Rain Returns to North Texas
Good morning everyone! Here's the latest on today's severe weather threat. We're still under an ENHANCED risk here in portions of North Texas, including the DFW Metroplex. Possible threats include; tornadoes, damaging hail and damaging winds. ANY storm that forms this afternoon will be capable and likely of becoming quickly severe. Storms should begin forming West of I-35 around 4 pm this afternoon till about 7 pm this evening. Storms should begin to make their way into DFW around 7 pm until Midnight. Do not take these timelines literally, these are only an estimate and could change. BE WEATHER ALERT TODAY. SPC AC 261246 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0746 AM CDT TUE APR 26 2016 VALID 261300Z - 271200Z ...THERE IS A MDT RISK OF SVR TSTMS PORTIONS SRN NEB...CENTRAL/ERN KS...N-CENTRAL THROUGH S-CENTRAL OK... ...THERE IS AN ENH RISK OF SVR TSTMS ELSEWHERE FROM SRN NEB TO CENTRAL TX...WITH LOBE FROM ERN KS TO ERN MO... ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING ENH AREA AND EXTENDING EWD TO LOWER OH VALLEY AND SSWWD TO PORTIONS S-CENTRAL/SW TX... ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS ERN WV TO JERSEY SHORE... ...THERE IS A MRGL RISK OF SVR TSTMS BETWEEN AND IMMEDIATELY SURROUNDING SLGT-RISK AREAS... ...SUMMARY... A SUBSTANTIAL SEVERE-WEATHER EVENT IS EXPECTED TODAY AND TONIGHT OVER PARTS OF THE CENTRAL AND SOUTHERN PLAINS...WITH TORNADOES...DESTRUCTIVE HAIL AND DAMAGING WIND ALL POSSIBLE. DAMAGING WIND ALSO IS EXPECTED FROM A COMPLEX OF THUNDERSTORMS MOVING ACROSS THE LOWER MISSOURI VALLEY AND MIDDLE MISSISSIPPI VALLEY REGION THIS MORNING INTO EARLY AFTERNOON. --- TECHNICAL DISCUSSION --- ...SYNOPSIS... TWO PRINCIPAL MID/UPPER LEVEL FEATURES WILL PLAY PROMINENT ROLES IN CONVECTIVE POTENTIAL TODAY... 1. SHORTWAVE TROUGH -- NOW EVIDENT IN MOISTURE-CHANNEL IMAGERY OVER LH AND SERN LOWER MI -- AND FCST TO MOVE ESEWD TO CENTRAL NY/PA BY 18Z. THIS FEATURE THEN SHOULD WEAKEN AND MOVE OFFSHORE NEW ENGLAND BY 00Z. 2. MAJOR CYCLONE ALOFT...CURRENTLY CENTERED OVER GJT AREA...WITH BASAL SHORTWAVE TROUGH/VORTICITY LOBE LOCATED OVER SERN AZ. INITIALLY PRIMARY 500-MB LOW SHOULD PIVOT NWD TO CENTRAL/ERN WY BY 00Z AND WEAKEN...WITH SHORTWAVE TROUGH EJECTING ENEWD TO TX PANHANDLE/SOUTH PLAINS REGION. LATTER FEATURE SHOULD EVOLVE INTO PRIMARY 500-MB LOW OVER NWRN KS/SWRN NEB REGION BY END OF PERIOD...WITH TROUGH SSEWD ACROSS WRN OK AND SWD OVER EDWARDS PLATEAU REGION OF TX. AT SFC...DUAL 998-MB LOWS WERE ANALYZED AT 11Z...ONE OVER NERN CO NEAR AKO AND ANOTHER BETWEEN RSL-HLC. OUTFLOW BOUNDARY FROM ONGOING NERN KS/SERN NEB CONVECTION HAS REINFORCED BAROCLINICITY OF ANTECEDENT WARM-FRONTAL ZONE...WITH COMBINED BOUNDARY EXTENDING ESEWD TO NW