Jul 12, 2011 2000 UTC Day 1 Convective Outlook | |
Updated: Tue Jul 12 20:03:10 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 121959 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0259 PM CDT TUE JUL 12 2011 VALID 122000Z - 131200Z ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN ROCKIES...NRN HIGH PLAINS...CNTRL ROCKIES...CNTRL PLAINS...MID-MO VALLEY...MID-MS VALLEY...OH VALLEY...TN VALLEY AND SRN APPALACHIAN MTNS... ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF FAR NRN MAINE... SEVERAL CHANGES HAVE BEEN MADE TO THE OUTLOOK FOR THE 20Z ISSUANCE. THE FIRST IS TO REDUCE THE AREAL COVERAGE OF THE 30 PERCENT WIND DAMAGE PROBABILITY. THE ENHANCED WIND DAMAGE THREAT SHOULD BE CONFINED TO NE MO...SCNTRL IL AND WRN KY. THIS WILL BE THE FAVORED CORRIDOR ALONG A GRADIENT OF STRONG INSTABILITY FOR A LINE-SEGMENT IF A COLD POOL CAN BECOME ESTABLISHED WITH THE INTENSE STORMS IN NE MO. THE SECOND CHANGE IS TO REMOVE THE CAROLINAS FROM THE SLIGHT RISK AREA. VISIBLE SATELLITE IMAGERY SUGGESTS CUMULUS DEVELOPMENT IN THE CAROLINAS IS LIMITED AND MAY BE DUE TO SUBSIDENCE. ALTHOUGH A FEW MARGINALLY SEVERE STORMS MAY INITIATE LATE THIS AFTERNOON IN THE CAROLINAS AS SHORT-TERM MODELS SUGGEST...CONVECTIVE COVERAGE IS EXPECTED TO REMAIN ISOLATED DUE TO SATELLITE TRENDS. THE THIRD CHANGE TO THE OUTLOOK IS TO ADD A SLIGHT RISK AREA TO FAR NRN MAINE WHERE RADAR SUGGESTS SEVERE STORMS ARE ONGOING WITH A THREAT FOR HAIL AND WIND DAMAGE. OTHERWISE...THUNDER HAS BEEN REMOVED FAR PARTS OF SOUTH TX AND THUNDER HAS BEEN ADDED TO PARTS OF AZ NEAR THE MOGOLLON RIM. ..BROYLES.. 07/12/2011 .PREV DISCUSSION... /ISSUED 1127 AM CDT TUE JUL 12 2011/ ...LOWER MO VALLEY INTO KY... BAND OF ELEVATED STORMS IS MOVING EWD ACROSS CENTRAL IA THIS MORNING...WITH INDICATIONS OF NEW UPDRAFTS DEVELOPING ALONG THE LEADING EDGE OF CONVECTION. THIS ACTIVITY IS CURRENTLY JUST NORTH OF THE PRIMARY SURFACE COLD FRONT THAT EXTENDS FROM THE SRN GREAT LAKES INTO NRN KS. A VERY MOIST AIR MASS IS PRESENT SOUTH OF THE FRONT WHERE SURFACE DEW POINTS ARE IN THE LOW/MID 70S FROM NRN/ERN MO INTO THE OH AND TN VALLEYS...AND WITH CLEAR SKIES OVER THIS AREA...STRONG DIABATIC HEATING WILL OCCUR AND CONTRIBUTE TO FURTHER DESTABILIZATION /MLCAPE REACHING 3000-4000 J PER KG/. THERE IS POTENTIAL FOR THE IA CONVECTION TO GRADUALLY INCREASE AND BUILD SWD INTO THE MORE UNSTABLE ENVIRONMENT ALONG THE SRN EDGE OF 25-30 KT WLY FLOW ALOFT. IF AN ORGANIZED COLD POOL CAN DEVELOP AND STORMS BEGIN TO PROPAGATE EWD/ESEWD...THERE WILL BE INCREASING POTENTIAL FOR DAMAGING WINDS TO OCCUR WITH THE MCS. ADDITIONAL STORMS MAY ALSO DEVELOP ALONG A CONVERGENCE ZONE FROM CENTRAL MO EWD INTO THE LOWER OH VALLEY AS THE CAP GRADUALLY WEAKENS THIS AFTERNOON. ALTHOUGH FLOW ALOFT AND VERTICAL SHEAR WILL BE WEAKER WITH SWD EXTENT...VERY LARGE INSTABILITY WILL SUPPORT OCCASIONAL SEVERE MICROBURSTS WITH STRONGER CELLS. ...SRN APPALACHIANS INTO SERN STATES... 