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SPC Day 2 Outlook Text Only
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Forecast DiscussionSPC AC 110700 DAY 2 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0100 AM CST THU MAR 11 2010 VALID 121200Z - 131200Z ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE SOUTHERN HALF OF THE FL PENINSULA... ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF AL/GA AND SOUTHERN APPALACHIANS... ...SYNOPSIS... CENTROID OF CLOSED/EXTENSIVE LONGWAVE TROUGH WILL SLOWLY PIVOT EAST-SOUTHEASTWARD OVER THE LOWER MO/MIDDLE MS RIVER VALLEYS ON FRIDAY...WITH A SOUTHERN PERIPHERY/BASAL SHORTWAVE TROUGH PROGRESSING EAST-NORTHEASTWARD OVER THE GULF COAST STATES/TN VALLEY IN CONJUNCTION WITH PHASING POLAR/SUBTROPICAL JETS OVER THE GULF OF MEXICO/SOUTHEAST STATES/FL PENINSULA. IN THE WEST...THE INLAND ADVANCEMENT OF A CONSIDERABLE UPPER TROUGH AND STEEPENING LAPSE RATES IN THE WAKE OF ASSOCIATED COLD FRONT MAY YIELD ISOLATED TSTMS FOR COASTAL PORTIONS OF THE PACIFIC NORTHWEST/NORTHERN CA AND OFFSHORE PACIFIC WATERS. ...FL PENINSULA/FL KEYS... FULL-PERIOD SEVERE RISK IS PROBABLE ACROSS THE SOUTHERN THIRD TO HALF OF THE FL PENINSULA/PERHAPS FL KEYS ON FRIDAY. CURRENT THINKING IS THAT PLENTIFUL EARLY DAY SHOWERS/TSTMS...WITH AT LEAST SOME ISOLATED SEVERE THREAT...SHOULD SERVE TO ESTABLISH/REINFORCE A RAIN-COOLED EFFECTIVE WARM FRONT...MOST LIKELY ACROSS THE CENTRAL FL PENINSULA VICINITY. WHILE DETAILS OF SUCH ONGOING SHOWERS/TSTMS ARE DIFFICULT TO PORTEND IN ADVANCE...IT DOES SEEM PROBABLE THAT A GRADUALLY MOISTENING BOUNDARY LAYER /UPPER 60S TO LOWER 70S F SURFACE DEWPOINTS/ AND POCKETS OF STRONGER HEATING SOUTH OF THE AFOREMENTIONED WARM FRONT SHOULD SUPPORT A DAYTIME UPSWING IN DEEP CONVECTIVE VIGOR COINCIDENT WITH GRADUAL HEIGHT FALLS AND THE APPROACH OF A MID LEVEL IMPULSE. WHILE LOW LEVEL FLOW MAY TEND TO VEER /BUT STRENGTHEN/ DURING THE DAY...VERY STRONG DEEP TROPOSPHERIC WIND FIELDS WILL SUPPORT A MIXED MODE OF SEMI-DISCRETE HIGH PRECIPITATION SUPERCELLS AND/OR LINEAR EMBEDDED BOWS...WITH THE POSSIBILITY OF TORNADOES/DAMAGING WINDS AS THE PRIMARY CONCERNS ASIDE FROM HEAVY RAINFALL. ...AL/GA TO SOUTHERN APPALACHIANS... SHOWERS/TSTMS WILL LIKELY BE ONGOING EARLY FRIDAY ACROSS PORTIONS OF THE TN VALLEY/CENTRAL GULF COAST STATES TO FL. AN EARLY DAY SEVERE THREAT IS POSSIBLE MAINLY ACROSS PORTIONS OF AL...BUT THE SEVERE POTENTIAL MAY CONTINUE/INCREASE AND DEVELOP EASTWARD DURING THE DAY AS A MID LEVEL SHORTWAVE TROUGH/SPEED MAX APPROACHES WITHIN A BROADER DIFFLUENT REGIME/EXIT REGION OF POLAR JET. WHILE THE TRUE MARITIME WARM/MOIST SECTOR WILL BE CONFINED TO FL/ADJACENT GULF COAST...AND EXTENSIVE CLOUD COVER/PRECIPITATION MAY EXIST EARLY IN THE DAY...50S F SURFACE DEWPOINTS AHEAD OF A POSSIBLE WEAK SURFACE LOW AND NORTH-SOUTH COLD FRONT/DEVELOPING OCCLUSION COULD LEAD TO AN UPSWING IN DEEP CONVECTIVE COVERAGE/VIGOR DURING THE DAY. EVEN WITH MARGINAL BOUNDARY LAYER MOISTURE AND RELATIVELY MODEST BUOYANCY /PERHAPS ONLY 500-1000 J PER KG MLCAPE/...STEEPENING MID LEVEL LAPSE RATES VIA MID/UPPER DRY SLOT AND VERY STRONG LOW TO MID TROPOSPHERIC FLOW WILL SUPPORT A RISK FOR SEVERE HAIL/DAMAGING WINDS. ...OH/TN RIVER VALLEYS... AS THE COLD/CLOSED UPPER LOW SLOWLY SHIFTS TOWARD THE MIDDLE MS RIVER VALLEY...IT APPEARS THAT MULTIPLE LOW AMPLITUDE/MID LEVEL DISTURBANCES WILL PIVOT NORTH-NORTHEASTWARD OVER THE OH/TN VALLEYS ON FRIDAY. GIVEN COOL THERMAL PROFILES ALOFT /-20 TO -22C AT 500 MB/ IN PROXIMITY TO THE COLD/CLOSED UPPER LOW...EVEN MODEST DAYTIME HEATING AND UPPER 40S/LOWER 50S F SURFACE DEWPOINTS COULD YIELD STRONG/SEVERE LOW-TOPPED TSTMS...ESPECIALLY FRIDAY AFTERNOON IN VICINITY OF THE SURFACE LOW AND ASSOCIATED ROUGHLY NNW-SSE ORIENTED COLD/OCCLUDED FRONT. MARGINALLY SEVERE HAIL WILL LIKELY BE THE PRIMARY HAZARD...WITH ANY SUCH RISK TENDING TO WANE BY AROUND SUNSET. ..GUYER.. 03/11/2010 CLICK TO GET WUUS02 PTSDY2 PRODUCT NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z