DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1120 PM CST WED DEC 03 2014 VALID 041200Z - 051200Z ...NO TSTM AREAS FORECAST... ...SUMMARY... THE RISK FOR THUNDERSTORMS APPEARS VERY LOW TO NEGLIGIBLE ACROSS MOST OF THE U.S. TODAY AND TONIGHT. ...SYNOPSIS... A MORE ZONAL MID/UPPER FLOW EMERGING FROM THE PACIFIC...AND NOW PROMINENT ACROSS MUCH OF THE WESTERN U.S...AND CENTRAL AND SOUTHERN TIER EAST OF THE ROCKIES...APPEARS LIKELY TO CONTINUE TO DEVELOP NORTHWARD AND EASTWARD DURING THIS PERIOD. THIS IS EXPECTED TO OCCUR AS CYCLONIC FLOW...ASSOCIATED WITH THE COLD VORTEX TO THE NORTHWEST OF HUDSON BAY...CONTINUES TO GRADUALLY RECEDE NORTHWARD TO THE FAR NORTHERN PLAINS/UPPER GREAT LAKES AND NORTHERN NEW ENGLAND. WHILE SOUTHWARD DAMMING OF COLD SURFACE AIR TO THE EAST OF THE CENTRAL AND SOUTHERN APPALACHIANS LIKELY WILL PROCEED...AS THE CENTER OF COLD SURFACE RIDGING SHIFTS FROM THE UPPER MIDWEST TO THE NORTHEAST...FURTHER MODERATION OF TEMPERATURES IS EXPECTED ACROSS MOST OTHER AREAS EAST OF THE ROCKIES. A SOUTHERLY RETURN FLOW OFF THE WESTERN GULF OF MEXICO ALSO APPEARS LIKELY TO CONTRIBUTE TO SUBSTANTIVE MOISTENING ACROSS MUCH OF THE SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY. THIS WILL OCCUR IN ADVANCE OF A LOW AMPLITUDE SHORT WAVE TROUGH...NOW PROGRESSING TOWARD THE SOUTHERN CALIFORNIA/NORTHERN BAJA COAST...AND FORECAST TO CROSS THE SOUTHERN ROCKIES BY EARLY THIS EVENING...BEFORE CONTINUING THROUGH THE CENTRAL PLAINS OVERNIGHT. WHILE ISOLATED TO WIDELY SCATTERED WEAK THUNDERSTORMS STILL SEEM POSSIBLE ACROSS PARTS OF THE LOWER COLORADO VALLEY INTO THE COLORADO PLATEAU PRIOR TO 12Z THIS MORNING...LOW THUNDERSTORM PROBABILITIES ARE EXPECTED TO BECOME INCREASINGLY NEGLIGIBLE SHORTLY THEREAFTER...WITH DRYING IN THE WAKE OF THE UPPER IMPULSE. DESPITE THE DOWNSTREAM MOISTURE INCREASES...MODELS INDICATE LITTLE SUBSTANTIVE STEEPENING OF LOWER/MID TROPOSPHERIC RATES ACROSS THE SOUTHERN PLAINS INTO THE LOWER MISSISSIPPI VALLEY WITH THE UPPER IMPULSE. THIS CURRENTLY APPEARS TO LIMIT THE POTENTIAL FOR APPRECIABLE DESTABILIZATION...AND ANY RISK FOR THUNDERSTORMS TO PROBABILITIES BELOW THE MINIMUM 10 PERCENT THRESHOLD FOR A CATEGORICAL OUTLOOK AREA. ..KERR/PICCA.. 12/04/2014 spc.noaa.gov/products/outlook/day1otlk_1200.gif?1417687672107
Posted on: Thu, 04 Dec 2014 10:09:03 +0000
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