spc.noaa.gov/products/outlook/day1otlk_1200.gif?1417780479178 SPC AC 050538 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1138 PM CST THU DEC 04 2014 VALID 051200Z - 061200Z ...THERE IS A MRGL RISK OF SVR TSTMS LATE THIS AFTERNOON AND EVENING ACROSS PARTS OF CENTRAL AND EASTERN ARKANSAS...PERHAPS ADJACENT AREAS OF WESTERN TENNESSEE AND NORTHWESTERN MISSISSIPPI... ...SUMMARY... SCATTERED THUNDERSTORMS ARE POSSIBLE TODAY ACROSS PARTS OF THE OZARK PLATEAU INTO PORTIONS OF THE TENNESSEE AND LOWER OHIO VALLEYS. ONE OR TWO OF THESE COULD BECOME STRONG TO SEVERE...MAINLY ACROSS PARTS OF CENTRAL AND EASTERN ARKANSAS...WITH SOME RISK FOR LOCALLY DAMAGING WIND GUSTS...OR PERHAPS A TORNADO. ...SYNOPSIS... MUCH OF THE NATION WILL REMAIN UNDER THE INFLUENCE OF SEASONABLY MODEST WESTERLY MID/UPPER FLOW...OFF THE PACIFIC...THROUGH THIS FORECAST PERIOD AND BEYOND. WITHIN THIS REGIME...ONE LOW-AMPLITUDE SHORT WAVE TROUGH...OF SUBTROPICAL PACIFIC ORIGINS...IS FORECAST TO PROGRESS EAST OF THE CENTRAL PLAINS...INTO THE LOWER OHIO AND TENNESSEE VALLEYS BY 12Z SATURDAY. MODELS SUGGEST THAT THIS FEATURE MAY PROVIDE SUPPORT FOR WEAK SURFACE CYCLOGENESIS...ALONG A FRONTAL ZONE FROM OKLAHOMA INTO KENTUCKY. THIS IS BEING PRECEDED BY A RETURN FLOW OF MOISTURE OFF THE WESTERN GULF OF MEXICO...WHICH COULD BECOME CHARACTERIZED BY LOWER/MID 60S SURFACE...OR NEAR SURFACE...DEW POINTS AS FAR NORTH AS THE OZARK PLATEAU BY LATE THIS AFTERNOON. AND DESTABILIZATION PROBABLY WILL BECOME SUFFICIENT TO SUPPORT THUNDERSTORM ACTIVITY. A COUPLE OF ADDITIONAL PERTURBATIONS PROGRESSING INLAND ACROSS THE PACIFIC COAST MAY BE ACCOMPANIED BY SOME RISK FOR WEAK THUNDERSTORM ACTIVITY...BUT PROBABILITIES MUCH ABOVE THE MINIMUM 10 PERCENT THRESHOLD FOR A CATEGORICAL THUNDER OUTLOOK WILL MOSTLY BE WELL OUT OVER THE OPEN WATERS OF THE PACIFIC. ...OZARK PLATEAU... DESPITE THE LOW-LEVEL MOISTURE INCREASES...SUBSTANTIVE STEEPENING OF LOWER/MID TROPOSPHERIC LAPSE RATES APPEARS UNLIKELY WITH THE APPROACHING UPPER TROUGH. THIS WILL LIMIT THE CAPE...AND APPEARS THE PRIMARY LIMITING FACTOR CONCERNING SEVERE POTENTIAL TODAY. HOWEVER...THE ASSOCIATED MID-LEVEL JET STREAK /ON THE ORDER OF 50 KT/...WHILE STRONG ENOUGH TO CONTRIBUTE TO SUFFICIENT SHEAR FOR SUPERCELLS...IS NOT PARTICULARLY STRONG FOR THE TIME OF YEAR AND AVAILABLE INSTABILITY. AND IT IS POSSIBLE THAT LOW CLOUDS AND RAIN COULD MAINTAIN A SHALLOW SURFACE BASED STABLE LAYER...EVEN IN THE WARM SECTOR OF THE WEAK FRONTAL WAVE. ANY SEVERE WEATHER POTENTIAL SEEMS TO LARGELY HINGE ON WHETHER BREAKS IN LOW-LEVEL CLOUD COVER ALLOW FOR AT LEAST WEAK BOUNDARY LAYER DESTABILIZATION. THIS MAY BE POSSIBLE BY LATE THIS AFTERNOON ACROSS PARTS OF CENTRAL AND EASTERN ARKANSAS...BENEATH A DEVELOPING MID-LEVEL DRY SLOT...JUST AHEAD OF THE TRAILING MID-LEVEL CYCLONIC VORTICITY CENTER ASSOCIATED WITH THE LOW AMPLITUDE UPPER TROUGH. ..KERR.. 12/05/2014
Posted on: Fri, 05 Dec 2014 11:55:18 +0000
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