TOP. WAVY/QUASISTATIONARY FRONT EXTENDED FROM THERE ACROSS NWRN/E-CENTRAL MO...BECOMING COLD FRONT FROM CENTRAL IL ENEWD TO SFC LOW OVER CENTRAL NY. NERN-CONUS COLD FRONT SHOULD MOVE ESEWD ACROSS MID ATLC...WHILE LOWER OH VALLEY SEGMENT BECOMES QUASISTATIONARY. BLENDED BOUNDARY OVER CENTRAL PLAINS SHOULD MOVE NWD AS WARM FRONT DURING MIDDAY AND AFTN AHEAD OF PRIMARY SFC LOW TAKING SHAPE OVER NRN KS. DRYLINE...INITIALLY OVER SWRN KS...SERN TX PANHANDLE AND PERMIAN BASIN REGION...SHOULD SHIFT EWD TO WRN OK...W-CENTRAL TX AND NRN COAHUILA THIS AFTN...BEFORE BEING OVERTAKEN FROM N-S BY COLD FRONT EXTENDING SSWWD/SWWD FROM KS LOW. ...CENTRAL/SRN PLAINS... TWO OR THREE ROUNDS OF TSTMS ARE EXPECTED THIS AFTN AND EVENING... INITIATING NEAR DRYLINE AND PERHAPS OVER FREE WARM SECTOR AS WELL. GREATEST THREAT WILL BE ALONG AND S OF COMPOSITE WARM FRONT/OUTFLOW BOUNDARY THAT SHOULD RETREAT BACK TO NEAR KS/NEB BORDER...AND SWD ACROSS CENTRAL/ERN KS AND CENTRAL/ERN OK...INTO CENTRAL TX. COVERAGE SHOULD LESSEN WITH SWD EXTENT FROM THERE. TSTMS WILL PRODUCE VERY LARGE HAIL AND DAMAGING GUSTS. TORNADOES ALSO ARE LIKELY FROM ANY MATURE/DISCRETE SUPERCELLS EITHER 1. IMPINGING ON WARM FRONT/OUTFLOW BOUNDARY OVER KS/NEB BORDER REGION...OR 2. OCCURRING IN WARM-SECTOR ENVIRONMENT OF ENLARGING HODOGRAPHS FROM LATE AFTN INTO EVENING. BEYOND THAT...SPECIFICS ARE STILL RATHER NEBULOUS. FORECAST CERTAINTY AND CLARITY OFTEN INCREASE AS EVENTS GET CLOSER -- BUT NOT ALWAYS. SOMETIMES MESOSCALE AND SMALLER-SCALE ISSUES WITH TIMING AND MODE...THAT ARE NOT APPARENT IN FAVORABLE-LOOKING PATTERNS OF SYNOPTIC MODELS 3-5 DAYS OUT...CAN COMPLICATE FORECAST SCENARIOS AND CAN MAINTAIN IMPORTANT LEVELS OF UNCERTAINTY. THAT IS TRUE IN THIS OUTLOOK. NEVERTHELESS...POTENTIAL REMAINS FOR VERY LARGE/DAMAGING HAIL...SEVERE GUSTS...AND TORNADOES FROM SRN NEB TO NRN AND PERHAPS CENTRAL TX THIS AFTN/EVENING. AS SUCH...HAIL-DRIVEN MDT RISK IS MAINTAINED AND A FEW SIGNIFICANT TORNADOES STILL APPEAR POSSIBLE. IN FACT...SIG-TOR RISK AREA IS EXTENDED SWD INTO PORTIONS N TX TO ACCOUNT FOR POTENTIAL THIS EVENING WHERE SUPERCELLS MAY ENCOUNTER LOW LCL AND FAVORABLE HODOGRAPHS. 12Z RAOBS SHOWED CAPPING STRENGTHENING WITH SWD EXTENT. REGARDLESS...SHORT-FUSED/CONVECTION-ALLOWING GUIDANCE OVER PAST SEVERAL HOURS HAS OFFERED MIXED MESSAGES IN TERMS OF TIMING...COVERAGE AND MODE OF AFTN CONVECTION THROUGH MOST OF THIS CORRIDOR...INCLUDING MODAL TRANSITION AFTER INITIAL RELATIVELY DISCRETE/SUPERCELLULAR STATE. TIMING UNCERTAINTY...AND COVERAGE OF EARLIER VERSUS LATER CONVECTION...ARE IMPORTANT BECAUSE EARLIER TSTMS DURING AFTN WILL MOVE THROUGH LESS-FAVORABLE SRH PRIOR TO MOST FAVORABLE BOUNDARY-LAYER MASS RESPONSE...AND WIND PROFILES CHARACTERIZED BY VEER/BACK/VEER SHAPE. THEY