12Z SOUNDINGS AT FFC/BMX EXHIBITED A LAYER OF 15-20 KT NELY WINDS JUST ABOVE 700 MB...SUGGESTING THAT CURRENT STORMS FROM ERN TN INTO NWRN GA/NERN AL WILL SLOWLY SPREAD SWD/SWWD THIS AFTERNOON. STRONG HEATING WILL FURTHER INCREASE LARGE DCAPE PRESENT IN THE 12Z SOUNDINGS AND SUGGEST POTENTIAL FOR WIDELY SCATTERED WET MICROBURSTS THIS AFTERNOON. ...SRN VA/CAROLINAS... VERY MOIST AND UNSTABLE AIR WILL BE PRESENT THIS AFTERNOON FROM SE VA INTO THE CNTRL AND ERN CAROLINAS...WITH LOW TO MID 70S F DEWPOINTS AND PW CLOSE TO 2 INCHES. EARLIER CLOUDS ARE THINNING AND WILL THIS WILL PERMIT AREAS OF STRONGER HEATING AND DESTABILIZATION. MODERATE NW FLOW WILL PERSIST ON THE NE FRINGE OF UPR RIDGE...AND THIS SETUP MAY SUPPORT SCTD STRONG TO SVR STORMS BY LATE AFTN OR EVE. THESE MAY MERGE INTO A SMALL MCS...WITH A THREAT FOR MAINLY DMGG WIND AND POSSIBLY MARGINALLY SVR HAIL CONTINUING THROUGH EARLY TNGT. ...NRN/CENTRAL HIGH PLAINS... MOIST SELY UPSLOPE FLOW IS FORECAST TO STRENGTHEN THIS AFTERNOON AS PRESSURES FALL OVER THE NRN ROCKIES/INTERMOUNTAIN REGION. THIS IS MAINTAINING CURRENT LOW CLOUD DECK OVER ERN WY/SWRN SD AND THE NEB PANHANDLE...BUT CLOUDS ARE EXPECTED TO DIMINISH THIS AFTERNOON AND ALLOW HEATING/DESTABILIZATION TO OCCUR. STORMS ARE EXPECTED TO DEVELOP OVER THE HIGHER TERRAIN DURING THE MID/LATE AFTERNOON AND SLOWLY MOVE NEWD INTO THE HIGH PLAINS. ALTHOUGH MID LEVEL SWLY FLOW WILL BE MODEST AT BEST /20-25 KT/...STRONG DIRECTIONAL SHEAR WILL AID IN STORM ORGANIZATION WITH MULTICELL AND ISOLATED SUPERCELL STRUCTURES POSSIBLE. HAIL AND STRONG WIND GUSTS WILL BE THE PRIMARY THREATS. ...WRN/CENTRAL MT... SMALL CLUSTER OF MORNING STORMS OVER SERN ID/EXTREME NWRN WY APPEARS TO BE ASSOCIATED WITH A WEAK PERTURBATION IN THE UPPER FLOW THAT HAS LIFTED NWD ACROSS THE ERN GREAT BASIN. THIS FEATURE IS LIKELY TO CONTINUE NEWD AND ENHANCE THUNDERSTORM POTENTIAL INTO PARTS OF CENTRAL AND POSSIBLY NERN MT. PERSISTENT SELY LOW LVL FLOW WILL MAINTAIN/AUGMENT LOW LVL MOISTURE OVER NRN AND ERN MT TODAY...WHERE SFC DEWPOINTS IN THE 50S SHOULD YIELD SBCAPE OF 1000-1500 J/KG BY AFTN. 30-35 KT DEEP SW TO WSWLY SHEAR WILL EXIST OVER REGION...DESPITE FACT THAT LOW NOW OFF VANCOUVER ISLAND WILL REMAIN WELL TO THE WEST. COMBINATION OF MODEST UPSLOPE FLOW AND HEATING SHOULD SUPPORT ADDITIONAL STORM DEVELOPMENT FROM NRN/CNTRL ID INTO WRN/SW MT BY AFTN. THE STORMS SUBSEQUENTLY SHOULD SPREAD NNE ACROSS CNTRL AND NRN MT...POSING A THREAT FOR HAIL AND LOCALLY DMGG WIND. ...SRN KS/NRN OK AREA... UPR VORT NOW OVER EXTREME NWRN OK SHOULD MOVE SLOWLY ENE TODAY/TNGT...ON WRN FRINGE OF LWR MS VLY UPR RIDGE. SFC HEATING AND WEAK ASCENT WITH SYSTEM MAY FOSTER ISOLD TO WDLY SCTD TSTMS OVER PARTS OF NW TX...WRN/NRN OK...AND SRN KS. GIVEN VERY WARM/DRY SUB CLOUD LAYER ENVIRONMENT...SOME STORMS MAY YIELD MICROBURSTS THIS AFTERNOON AND EVENING. CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z