000 FXUS63 KIWX 260015 AFDIWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 815 PM EDT WED JUL 25 2007 .AVIATION... CONTINUED CONVECTION ASSOCIATED WITH UL LOW CENTERED OVER WRN LK ERIE THIS EVENING. COOLING 5H TEMPS COINCIDENT WITH WESTERN EDGE OF N-S SFC HEATING/DESTABILIZATION ZONE LEADING TO MUCAPES ON ORDER OF 1000-1500 J/KG. WIDESPREAD SHRA AND FEW ISOLD TSRA TO CONTINUE NEXT COUPLE OF HOURS THEN EXPECTED TO TAPER OFF BY MIDNIGHT AS BL STABILIZES. HOWEVER SOME CONCERN WITH ISENT/CONVERGENT FLOW AROUND 8H WITH JETLET VEERING ACROSS NRN INDIANA THAT MAY PEG ADDITIONAL TSRA DEVELOPMENT OVERNIGHT...PREFER TO MONITOR AND ASSESS FOR 06 UTC ISSUANCE BEFORE ADDING SEVERAL HOURS OF FUEL ALT. AT LEAST MVFR VSBYS FAVORED OVERNIGHT WITH COOLING TO AT LEAST A FEW DEGREES BLO XOVER TEMPS AND MOISTENED GROUND. ADDITIONAL SHRA/CB DEVELOPMENT BY MIDDAY THU AS UPR LOW MEANDERS FURTHER NW INTO NCNTRL LWR MI. && .SHORT TERM... TODAY THROUGH TOMORROW WANDERING UPPER LOW WILL CONTINUE TO DRIFT SLOWLY NORTHWEST OVERNIGHT. MID LEVEL COOLING COUPLED WITH WEAK WESTERLY MOISTURE ADVECTION WILL CONTINUE TO PROMOTE SCATTERED SHOWERS AND THUNDERSTORMS THROUGH THE PERIOD. SHORT RANGE MODELS BOTH INDICATE SIMILAR EVOLUTION IN DYNAMICS. HOWEVER...WRF SEEMS TO BE OVERDONE WITH QPF AND HAVE SHIED FROM SOLUTION. THINKING GENERAL 0.25 TO HALF INCH IS POSSIBLE WITH LOCALLY HEAVIER AMOUNTS DUE TO SLOW STORM MOVEMENT/TRAINING...ESPECIALLY THIS EVENING. HAVE WORDED HEAVY RAINFALL IN FORECAST. LL MOISTURE TRANSPORT WILL INCREASE TONIGHT AS WINDS TURN WEST/SOUTHWESTERLY. 800-700MB ISENTROPIC LIFT PER GFS/WRF INTENSIFIES IN THE NIGHT PERIOD...WITH INTENSIFYING FLOW. COUPLED WITH LARGE SCALE ASCENT...THIS SHOULD ALLOW PRECIP CHANCES TO LINGER THROUGH THE NIGHT. PRECIP CHANCES WILL CONTINUE THROUGH TOMORROW WITH COLD POOL IN PLACE. DIURNAL HEATING WILL PROMOTE THUNDERSTORM DEVELOPMENT WITH EASTERN ZONES FAVORING BEST DYNAMIC LIFT. HAVE INCREASED POPS TO LIKELY IN EASTERN ZONES. NOT EXPECTING SEVERE WEATHER AT THIS TIME. HOWEVER...ISOLATED SMALL HAIL MAY BE POSSIBLE WITH LOWER FREEZING LEVEL IN PLACE. && .LONG TERM... THURSDAY NIGHT THROUGH FRIDAY... EARLY ON IN THE PERIOD SPREAD AMONG THE SHORT TERM MODELS IS FAIRLY SMALL...WILL FOLLOW CLOSE TO THE GFS WHICH HAS BEEN STRONG DEALING WITH THE UPPER LEVEL LOW THE LAST WEEK. START TO THE END OF THE ANOMALOUS UPPER LEVEL LOW...AS COLD FRONT PRESSES THROUGH THE REGION. UPPER LEVEL LOW HAS DRIFTED WESTWARD INTO GREAT LAKES REGION NEAR THE LP OF MICHIGAN BY THURSDAY NIGHT...WITH COLD FRONT APPROACHING FROM THE NORTHWEST. LINGERING SHOWERS AND THUNDERSTORMS SHOULD DIMINISH SOME WITH THE LOSS OF HEATING OVERNIGHT...WITH THE FRONT STILL OFF TO THE NORTHWEST AS OF 12Z FRIDAY. HAVE RAISED POPS SLIGHTLY EARLY IN THE EVENING PERIOD...TAILING THEM OFF AS THE NIGHT TRANSPIRES. COLD FRONT WILL WORK ACROSS THE SOUTHERN GREAT LAKES ON FRIDAY. MOISTURE WILL INCREASE TO PLENTIFUL LEVELS AS PWATS NEAR 1.8 TO 2 INCHES BY AFTERNOON...AND DEWPOINTS MAY REACH THE UPPER 60S. FRZ LVLS ARE ABV 14.5 KFT...SO DEEP WARM CLOUD LAYER MAY ALLOW FOR LOCALLY HEAVY RAINFALL. ALSO IF THE LATE AFTERNOON/EARLY EVENING TIMING STICKS