After being basically thunderstorm free since I moved here late last summer, it appears that the Northwestern CASI region may be in for a few thunderstorms, with the possibility of severe thunderstorms, late this afternoon and evening. In addition, a general risk of thunderstorms encompasses most of the CASI Region today. The SPC has issued a Slight Risk of Severe Thunderstorms this afternoon and evening for Western PA, Eastern OH, Western WV, and Northeast KY. The Weather Channle has issued a Risk for Severe Storms for an area slightly larger. For these and other weather companies' severe graphics, see http://casi.simplenet.com/j/oldsite/wx/severe.html The primary threats with these storms will be hail and wind. At 1:30pm this afternoon there were no echoes on the radar yet, in fact the entire eastern two-thirds of the nation is rain free. However, a weak frontal system will interact with the very hot and somewhat humid air over the area to give a chance of isolated thunderstorms. Here in Central PA my thermometers here read "89", "87", and "86" here today, the latter probably being more correct. My dewpoint stands at 61, the highest this year. CASI Members in this area should be on the alert for the possibility of widely scattered thunderstorms this evening. One thing that we're not going to have today is a good photo day. Visibility will be significantly reduced by the thick smoke that has made its way up from the Central American fires. This smoke was pulled into Canda yesterday by the frontal system and continues to flow northward today as the frontal system moves eastward. Already a thick haze has overtaken CASI HeadQuarters. Part of a Special Weather Statement (issued by the NWS office here in State College) in effect for Western PA follows: 1156 AM EDT SAT MAY 16 1998 ...STRONG THUNDERSTORMS POSSIBLE LATE THIS AFTERNOON AND THIS EVENING OVER THE MOUNTAINS OF WESTERN PENNSYLVANIA... ...FORECAST DETAILS... SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP LATE THIS AFTERNOON AND CONTINUE INTO THE EVENING HOURS. ANY THUNDERSTORM THAT FORMS THIS AFTERNOON OR EVENING WILL HAVE THE POTENTIAL TO PRODUCE GUSTY WINDS TO 40 MPH AND SMALL HAIL. Part of the SPC's discussion follows: ...UPPER OHIO VALLEY... VIGOROUS UPPER VORTICITY MAX HAS MOVED NNEWD INTO SWRN ONTARIO AS SHORT WAVE TROUGH ROTATES NEWD ACROSS THE UPPER GREAT LAKES. THIS SYSTEM IS FORECAST TO CONTINUE LIFTING NEWD TODAY AS MORE ZONAL FLOW DEVELOPS ACROSS THE GREAT LAKES AND OH VALLEY. COLD FRONT ARCING SWD FROM THE DEEP SURFACE LOW OVER SWRN ONTARIO WILL MOVE EWD ACROSS PARTS OF THE LOWER GREAT LAKES AND UPPER OHIO VALLEY THIS AFTERNOON CONTINUING INTO THE APPALACHIANS TONIGHT. LOW LEVEL MOISTURE HAS INCREASED NEAR THE COLD FRONT WITH MID TO UPPER 60S DEW POINTS EVIDENT THIS MORNING. ALTHOUGH PLUME OF SMOKE/HAZE AHEAD OF THE FRONT MAY SLIGHTLY INHIBIT DIURNAL HEATING TEMPERATURES ARE EXPECTED TO WARM INTO THE MID 80S THIS AFTERNOON. MODERATELY STEEP LAPSE RATES OF 7-7.5 C/KM WILL CONTRIBUTE TO DEVELOPMENT OF STRONG INSTABILITY WITH CAPE OF 2000-3000 J/KG FROM ERN OH/WRN PA INTO PARTS OF WV AND ERN KY. WEAK CONVERGENCE ALONG THE FRONT COUPLED WITH CONTINUED HEATING SHOULD RESULT IN SUFFICIENT LIFT AND WEAKENING OF THE CAP FOR A FEW PARCELS TO REACH THE LFC. DESPITE RELATIVELY WEAK WINDS OF 25-30 KT ALOFT...STRONG INSTABILITY AND PRESENCE OF DRY AIR ABOVE THE BOUNDARY LAYER SUGGEST POTENTIAL FOR ISOLATED SEVERE THUNDERSTORM DEVELOPMENT THIS AFTERNOON AND EVENING. PRIMARY THREAT WILL BE FOR DAMAGING WIND GUSTS AND POSSIBLY HAIL. -- ============================================================== Jesse Ferrell - Meteorologist/Web Dev. - j{at}weatherwatchers.org Central Atlantic Storm Investigators - www.weatherwatchers.org "And here a twister comes... here comes the twister." --Talking Heads || ICQ No. 136862 ||