SWODY2
SPC AC 231728
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1228 PM CDT MON MAR 23 2009
VALID 241200Z - 251200Z
...THERE IS A SLGT RISK OF SVR TSTMS TUE AFTN AND EVE FROM PARTS OF
THE SERN PLAINS INTO THE MID MS VALLEY....
...SYNOPSIS...
WITH A PROMINENT BLOCK IN THE LARGE-SCALE UPPER PATTERN STILL
DEVELOPING ACROSS THE NORTH ATLANTIC...BROAD UPPER TROUGHING
ENCOMPASSING MUCH OF THE WESTERN AND CENTRAL U.S. WILL BE SLOW TO
DEVELOP EASTWARD. THUS...AS THE NEXT COUPLE IN A SERIES OF SHORT
WAVE IMPULSES DIG EAST OF A NORTHEAST PACIFIC UPPER RIDGE...INTO THE
UPPER TROUGH...THE VIGOROUS DOWNSTREAM CLOSED LOW...NOW LIFTING INTO
THE NORTH CENTRAL PLAINS...IS PROGGED TO CONTINUE PERHAPS A BIT MORE
NORTHWARD THAN EASTWARD...TOWARD THE UPPER MISSISSIPPI VALLEY DURING
THIS PERIOD. MODELS INDICATE THAT THIS WILL OCCUR AS A SIGNIFICANT
SMALLER SCALE IMPULSE PIVOTS AROUND THE SOUTHERN/EASTERN PERIPHERY
OF THE MID-LEVEL CIRCULATION. GUIDANCE GENERALLY INDICATES THAT
ASSOCIATED LOW-LEVEL COOLING WILL ADVANCE ACROSS THE SOUTHERN PLAINS
TOWARD THE LOWER MISSISSIPPI VALLEY...WITH A TENDENCY TO OUTRUN AND
SHIFT SOUTHEAST OF STRONGER MID-LEVEL FORCING FOR UPWARD VERTICAL
MOTION AND COOLING. THIS...COUPLED WITH LOW-LEVEL DRYING ASSOCIATED
WITH A LINGERING SURFACE RIDGE OVER THE EASTERN STATES...WILL LIMIT
THE BREADTH OF AND DESTABILIZATION WITHIN THE WARM SECTOR OF THE
DEEP SURFACE CYCLONE MIGRATING THROUGH THE UPPER MIDWEST.
...EASTERN TEXAS THROUGH MIDDLE MISSISSIPPI VALLEY...
DESPITE THE AFOREMENTIONED LIMITING FACTORS...A WINDOW OF
OPPORTUNITY APPEARS TO EXIST FOR THE DEVELOPMENT OF STRONG/SEVERE
STORMS LATE TUESDAY AFTERNOON AND EARLY TUESDAY EVENING. AN AXIS OF
AT LEAST WEAK TO...PERHAPS...MODERATE INSTABILITY IS EXPECTED AHEAD
OF THE FRONT BY LATE AFTERNOON...FROM THE ARKLATEX THROUGH THE
MISSOURI OZARKS...WHERE SUFFICIENT BOUNDARY LAYER MOISTURE IS
EXPECTED FOR MIXED LAYER CAPE OF 500-1000 J/KG. AND...FRONTAL
FORCING COULD BE SUFFICIENT TO SUPPORT THE EVOLUTION OF A SQUALL
LINE IN THE PRESENCE OF A KINEMATIC ENVIRONMENT CHARACTERIZED BY
STRONG DEEP LAYER SHEAR AND 40-50+ KT SOUTHWESTERLY MEAN FLOW.
DAMAGING SURFACE WIND GUSTS SEEM TO BE THE PRIMARY SEVERE THREAT.
HOWEVER...MODEL FORECAST SOUNDINGS INDICATE THAT LARGE CLOCKWISE
CURVED LOW-LEVEL HODOGRAPHS ARE PROBABLE AHEAD OF THE FRONT/
CONVECTIVE LINE. THIS WILL BE SUPPORTIVE OF TORNADIC POTENTIAL...
IF DAYTIME HEATING AND LARGE SCALE LIFT BECOME SUFFICIENT TO
OVERCOME INHIBITION...AND SUPPORT DISCRETE CONVECTIVE DEVELOPMENT.
PROBABILITIES FOR THIS APPEAR SOMEWHAT LOW AT THE PRESENT TIME...
WITH BEST POTENTIAL PERHAPS ALONG A PRE-FRONTAL CONFLUENCE EXTENDING
FROM PARTS OF THE ARKLATEX THROUGH CENTRAL ARKANSAS. COMPARED TO
AREAS FARTHER NORTH...LOW-LEVEL MOISTURE WILL BE A BIT MORE
FAVORABLE ACROSS THIS REGION. AND...CAPPING MAY BE A BIT WEAKER
THAN AREAS SOUTHWARD TOWARD THE WESTERN/CENTRAL GULF COAST.
..KERR.. 03/23/2009
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