THEN AND A THREAT FOR STRONG TO SEVERE STORMS WILL BE POSSIBLE. THE DYNAMICS ARE DECENT...BUT THE LIMITING FACTOR MAY BE THE CLOUD COVER WHICH COULD LIMIT HEATING AND DESTABILIZATION. AFTERNOON CLOUDINESS MAY ALSO HOLD TEMPS DOWN SOME SLIGHTLY FROM PREVIOUS PACKAGE...HAVE LOWERED A FEW DEGREES...ESPECIALLY ACROSS THE NORTHERN HALF OF THE FORECAST AREA. DRIER AIR WILL START TO MOVE SOUTH INTO THE AREA BY EARLY SATURDAY WITH JUST SOME FEW LINGERING SHOWERS TOWARDS SAT MORNING. SATURDAY THROUGH WEDNESDAY... EXTENDED MODELS HAVE BEEN IN FAIRLY DECENT AGREEMENT OVERALL...YET THE VERIFICATION STATS HAVE BEEN SOMEWHAT BELOW NORMAL THE LAST 3 OR 4 DAYS FOR ALL THE OPERATIONAL MODELS. WILL LEAN TOWARDS THE GFS ENSEMBLES/EURO BLEND THRU THE PERIOD...WHICH REMAINS CLOSE TO HPC GUIDANCE. MAIN CHANGE THRU THE PERIOD...WILL TREND DRIER SATURDAY. UPPER LEVEL PATTERN WILL START TO MAKES SOME DISTINCT CHANGES THIS PERIOD...AS TROUGHING WILL PUSH FURTHER TOWARDS THE EAST COAST AND RIDGING STARTS TO BUILD ACROSS THE GREAT LAKES BY EARLY NEXT WEEK. COLD FRONT WILL BE EXITING THE REGION SATURDAY...PUSHING DEEPER INTO THE OHIO VALLEY. HAVE LOWERED POPS FOR SATURDAY...BEST CHANCE WILL BE ACROSS THE EASTERN PORTIONS OF THE REGION NEAR THE IN/OH BORDER THROUGH MIDDAY SATURDAY. DRIER AIR WILL FILTER INTO THE SOUTHERN GREAT LAKES REGION LATER SATURDAY INTO SUNDAY BEHIND THE FRONT AS SURFACE HI PRESSURE SETTLES ACROSS THE AREA. SLIGHTLY BELOW NORMAL TEMPS WILL BE FOUND THRU MONDAY AS SURFACE HI PRESSURE DOMINATES THE FORECAST AREA. AS THE MID AND UPPER LEVEL RIDGING START TO INCREASE LATER MONDAY INTO TUESDAY...SOME DECENT WARMING AT H850...AS H850 TEMPS CLIMB TO NEAR 18 OR 19C BY WEDNESDAY. SURFACE HI MOVES EAST INTO THE NORTHEAST CONUS...WITH SLOWLY CLIMBING DEWPOINTS AND TEMPS EACH DAY. HIGHS SHOULD REACH TO JUST ABOVE SEASONAL NORMS EACH DAY AS DEWPOINTS CLIMB BACK INTO THE 60S. DRY WITH AMPLE SUNSHINE INTO THE MID WEEK. && .AVIATION... UPPER LEVEL LOW CENTERED OVER EASTERN OH WILL CONTINUE TO DRIFT SLOWLY WEST INTO THE REGION TODAY. EXPECTING CONCENTRATED BANDS OF SHRA/TSRA...ALREADY EVIDENT ON RADAR...TO CONTINUE TO DEVELOP WITH COOLING ALOFT COUPLED WITH DAYTIME HEATING. HAVE OPTED FOR TEMPO GROUPS AT SBN WHERE BETTER LL CONVERGENCE AND INSTABILITY ARE ALLOWING SOME ENHANCEMENT OF SHOWERS ALONG THE EASTERN SHORE OF LK MI. HAVE DROPPED VISBY TO 5SM IN TEMPO. HOWEVER...BRIEF RESTRICTIONS DOWN TO 2SM MAY OCCUR WITH HEAVIER CELLS. ISOLATED TS WILL ALSO BE POSSIBLE. OTHER CONCENTRATED AREAS OF RAIN IN WESTERN OH WILL AVOID THE FWA TERMINAL. HOWEVER...TCU AS INDICATED IN SAT AND OB REMARKS...ARE DEVELOPING WITH DIURNAL HEATING. THINKING ISOLATED CONVECTION WILL BE POSSIBLE. THUS...HAVE RETAINED VCSH. AVOIDED TEMPO AT FWA DUE TO EXPECTED LOW COVERAGE. SFC WINDS WILL GRADUALLY SHIFT TO THE SOUTHEAST...ESPECIALLY INTO THE EVENING AS PRESSURE GRADIENT ORGANIZES AND STRENGTHENS OVER THE REGION. LINGERING SHRA WILL BE POSSIBLE THROUGH THE NIGHT ACROSS THE AREA. TIMING/COVERAGE ISSUES WILL PRECLUDE ANY TEMPOS AT THIS POINT. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ SHORT TERM...CHAMBERLAIN LONG TERM....SCHOTT AVIATION...MURPHY