SPC AC 181240
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0740 AM CDT SUN JUL 18 2010
VALID 181300Z - 191200Z
...THERE IS A SLGT RISK OF SVR TSTMS TODAY FROM LOWER MI SWWD TO
INDIANA/IL/MO...THEN CONTINUING OVERNIGHT FROM NW MO/SW IA NWWD TO
SW SD...
...MO/IL/INDIANA/LOWER MI/OH THROUGH TONIGHT...
AN ONGOING MCS AND ASSOCIATED MCV ACROSS NE MO/WRN IL WILL LIKELY
PERSIST THROUGH THE DAY WHILE CONTINUING TO MOVE ESEWD/SEWD ACROSS
ERN MO AND CENTRAL/SRN IL...WITH THE POSSIBILITY OF DAMAGING GUSTS.
DURING THE AFTERNOON...ADDITIONAL THUNDERSTORM DEVELOPMENT WILL BE
POSSIBLE ACROSS CENTRAL/SE MO ALONG THE OUTFLOW BOUNDARY TRAILING W
OF THE MORNING MCS. SURFACE TEMPERATURES IN THE 90S AND DEWPOINTS
IN THE 70S WILL DRIVE STRONG INSTABILITY ALONG THE OUTFLOW BOUNDARY
THIS AFTERNOON ACROSS MO. THIS AREA WILL BE S OF THE STRONGER
MID-UPPER FLOW AND DEEP-LAYER VERTICAL SHEAR WILL LIKEWISE BE
MARGINAL FOR ORGANIZED SEVERE STORMS. HOWEVER...THE MAGNITUDE OF
THE INSTABILITY AND FOCUSED LIFT ALONG THE OUTFLOW BOUNDARY COULD
SUPPORT ANOTHER SWD-MOVING THUNDERSTORM CLUSTER FROM MO INTO N/NE AR
THIS AFTERNOON/EVENING...WITH THE POTENTIAL FOR DAMAGING GUSTS.
FARTHER E/NE INTO INDIANA/LOWER MI...ASIDE FROM SOME LINGERING ANVIL
DEBRIS ENE OF THE MO/IL CLUSTER...THE BOUNDARY LAYER DOES NOT APPEAR
THAT IT WILL BE OVERTURNED BY EARLY CONVECTION.
INSTEAD...THUNDERSTORM DEVELOPMENT IS EXPECTED BY EARLY AFTERNOON
ALONG OR IMMEDIATELY IN ADVANCE OF THE SURFACE LOW MOVING EWD ACROSS
WI AND THE COLD FRONT MOVING SEWD FROM IA TO NRN IL/NW INDIANA...IN
ASSOCIATION WITH THE MIDLEVEL SHORTWAVE TROUGH TRAVERSING THE GREAT
LAKES FROM MN/WI. STORMS MAY ALSO DEVELOP EWD IN ASSOCIATION WITH
THE REMNANT MCV FROM THE MORNING MCS IN IL. SURFACE HEATING AND
BOUNDARY LAYER DEWPOINTS IN THE UPPER 60S TO LOW 70S WILL CONTRIBUTE
TO AFTERNOON MLCAPE VALUES RANGING FROM 2000 J/KG IN LOWER MI TO
3000 J/KG IN INDIANA. DEEP-LAYER FLOW AND VERTICAL SHEAR WILL BE
SUFFICIENT FOR SUPERCELLS ALONG THE FRONT DURING THE AFTERNOON
/ESPECIALLY ACROSS LOWER MI/...PRIOR TO VEERING OF THE LOW-LEVEL
FLOW AND WEAKENING OF VERTICAL SHEAR IN THE EVENING WITH PASSAGE OF
THE MIDLEVEL WAVE. A TORNADO OR TWO MAY OCCUR IN LOWER MI IN THE
ZONE OF STRONGER LOW-LEVEL SHEAR...BUT DAMAGING WINDS AND ISOLATED
LARGE HAIL WILL BE THE PRIMARY THREATS AS STORMS MOVE EWD/SEWD
ACROSS INDIANA AND OH INTO KY THROUGH EARLY TONIGHT.
...ERN NEB/SW IA/NW MO TONIGHT...
THE QUASI-STATIONARY BAROCLINIC ZONE NEAR THE MO/NEB BORDER WILL
BEGIN TO MOVE SLOWLY NWD TONIGHT IN RESPONSE TO AN INCREASING SWLY
LLJ. LOW-LEVEL WAA N OF THE BOUNDARY SHOULD BE SUFFICIENT TO
ACHIEVE PARCEL SATURATION AND ALLOW THE DEVELOPMENT OF ELEVATED
THUNDERSTORMS IN A NW-SE ORIENTED BAND LATE TONIGHT. GIVEN THE
MAGNITUDE OF THE UPSTREAM INSTABILITY AND REMAINING STEEP MIDLEVEL
LAPSE RATES...THE STRONGER STORMS COULD PRODUCE LARGE HAIL.
...SW SD AREA LATE TONIGHT...
SUBTLE SPEED MAXIMA WILL EJECT EWD IN ADVANCE OF A MIDLEVEL TROUGH
MOVING EWD FROM THE PAC NW TO THE NRN ROCKIES. DOWNSTREAM LEE
CYCLOGENESIS WILL OCCUR INVOF ERN WY...WHICH WILL HELP DRAW
LOW-LEVEL MOISTURE NWD/NWWD FROM NEB INTO SD BENEATH ALREADY STEEP
MIDLEVEL LAPSE RATES. THE NET RESULT WILL BE SUFFICIENT
DESTABILIZATION AND ASCENT TO SUPPORT THE DEVELOPMENT OF A
THUNDERSTORM CLUSTER LATE TONIGHT ON THE NOSE OF A WRN SEGMENT OF
THE PLAINS LLJ. POTENTIALLY MODERATE INSTABILITY AND EFFECTIVE BULK
SHEAR IN EXCESS OF 50 KT COULD SUPPORT ISOLATED LARGE HAIL ...WHILE
SUBSTANTIAL DCAPE COULD SUPPORT STRONG/DAMAGING GUSTS DESPITE A
NEAR-SURFACE STABLE LAYER.
..THOMPSON/GRAMS/DEAN.. 07/18/2010
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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