURE INFLOW AND STRENGTHENING SWLY LLJ MAY SUPPORT OVERNIGHT
STRENGTHENING OF STORMS...AND POSSIBLE DEVELOPMENT OF ONE OR TWO
CONVECTIVE CLUSTERS. THESE SYSTEMS SHOULD MOVE GENERALLY E...WITH
EMBEDDED STORMS POSING A THREAT FOR SVR HAIL...WIND AND ISOLD
TORNADOES.
..CORFIDI.. 02/26/2009
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