SPC kicks risk up a notch
Posted by
JAC on 6/9/2011, 2:57 pm

DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1129 AM CDT THU JUN 09 2011 VALID 091630Z - 101200Z ...THERE IS A MDT RISK OF SVR TSTMS ACROSS SOUTHERN VERMONT...SOUTHERN NEW HAMPSHIRE...MUCH OF MASSACHUSETTS...CONNECTICUT...SOUTHEAST NEW YORK...AND PENNSYLVANIA... ...THERE IS A SLGT RISK OF SVR TSTMS NEW ENGLAND WSWWD INTO THE CENTRAL PLAINS... ...THERE IS A SLGT RISK OF SVR TSTMS ERN WY AND VICINITY... ...SYNOPSIS... SUPPRESSION OF THE S CENTRAL AND SERN U.S. UPPER RIDGE IS FORECAST TO CONTINUE TODAY...AS THE WRN U.S. TROUGH SHIFTS EWD AND AT THE SAME TIME AN ERN CANADA TROUGH MOVES EWD -- FORCING FALLING HEIGHTS/CYCLONIC FLOW TO SPREAD ACROSS THE NORTHEAST CONUS. AT THE SURFACE...COLD FRONT WILL CONTINUE CROSSING THE ST. LAWRENCE VALLEY/LOWER GREAT LAKES REGION THIS MORNING...AND WILL BECOME A FOCUS FOR WIDESPREAD SEVERE STORM DEVELOPMENT AS IT SHIFTS INTO NEW ENGLAND/NY/PA. THE OUTFLOW-REINFORCED FRONT WILL LINGER WWD ACROSS THE OH VALLEY...AND WILL RETREAT NWD WITH TIME ACROSS THE MO VALLEY REGION WITH FRONTAL LOW DEVELOPMENT EXPECTED IN THIS AREA IN RESPONSE TO EJECTING PIECES OF THE WRN U.S. TROUGH. ...NEW ENGLAND WSWWD ACROSS THE MIDWEST/OH VALLEY... POTENTIALLY WIDESPREAD/DAMAGING WIND EVENT IS FORECAST ACROSS THE NORTHEAST U.S. TODAY. ONGOING CONVECTION ACROSS THIS RISK AREA HAS DIMINISHED EARLY THIS MORNING...WITH CONVECTIVE-COOLED AIR OVER SRN NEW ENGLAND EXPECTED TO CONTINUE RECOVERING. AS A LARGE PLUME OF VERY STEEP LAPSE RATES ATOP A VERY MOIST /NEAR 70 DEWPOINTS/ BOUNDARY LAYER COMBINES WITH CLEARING SKIES SUPPORTING STRONG WARM SECTOR HEATING...MIXED-LAYER CAPE OF 2000 TO 3000 J/KG IS EXPECTED TO DEVELOP QUICKLY THROUGH EARLY AFTERNOON. AN OUTFLOW BOUNDARY INVOF THE MID AND UPPER OH VALLEY -- AND THE COLD FRONT NOW CROSSING THE LOWER GREAT LAKES/ST. LAWRENCE VALLEY -- WILL BECOME THE FOCUS FOR WIDESPREAD STORM DEVELOPMENT OVER THE NEXT COUPLE OF HOURS...SHIFTING SEWD WITH TIME ACROSS NY/PA/OH AND MUCH OF NEW ENGLAND. WITH STRONGEST DEEP-LAYER WLYS PROGGED TO REMAIN N OF THE MASON/DIXON LINE...MOST WIDESPREAD SEVERE THREAT APPEARS TO EXIST FROM SWRN PA ENEWD ACROSS SRN AND ERN NY INTO SRN NEW ENGLAND. HERE...VERY LARGE HAIL THREAT WITH INITIAL SUPERCELL STORMS SHOULD EVOLVE INTO MORE OF A DAMAGING WIND THREAT AS CONVECTION EVOLVES INTO ONE OR MORE BOWING LINES WHICH WILL MOVE QUICKLY EWD. A COUPLE OF TORNADOES MAY ALSO OCCUR -- PARTICULARLY EARLY ON WITH MORE ISOLATED STORMS. BY THIS EVENING...CONVECTION WILL HAVE SHIFTED WELL SEWD...FROM SRN AND ERN NEW ENGLAND WSWWD INTO NRN VA/WV. WITH WEAKER FLOW S OF THE MASON/DIXON LINE...MORE ISOLATED SEVERE POTENTIAL IS FORECAST. ...MID MO VALLEY REGION AND VICINITY SWWD INTO NRN OK... COMPLEX SCENARIO EXISTS ACROSS THE CENTRAL