SPC 1300Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0758 AM CDT SAT AUG 03 2013 VALID 031300Z - 041200Z ...THERE IS A SLGT RISK OF SVR TSTMS OVER MUCH OF THE CNTRL AND NRN HIGH PLNS... ...SYNOPSIS... BROAD...LOW-AMPLITUDE RIDGE WILL PERSIST OVER THE SRN HALF OF THE RCKYS AND PLNS THROUGH SUNDAY WHILE CYCLONIC FLOW CONTINUES OVER THE NE QUARTER OF THE COUNTRY....ALONG THE SRN FRINGE OF HUDSON BAY LOW. OTHERWISE...POSITIVE TILT TROUGH WILL LINGER OVER THE PACIFIC NW AS PART OF THAT SYSTEM /IN THE FORM OF VORT MAX NOW OVER NRN ID/ SHEARS ENE ACROSS NRN MT/SRN SK. AT THE SFC...HIGH PRESSURE WILL PREVAIL FROM THE NRN PLAINS THROUGH THE MID/UPR MS VLY TO THE UPR GRT LKS. S OF THE HIGH...A WEAK COLD FRONT WILL ADVANCE SLOWLY S AND SE ACROSS THE OZARKS...THE LWR OH VLY...THE NRN MID-ATLANTIC STATES AND NEW ENGLAND. THE WRN PART OF THE BOUNDARY SHOULD BECOME STNRY OVER KS...FROM WHERE IT WILL CONTINUE W AND NW INTO ERN CO AND WY. UPSLOPE FLOW AND MOISTURE RETURN NEAR THE FRONT OVER THE CNTRL HIGH PLNS...AND FARTHER N ACROSS PARTS OF MT AND ND...MAY SUPPORT SCTD STRONG TO SVR STORMS IN THOSE REGIONS LATER TODAY INTO TNGT. ...CNTRL HIGH PLNS TODAY THROUGH EARLY SUN... SELY LOW-LVL FLOW INVOF STALLING FRONT WILL ADVECT FAIRLY RICH MOISTURE BY REGIONAL STANDARDS /SFC DEWPOINTS IN THE MID 60S F WITH PW AOA 1.25 IN/ INTO THE HIGH PLNS OF NE CO...ERN WY...AND WRN NEB TODAY THROUGH TNGT...WITH SOMEWHAT LESSER MOISTURE EXPECTED ALONG THE IMMEDIATE CO/WY FRONT RANGE. COUPLED WITH SFC HEATING AND CONTINUING PRESENCE OF STEEP MID-LVL LAPSE RATES ON NW FLANK OF UPR RIDGE...EXPECT AFTN MLCAPE TO RANGE FROM 1500 TO ABOVE 3000 J/KG ACROSS THE REGION. SATELLITE AND MODEL DATA SUGGEST THAT LARGE-SCALE FORCING FOR ASCENT WILL REMAIN LIMITED...TIED LARGELY TO APPARENT UPR IMPULSE NOW IN WRN CO. BUT COMBINATION OF UPSLOPE FLOW AND FRONTAL UPLIFT SHOULD BE SUFFICIENT TO INITIATE SEVERAL ROUNDS OF STORMS THIS AFTN THROUGH TNGT. WITH SELY LOW-LVL WINDS VEERING TO WLY AT 15-20 KTS AT 500 MB...AND WITH SPEEDS OF 50-70 KTS EXPECTED AT 250 MB...SETUP COULD YIELD A FEW SUPERCELLS CAPABLE OF LARGE HAIL AND LOCALLY DMGG WIND. TORNADOES ALSO MAY OCCUR GIVEN LOW LCLS AND BACKED FLOW ALONG AND N OF FRONT IN NE CO/SE WY. ALTHOUGH DEEP SHEAR WILL WEAKEN WITH SWD EXTENT INTO SE CO...NE NM...AND SW KS...SCTD MAINLY MULTICELLULAR STORMS APPEAR LIKELY THAT MAY PRODUCE STG-SVR GUSTS AND SVR HAIL. THIS ACTIVITY MAY EVOLVE INTO ONE OR MORE SLOWLY MOVING CLUSTERS THAT AFFECT THE OK/TX PANHANDLES AND CNTRL KS TNGT. ...NRN PLNS THIS AFTN THROUGH TNGT... WIDELY SCTD TSTMS SHOULD FORM WITH SFC HEATING IN CNTRL MT THIS AFTN...AND PERHAPS ALSO FARTHER E ALONG INVERTED SFC TROUGH. THE STORMS SHOULD INCREASE IN COVERAGE/INTENSITY INTO EARLY EVE...WITH DMGG WIND AND SVR HAIL POSSIBLE AS REGION IS GLANCED BY UPR IMPULSE NOW OVER ID. BACKED LOW-LVL WINDS INVOF SFC TROUGH BENEATH 40-50 KT WLY FLOW AT 500 MB WILL YIELD LONG HODOGRAPHS ABOVE SOME BOUNDARY-LAYER CURVATURE. THIS COULD FOSTER A FEW LONGER LIVED SUPERCELLS POSING A RISK FOR WITH VERY LARGE HAIL AND POSSIBLY A TORNADO OR TWO IN SE MT/NE WY GIVEN FAIRLY RICH MOISTURE /SFC DEWPOINTS IN THE UPR 50S TO LOW 60S F/. MORE DEEPLY-MIXED ENVIRONMENT FARTHER N IN MT MAY FAVOR A SVR WIND THREAT. ONE OR TWO CLUSTERS OF TSTMS MAY PERSIST INTO THE OVERNIGHT EWD INTO THE DAKOTAS...WITH AN ADDITIONAL ISOLD SVR WIND/HAIL POTENTIAL. ...MID-ATLANTIC THIS AFTN/EVE... MODEST SFC HEATING WILL OCCUR AHEAD OF WEAK COLD FRONT MOVING SEWD FROM THE UPR OH VLY/NRN APPALACHIANS. SOMEWHAT GREATER HEATING MAY OCCUR ALONG ERN NC/SE VA/SRN DELMARVA LEE TROUGH. MID-LVL LAPSE RATES WILL REMAIN WEAK. LARGE-SCALE FORCING FOR ASCENT ALSO WILL BE LIMITED AS IT APPEARS THAT REGION WILL BE SUBJECT TO WEAK SHORTWAVE RIDGING OR NEUTRAL HEIGHT CHANGES THROUGH THE DAY. NEVERTHELESS...DAYTIME HEATING OF MODERATELY MOIST AIR...AND FRONTAL/LEE TROUGH UPLIFT...MAY PROVE SUFFICIENT TO PROMOTE A FEW STRONG TO MARGINALLY SVR AFTN STORMS GIVEN 30-40 WLY 700-500 MB MEAN FLOW. LOCALLY DMGG WIND SHOULD BE THE MAIN SVR THREAT...WITH THE ACTIVITY WEAKENING EARLY TNGT. ..CORFIDI/COHEN.. 08/03/2013
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1300.html
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