SWODY3
SPC AC 180729
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0129 AM CST FRI NOV 18 2011
VALID 201200Z - 211200Z
...SYNOPSIS...
GRADUAL MID-UPPER HEIGHT RISES ARE FCST GENERALLY E OF MS RIVER
THROUGH PERIOD...AS LOW-AMPLITUDE MEAN TROUGHING BUILDS OVER WRN
CONUS. SHORTWAVE TROUGH -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY
INVOF CENTRAL-ERN ALEUTIANS -- IS EXPECTED TO TURN SEWD AND AMPLIFY
CONSIDERABLY THROUGH EARLY DAY-3. BY 20/12Z...CLOSED 500-MB LOW MAY
DEVELOP IN THIS PERTURBATION OFFSHORE CENTRAL/NRN CA.
THEREAFTER...SOME SPREAD IN TRACK/AMPLITUDE OCCURS IN MODELS. BY
21/12Z...OPERATIONAL SPECTRAL PROGS TROUGH APCHG CENTRAL/NRN
BAJA...WITH NAM OVER LOWER CO RIVER REGION AND NRN GULF OF CA. SREF
CONSENSUS IS CLOSER TO NAM...BUT WITH EXTREMES SHOWING SUBSTANTIAL
VARIATION FASTER/NEWD AND SLOWER/SWWD THAN OPERATIONAL MODELS.
DOWNSTREAM SHORTWAVE TROUGH -- CURRENTLY MOVING OVER COASTAL PAC NW
-- IS FCST TO EJECT ACROSS UPPER GREAT BY AROUND 20/12Z. RELATED
SFC FRONTAL ZONE SHOULD EXTEND FROM LH TO OZARKS...SRN OK AND ERN NM
AROUND BEGINNING OF PERIOD. BY 21/00Z...THIS FRONT IS EXPECTED TO
MOVE SLOWLY SWD TO SRN PORTIONS IL/INDIANA...SERN OK...CENTRAL/WRN
AR...N-CENTRAL TX AND TX SOUTH-PLAINS REGIONS...BECOMING
QUASISTATIONARY THROUGH REMAINDER PERIOD.
...CENTRAL TX TO RED RIVER REGION...
WEAKLY CONFLUENT AND NEARLY FRONT-PARALLEL FLOW ALOFT IS FCST
THROUGH MOST OF PERIOD...RENDERING THIS PRIMARILY AN ANAFRONTAL
SITUATION GIVEN SLOW SWD MOTION OF BOUNDARY. AS SUCH...BULK OF
PRECIP AND TSTMS THROUGH PERIOD SHOULD BE N OF BOUNDARY AND ELEVATED
IN NATURE...AMIDST LOW-LEVEL WAA AND ISENTROPIC/FRONTAL ASCENT TO
LFC. THOUGH ISOLATED HAIL MAY OCCUR WITH SUCH ACTIVITY...RATHER
WEAK MIDLEVEL LAPSE RATES AND BUOYANCY...COMBINED WITH MODEST
EFFECTIVE SHEAR FOR ELEVATED CAPE...SUGGEST THREAT TOO
LOW/CONDITIONAL WITH ELEVATED REGIME FOR PROBABILITIES ATTM.
HOWEVER...MODIFIED FCST SOUNDINGS SUGGEST CAP MAY BECOME
SUFFICIENTLY WEAK DURING AFTERNOON TO PERMIT SFC-BASED TSTMS ALONG
FRONT...WITH ENOUGH EWD MOTION TO KEEP THEM THAT WAY AT LEAST
BRIEFLY. WEAK NEAR-SFC WINDS SHOULD LIMIT HODOGRAPH SIZE...HOWEVER
MLCAPE POTENTIALLY EXCEEDING 1500 J/KG AND ROUGHLY 40 KT
EFFECTIVE-SHEAR MAGNITUDE INDICATE CONDITIONAL THREAT FOR ORGANIZED
MULTICELLS OR BRIEF SUPERCELLS.
..EDWARDS.. 11/18/2011
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