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| Probabilistic Tornado Graphic | |||||||||
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| 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. |
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| Probabilistic Damaging Wind Graphic | |||||||||
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| 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. |
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| Probabilistic Large Hail Graphic | |||||||||
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| 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. |
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SPC AC 031931 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0231 PM CDT TUE SEP 03 2013 VALID 032000Z - 041200Z ...NO SVR TSTM AREAS FORECAST... ASIDE FROM SLIGHT SPATIAL ADJUSTMENTS TO THE GENERAL TSTM AND SEVERE PROBABILITY LINES...THE CURRENT FORECAST APPEARS ON TRACK WITH NO SUBSTANTIVE CHANGES MADE. ..MEAD.. 09/03/2013 .PREV DISCUSSION... /ISSUED 1129 AM CDT TUE SEP 03 2013/ ...SYNOPSIS... AN UPPER LOW IS FORECAST TO REMAIN IN PLACE JUST OFF THE PAC NW COAST THIS PERIOD...WHILE AN EXPANSIVE RIDGE PERSISTS FROM THE S CENTRAL PORTION OF THE COUNTRY NWD ACROSS THE ROCKIES. MEANWHILE...SLOW EWD PROGRESS OF THE ERN U.S. UPPER TROUGH IS EXPECTED. AT THE SURFACE...A ROUGHLY N-S BAROCLINIC ZONE WILL REMAIN OVER THE PAC NW...WHILE IN THE EAST A COLD FRONT ADVANCES SLOWLY ACROSS THE ATLANTIC COAST REGION THROUGH THE PERIOD. ...ERN NEW ENGLAND... WHILE CLOUD COVER REMAINS FAIRLY EXPANSIVE ACROSS A GOOD PORTION OF NEW ENGLAND...ADDITIONAL/MODEST PRE-FRONTAL DESTABILIZATION WILL OCCUR INTO THIS AFTERNOON...SUPPORTING AN INCREASE IN CONVECTIVE COVERAGE OVER SRN NEW ENGLAND...AND INITIATION OF ISOLATED STORMS FARTHER N. A CLUSTER OF CELLS ONGOING ATTM INVOF LONG ISLAND MAY PROVE TO BE THE MOST VIGOROUS CONVECTION OF THE EVENT AS THE CONVECTION SPREADS/EXPANDS ENEWD ACROSS RI AND SERN MA. HOWEVER...EXTENSIVE ANVIL DEBRIS WILL HINDER FURTHER DESTABILIZATION AND THUS SHOULD LIMIT OVERALL SEVERE RISK. GIVEN MID-LEVEL FLOW IN THE 35 TO 4O KT RANGE ACROSS THIS REGION...A FEW STRONGER CELLS WILL LIKELY ORGANIZE LOCALLY THIS AFTERNOON. HOWEVER...OVERALL SEVERE RISK STILL SEEMS LIKELY TO REMAIN BELOW SLIGHT RISK/15% COVERAGE THRESHOLD. ...ERN NC VICINITY... STORMS ARE ONGOING ATTM ACROSS PORTIONS OF ERN NC AND ADJACENT SERN VA...AND ARE FORECAST TO INCREASE/EXPAND IN COVERAGE OVER THE NEXT 1-2 HOURS FROM SERN VA SWWD INTO ERN SC AS A VERY MOIST LOW-LEVEL AIRMASS CONTINUES TO HEAT/DESTABILIZE. DESPITE LIKELIHOOD FOR NUMEROUS STORMS BY THIS AFTERNOON...BACKGROUND WIND FIELD IS -- AND IS EXPECTED TO REMAIN -- GENERALLY UNSUPPORTIVE OF SUBSTANTIAL CONVECTIVE ORGANIZATION...AND THUS ISOLATED/PULSE-TYPE SEVERE RISK IS EXPECTED TO BE MOST PREVALENT. STILL...THE DEGREE OF INSTABILITY AND NUMBER OF STORMS EXPECTED SUGGESTS SOME POTENTIAL FOR UPSCALE GROWTH DUE TO COLD POOL ORGANIZATION -- WHICH COULD LOCALLY ENHANCE SEVERE RISK. THAT SAID...EXPECTED SEVERE WEATHER COVERAGE OVERALL STILL APPEARS LIKELY TO REMAIN BELOW 15%/SLIGHT RISK THRESHOLD -- AND THUS PROBABILITY UPGRADE WILL BE LIMITED TO ONLY 5% COVERAGE ATTM. FOR ADDITIONAL SHORT-TERM DETAILS...PLEASE REFER TO SWOMCD #1831. ...INTERIOR PAC NW... SCATTERED STORM DEVELOPMENT IS FORECAST ACROSS THE PAC NW VICINITY...IN CYCLONIC/SSWLY FLOW ALOFT AHEAD OF THE OFFSHORE UPPER LOW. WITH A RELATIVELY MOIST/HIGH PW AIRMASS IN PLACE...DIFFERENTIAL HEATING OVER THE HIGHER TERRAIN WILL RESULT IN AT LEAST MODEST DESTABILIZATION AND SUBSEQUENT CONVECTIVE INITIATION. THOUGH LOW-LEVEL FLOW IS PROGGED TO REMAIN FAIRLY WEAK...THE BELT OF ENHANCED MID-LEVEL SSWLYS ATOP THE AREA MAY SUPPORT LOCAL/MULTICELL ORGANIZATION...AND THUS POTENTIAL FOR A FEW LOCALLY DAMAGING WIND GUSTS AND/OR HAIL EVENTS. ...NRN HIGH PLAINS/BLACK HILLS AREA... DESPITE PRESENCE OF LARGE-SCALE UPPER RIDGING...A WEAK VORT MAX MOVING SLOWLY ACROSS THE NRN HIGH PLAINS MAY NEUTRALIZE THE BROADER TENDENCY FOR BACKGROUND SUBSIDENCE TO SOME DEGREE. AS SUCH...DIFFERENTIAL HEATING OVER THE BLACK HILLS -- AND POSSIBLY WEAK UPSLOPE FLOW INTO NWRN WY -- MAY ALLOW A COUPLE OF ISOLATED CELLS TO DEVELOP THIS AFTERNOON. SHEAR WILL REMAIN MODEST ACROSS THIS REGION. HOWEVER...A DRY/WELL-MIXED BOUNDARY LAYER MAY FACILITATE POTENTIAL FOR A STRONGER DOWNDRAFT OR TWO -- WARRANTING MAINTENANCE OF ONGOING 5% WIND PROBABILITY IN THIS AREA. STORMS MAY LINGER INTO THE EVENING...SHIFTING SEWD ACROSS SWRN SD AS A LOW-LEVEL JET DEVELOPS...BUT EXPECT ANY SEVERE POTENTIAL TO WANE AFTER SUNSET AS THE BOUNDARY LAYER STABILIZES. CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z |
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