Dec 16, 2011 0600 UTC Day 1 Convective Outlook | |
Updated: Fri Dec 16 05:44:09 UTC 2011 | |
Probabilistic to Categorical Outlook Conversion Table |
Categorical Graphic |
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Probabilistic Tornado Graphic |
Probability of a tornado within 25 miles of a point. Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point. |
Probabilistic Damaging Wind Graphic |
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point. |
Probabilistic Large Hail Graphic |
Probability of hail 1" or larger within 25 miles of a point. Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point. |
SPC AC 160540 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1140 PM CST THU DEC 15 2011 VALID 161200Z - 171200Z ...NO TSTM AREAS FORECAST... ...SYNOPSIS... THE MID-LEVEL PATTERN ACROSS THE CONUS WILL GRADUALLY TRANSITION FROM AN INITIALLY SPLIT-FLOW REGIME TO A PREDOMINANT NRN STREAM. THIS WILL OCCUR AS A SHORTWAVE TROUGH QUICKLY SHIFTS ENEWD ACROSS WRN TX AND OK BEFORE BECOMING ABSORBED INTO A LARGER-SCALE TROUGH OVER THE ERN STATES. AN ASSOCIATED SFC COLD FRONT WILL SLOWLY MOVE SEWD ACROSS PORTIONS OF THE SERN CONUS...WHILE A WEAK FRONTAL WAVE SHIFTS ENEWD ALONG THE FRONT OVER THE CAROLINAS. MEANWHILE...A MID-LEVEL RIDGE OVER THE ERN PACIFIC WILL PENETRATE THE NWRN CONUS WHILE A DEEP-LAYER LOW CUTS OFF AND MEANDERS ACROSS PARTS OF FAR SRN CA...NRN BAJA CA...AND THE ADJACENT PACIFIC WATERS. ...TN VALLEY... AT LEAST MODEST MID-LEVEL ASCENT LEADING THE AFOREMENTIONED SHORTWAVE TROUGH WILL COMBINE WITH VERY LIMITED ELEVATED INSTABILITY TO SUPPORT A BROAD AREA OF SHOWERS TO THE NW OF THE SFC FRONT. FORECAST SOUNDINGS SUGGEST THAT THE ELEVATED BUOYANCY THAT COINCIDES WITH THE ASCENT WILL BE MEAGER -- I.E. MUCAPE VALUES GENERALLY LESS THAN 100 J/KG -- AND SUPPORT NOTHING MORE THAN VERY ISOLATED LIGHTNING STRIKES...AT MOST. AS SUCH...THUNDERSTORM ACTIVITY CURRENTLY UPSTREAM OVER NERN TX IS EXPECTED TO DECREASE IN COVERAGE AS THE ASCENT BECOMES INCREASINGLY REMOVED FROM GREATER INSTABILITY CLOSER TO THE GULF COAST. ACCORDINGLY...IT APPEARS THAT THE COVERAGE OF THUNDERSTORMS WILL BE SUFFICIENTLY LIMITED AFTER 12Z FRI TO PRECLUDE A GENERAL THUNDER AREA...AS ANY APPRECIABLE BUOYANCY WILL RESIDE TO THE SOUTH OF THE SPATIALLY COMPACT REGION OF FORCED ASCENT IN ASSOCIATION WITH THE DEAMPLIFYING MID-LEVEL WAVE. ...SRN CA AND SRN AZ... IN ASSOCIATION WITH THE PREVIOUSLY MENTIONED DEEP-LAYER LOW CUTTING OFF...500-MB TEMPERATURES AROUND -25C WILL SUPPORT 700-500-MB LAPSE RATES OF 7-7.5 C/KM. DESPITE THESE RELATIVELY STEEP LAPSE RATES...TRAJECTORIES AROUND THE ERN/NRN SEMICIRCLES OF THE LOW WILL NOT SUPPORT SUFFICIENT LOW/MID-LEVEL MOISTURE FOR ANY APPRECIABLE BUOYANCY. WHILE NAM FORECAST SOUNDINGS SUGGEST MARGINAL DESTABILIZATION DURING PEAK HEATING...MOST OTHER GUIDANCE SUGGESTS THAT DRY AIR IN THE LOW/MID LEVELS AND NEAR-ZERO CAPE WILL KEEP THUNDER PROBABILITIES BELOW 10 PERCENT. ..COHEN/EDWARDS.. 12/16/2011 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z