DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0100 AM CDT FRI MAY 08 2015 VALID 081200Z - 091200Z ...THERE IS A MDT RISK OF SVR TSTMS OVER SW OK AND FAR NW TX... ...THERE IS AN ENH RISK OF SVR TSTMS FROM SERN CO TO MOST OF OK AND PARTS OF N TX... ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN GREAT PLAINS... ...THERE IS A MRGL RISK OF SVR TSTMS FROM THE MIDWEST TO THE CNTRL/SRN GREAT PLAINS... ...SUMMARY... SCATTERED TO PERHAPS WIDESPREAD SEVERE THUNDERSTORMS MAY DEVELOP ACROSS PORTIONS OF THE SOUTHERN HIGH PLAINS TO ALONG THE RED RIVER...MAINLY FROM MIDDAY THROUGH THIS EVENING. VERY LARGE HAIL...DAMAGING WINDS...AND TORNADOES WILL BE POSSIBLE. ...SYNOPSIS... INITIALLY VIGOROUS SHORTWAVE TROUGH OVER SRN CA WILL DAMPEN AS IT EJECTS TOWARDS THE FOUR CORNERS AREA THROUGH EARLY SAT. A SUBTLE MID-LEVEL IMPULSE EVIDENT IN WATER-VAPOR IMAGERY OVER AZ TO NW MEXICO SHOULD REACH THE SRN HIGH PLAINS BY EARLY TO MID AFTERNOON WITH AN ASSOCIATED JET STREAK FROM THE TRANS-PECOS TO NW TX. GUIDANCE VARIES MARKEDLY WITH THE EVOLUTION OF THE DRYLINE BY AFTERNOON IN THE WAKE OF AN ONGOING MCS FROM ERN OK TO N-CNTRL TX AND POTENTIAL MORNING CONVECTION N OF THE TRAILING MCS OUTFLOW THAT EXTENDS TOWARDS THE CONCHO VALLEY. THE DRYLINE SHOULD MIX INTO PARTS OF WRN TX BEFORE RETREATING WWD TONIGHT WITH A LOW-LEVEL MOISTURE SURGE TOWARDS THE TX/NM BORDER IN ADVANCE OF THE FOUR CORNERS TROUGH. ...SRN GREAT PLAINS... CONFIDENCE IS LOWER THAN PREVIOUS FORECAST WITH A POTENTIALLY COMPLEX/MESSY CONVECTIVE EVOLUTION THAT COULD LIMIT THE OVERALL RISK. CONSIDERED A CATEGORICAL DOWNGRADE THIS OUTLOOK...BUT A HIGHER-END SCENARIO CANNOT BE COMPLETELY DISCOUNTED AT THIS TIME. MOISTURE RETURN IS ONGOING ACROSS THE EDWARDS PLATEAU WITH UPPER 60S TO LOWER 70S SURFACE DEW POINTS S OF THE TRAILING OUTFLOW BOUNDARY OVER THE CONCHO VALLEY WITHIN A 40-KT LLJ. ISENTROPIC ASCENT N OF THIS BOUNDARY COUPLED WITH DIFLUENT HIGH-LEVEL FLOW AND MID-LEVEL DCVA ASSOCIATED WITH THE LEAD MID-LEVEL IMPULSE SHOULD RESULT IN CONVECTION DEVELOPING LATER THIS MORNING FROM THE TX S PLAINS TOWARDS THE PANHANDLE. THIS TIMING APPEARS UNFAVORABLE FOR ROBUST DIURNAL DESTABILIZATION WITHIN THIS CORRIDOR AND ALSO APPEARS QUESTIONABLE FARTHER E IN THE WAKE OF EXTENSIVE CONVECTIVE OVERTURNING ON THU. MORNING CONVECTION MAY GROW UPSCALE INTO AN MCS BY MIDDAY IN SOMEWHAT SIMILAR FASHION TO THU OWING TO THE LACK OF A VERY STRONG EML RELATIVE TO THE DEGREE OF TROPICAL MOISTURE...CHARACTERIZED BY MEAN MIXING RATIOS OF 15-17 G/KG IN 08/00Z RAOBS ALONG THE WRN GULF COAST. STRENGTHENING MID-LEVEL SWLYS SHOULD FAVOR EMBEDDED SUPERCELL AND BOWING/LEWP STRUCTURES AS ACTIVITY PROBABLY DEVELOPS E/S THROUGH THE AFTERNOON. LARGE HAIL /SOME SIGNIFICANT/...DAMAGING WINDS AND A FEW TORNADOES ARE ALL POSSIBLE ALONG THE LEADING EDGE OF THE MCS...AND POTENTIAL REDEVELOPMENT SWWD ALONG TRAILING OUTFLOW/DRYLINE INTERSECTION. LOW-LEVEL FLOW SHOULD REMAIN MODEST THROUGH MUCH OF THE AFTERNOON...PRIOR TO INCREASING TOWARDS 00Z. WITH EXTENSIVE CONVECTION AND MESSY CONVECTIVE MODE PROBABLY ONGOING BY THIS TIME...THE EXTENT OF HIGHER-END TORNADO POTENTIAL MAY BE SUBDUED. ADDITIONAL STORMS SHOULD FORM WITHIN THE LOW-LEVEL UPSLOPE REGIME ACROSS THE HIGH PLAINS FROM SERN CO INTO PARTS OF THE TX PANHANDLE. DEEP-LAYER WIND PROFILES WOULD SUPPORT ALL SEVERE HAZARDS...BUT THE OVERALL RISK WILL LIKELY BE DEPENDENT ON THE DEGREE OF BOUNDARY-LAYER MOISTURE WHICH MAY BE TEMPERED BY MORNING CONVECTION TO THE SE. ANOTHER ROUND OF NOCTURNAL STORMS MAY FORM BY 12Z/SAT AS MID-LEVEL HEIGHT FALLS OVERSPREAD A SURGE OF LOW-LEVEL MOISTURE APPROACHING THE TX/NM BORDER. ISOLATED SEVERE HAIL SHOULD BE THE MAIN RISK.
vendredi 8 mai 2015
May 8, 2015 0600 UTC Day 1 Convective Outlook
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