Categorical Day1 1200Z Outlook Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area SLIGHT 218,492 36,955,106 Chicago, IL...Detroit, MI...Milwaukee, WI...Cleveland, OH...Toledo, OH... Forecast Discussion SPC AC 190552 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1252 AM CDT FRI JUL 19 2013 VALID 191200Z - 201200Z ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CNTRL GREAT LAKES TO NRN NEW ENGLAND... ...GREAT LAKES TO NRN NEW ENGLAND... WHILE STRONGEST MID LEVEL HEIGHT FALLS ARE EXPECTED TO REMAIN NORTH OF THE U.S. BORDER ACROSS ONTARIO...SRN EXTENT OF LARGE SCALE FORCING SHOULD SPREAD ACROSS THE GREAT LAKES DURING THE DAY. LATEST SHORT-RANGE MODEL GUIDANCE SUGGESTS MID LEVEL FLOW WILL INCREASE TO AROUND 50KT ALONG A CORRIDOR FROM SRN WI...ACROSS NRN LOWER MI INTO NRN MAINE BY 20/00Z. THIS BELT OF INCREASING LARGE SCALE FLOW WILL COINCIDE WITH ADVANCING COLD FRONT THAT IS EXPECTED TO ADVANCE ESEWD AHEAD OF PROGRESSIVE SHORT-WAVE TROUGH. EARLY IN THE PERIOD IT APPEARS SCT TSTMS MAY BE NOTED ALONG COLD FRONT FROM SERN MN...NEWD ACROSS NRN WI INTO CNTRL ONTARIO. THIS ACTIVITY COULD BE LOCALLY STRONG AND PERHAPS EVEN PRODUCE MARGINALLY SEVERE HAIL OR GUSTY WINDS. HOWEVER...MORE SIGNIFICANT CONVECTION IS EXPECTED LATER IN THE DAY AS BOUNDARY LAYER HEATING IS EXPECTED TO ENHANCE INSTABILITY SUCH THAT ANY STORMS THAT FORM ALONG THE COLD FRONT WILL DO SO WITHIN A THERMODYNAMIC ENVIRONMENT SUPPORTIVE OF ROBUST UPDRAFTS. FORECAST SOUNDINGS ACROSS PORTIONS OF LOWER MI SUGGEST CONVECTIVE TEMPERATURES...NEAR 90F...SHOULD BE REACHED AND WITH LOW LEVEL FRONTAL CONVERGENCE SCT THUNDERSTORMS ARE EXPECTED BY 19Z. DEEP WLY FLOW AND SFC-6KM BULK SHEAR ON THE ORDER OF 25KT FAVOR ORGANIZED MULTI-CELL UPDRAFTS AND PERHAPS EVEN WEAK SUPERCELLS...THROUGH ENVIRONMENTAL SHEAR FAVORS LINE SEGMENTS. DAMAGING WINDS AND HAIL ARE THE PRIMARY THREATS WITH THIS ACTIVITY. DOWNSTREAM ACROSS UPSTATE NY INTO NRN NEW ENGLAND...WLY LLJ IS EXPECTED TO INCREASE MARKEDLY AHEAD OF COLD FRONT WITH FLOW APPROACHING 50KT AT 850MB ACROSS NRN MAINE BY 18Z. WHILE FLOW WILL BE DECIDEDLY VEERED LOW LEVEL SHEAR IS EXPECTED TO BE FAIRLY STRONG AND ANY CONVECTION THAT EVOLVES ACROSS THIS REGION COULD CERTAINLY ROTATE. LOW LEVEL WARM ADVECTION MAY CONTRIBUTE TO DISCRETE SUPERCELL ACTIVITY AHEAD OF COLD FRONT THOUGH MORE CONCENTRATED ACTIVITY SHOULD BE CONFINED TO NEAR FRONTAL ENVIRONMENT. THIS MORE CONCENTRATED ACTIVITY SHOULD PROGRESS ACROSS SERN ONTARIO/QUEBEC DURING THE LATE AFTERNOON/EARLY EVENING HOURS INTO UPSTATE NY/NRN VT/NH AND NRN MAINE. ISOLATED TORNADOES...LARGE HAIL AND DAMAGING WINDS CAN BE EXPECTED WITH THIS CONVECTION. ...CNTRL HIGH PLAINS... STRONG HEATING ACROSS THE CNTRL HIGH PLAINS WILL CONTRIBUTE TO DESTABILIZATION ACROSS SERN WY/NERN CO/WRN NEB ALONG FRINGE OF MODEST NWLY FLOW REGIME. WEAK LOW LEVEL UPSLOPE COMPONENT WILL CONTRIBUTE FAVORABLY TO SHEAR PROFILES AND WEAK ORGANIZATION IS POSSIBLE WITH STRONGEST CONVECTION THAT EVOLVES DURING THE LATE AFTERNOON STEEP LAPSE RATE ENVIRONMENT. LOCALLY STRONG DOWNBURSTS OR HAIL COULD ACCOMPANY THE MOST ROBUST CONVECTION. ...LOWER MS VALLEY... WWD MIGRATING UPPER TROUGH IS EXPECTED TO PROGRESS SLOWLY ACROSS LA DURING THE DAY FRIDAY. THIS FEATURE HAS CONTRIBUTED TO SIGNIFICANT DAYTIME CONVECTION OVER THE LAST FEW DAYS...ESPECIALLY AFTER 18Z BENEATH COOLER MID LEVEL TROUGH AXIS...AND STRONG CONVECTION IS ONCE AGAIN EXPECTED DURING THE DAY1 PERIOD. LOCALLY STRONG WET MICROBURSTS ARE POSSIBLE WITHIN VERY MOIST REGIME CHARACTERIZED BY PW VALUES IN EXCESS OF 2 INCHES. ..DARROW/DIAL.. 07/19/2013 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z CURRENT UTC TIME: 0951Z (5:51AM), RELOAD THIS PAGE TO UPDATE THE TIME
Posted on: Fri, 19 Jul 2013 09:53:03 +0000
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