SPC AC 100600
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT TUE MAR 10 2009
VALID 101200Z - 111200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE ARKLATEX REGION NEWD
INTO THE SRN UPPER GREAT LAKES...
...SYNOPSIS...
STRONG MID-LEVEL SHORT-WAVE TROUGH CROSSING THE ROCKIES AT THE START
OF THE PERIOD -- WITHIN THE LARGER-SCALE TROUGH OVER THE WRN HALF OF
NOAM -- IS FORECAST TO TAKE ON AN INCREASINGLY-NEGATIVE TILT AS IT
LIFTS NEWD ACROSS THE PLAINS THROUGH THE DAY. THIS FEATURE WILL
THEN CONTINUE SHIFTING RAPIDLY NEWD ACROSS THE UPPER GREAT LAKES --
AND ON INTO ONTARIO BY THE END OF THE PERIOD. ELSEWHERE...WEAKER
TROUGHING WILL REMAIN OVER THE WRN CONUS IN THE WAKE OF THIS
FEATURE...WHILE THE ERN U.S. RIDGE GETS SUPPRESSED/SHUNTED EWD WITH
TIME.
AT THE SURFACE...A WEAK LOW IS FORECAST OVER MO AT THE START OF THE
PERIOD...WITH A TRAILING COLD FRONT MOVING SWD ACROSS THE CENTRAL
PLAINS/SRN HIGH PLAINS. AS THIS LOW MOVES NEWD THROUGH THE DAY
TOWARD WI....THE TRAILING FRONT WILL CONTINUE SWD...WHILE A WARM
FRONT MOVES NWD ACROSS THE MID MS VALLEY/MIDWEST REGION. BY LATE
AFTERNOON...THE APPROACH OF THE SHORT-WAVE TROUGH SHOULD CONTRIBUTE
TO SUBSTANTIAL SURFACE CYCLOGENESIS...WITH A RAPIDLY-DEEPENING LOW
EXPECTED TO CROSS THE UPPER GREAT LAKES THROUGH THE END OF THE
PERIOD. AS THIS OCCURS...THE TRAILING COLD FRONT WILL BEGIN SURGING
MORE QUICKLY EWD ACROSS THE MIDWEST/OH VALLEY...AND SEWD ACROSS THE
S CENTRAL CONUS THROUGH THE PERIOD.
...ARKLATEX NEWD INTO THE UPPER GREAT LAKES REGION...
SHOWERS AND ISOLATED TO SCATTERED THUNDERSTORMS ARE FORECAST TO BE
ONGOING AT THE START OF THE PERIOD...FROM PARTS OF THE MID MS VALLEY
REGION SWWD ACROSS THE OZARKS/SERN OK AND INTO TX. WHILE MODEST
BOUNDARY-LAYER MOISTURE WILL BE ADVECTING NWD WITH TIME ACROSS MO
TOWARD THE MID MS AND LOWER OH VALLEYS...DEGREE OF
MOISTURE/INSTABILITY SHOULD AGAIN PROVE TO BE A LIMITING FACTOR WITH
RESPECT TO THE DEGREE OF SEVERE POTENTIAL THIS PERIOD.
THIS LACK OF INSTABILITY -- PARTICULARLY WITH NWD EXTENT -- WILL BE
AT LEAST PARTIALLY OFFSET BY THE INTENSIFYING SURFACE SYSTEM AND
ASSOCIATED UVV...AND BY A VERY STRONG DEEP-LAYER WIND FIELD
/INCLUDING 80 TO 100 KT SWLY FLOW AT MID LEVELS/. ATTM...IT APPEARS
THAT THE GREATEST JUXTAPOSITION OF FAVORABLE INSTABILITY AND SHEAR
WILL EVOLVE FROM ROUGHLY CENTRAL IL SWWD ACROSS MO AND AR TO THE
ARKLATEX REGION. WHILE THE GREATEST POTENTIAL FOR A TORNADO OR TWO
APPEARS TO EXIST ACROSS PARTS OF ERN MO AND IL DURING THE AFTERNOON
-- NEAR THE LEADING EDGE OF RETURNING MOISTURE -- THE THREAT FOR
DAMAGING WINDS AND HAIL SHOULD INCREASE THROUGH THE AFTERNOON AND
INTO THE EVENING AS THE COLD FRONT SHARPENS AND FORCES A MORE
ORGANIZED LINE OF STORMS. THE THREAT FOR WIND DAMAGE WITH A FORCED
LINE OF CONVECTION MAY SPREAD ACROSS PARTS OF NRN IL/IN AND PERHAPS
EVEN INTO LOWER MI LATE IN THE PERIOD...BUT VERY MEAGER INSTABILITY
SHOULD GENERALLY LIMIT THE NWD EXTENT OF THE THREAT DESPITE VERY
STRONG FORCING CROSSING THE UPPER GREAT LAKES REGION.
THE THREAT SHOULD BEGIN TO DIMINISH THROUGH LATE EVENING/OVERNIGHT
AS THE FRONT SURGES EWD ACROSS THE MIDWEST/OH VALLEY AREA...THOUGH
SOME THREAT MAY LINGER ACROSS E TX/THE ARKLATEX REGION THROUGH THE
END OF THE PERIOD AS FRONT CONTINUES SEWD THROUGH
MARGINALLY-UNSTABLE/AMPLY-SHEARED ENVIRONMENT.
..GOSS/HURLBUT.. 03/10/2009
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
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