Wednesday, August 29, 2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 291254
SWODY1
SPC AC 291252

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0752 AM CDT WED AUG 29 2007

VALID 291300Z - 301200Z

..THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF LWR MI...NRN IND
AND NW OH...

..SYNOPSIS...
LARGELY ZONAL FLOW WILL PREVAIL ACROSS THE FAR NRN TIER OF THE U.S.
AND SRN CANADA AS DUAL RIDGES PERSIST OVER THE SWRN STATES AND OVER
THE SOUTHEAST. LOW AMPLITUDE TROUGH NOW OVER WRN ONTARIO EXPECTED
TO AMPLIFY SLIGHTLY AS IT CONTINUES E INTO WRN QUEBEC LATE IN THE
PERIOD...BUT STRONGEST ASSOCIATED UVV LIKELY WILL REMAIN WELL N OF
THE CANADIAN BORDER.

A BIT FARTHER S...REMNANT SRN BRANCH JET NOW EXTENDING FROM NRN MO
TO LWR MI WILL CONTINUE TO BECOME ABSORBED IN MODERATE WSW FLOW IN
SE QUADRANT OF ONTARIO TROUGH. WEAK DISTURBANCES IN THIS FLOW WILL
CROSS LWR MI AND THE LWR GRT LKS REGION TODAY/TONIGHT.

AT THE SFC...COLD FRONT WITH ONTARIO SYSTEM WILL PROGRESS STEADILY
SE/S ACROSS LWR MI...THE MID MS VLY...SRN PLNS AND SRN RCKYS TODAY.
THE BOUNDARY SHOULD WEAKEN AS IT CONTINUES FARTHER SE/S TONIGHT AND
EARLY THURSDAY.

..LWR MI/NRN IL/NRN IND/NW OH...
AFOREMENTIONED COLD FRONT ATTM EXTENDS FROM NEAR SSM SW TO NEAR
MS...WHILE A WIND SHIFT LINE AHEAD OF THE FRONT EXTENDS FROM NEAR
APN TO NEAR ORD. STRONG HEATING SHOULD OCCUR ALONG/AHEAD OF WIND
SHIFT IN SRN LWR MI/NRN IND AND NW OH...WHILE CLOUDS WILL TEMPER
WARM-UP CLOSER TO THE FRONT FROM NRN IL INTO WRN LWR MI. MID LVL
LAPSE RATES WILL REMAIN MODEST...BUT COUPLED WITH INCREASING LOW LVL
MOISTURE...HEATING SHOULD BOOST AFTN MLCAPE TO AOA 1000 J/KG FROM E
CNTRL IL NEWD INTO SRN/ERN LWR MI.

HEATING...MODEST UVV ASSOCIATED WITH SRN BRANCH IMPULSES AND
CONVERGENCE ALONG WIND SHIFT LINE AND/OR FRONTAL SEGMENTS SHOULD
SUPPORT SCTD TSTMS BY MID-AFTN. 30-40 KT DEEP UNIDIRECTIONAL WSWLY
FLOW WILL FOSTER ORGANIZATION INTO FAST MOVING LINE
SEGMENTS/BOWS...SOME OF WHICH COULD YIELD DAMAGING WIND. THE STORMS
SHOULD DECREASE TOWARD SUNSET AS BOUNDARY LYR COOLS AND MAIN UPR
TROUGH CONTINUES E TOWARD QUEBEC.

..CNTRL RCKYS...
POST-FRONTAL MOISTURE SPREADING N/NW ALONG THE CO AND SRN WY
FOOTHILLS MAY SUPPORT SCTD STRONG STORMS AS TERRAIN-INDUCED
CIRCULATIONS STRENGTHEN THIS AFTERNOON. CAPPING SHOULD PROHIBIT
DEVELOPMENT IN THE LWR PLNS...BUT WEAK NNWLY MID LVL WINDS MAY ALLOW
MOUNTAIN STORMS TO DRIFT OVER FAR WRN PARTS OF THE ADJACENT PLNS. A
WEAK DISTURBANCE MOVING SE FROM THE NRN GRT BASIN MAY ENHANCE
VERTICAL MOTION AND POTENTIAL FOR A FEW COUPLE SUSTAINED CELLS...AND
MLCAPE OF 1000-1500 J/KG WITH 25 KT DEEP NNWLY SHEAR MAY SUPPORT
ISOLD HAIL/GUSTY WINDS TIL SUNSET.

..SRN HI PLNS...
COLD FRONT...AUGMENTED BY OUTFLOW AIR...WILL CONTINUE S ACROSS
THE NM/TX HI PLNS TODAY. ASSOCIATED MOISTURE INFLUX/POST FRONTAL
ENELY FLOW MAY SUPPORT DEVELOPMENT OF A CLUSTER OR TWO OF
STORMS OVER THE TX PANHANDLE AND NE NM. STEEP LOW LEVEL LAPSE
RATES WILL CONTRIBUTE TO MODEST BUOYANCY AND THE POTENTIAL FOR ISOLD
SVR WIND GUSTS...BUT WEAK VERTICAL SHEAR SHOULD LIMIT STORM
ORGANIZATION/LONGEVITY.

.CORFIDI/CROSBIE.. 08/29/2007

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