SWODY1
SPC AC 211958
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0258 PM CDT MON MAY 21 2007
VALID 212000Z - 221200Z
..THERE IS A SLGT RISK OF SVR TSTMS THROUGH THE SRN...CENTRAL AND
NRN PLAINS...
..THERE IS A SLGT RISK OF SVR TSTMS PORTIONS OF NRN AND ERN TX...
..SYNOPSIS...
INTENSE UPR LOW MOVING INTO ID IS EXPECTED TO SHIFT EWD THROUGHOUT
THE PERIOD AND INTO WRN WY LATE TONIGHT. THIS WILL RESULT IN 40-50
KT SWLY MID LEVEL FLOW OVERSPREADING THE NRN PLAINS BY EVENING. IN
ASSOCIATION WITH THIS SYSTEM..A WEAK COLD FRONT EXTENDED FROM MT/ND
BORDER SWWD INTO CENTRAL WY...WITH A WAVE LOCATED ON THE FRONT IN
EXTREME WRN SD. OTHER CONVECTIVE FEATURES OF INTEREST WERE A COUPLE
OF WEAK SRN BRANCH IMPULSES...ONE LOCATED IN THE TX PANHANDLE AND
THE OTHER NORTH OF SAT.
..NRN PLAINS...
THE MOST FAVORABLE COMBINATION OF INSTABILITY AND DEEP SHEAR FOR
SUSTAINED SEVERE STORMS WILL BE LOCATED IN THIS REGION OF THE
COUNTRY. TEMPERATURES HAVE WARMED INTO THE 80S AND WITH STEEP MID
LEVEL LAPSE RATES...MLCAPES WERE BETWEEN 1500 AND 3000 J/KG. THIS
DESTABILIZATION...COUPLED WITH CONVERGENCE ALONG AND AHEAD OF COLD
FRONT...WILL SUPPORT TSTM DEVELOPMENT ACROSS THE DAKOTAS. DEEP LAYER
SHEAR WILL BE STRENGTHENING AS WINDS ALOFT INCREASE AND SHOULD
BECOME SUFFICIENT FOR A FEW SUPERCELLS AND/OR BOWING SEGMENTS...WITH
HAIL/HIGH WIND THE MAIN THREATS. AS THE LOW LEVEL JET INCREASES THIS
EVENING...THE ACTIVITY SHOULD CONGEAL INTO AN MCS...WITH A GRADUALLY
DIMINISHING SEVERE THREAT AS THE SYSTEM MOVES EWD INTO ERN
ND/SD...AWAY FROM THE STRONGER INSTABILITY AND UPPER LEVEL FORCING.
REF WW 282.
..MN...
AN MCV...EVIDENT EARLIER IN SATELLITE NEAR DTL...WAS ENHANCING THE
LIFT FOR THUNDERSTORMS ACROSS PORTIONS OF WEST CENTRAL MN ALONG AND
NORTH OF A WARM FRONT. STRONGEST STORMS WILL BE FAVORED NEAR THE
WARM FRONT WHERE INSTABILITY AND CONVERGENCE WILL BE MAXIMIZED. WEAK
VERTICAL SHEAR...0 TO 6KM AOB 20 KT...SHOULD RESULT IN MAINLY
MULTICELLULAR STORMS WITH BRIEF SEVERE WEATHER EVENTS POSSIBLE
THROUGH THE AFTERNOON HOURS.
..TX...
MCS WAS EVIDENT ON SATELLITE NORTH OF SAT AND WAS MOVING NEWD AT 30
KT. LOCAL VAD WIND PROFILES SHOW THAT 40-50KT WLY WIND MAX WAS
LOCATED ON THE SOUTH SIDE OF THE SYSTEM AND WAS LIKELY RESULTING IN
ARC OF CONVECTION TO MOVE RAPIDLY EWD ACROSS THE SOUTH CENTRAL
COASTAL PLAINS. GIVEN THIS RELATIVELY ORGANIZED UPPER SYSTEM AND
VERTICAL SHEAR PROFILES...ISOLATED SEVERE...INCLUDING A BRIEF WIND
AND OR TORNADO THREAT...WILL BE POSSIBLE INTO THE EVENING HOURS.
FARTHER W...STORMS ARE DEVELOPING OVER THE DAVIS MOUNTAINS AND SERN
NM. ENHANCED FLOW ASSOCIATED WITH SRN STREAM WILL RESULT IN
FAVORABLE SHEAR FOR STORM ORGANIZATION. COMBINATION OF SURFACE
DEWPOINTS NEAR 60F AND STEEP LOW TO MID LEVEL LAPSE RATES SHOULD
BOOST SBCAPE VALUES TO NEAR 2000 J/KG BY LATE AFTERNOON. THIS SHEAR
AND INSTABILITY SHOULD SUPPORT A FEW ORGANIZED STORMS/SUPERCELLS
WITH LARGE HAIL/DAMAGING WIND.
..CENTRAL PLAINS...
CONVECTION IS BEGINNING TO DEVELOP FROM THE NWRN TX PANHANDLE NWWD
ACROSS THE HIGHER TERRAIN OF CO AND INTO SERN WY. DESPITE RELATIVELY
WEAK DEEP LAYER SHEAR AT 20-30 KT...MODERATE INSTABILITY WILL
SUPPORT A SEVERE STORM THREAT INTO THE EVENING HOURS.
..UT AND SWRN WY...
CONVECTION IS EXPECTED TO INCREASE AS LARGE SCALE FORCING INCREASES
WITH APPROACH OF UPPER TROUGH. LARGE SURFACE TEMPERATURE/DEWPOINT
SPREADS WILL SUPPORT STRONG WIND GUSTS WITH ANY SUSTAINED
UPDRAFTS...UNTIL MID EVENING.
.IMY.. 05/21/2007
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