SWODY1
SPC AC 240058
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0758 PM CDT THU APR 23 2009
VALID 240100Z - 241200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
PROGRESSIVE UPPER AIR PATTERN CONTINUES ACROSS CONUS...WITH SERIES
OF SHORTWAVES OF VARYING AMPLITUDE IN NRN AND SRN STREAMS.
PERTURBATION NOW OVER NM...FAR W TX AND CHIHUAHUA IS FCST TO MOVE
EWD ACROSS W TX OVERNIGHT...REACHING SW OK AND CENTRAL TX BY END OF
PERIOD. MEANWHILE...COMPACT SHORTWAVE TROUGH AND EMBEDDED MVC --
INITIALLY OVER SERN IA/NWRN IL REGION -- SHOULD MOVE ENEWD TO SRN
LOWER MI. HIGH-AMPLITUDE/POSITIVELY-TILTED SHORTWAVE TROUGH -- NOW
EVIDENT IN MOISTURE CHANNEL IMAGERY ACROSS SRN AB...WA AND WRN ORE
-- IS EXPECTED TO MOVE TO SWRN SASK...W-CENTRAL ID AND EXTREME NWRN
CA BY 12Z...WITH EMBEDDED 500 MB LOW DEVELOPING INVOF NWRN CA COAST.
AT SFC...COLD FRONT ANALYZED AT 23Z FROM NWRN MN SWWD ACROSS WRN SD
WILL CONTINUE TO SAG SWD ACROSS MN AND MOST OF SD BY END OF PERIOD.
SFC REFLECTION OF MVC -- INITIALLY INVOF SERN CORNER IA -- WILL MOVE
ENEWD WITH MIDLEVEL PERTURBATION. WARM FRONTAL ZONE -- ANALYZED
FROM THIS LOW SEWD ACROSS MID TN AND NRN GA -- SHOULD DRIFT NWD
THROUGH REST OF PERIOD.
...SRN APPALACHIANS/PIEDMONT...
SCATTERED MULTICELLULAR TSTMS IN CLUSTERS SHOULD MOVE SEWD ACROSS
PORTIONS NRN /CENTRAL GA FOR ANOTHER FEW HOURS WITH POTENTIAL FOR
OCCASIONAL HAIL OF MRGL SVR SIZE. ACTIVITY IS SUPPORTED BY STEEP
MIDLEVEL LAPSE RATES ASSOCIATED WITH ERN TONGUE OF EML PLUME...AND
LOW 60S F SFC DEW POINTS CONTRIBUTING TO MLCAPE 800-1200 J/KG.
ALTHOUGH SFC-BASED LIFTED PARCELS WILL CONTINUE TO BECOME MORE
STABLE WITH DIABATIC COOLING...ACTIVITY MAY CONGEAL INTO
FORWARD-PROPAGATING SMALL MCS WITH SHORT-LIVED POTENTIAL FOR
DAMAGING GUSTS APCHG 50 KT SVR CRITERIA...BASED ON DRY/WELL-MIXED
SUBCLOUD AIR EVIDENT IN FFC SOUNDING.
...IL...
SVR POTENTIAL FCST TO DIMINISH THROUGH LATE EVENING AS BOUNDARY
LAYER INSTABILITY WEAKENS...BUT ISOLATED HAIL/GUSTS ARE POSSIBLE IN
MEANTIME. REF SPC MESOSCALE DISCUSSION 549 FOR NOWCAST INFO.
...DAKOTAS/MN...
ISOLATED TO WIDELY SCATTERED TSTMS MAY PRODUCE HAIL INVOF SFC COLD
FRONT THROUGH LATE EVENING...IN REGIME CHARACTERIZED BY STG LOW
LEVEL WAA AND FAVORABLE LOW LEVEL SHEAR...BUT MRGL
MOISTURE/BUOYANCY.
...SW TX TO CENTRAL OK...
DRY/WELL-MIXED SUBCLOUD LAYERS WILL CONTRIBUTE TO POTENTIAL FOR
ADDITIONAL/ISOLATED STG-SVR GUSTS FROM HIGH-BASED CONVECTION OVER
REGION. POTENTIAL SHOULD DIMINISH AS NEAR-SFC STABLE LAYER DEEPENS
WITH CONTINUED SFC DIABATIC COOLING.
..EDWARDS.. 04/24/2009
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