Severe Thunderstorm Warning 22, NWS San Angelo, TX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN ANGELO TX
155 PM CST MON MAR 24 1997

SURFACE MOISTURE CONTINUES TO STUBBORNLY HANG ON THIS AFTERNOON...
WITH DEWPOINTS STILL IN THE UPPER 50S AND LOWER 60S ACROSS WEST
CENTRAL TEXAS. DESPITE SURFACE BASED LIFTED INDICES AROUND
MINUS 6...SOUTHWEST WINDS JUST OFF THE SURFACE WHICH HAVE LIMITED
MOISTURE DEPTH AND A CAPPING LAYER ALOFT HAVE COMBINED TO SHUT
CONVECTION DOWN SO FAR. AS OF 19Z...SURFACE DRYLINE EXTENDED FROM
WESTERN OKLAHOMA TO EAST OF CDS TO BETWEEN MAF AND SJT...WITH A COLD
FRONT ACROSS WESTERN KANSAS. ALOFT...12Z UPPER AIR ANALYSIS
INDICATED A LONG WAVE TROUGH OVER THE ROCKIES...WITH LASTEST
SATELLITE LOOPS SHOWING A POTENT VORTICITY MAXIMUM HEADING INTO NEW
MEXICO.

FOR TONIGHT...12Z ETA AND NGM AND THE 15Z RUC ALL INDICATING THE
SURFACE DRYLINE TO DRIFT EASTWARD TO NEAR A SJT TO ABI LINE BY
AROUND 00Z. WILL NOT RULE OUT A STRAY STORM OVER THE NORTHEAST BIG
COUNTRY THIS EVENING...WHERE CONVERGENCE AND MOISTURE DEPTH WILL BE
GREATEST...AND WHERE COOLING ALOFT WITH THE APPROACHING VORTICITY
MAXIMUM MAY BEGIN TO BREAK DOWN THE CAP. HOWEVER...IT APPEARS MOST
OF THE EXCITEMENT WILL HAVE TO WAIT UNTIL THE APPROACH OF THE SURFACE
COLD FRONT OVERNIGHT.

COLD FRONT EXPECTED TO PUSH THROUGH THE AREA AROUND SUNRISE TUESDAY
MORNING...WITH THE BEST LIFT FROM THE UPPER LEVEL VORTICITY MAXIMUM
STAYING MAINLY NORTH OF THE AREA. OVERNIGHT THUNDERSTORM CHANCES
WILL DEPEND MAINLY ON AVAILABLE MOISTURE SUPPLY. MODELS MOISTURE
FORECASTS KEEP THE SURFACE AND ELEVATED DRYLINES ABOUT WHERE THERE
WILL BE AT 00Z...ROUGHLY FROM SJT TO ABI. WITH THAT IN MIND...BEST
PRECIPITATION CHANCES APPEAR TO BE ACROSS THE EASTERN HALF OF THE
AREA AFTER MIDNIGHT...WHERE CONVERGENCE ALONG THE FRONT WILL HAVE
THE BEST MOISTURE TO WORK ON.

FOR TUESDAY...WITH THE FRONT NOT EXPECTED UNTIL NEAR 12Z...WILL
PROBABLY NEED TO KEEP DECENT PRECIPITATION CHANCES INTO THE MORNING
ACROSS THE EASTERN SECTIONS AS WELL. MODELS STILL DO NOT MOVE THE
UPPER TROUGH COMPLETELY THROUGH THE AREA UNTIL LATE TUESDAY...WHICH
MEANS CLOUD COVER MAY PERSIST THROUGH AT LEAST THE MORNING. MODEL
DATA ALSO SHOWING A TIGHT PRESSURE GRADIENT FOLLOWING THE FRONT
THROUGH MUCH OF TUESDAY...SO BRISK NORTHERLY WINDS WILL PREVAIL.
TEMPERATURES LOOK TO BE SUBSTANTIALLY COOLER... WITH BOUNDARY LEVEL
TEMPERATURES OFF THE ETA AND NGM ONLY AROUND 10 DEGREES C. GUIDANCE
NUMBERS IN THE MID 50S TO NEAR 60 LOOK ON TRACK.

ABI 047/057 42
SJT 055/058 21

PMCCULLOUGH