ALSO MAY STABILIZE AIR MASS IN INFLOW REGION OF SOME LATER STORMS. LATER ACTIVITY...ESPECIALLY THAT WHICH IS STILL RELATIVELY DISCRETE IN 22-03Z TIME WINDOW AND NOT INGESTING COLD OUTFLOW -- SHOULD POSE GREATEST THREAT FOR TORNADOES...INCLUDING A FEW SIGNIFICANT ONES. STG MERIDIONAL COMPONENT OF FLOW ALSO INDICATES POTENTIAL FOR MIXED CONVECTIVE MODES TO EVOLVE REASONABLY QUICKLY FROM EARLY-DISCRETE TSTMS. IN ANY EVENT...LARGE HAIL SHOULD BE QUITE COMMON...AND GIANT/DESTRUCTIVE HAIL EXCEEDING 3 INCHES IN DIAMETER IS PROBABLE FROM AT LEAST A FEW STORMS. GIVEN VERY LARGE PRECONVECTIVE BUOYANCY EXPECTED -- E.G. MLCAPE 3500-4500 J/KG AS STEEP MIDLEVEL LAPSE RATES OVERLIE UPPER 60S TO NEAR 70 F SFC DEW POINTS -- RAPID TO EXPLOSIVE UPDRAFT GROWTH IS LIKELY. IN TANDEM WITH PROCESSING OF RICH INFLOW-LAYER MOISTURE BY LARGE UPDRAFTS...PROFUSE HAIL PRODUCTION SHOULD BE EXPECTED. SRH WILL BE MRGL FOR MUCH OF EARLY/MID AFTN OVER WARM SECTOR...BUT INCREASE DURING 22-03Z TIME FRAME...IN SUPPORT OF TORNADO RISK ESPECIALLY WITH ANY DISCRETE TSTMS STILL PRESENT. ...LOWER MO VALLEY TO LOWER OH VALLEY...MORNING INTO AFTN... CLUSTER OF SVR TSTMS INITIALLY OVER NERN KS AND EXTREME SERN NEB IS EXPECTED TO CONTINUE BUILDING ITS COLD POOL AND MOVING ESEWD TO SEWD ACROSS MO INVOF LOW-LEVEL WARM-FRONTAL ZONE. LARGE HAIL...SOME SIGNIFICANT...WILL BE POSSIBLE FOR A FEW HOURS WHILE DISCRETE OR EMBEDDED SUPERCELLS STILL COULD BE FOUND. HOWEVER...PRIMARY THREAT WILL EVOLVE TO DAMAGING WIND AS COLD POOL GROWS IN SIZE AND ORGANIZATION...AND MCS ACCORDINGLY ACCELERATES AND EXPANDS LATERALLY. REF WWS 104/105 AND RELATED MESOSCALE DISCUSSIONS FOR MORE DETAILED NEAR-TERM GUIDANCE. DAMAGING-WIND THREAT MAY EXTEND AS FAR AS LOWEST PART OF OH VALLEY BEFORE MCS ENCOUNTERS SMALLER BUOYANCY AND WEAKENS. ...MID ATLC... WIDELY SCATTERED TSTMS SHOULD DEVELOP MIDDAY INTO AFTN ALONG/AHEAD OF SFC COLD FRONT...IN PLUME OF DCVA IMMEDIATELY PRECEDING MID/UPPER PERTURBATION. ACTIVITY SHOULD MOVE ESEWD...OFFERING SPORADIC SVR HAIL AND DAMAGING GUSTS. CLEARING BEHIND CLOUD/PRECIP REMNANTS OF OVERNIGHT/OH CONVECTION SHOULD PERMIT POCKETS OF FAVORABLE LOW-LEVEL INSOLATION/DESTABILIZATION...LEADING TO WELL-MIXED SUBCLOUD LAYER BENEATH 500-1000 J/KG MLCAPE. NEAR-SFC FLOW WILL BE VEERED WITH STG WLY COMPONENT...AND DEEP-LAYER PROFILES ESSENTIALLY UNIDIRECTIONAL...LIMITING CONVERGENCE. HOWEVER...LACK OF SUBSTANTIAL CINH SHOULD SUPPORT TSTM DEVELOPMENT/MAINTENANCE FOR SEVERAL HOURS AMIDST FAVORABLE SPEED SHEAR. POTENTIAL SHOULD DIMINISH RAPIDLY AFTER DARK AS COLD FROPA OCCURS OVER LARGER SHARE OF AREA AND REMAINING SFC WARM SECTOR COOLS DIABATICALLY. ..EDWARDS/COOK.. 04/26/2016 CLICK TO GET WUUS01 PTSDY1 PRODUCT
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