Jul 8, 2011 1300 UTC Day 1 Convective Outlook | |
Updated: Fri Jul 8 13:04:06 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 081300 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0800 AM CDT FRI JUL 08 2011 VALID 081300Z - 091200Z ...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE NRN PLNS AND NRN HI PLNS... ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE TN VLY/SRN APPALACHIANS TO THE MID ATLANTIC/SRN NEW ENGLAND CST... ...SYNOPSIS... UPR RIDGE WILL REMAIN STNRY ACROSS THE SRN RCKYS AND SRN HALF OF THE PLNS THIS PERIOD AS A FAIRLY STRONG UPR LOW MOVES FROM SRN BC TO THE AB/SK BORDER...AND A LOOSELY ORGANIZED TROUGH PROGRESSES FROM UPR GRT LKS/OH VLY TO THE NEW ENGLAND AND MID ATLANTIC STATES BY 12Z SAT. AT THE SFC...A WELL-DEFINED FRONTAL SYSTEM WILL PRECEDE THE BC UPR LOW. THE COLD FRONT SHOULD REACH ERN AND SRN PORTIONS OF MT BY THIS EVE...AND NE ND...NW SD...AND CNTRL WY BY THE END OF THE PERIOD. AHEAD OF THE COLD FRONT...LEE TROUGH WILL PROGRESS E INTO THE WRN DAKOTAS LATER TODAY...WHILE WARM FRONT NOW FORMING OVER SRN SD ADVANCES NWD INTO CNTRL/ERN ND. ...NRN PLNS TODAY/TNGT... MAIN AREA OF FORCING FOR ASCENT WITH BC LOW WILL REMAIN N OF THE CANADIAN BORDER THROUGH THE PERIOD. BUT ASSOCIATED LWR AMPLITUDE DISTURBANCES MOVING ENE FROM THE NRN INTERMOUNTAIN REGION WILL SPREAD WAVES OF ASCENT ACROSS THE NRN HI PLNS AND THE DAKOTAS TODAY/TNGT AS DEVELOPING WARM FRONT ADVANCES NEWD INTO ND WITH SUBSTANTIAL MOISTURE /PW 1.25-1.75 INCHES/. BY EARLY AFTN...COMBINATION OF RETURNING MOISTURE AND SFC HEATING SHOULD YIELD AN AXIS OF SBCAPE AOA 2000 J/KG FROM FAR ERN MT AND WRN ND SEWD INTO MUCH OF SD...ALONG/AHEAD OF LEE TROUGH AND ALONG/SW OF WARM FRONT. THIS DESTABILIZATION ALONG WITH MODEST ASCENT WITH THE LOW AMPLITUDE WAVES SHOULD FOSTER INTENSIFICATION OF EXISTING STORMS OVER THE WRN DAKOTAS BY EARLY AFTN. OTHER STORMS LIKELY WILL FORM A BIT LATER INVOF LEE TROUGH SWD INTO NEB...AND THE WARM AND COLD FRONTS. 40 KT WSWLY MID LVL FLOW AND INCREASING HIGH LVL WINDS SHOULD SUPPORT SUPERCELLS...EVEN WITHIN STRENGTHENING ACTIVITY LEFT OVER FROM OVERNIGHT CONVECTION. THESE STORMS COULD YIELD VERY LARGE HAIL...LOCALLY DMGG WIND...AND POSSIBLY A COUPLE TORNADOES. THE LATTER THREAT SHOULD BE GREATEST NEAR THE WARM FRONT IN CNTRL ND/SD LATE THIS AFTN THROUGH EARLY TNGT. A MORE ORGANIZED SVR WIND THREAT MAY EVOLVE THIS EVE/TNGT IN THE