PLAINS/MID MO VALLEY REGION...AS EARLY MORNING SHORT-WAVE RIDGING ALOFT IS FORECAST TO CONTINUE WEAKENING AS TROUGHING SHIFTS ENEWD. AS SURFACE LOW REDEVELOPS NWD INTO THE MID MO VALLEY REGION IN RESPONSE TO THE APPROACHING TROUGH...AND THE SURFACE FRONT OVER NRN MO RETREATS NWD INTO IA...STORM DEVELOPMENT WILL OCCUR -- SUPPORTED BY MODERATE TO STRONG WARM SECTOR DESTABILIZATION. WITH BACKING/STRENGTHENING LOW-LEVEL FLOW INVOF THE DEVELOPING LOW/WARM FRONT BENEATH 50 KT SWLYS AT MID LEVELS SPREADING ATOP THIS AREA...SHEAR/INSTABILITY COMBINATION WILL BE QUITE SUPPORTIVE OF SUPERCELLS. ALONG WITH THREAT FOR VERY LARGE HAIL...ISOLATED TORNADOES WILL ALSO BE POSSIBLE -- MAINLY FROM SERN NEB/NERN KS EWD INTO NRN MO/SRN IA. LOCALLY DAMAGING WINDS WILL ALSO BE POSSIBLE...POSSIBLY BECOMING MORE LIKELY WITH TIME AS SOME CLUSTERING OF CONVECTION OCCURS INTO THE EVENING HOURS. MORE ISOLATED STORM DEVELOPMENT IS FORECAST TO OCCUR SWD ACROSS CENTRAL/ERN KS AND INTO OK...NEAR AND AHEAD OF THE SURFACE COLD FRONT. ALONG WITH POTENTIAL FOR HAIL...DEEP/DRY SUB-CLOUD MIXED LAYER WILL SUPPORT EVAPORATIVELY-ENHANCED DOWNDRAFTS -- AND THUS SOME LIKELIHOOD FOR LOCALLY DAMAGING GUSTS. ...ERN WY AND VICINITY... DESPITE FAIRLY EXTENSIVE MORNING CLOUD COVER...SOME DESTABILIZATION WILL SUPPORT AFTERNOON STORM DEVELOPMENT -- INITIALLY OVER THE HIGHER TERRAIN BUT THEN SPREADING EWD INTO LOWER ELEVATIONS. WITH STRONG /50 TO 60 KT/ MID-LEVEL WLY JET STREAK SHIFTING ACROSS THIS REGION...SHEAR WILL SUPPORT ORGANIZED/SUPERCELL STORMS...AND THUS -- DESPITE POSSIBLY LIMITED INSTABILITY IN PARTS OF THE AREA -- CONTINUATION OF SLIGHT RISK FOR HAIL IS WARRANTED. MORE ISOLATED THREAT APPEARS TO EXTEND SWD INTO THE CO FRONT RANGE AREA...AS SUBSIDENCE EVIDENT IN THE WAKE OF A SEPARATE/DEPARTING SHORT-WAVE TROUGH SHOULD LIMIT COVERAGE A BIT WITH SWD EXTENT. ..GOSS/SMITH.. 06/09/2011 |
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In this thread:
Squall Line could hit NYC around Rush Hour -
JAC,
6/9/2011, 2:53 pm- Re: Squall Line could hit NYC around Rush Hour - Fred, 6/10/2011, 2:29 pm
- CONCERNING...SEVERE THUNDERSTORM WATCH - JAC, 6/9/2011, 4:52 pm
- Re: Squall Line could hit NYC around Rush Hour - ArgosyTn, 6/9/2011, 4:04 pm
- Re: Squall Line could hit NYC around Rush Hour - ArgosyTn, 6/9/2011, 3:35 pm
- Re: Squall Line could hit NYC around Rush Hour - Fred, 6/9/2011, 3:23 pm
- Boston has a slight chance for a tornado. High probability for damaging winds. - JAC, 6/9/2011, 3:16 pm
- Mt Holly Radar - JAC, 6/9/2011, 3:04 pm
- Hail and High Winds could be a big time threat - JAC, 6/9/2011, 3:02 pm
- SPC kicks risk up a notch - JAC, 6/9/2011, 2:57 pm
- 5500 CAPE between NYC and the Squall Line - this could be nasty - JAC, 6/9/2011, 2:55 pm
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