SPC AC 181242
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0742 AM CDT FRI MAR 18 2011
VALID 181300Z - 191200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
COLD UPPER LOW OFF THE PACIFIC NW COAST IS FORECAST TO REMAIN
OFFSHORE THROUGH TONIGHT AS A STRONG SHORT WAVE TROUGH ROTATES INTO
THE BASE OF THE LOW...WITH HEIGHTS FALLING ALONG THE NRN/CNTRL
PACIFIC COAST. THIS AMPLIFICATION WILL RESULT IN GRADUAL BUILDING
OF A RIDGE OVER THE CENTRAL AND NRN HIGH PLAINS BY TONIGHT.
DOWNSTREAM FROM THE PACIFIC LOW...WATER VAPOR IMAGERY INDICATES A
LOW AMPLITUDE SHORT WAVE TROUGH MOVING RAPIDLY ENEWD ACROSS THE
CENTRAL ROCKIES. THIS FEATURE IS EXPECTED TO MOVE ACROSS THE GREAT
LAKES TONIGHT.
AT THE SURFACE...A COLD FRONT EXTENDS FROM THE LOWER GREAT LAKES
SWWD ACROSS THE MIDDLE MS VALLEY AND INTO NWRN TX AND NERN NM. THE
FRONT WILL MOVE SEWD/SWD THROUGH THE PERIOD...EXTENDING FROM ERN NC
ACROSS NRN AL...SRN AR AND SWRN TX BY 19/12Z.
...MO/NRN AR INTO LOWER OH VALLEY...
ELEVATED CONVECTION IS DEVELOPING OVER NRN/CENTRAL MO WITHIN A WARM
ADVECTION ZONE NORTH OF THE SURFACE COLD FRONT ON THE NOSE OF A SWLY
LOW LEVEL JET. THIS ACTIVITY IS EXPECTED TO SPREAD EWD TODAY TOWARD
THE LOWER OH VALLEY. A FEW THUNDERSTORMS MAY ALSO FORM DURING THE
MID/LATE AFTERNOON CLOSER TO THE SURFACE FRONT FROM THE OZARKS EWD
INTO WRN KY AND POSSIBLY NWRN TN WHERE DIURNAL HEATING WILL
CONTRIBUTE TO A GRADUAL WEAKENING OF THE CAP. A PLUME OF STEEPER
MID LEVEL LAPSE RATES EXTENDING EWD ACROSS THE OZARKS REGION WILL
ENHANCE UPDRAFT INTENSITY...WITH ISOLATED STORMS CAPABLE OF
PRODUCING GUSTY SURFACE WINDS AND MARGINAL HAIL. THESE STORMS ARE
LIKELY TO DIMINISH THIS EVENING.
...NWRN TX INTO WRN OK...
THE AREA SOUTH OF THE SURFACE FRONT IS LIKELY TO REMAIN CAPPED
THROUGH MUCH OF THE AFTERNOON. DESPITE LITTLE DYNAMIC FORCING FOR
LARGE SCALE ASCENT...STRONG DIURNAL HEATING MAY WEAKEN THE CAP
SUFFICIENTLY FOR ISOLATED THUNDERSTORMS TO DEVELOP LATE THIS
AFTERNOON AND EVENING OVER NWRN TX. STEEP LAPSE RATES WILL AID IN
DEVELOPMENT OF AN UNSTABLE ENVIRONMENT WITH MLCAPE OF 1000-1500
J/KG. THE AREA WILL BE ALONG THE SRN EDGE OF STRONGER SWLY WINDS
ALOFT WITH DEEP LAYER SHEAR OF 25-35 KT IN THE LOWEST 6 KM. THE
VERTICAL SHEAR WILL ENHANCE STORM ORGANIZATION WITH ORGANIZED
MULTICELL AND ISOLATED SUPERCELLS CAPABLE OF PRODUCING HAIL AND
GUSTY WINDS.
MODEL GUIDANCE INDICATES A MODEST LOW LEVEL JET WILL DEVELOP THIS
EVENING OVER PARTS OF WRN TX INTO SWRN OK WITH THE 850 MB FRONT
RETREATING NWD INTO NRN OK. INCREASING LOW LEVEL WARM ADVECTION
NORTH OF THE SURFACE FRONT WILL SUPPORT ISOLATED ELEVATED
THUNDERSTORMS FROM THE ERN TX PANHANDLE INTO PARTS OF WRN OK
TONIGHT. MODEL FORECAST SOUNDINGS MAINTAIN STEEP MID LEVEL LAPSE
RATES SUGGESTING STRONGER CELLS WILL BE CAPABLE OF PRODUCING
MARGINAL HAIL.
..WEISS/GRAMS.. 03/18/2011
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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