SWODY1
SPC AC 021615
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1115 AM CDT TUE OCT 02 2007
VALID 021630Z - 031200Z
..THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF THE SRN PLAINS
INTO THE MID MS RIVER VALLEY...
..PORTIONS OF SRN PLAINS ACROSS THE MID/UPPER MS RIVER VALLEY...
PROGRESSIVE SHORTWAVE TROUGH AND ASSOCIATED 50-60 KT MID LEVEL JET
NOW EJECTING ACROSS THE CENTRAL PLAINS WILL CONTINUE LIFTING NEWD
ACROSS THE MID/UPPER MS RIVER VALLEY TODAY. THIS WILL ALLOW STRONG
SURFACE COLD FRONT /WHICH EXTENDED FROM ERN SD INTO SWRN KS/NRN TX
PANHANDLE AT 15Z/ TO PUSH STEADILY SEWD THROUGH THE DAY. PREFRONTAL
AIR MASS IS UNSEASONABLY WARM AND MOIST LATE THIS MORNING ACROSS THE
SRN PLAINS INTO THE LOWER MO RIVER VALLEY...AND THIS WILL DEVELOP
NEWD THROUGH THE DAY ACROSS THE MID MS RIVER VALLEY. DESPITE
PRESENCE OF HIGH THETA-E AIR IN PLACE AHEAD OF THE FRONT...SOME
FACTORS REMAIN ACROSS THIS REGION WHICH ARE UNFAVORABLE FOR SEVERE
THUNDERSTORMS. THIS INCLUDE THE RATHER WEAK LAPSE RATES SAMPLED ON
12Z SOUNDINGS AND HAVING LARGER SCALE ASCENT LIFTING AWAY FROM
MODEST INSTABILITY AXIS OVER OK/ERN KS/WRN MO DURING THE AFTERNOON.
MODELS ARE CONSISTENT IN MAINTAINING ONGOING BAND OF THUNDERSTORMS
WITH SLOW INCREASE IN COVERAGE AND INTENSITY EXPECTED FROM
N-CENTRAL/NERN OK INTO SERN IA THROUGH THE EARLY AFTERNOON AS
HEATING BOOSTS INSTABILITY. ALTHOUGH LAPSE RATES REMAIN
WEAK...MODEST SURFACE HEATING AND VERY MOIST BOUNDARY LAYER /SFC DEW
POINTS NEAR 70F/ SHOULD SUPPORT AXIS OF 1000-1500 J/KG MLCAPE FROM
SWRN OK INTO SWRN/CENTRAL MO. MLCAPE WILL LIKELY REMAIN NEAR OR
BELOW 1000 J/KG INTO THE MID MS RIVER VALLEY. THIS AMOUNT OF
INSTABILITY WILL LIKELY SUFFICE FOR INCREASE IN SEVERE THREAT
THROUGH THE MID/LATE AFTERNOON AND EARLY EVENING GIVEN STRONG LOW
AND MID LEVEL SHEAR.
/SW MO INTO THE MID MS RIVER VALLEY/
SHEAR WILL BE STRONGEST FROM THE LOWER MO RIVER VALLEY/OZARK PLATEAU
NNEWD AS 50 KT MID LEVEL JET AND 40+ KT LLJ EJECT TOWARDS THE WRN
GREAT LAKES. GREATEST SEVERE THREAT ACROSS THIS AREA WILL DEPEND
UPON OVERALL STORM MODE...WITH 150+ SFC-1 KM SRH AND HIGH BOUNDARY
LAYER RH FAVORING A TORNADO THREAT SHOULD SUPERCELLS REMAIN
DISCRETE. GIVEN STRONG SEWD MOVING COLD FRONT ALMOST NORMAL TO
EXPECTED STORM MOTIONS...ACTIVITY MAY EVOLVE INTO SMALL LINES AND
SUPPORT MAIN THREAT OF ISOLATED DAMAGING WINDS UNTIL STORMS ARE
UNDERCUT BY THE COLD FRONT. ACTIVITY SHOULD DEVELOP INTO A BROKEN
SQUALL LINE ACROSS THE MID/UPPER MS RIVER VALLEY DURING THE
EVENING...ALTHOUGH SEVERE THREAT SHOULD WANE AS ACTIVITY SHIFTS ENE
OF MARGINAL INSTABILITY AXIS DURING THE EVENING.
/NW TX INTO THE OZARK PLATEAU/
FORECAST SOUNDINGS STILL YIELD SUFFICIENT SHEAR FOR SUPERCELLS AS
FAR SW AS THE OZARK REGION/NERN OK...WITH WEAKER SHEAR FAVORING MORE
MULTICELL MODES INTO SWRN OK/NWRN TX. ISOLATED DAMAGING WINDS AND
LARGE HAIL COULD ACCOMPANY STORMS DEVELOPING WITHIN UNSEASONABLY
STRONG HEATING AHEAD OF THE FRONT INTO SWRN OK/NWRN TX THROUGH THE
EARLY EVENING.
..FL...
S TO SELY LOW LVL FLOW WILL STRENGTHEN OVER THE FL PENINSULA TODAY
AS SUB TROPICAL LOW CONTINUES WWD. ASSOCIATED INCREASE IN TROPICAL
MOISTURE NWD AND SFC HEATING SHOULD AID IN DEVELOPMENT OF BANDS OF
DIURNALLY-ENHANCED STORMS. MODERATE LOW LEVEL SPEED AND DIRECTIONAL
SHEAR WILL EXIST...ESPECIALLY INTO NRN FL /AS EVIDENCED ON MORNING
VWPS/ INVOF DIFFUSE BOUNDARY STALLED NE/SW ACROSS REGION. SETUP MAY
YIELD A FEW STORMS POSING A THREAT FOR BRIEF TORNADOES AND/OR A
DAMAGING WIND GUST OR TWO.
.EVANS/GRAMS.. 10/02/2007
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