SWODY1
SPC AC 011732
DAY 1 CONVECTIVE OUTLOOK AMEND 1
NWS STORM PREDICTION CENTER NORMAN OK
1232 PM CDT FRI JUN 01 2007
VALID 011730Z - 021200Z
..THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON AND TONIGHT
ACROSS W TX AND SW OK...
..THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON ACROSS ERN
IA...NW IL...AND SW WI...
AMENDED FOR TORNADO PROBABILITIES IN THE UPPER MIDWEST
FOR DETAILS ON HIGHER TORNADO PROBABILITIES...PLEASE REFER TO SPC
MESOSCALE DISCUSSION 949 AND TORNADO WATCH 321.
..SRN AND CENTRAL PLAINS TODAY INTO TONIGHT...
A COMPLEX SITUATION EXISTS THIS MORNING TRYING TO ACCOUNT FOR THE
EVENTUAL INFLUENCES OF OVERNIGHT AND ONGOING CONVECTION. AN
OVERNIGHT MCS STABILIZED MUCH OF KS/WRN MO...AND THE OUTFLOW
BOUNDARY EMANATING FROM THIS CONVECTION APPEARS TO HAVE STALLED FROM
NW AR INTO SRN OK. THIS OUTFLOW BOUNDARY EXTENDS WWD ALONG THE RED
RIVER INTO THE SRN TX PANHANDLE WHERE IT INTERSECTS ANOTHER
DEVELOPING COLD POOL ACROSS THE CENTRAL TX PANHANDLE. RICH BOUNDARY
LAYER MOISTURE /DEWPOINTS IN THE LOW-MID 60S/ IS PRESENT ALONG AND S
OF THE OUTFLOW BOUNDARIES IN TX AND ERN NM...WITH MID LEVEL LAPSE
RATES IN EXCESS OF 8 C/KM ATOP THE MOIST LAYER OVER W TX. THE NET
RESULT WILL BE STRONG INSTABILITY /MLCAPE VALUES NEAR 3000 J/KG/
WITH AFTERNOON TEMPERATURES IN THE 80S.
EXPECT THE ONGOING STORMS NEAR AND N OF AMA TO PERSIST WHILE
DEVELOPING ESEWD TOWARD THE ERN TX PANHANDLE AND WRN OK...ALONG AND
N OF THE OUTFLOW BOUNDARY. OTHER STORMS SHOULD FORM LATER IN THE
AFTERNOON ALONG THE W EDGE OF THE MOISTURE IN ERN NM...AS WELL AS
ALONG THE OUTFLOW BOUNDARIES AS THE BOUNDARY LAYER DESTABILIZES AND
CONVECTIVE INHIBITION WEAKENS WHEN SURFACE TEMPERATURES REACH AT
LEAST THE MID 80S. VERTICAL SHEAR ACROSS W TX IS FAVORABLE FOR
SUPERCELLS WITH STRONGLY VEERING FLOW IN THE LOW LEVELS /ESPECIALLY
ALONG THE OUTFLOW BOUNDARIES/...AND STRONG SPEED SHEAR ALOFT ON THE
CYCLONIC SIDE OF THE SUBTROPICAL JET FROM SRN AZ INTO SW TX.
THEREFORE...EXPECT SOME OF THE INITIAL STORMS TO BE SUPERCELLS
CAPABLE OF PRODUCING VERY LARGE HAIL...DAMAGING GUSTS...AND A FEW
TORNADOES. UPSCALE GROWTH OF THE CONVECTION IS ALSO EXPECTED BY
EVENING...WITH ONE OR TWO MCS/S LIKELY ACROSS W/NW TX INTO OK.
..ERN IA/WRN IL/SW WI TODAY...
A CONVECTIVELY ENHANCED MID LEVEL WAVE IS LIFTING NNEWD OVER CENTRAL
IA AS OF MID MORNING...AND THIS SYSTEM WILL CONTINUE TOWARD WI
DURING THE AFTERNOON. THOUGH INSTABILITY IS NOT PARTICULARLY STRONG
IN ADVANCE OF THIS WAVE...MID 60S BOUNDARY LAYER DEWPOINTS AND SOME
SURFACE HEATING SHOULD MAINTAIN MLCAPE VALUES APPROACHING 1000-2000
J/KG AND A FAVORABLE ENVIRONMENT FOR MAINTENANCE OF DEEP CONVECTION.
