SWODY3
SPC AC 010730
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0230 AM CDT THU MAY 01 2008
VALID 031200Z - 041200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS MID-SOUTH TO SRN
MS/AL...
...SYNOPSIS...
BROAD UPPER LEVEL CYCLONE NOW OVER WRN CONUS IS FCST TO CONSOLIDATE
AND OCCLUDE THROUGH DAY-2...BEFORE WEAKENING AND BEGINNING TO EJECT
EWD OR ENEWD FROM CENTRAL PLAINS LATE DAY-2. OPERATIONAL MODELS AND
SREF MEMBERS BEGIN TO DIVERGE CONSIDERABLY WITH TRACK OF PRIMARY 500
MB CIRCULATION CENTER WITHIN LAST 6-12 HOURS BEFORE BEGINNING OF
THIS PERIOD...AS WELL AS THROUGH DAY-3...BUT ARE MORE CONSISTENT
WITH ONE ANOTHER REGARDING POSITION/MOVEMENT OF HIGH-AMPLITUDE
TROUGH WITHIN WHICH LOW IS EMBEDDED. BY AROUND 03/00Z...THIS TROUGH
SHOULD EXTEND FROM VORTEX OVER WRN HUDSON BAY REGION...SWD ACROSS
LS/WI/IL TO LOWER MS VALLEY. ASSOCIATED SFC COLD FRONT SHOULD MOVE
EWD ACROSS LOWER MS VALLEY AND PORTIONS TN/KY/OH DAY-3.
...MID-SOUTH SWD...
THIS AREA CONTAINS GREATEST PROBABILITY OF STG DIURNAL SFC HEATING
AND MID-UPPER 60S F DEW POINTS...JUXTAPOSED WITH FAVORABLE SHEAR
AROUND SRN/SERN RIM OF CYCLONIC FLOW ALOFT ASSOCIATED WITH DEEP
SHORTWAVE TROUGH. MLCAPES AOA 1500 J/KG SHOULD BE COMMON DURING
AFTERNOON...WITH RELATIVELY WEAK CIN...AND LOW LEVEL LIFT PROVIDED
BY FOCI SUCH AS FRONT AND MESOSCALE/OUTFLOW BOUNDARIES. SFC FLOW IS
PROGGED TO BE RELATIVELY WEAK ACROSS THIS AREA...WHICH IS REASONABLE
CONSIDERING LOCATION OF MOST ISALLOBARIC FORCING WELL N AND NE OF
REGION. HOWEVER...LOW LEVEL SHEAR VECTORS STILL ARE FCST TO BE
RATHER LARGE...ALONG WITH FAVORABLE DEEP-LAYER SHEAR.
THEREFORE...POTENTIAL WILL PERSIST FOR SUPERCELLS WITH ANY
RELATIVELY DISCRETE CONVECTION...AND BOWS/LEWPS WITHIN QUASI-LINEAR
ACTIVITY. SOME PROGS DEVELOP MCS OVER THIS REGION...MOVING EWD OR
SEWD ACROSS AL INTO FAVORABLY MOIST AND UNSTABLE AIR MASS...WITH
RELATIVELY DENSE CONCENTRATION OF SVR EVENTS POSSIBLE.
...OH VALLEY...UPPER GREAT LAKES...
CONDITIONAL SVR POTENTIAL EXTENDS NWD FROM CATEGORICAL AREA IN TWO
REGIMES --
1. CONVECTION ALONG/AHEAD OF FRONT IN REGIME OF FAVORABLE DEEP-LAYER
SHEAR. GENERAL DECREASE OF INSTABILITY IS EXPECTED WITH NWD
EXTENT...ALTHOUGH POCKETS OF DIURNAL/DIABATIC HEATING MAY ENHANCE
BUOYANCY ON MESOSCALE. SOME PORTIONS OF THIS AREA MAY NEED TO BE
ANNEXED INTO CATEGORICAL OUTLOOK NOW PLACED FARTHER S...WHERE
CONFIDENCE INCREASES IN FAVORABLE BUOYANCY SHEAR COMBINATION DURING
AFTERNOON.
2. COLD-CORE CONVECTIVE POTENTIAL BEHIND SFC COLD FRONT...CLOSE TO
MID-UPPER LEVEL TROUGH. THIS AREA WILL BE CHARACTERIZED BY WEAKER
LOW LEVEL CONVERGENCE/SHEAR RELATED TO VEERED/POSTFRONTAL SFC WINDS.
HOWEVER...RESIDUAL MOISTURE...SFC DIABATIC HEATING AND RELATIVELY
STEEP MIDLEVEL LAPSE RATES MAY SUPPORT POTENTIAL FOR HAIL.
..EDWARDS.. 05/01/2008
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