DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0759 AM CDT SUN AUG 18 2013 VALID 181300Z - 191200Z ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN PLAINS REGION... ...SYNOPSIS... LITTLE CHANGE IN THE OVERALL LARGE-SCALE FLOW FIELD ALOFT IS PROGGED THIS PERIOD...WITH RIDGING ACROSS MUCH OF THE WEST AND A TROUGH EXTENDING FROM THE GREAT LAKES REGION SSWWD INTO THE LOWER MS VALLEY. MEANWHILE...AN UPPER LOW INVOF THE CENTRAL CA COAST IS FORECAST TO MAKE NO MORE THAN SCANT SWD/SSWWD PROGRESS THROUGH THE PERIOD. AT THE SURFACE...A WEAK LOW IS FORECAST TO DRIFT SLOWLY NWD ACROSS THE N CENTRAL GULF AND EVENTUALLY REACH COASTAL LA...WHILE AN ASSOCIATED/WEAK WARM FRONT LIFTS NWD ACROSS THE GULF COAST REGION. ELSEWHERE...A WEAK COLD FRONT IS FORECAST TO SHIFT SLOWLY SEWD ACROSS THE NRN PLAINS...WHILE LEE TROUGHING PERSISTS OVER THE HIGH PLAINS. ...NRN PLAINS SWWD INTO THE NEB PANHANDLE AND NERN CO... SHORT-WAVE TROUGHING MOVING ACROSS THE NRN PLAINS THIS AFTERNOON WILL PROVIDE SOME INCREASE IN LARGE-SCALE ASCENT...FOCUSED ALONG A WEAK COLD FRONT SLOWLY CROSSING THE AREA. AS DIURNAL HEATING RESULTS IN AN INCREASE IN CAPE...ISOLATED TO SCATTERED STORM DEVELOPMENT IS EXPECTED -- INITIALLY ACROSS THE CENTRAL/ERN ND VICINITY DURING THE AFTERNOON. WITH MODEST /AROUND 30 KT/ WLY MID-LEVEL FLOW ATOP LOW-LEVEL SLYS...SHEAR WILL BE SUPPORTIVE OF ORGANIZED STORMS -- AND ASSOCIATED THREATS FOR HAIL AND DAMAGING WINDS. STORMS WILL SPREAD EWD WITH TIME...AND POSSIBLY DEVELOP SWWD IN A MORE ISOLATED FASHION INTO THE CENTRAL HIGH PLAINS...WHERE A WEAK LEE TROUGH WILL RESIDE. AS A LOW-LEVEL JET INCREASES THIS EVENING...CONVECTION IS LIKELY TO SPREAD AS FAR E AS N CENTRAL/NERN MN...WHERE LOW-END SEVERE THREAT MAY PERSIST. ...THE CENTRAL GULF COASTAL REGION... BANDS OF SHOWERS AND EMBEDDED THUNDERSTORMS ARE ONGOING OVER PORTIONS OF THE CENTRAL GULF COAST REGION ATTM...AS A WEAK WARM FRONT INVOF THE CENTRAL GULF COAST LIFTS SLOWLY NWD. AS THE WEAK LOW FARTHER W -- S OF COASTAL LA -- LIKEWISE SHIFTS SLOWLY NWD THROUGH THE PERIOD...THE WARM FRONT IS PROGGED TO MOVE ONSHORE...WHILE MULTIPLE BANDS OF SHOWERS AND THUNDERSTORMS PERSIST ACROSS THE GULF COAST/SOUTHEAST THROUGH THE PERIOD. A FEW OF THE OFFSHORE CELLS HAVE EXHIBITED LOW-LEVEL ROTATION EARLY THIS MORNING...BUT A DECREASE IN ORGANIZATION/ROTATION HAS BEEN OBSERVED IN RECENT WSR-88D LOOPS. WITH LOW-LEVEL SHEAR FORECAST TO WEAKEN SLOWLY THIS MORNING AND INTO THE AFTERNOON...THE RISK FOR ANY TORNADO ACTIVITY REMAINS LOW. LATER...AS THE LOW REACHES COASTAL LA...SOME WWD SHIFT OF LOW-END TORNADO POTENTIAL IS EXPECTED...BUT OVERALL THREAT APPEARS LIMITED ENOUGH TO PRECLUDE SLIGHT RISK UPGRADE.
Posted on: Sun, 18 Aug 2013 16:17:34 +0000
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