CNTRL/ERN DAKOTAS AS THE STORMS EVOLVE INTO FORWARD-PROPAGATING SEGMENTS. ONE OR MORE NOCTURNAL MCSS WITH AT LEAST A SPORADIC SVR WIND/HAIL THREAT LIKELY WILL PERSIST THROUGH EARLY SAT. THESE SHOULD MOVE MAINLY ESE TO SE INTO NRN MN...NE NEB...AND POSSIBLY NW KS...SUPPORTED BY 40+ KT SW TO SSWLY LLJ. WEST OF THE HIGHER THETA-E ENVIRONMENT DESCRIBED ABOVE...A SEPARATE AREA OF HIGH-BASED SUPERCELLS AND/OR BRIEF BOWING LINE SEGMENTS MAY FORM INVOF COLD FRONT OVER THE HIGHER TERRAIN OF NRN WY/SRN MT LATER TODAY/TNGT AS REGION IS GLANCED BY BASE OF MAIN UPR TROUGH. ALTHOUGH SPARSE MOISTURE WILL LIMIT INSTABILITY...50 KT MID LVL WLY FLOW AND STEEPENING MID LVL LAPSE RATES MAY YIELD SVR HAIL AND WIND. THESE STORMS SHOULD WEAKEN OVER ERN MT OR PERHAPS THE FAR WRN DAKOTAS LATE TNGT/EARLY SAT. ...TN VLY/SRN APPALACHIANS TO MID ATLANTIC CST TODAY... SHORTWAVE TROUGH NOW OVER SRN IL SHOULD MOVE STEADILY E TODAY...MORE OR LESS IN TANDEM WITH IMPULSE AMPLIFYING ESE ACROSS ONT. AHEAD OF THE IL TROUGH...RADAR/SATELLITE LOOPS SUGGEST POSSIBLE PRESENCE OF WEAK CIRCULATIONS LEFT OVER FROM OVERNIGHT CONVECTION IN THE LWR TN VLY. A BELT OF SEASONABLY STRONG 35-40 KT WSWLY MID LVL FLOW WILL PRECEDE/ACCOMPANY THESE DISTURBANCES AS THEY CONTINUE E ACROSS PARTS OF THE APPALACHIANS AND THE MID ATLANTIC STATES. AT LWR LVLS...WEAK STNRY FRONT ORIENTED PARALLEL TO THE UPR JET...SIMILARLY ORIENTED OUTFLOW BOUNDARIES FROM OVERNIGHT STORMS...AND LEE TROUGH E OF THE MOUNTAINS EACH WILL SERVE TO FOCUS DIURNALLY ENHANCED STORMS OVER THE REGION TODAY. WITH VERY RICH MOISTURE IN PLACE /PW AOA 2.00 INCHES/...AND EXPECTED CORRIDORS OF STRONG SFC HEATING...SETUP COULD YIELD NUMEROUS BANDS/CLUSTERS OF STRONG STORMS WITH DMGG WIND AND MARGINALLY SVR HAIL...DESPITE MODEST MID LVL LAPSE RATES. WHILE A BRIEF SUPERCELL OR TWO MAY OCCUR...MAINLY OVER THE MID-ATLANTIC...MULTICELL CLUSTERS WITH BOWING SEGMENTS/WET MICROBURSTS SHOULD BE THE MAIN SVR THREAT. ONE OR TWO LARGER ENE-MOVING MCSS MAY EVOLVE...ESPECIALLY OVER NRN NC...VA AND ERN MD/DE/NJ. FARTHER N...AN ISOLD SVR RISK MAY EVOLVE AHEAD OF THE ONT DISTURBANCE AND ASSOCIATED COLD FRONT OVER WRN/CNTRL NY. INSTABILITY WILL BE WEAKER RELATIVELY TO POINTS FARTHER S...BUT MODEST WLY FLOW ALOFT MAY AUGMENT STORM ORGANIZATION...WITH HAIL/GUSTY WINDS POSSIBLE THROUGH EARLY EVE. ..CORFIDI/SMITH.. 07/08/2011 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z