SWODY1
SPC AC 180058
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0758 PM CDT MON SEP 17 2007
VALID 180100Z - 181200Z
..THERE IS A SLGT RISK OF SVR TSTMS FROM THE CENTRAL PLAINS TO THE
UPPER MS VALLEY...
..CENTRAL PLAINS TO UPPER MS VALLEY...
SUBSIDENCE IN THE WAKE OF A LEAD MID LEVEL IMPULSE...NOW TRACKING
NEWD TOWARD ONTARIO...APPEARS TO BE WEAKENING AS REGIONAL RADARS
INDICATED DISCRETE TSTMS DEVELOPING ALONG AND E OF COLD FRONT WHICH
EXTENDED FROM NRN/CENTRAL MN SWWD TO CENTRAL NEB AND WRN KS. SLY
LLJ EXTENDING FROM THE SRN PLAINS TO UPPER MS VALLEY WILL STRENGTHEN
FURTHER OVERNIGHT TO 50-55 KT BENEATH INCREASING SWLY MID LEVEL
WINDS ATTENDANT WITH CENTRAL HIGH PLAINS IMPULSE TRACKING TOWARD THE
MID MO VALLEY. UPWARD FORCING FOR ASCENT WITHIN EXIT REGION OF MID
LEVEL JET WILL SUPPORT ADDITIONAL TSTM DEVELOPMENT NEWD ALONG COLD
FRONT FROM SRN NEB INTO SERN SD/NWRN IA TO MN WITH APPROACH OF
UPSTREAM MID LEVEL TROUGH. MODERATE INSTABILITY AND STRONG
EFFECTIVE BULK SHEAR VALUES ALREADY IN PLACE FROM THE UPPER MS
VALLEY TO ERN NEB SUGGESTS SUPERCELLS WILL BE POSSIBLE WITH
DEVELOPING MORE DISCRETE STORMS. HOWEVER...ACTIVITY SHOULD
TRANSITION INTO MORE MULTICELL CLUSTERS OR LINEAR STRUCTURE WITH
ATTENDANT THREAT FOR HAIL AND DAMAGING WINDS...AS LLJ VEERS TO SWLY
RESULTING IN SHEAR VECTORS ORIENTED MORE PARALLEL TO THE COLD FRONT.
DESPITE EVENTUAL WEAKENING OF INSTABILITY...STRONG WIND FIELDS AND
SHEAR VALUES SUGGEST SEVERE WEATHER THREAT MAY PERSIST INTO THE LATE
EVENING/EARLY PART OF OVERNIGHT PERIOD.
SEVERE THREAT MAY TEND TO DIMINISH FARTHER S ALONG FRONT INTO KS
WHERE DEEP LAYER SHEAR IS WEAKER...BUT GIVEN STRENGTH OF LLJ...THIS
OUTLOOK WILL MAINTAIN SEVERE PROBABILITIES/CATEGORICAL RISK INTO
PARTS OF CENTRAL KS.
.PETERS.. 09/18/2007
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