DAMAGING WINDS SHOULD BE THE PRIMARY SEVERE THREAT DURING THE
AFTERNOON...THOUGH MARGINALLY SEVERE HAIL AND AN ISOLATED/BRIEF
TORNADO COULD ALSO OCCUR WHERE VERTICAL SHEAR IS LOCALLY ENHANCED
ALONG THE CONVECTIVE LINE.
..NEW ENGLAND TO THE APPALACHIANS...
VERTICAL PROFILES HAVE EITHER CHANGED LITTLE FROM YESTERDAY OVER
THIS AREA...OR LOW-LEVEL MOISTENING HAS CONTRIBUTED TO SOME
DESTABILIZATION. WITH AFTERNOON TEMPERATURES INTO THE MID-UPPER
80S...SCATTERED THUNDERSTORM DEVELOPMENT IS EXPECTED OVER THE HIGHER
TERRAIN OF THE APPALACHIANS...AS WELL AS A SUBTLE SURFACE TROUGH
FROM THE NRN CHESAPEAKE AREA INTO SE NY STATE. WEAK VERTICAL SHEAR
OVER THIS AREA SUGGESTS THAT A FEW PULSE-TYPE SEVERE STORMS WILL BE
THE PRIMARY THREAT DURING THE AFTERNOON...WITH ISOLATED DAMAGING
DOWNBURSTS AND MARGINALLY SEVERE HAIL.
FARTHER N...VERTICAL SHEAR IS MORE FAVORABLE FOR ORGANIZED SEVERE
STORMS FROM UPSTATE NY SEWD ACROSS VT/SRN NH INTO CENTRAL AND WRN
MA. A SUBTLE MID LEVEL WAVE CRESTING THE RIDGE OVER THE LOWER GREAT
LAKES...AS WELL AS THE WNW-ESE ORIENTED BAROCLINIC ZONE COULD HELP
FOCUS THUNDERSTORM DEVELOPMENT THIS AFTERNOON. THE COMBINATION OF
MODERATE INSTABILITY /MLCAPE VALUES NEAR 1500 J/KG/...STEEP
LOW-LEVEL LAPSE RATES...AND MODEST DEEP LAYER VERTICAL SHEAR /0-6 KM
BULK SHEAR OF ROUGHLY 35 KT/ COULD SUPPORT A FEW STORMS WITH
MARGINAL SUPERCELL STRUCTURES...WHICH MAY LOCALLY ENHANCE THE THREAT
FOR DAMAGING WINDS AND LARGE HAIL THIS AFTERNOON. CONVECTIVE
COVERAGE IS STILL IN QUESTION THIS AREA...SO WILL MAINTAIN ONLY LOW
HAIL/WIND PROBABILITIES ATTM.
..W/SW FL COAST TONIGHT...
A DEVELOPING LOW IN THE SE GULF OF MEXICO WILL LIFT NNEWD ACROSS THE
EXTREME ERN GULF...IN ADVANCE OF A BROAD MID LEVEL TROUGH OVER THE
CENTRAL AND WRN GULF. LOW-LEVEL VERTICAL SHEAR WILL INCREASE LATER
TODAY INTO TONIGHT OVER FL AS THE LOW APPROACHES.
HOWEVER...SUBSTANTIAL AIR MASS MODIFICATION IS NECESSARY OVER FL
/I.E. SURFACE DEWPOINTS IN THE LOW-MID 70S/...AND LOW-LEVEL
TRAJECTORIES NEED TO BECOME MORE SLY THAN ELY BEFORE INSTABILITY
WILL BECOME SURFACE BASED. THEREFORE...EXPECT ANY TORNADO THREAT TO
REMAIN NEGLIGIBLE UNTIL LATE IN THE PERIOD CLOSE TO THE W COAST.
.THOMPSON/KERR.. 06/01/2007
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