SWODY1
SPC AC 030059
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0759 PM CDT FRI OCT 02 2009
VALID 030100Z - 031200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
UPPER AIR PATTERN ACROSS CONUS FCST TO REMAIN DOMINATED BY TWO
CYCLONES ALOFT...NOW LOCATED OVER UPPER MS VALLEY AND SRN BC. NWRN
LOW WILL DIG SWD OVER WA...WHILE UPPER MS VALLEY LOW MOVES EWD OVER
LM. RELATED LOW LEVEL CYCLONE WILL CONTINUE TO OCCLUDE/FILL THROUGH
REMAINDER PERIOD. ACCOMPANYING SFC COLD FRONT -- INITIALLY
ANALYZED FROM UPPER OH VALLEY SWWD ACROSS ERN KY...ERN TN...BECOMES
QUASISTATIONARY SWWD ACROSS S-CENTRAL MS TO EXTREME NWRN GULF AND
DEEP S TX. WRN SEGMENT OF FRONT MAY RETREAT SLIGHTLY NWD ACROSS RIO
GRANDE VALLEY AND S TX OVERNIGHT...WHILE ERN SEGMENT MOVES EWD
ACROSS CENTRAL APPALACHIANS AND INTERIOR/INLAND MID-ATLANTIC REGION.
...S TX...
ALONG AND S OF FRONT...WHERE SFC MOISTURE REMAINS
ROBUST...THERMODYNAMIC ENVIRONMENT OTHERWISE WILL BECOME MORE
UNFAVORABLE FOR SFC-BASED TSTMS THROUGH REMAINDER EVENING AS
NEAR-SFC LAYER UNDERGOES GRADUAL DIABATIC COOLING. MODIFIED RAOBS
AND RUC SOUNDINGS SUGGEST 40-50 KT EFFECTIVE SHEAR MAGNITUDES AND
MLCAPE 2000-3000 J/KG REMAINING OVER MUCH OF DEEP S TX...THOUGH CINH
WILL STRENGTHEN CONSIDERABLY WITH TIME. A FEW STG TSTMS MAY DEVELOP
IN NEXT 1-2 HOURS ALONG OUTFLOW BOUNDARIES FROM EARLIER CONVECTION
OVER LOWER VALLEY REGION. OTHERWISE...CONDITIONAL POTENTIAL FOR STG
TO MRGL SVR TSTMS WILL SHIFT NWWD TO ELEVATED WAA REGIME
OVERNIGHT...WHERE SOME PROGS INDICATE SUFFICIENT MOISTENING ABOVE
SFC TO SUPPORT 500-1000 J/KG ELEVATED MUCAPE...WITH 40-45 KT
EFFECTIVE SHEAR MAGNITUDE. MAIN CONCERN WITH ANY SUCH ACTIVITY
WOULD BE HAIL...GIVEN ITS POSITION ATOP RELATIVELY STABLE BOUNDARY
LAYER...AND WEAK MID-UPPER LAPSE RATES SHOULD LIMIT POTENTIAL FOR
MORE THAN MRGL SVR HAIL SIZE.
...COASTAL MID-ATLANTIC TO EXTREME SRN NEW ENGLAND...
WIDELY SCATTERED TO SCATTERED TSTMS MAY DEVELOP OVERNIGHT AHEAD OF
SFC COLD FRONT INVOF COAST AND MOVE NEWD...AMIDST STG MID-UPPER
LEVEL FLOW. MOISTENING LOW LEVEL THERMODYNAMIC PROFILES MAY
CONTRIBUTE TO SUFFICIENT BUOYANCY FOR NEARLY SFC-BASED
CONVECTION...AS CURRENTLY UNFAVORABLE AIR MASS GRADUALLY IS REPLACED
BY MODIFYING ATLANTIC BOUNDARY LAYER. WHILE ISOLATED STG/DAMAGING
GUST CANNOT BE RULED OUT...THREAT APPEARS TOO CONDITIONAL...AND OVER
TOO LIMITED OF AN AREA...TO INTRODUCE UNCONDITIONAL SVR
PROBABILITIES AOA 5 PERCENT ATTM.
..EDWARDS.. 10/03/2009
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