SWODY2
SPC AC 090551
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1151 PM CST SUN FEB 08 2009
VALID 101200Z - 111200Z
...THERE IS A SLGT RISK OF SVR TSTMS LATE TUE AFTN/TUE NIGHT FROM
PARTS OF THE SRN PLAINS INTO THE LWR/MID MS VALLEY....
...SYNOPSIS...
A SUBSTANTIAL INCREASE IN CONVECTIVE POTENTIAL...INCLUDING THE RISK
FOR SEVERE STORMS...STILL APPEARS LIKELY ACROSS THE MIDDLE OF THE
COUNTRY DURING THIS FORECAST PERIOD...AS THE NEXT IN A SERIES OF
STRONG SHORT WAVE TROUGHS MIGRATES OUT OF THE FOUR CORNERS REGION.
THIS EAST NORTHEASTWARD ACCELERATION...OUT OF BROADER SCALE
TROUGHING WITHIN THE MAIN BELT OF POLAR WESTERLIES ACROSS THE
SOUTHWESTERN U.S...IS PROGGED...AS YET ANOTHER SIGNIFICANT IMPULSE
DIGS INTO THE NORTH CENTRAL PACIFIC COAST. IN THE WAKE OF A PRIOR
SYSTEM...WHICH INCLUDES A CYCLONE PROGGED TO BE SLOWLY WINDING DOWN
JUST WEST OF THE UPPER GREAT LAKES REGION...A MORE SOUTHERLY TRACK
APPEARS LIKELY TO SUPPORT LEE SURFACE CYCLOGENESIS IN CLOSE ENOUGH
PROXIMITY TO THE GULF OF MEXICO TO ALLOW FOR WEAK TO MODERATE
DESTABILIZATION IN THE WARM SECTOR.
LINGERING VARIABILITY/DISCREPANCIES AMONG MODEL DATA...WHICH COULD
AFFECT THE TIMING/LOCATION AND STRENGTH OF THUNDERSTORM
ACTIVITY...PRECLUDES A HIGHER CATEGORICAL OUTLOOK THAT COULD
POTENTIALLY ACCOMPANY A SYNOPTIC SYSTEM OF THIS STRENGTH.
HOWEVER...THE 09/00Z NAM RUN IS NOW SLOWER WITH THE PROGRESSION OF
THE UPPER SYSTEM THAN RECENT SREF HAVE INDICATED. THIS IS MORE IN
LINE WITH ECMWF AND GFS...CONTRIBUTING TO A SLIGHT WESTWARD SHIFT OF
HIGHER SEVERE PROBABILITIES...BACK TOWARD THE INTERSTATE 35 CORRIDOR
OF OKLAHOMA AND NORTH CENTRAL TEXAS...FOR LATE TUESDAY
AFTERNOON/TUESDAY NIGHT.
...SRN PLAINS THRU LWR HALF OF THE MISSISSIPPI VALLEY...
ALTHOUGH THE LOW-LEVEL RETURN FLOW OF MID 50S TO NEAR 60F SURFACE
DEW POINTS FROM THE WESTERN GULF OF MEXICO MAY INITIALLY BE ADVECTED
OFF TO THE EAST OF THE SOUTHERN PLAINS...A RAPID SURGE BACK TO THE
WEST IS ANTICIPATED DURING THE DAY TUESDAY. AND... MODELS INDICATE
MOISTURE VALUES WILL PROBABLY INCREASE AS THE BOUNDARY LAYER OVER
THE WESTERN GULF OF MEXICO CONTINUES TO SLOWLY MOISTEN. CONFIDENCE
IS INCREASING THAT A SIZABLE WARM SECTOR WILL EVOLVE ACROSS THE
SOUTHERN PLAINS INTO THE LOWER MISSISSIPPI VALLEY...WITH MIXED LAYER
CAPE ON THE ORDER OF 500-1000+ J/KG DEVELOPING AS LAPSE RATES
STEEPEN.
MID-LEVEL INHIBITION IS EXPECTED TO BE SUFFICIENTLY STRONG TO
PREVENT THE INITIATION OF STORMS PRIOR TO THE LATE AFTERNOON...
PERHAPS EARLY EVENING. BUT...GUIDANCE IS STILL SUGGESTIVE THAT
DISCRETE STORMS ARE A DISTINCT POSSIBILITY ACROSS PARTS OF NORTHEAST
TEXAS AND SOUTHEAST OKLAHOMA INTO WESTERN ARKANSAS BY THE EARLY
EVENING HOURS. A LOW-LEVEL CONFLUENCE ZONE/ZONE OF ENHANCED WARM
ADVECTION NEAR THE INTENSIFYING /50-70 KT/ 850 JET CORE...BENEATH
DIFLUENT UPPER FLOW...COULD PROVIDE THE FORCING FOR THIS ACTIVITY.
AND...IF THIS OCCURS...LARGE CLOCKWISE CURVED LOW LEVEL HODOGRAPHS
BENEATH STRONG WEST SOUTHWESTERLY MID/UPPER FLOW ...AHEAD OF AN
APPROACHING 90-100 KT 500 MB JET STREAK...WILL BE QUITE FAVORABLE
FOR SUPERCELLS CAPABLE OF PRODUCING TORNADOES.
ANY DISCRETE DEVELOPMENT IS EXPECTED TO SPREAD NORTHEASTWARD INTO/
THROUGH THE OZARK PLATEAU DURING THE EVENING HOURS...AS ADDITIONAL
STORMS FORM BACK TO THE WEST...NEAR OF JUST EAST OF THE INTERSTATE
35 CORRIDOR. THIS IS EXPECTED TO OCCUR ALONG OR JUST AHEAD OF AN
EASTWARD ADVANCING COLD FRONT...AS STRENGTHENING LINEAR FORCING
ENCOUNTERS THE BETTER MOISTURE ACROSS THE SOUTHEASTERN PLAINS. THE
EVOLUTION OF AN EXTENSIVE SQUALL LINE APPEARS POSSIBLE...ACCOMPANIED
BY THE POTENTIAL FOR STRONG CONVECTIVE GUSTS WITH THE RISK FOR
CONSIDERABLE WIND DAMAGE THROUGH THE NIGHT ...AS IT SURGES EASTWARD
INTO THE LOWER MISSISSIPPI VALLEY.
..KERR.. 02/09/2009
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