Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 210853 AFDILN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 453 AM EDT THU AUG 21 2014 .SYNOPSIS...
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A WARM FRONT WILL GRADUALLY LIFT NORTHEAST INTO THE GREAT LAKES THROUGH SATURDAY...THEN CONTINUE TO WAVER ACROSS THE REGION THROUGH THE BEGINNING OF NEXT WEEK. DISTURBANCES IN NORTHWEST FLOW ALOFT WILL INTERACT WITH A VERY WARM AND MOIST AIRMASS TO PRODUCE SHOWERS AND THUNDERSTORMS AT TIMES THROUGH THE PERIOD.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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A VERY COMPLEX CONVECTIVE FORECAST TODAY. EARLY THIS MORNING SHOWERS AND EMBEDDED THUNDERSTORMS DEVELOPED IN MOIST ASCENT ASSOCIATED WITH A WEAK LOW LEVEL JET ACROSS NORTHERN INDIANA. THESE WILL DRIFT INTO WEST CENTRAL OHIO THROUGH THE EARLY MORNING. MEANWHILE A WEAK DISTURBANCE OVER NORTHERN ILLINOIS WILL MOVE SOUTHEAST IN NORTHWEST FLOW ALOFT. THERE IS A CONSISTENT SIGNAL IN THE SUITE OF CONVECTIVE ALLOWING MODELS THAT THUNDERSTORMS WILL BLOSSOM OVER INDIANA THIS MORNING...ORGANIZING IN MODERATE WIND FIELDS...THEN SURGING SOUTHEAST ACROSS OUR AREA THROUGH MIDDAY. THIS MAY BE STARTING TO SHOW ITS HAND ACROSS NORTHWEST INDIANA...ALTHOUGH MANY OF THE MODELS DID NOT HANDLE THE DECAYING STORMS OVER SOUTHWEST INDIANA VERY WELL. THERE IS ALSO GENERAL AGREEMENT FROM THE SYNOPTIC MODELS ON THIS SCENARIO...ALTHOUGH PLACEMENT OF THE TRACK OF THE STORMS VARIES. MAINTAINED THE LIKELY POPS AND BROADENED THEM A BIT. DO NOT THINK THERE MUCH OF A SEVERE THREAT WITH THIS AND THAT THE SPC DAY 1 OUTLOOK IS MORE GEARED TOWARD AN OVERNIGHT SYSTEM (SEE BELOW). AFTER THIS COMPLEX MOVES OUT...THE CAMS HAVE THE REGION GENERALLY DRY FOR THE REST OF THE AFTERNOON AND EVENING...AND THIS SEEMS REASONABLE IF A LARGE COMPLEX OCCURS. QPF GENERATED IN THE SYNOPTIC MODELS MAY BE A RESULT OF PARAMETERIZATION...BUT MAINTAINED SOME CHANCE POPS INTO THE EVENING JUST IN CASE. HAVE A SLIGHTLY GREATER CHANCE IN THE NORTH SINCE THE EARLIER CONVECTION MAY TAKE A MORE SOUTHEASTWARD TRAJECTORY. HIGH TEMPERATURES WILL BE TRICKY AND POSSIBLY LIMITED BY CLOUDS AND PRECIPITATION. FORECAST FALLS IN BETWEEN THE WARM MAV AND COOL MET...BUT ANY SUN THIS AFTERNOON COULD LEAD TO A JUMP IN TEMPERATURES.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
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NEXT DISTURBANCE IN THE NORTHWEST FLOW ALOFT WILL AFFECT THE AREA TONIGHT. THERE ARE INDICATIONS A LARGE COMPLEX OF STORMS/MCS WILL FORM OVER MINNESOTA AND WISCONSIN AND DIVE SOUTHEASTWARD. SOME TIMING AND PLACEMENT DISCREPANCIES EXIST...BUT THE MOST LIKELY TRAJECTORY APPEARS TO BE TOWARD THE NORTHERN HALF OF THE CWA...SO HAVE ALIGNED POPS ACCORDINGLY. IF AN ORGANIZED MCS DEVELOPS...THERE MAY BE AN ATTENDANT RISK FOR STRONG TO DAMAGING WINDS. HOWEVER THE DIURNALLY UNFAVORABLE TIMING MAY LEAD TO A WEAKENING TREND. SPC HAS PLACED THE WESTERN HALF OF THE CWA IN A SLIGHT RISK. ALSO...WPC HAS PLACED THE AREA IN A SLIGHT RISK OF EXCESSIVE RAINFALL DUE TO THE MULTIPLE CLUSTERS OF THUNDERSTORMS WITH HEAVY RAIN. WITH A MOIST AIRMASS AND CLOUD COVER...LOWS WILL ONLY DROP INTO THE LOWER 70S IN MANY SPOTS. MORE STORMS WILL BE POSSIBLE ON FRIDAY...BUT COVERAGE IS IN QUESTION AS CONFIDENCE DECREASES ON INDIVIDUAL FEATURES IN THE NORTHWEST FLOW. HOWEVER...HIGH PRECIPITABLE WATER VALUES AND THE LINGERING BOUNDARY ACROSS THE REGION WILL ACT IN FAVOR OF THUNDERSTORM DEVELOPMENT DURING PEAK HEATING. A SIMILAR SCENARIO APPLIES TO SATURDAY. COMPLICATING MATTERS IS A SLIGHT CHANGE IN THE PATTERN ORIENTATION FROM SATURDAY INTO SUNDAY. THE CENTRAL CONUS RIDGE IS EXPECTED TO CONTINUE TO BUILD...AS A TROUGH DIGS OVER THE WESTERN ATLANTIC. THERE ARE NOW INDICATIONS THAT HIGH PRESSURE OVER THE ST. LAWRENCE VALLEY WILL NOSE SOUTHWESTWARD...SERVING TO BACK DOOR FRONT THE LOW LEVEL BOUNDARY. THIS MAY SHIFT THE FOCUS OF ANY STORMS THAT DEVELOP. BY SUNDAY THE LOW LEVEL BAROCLINIC ZONE BECOMES MORE DIFFUSE...LOW LEVEL FLOW WEAKENS...AND ATMOSPHERIC MOISTURE LESSENS...SO STORM CHANCES MAY BE PRETTY LOW. FRIDAY AND SATURDAY WILL LIKELY BE THE WARMEST DAYS OF THE SHORT TERM PERIOD WITH HIGHS IN THE UPPER 80S TO LOWER 90S. HEAT INDICES IN THE SOUTHWEST WILL BE NEAR 100. BY SUNDAY...THE NORTHEAST SURFACE FLOW MAY HELP LIMIT TEMPERATURES A BIT. WITH HIGH DEW POINTS...OVERNIGHT LOWS WILL CONTINUE TO RESIDE ON EITHER SIDE OF 70.
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&& .LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
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GETTING INTO MONDAY-TUESDAY...THE RIDGE CONTINUES TO BUILD WITH HEAT/HUMIDITY. FLOW BECOMES VERY LIGHT THROUGH THE BULK OF THE TROPOSPHERE AND IT BECOMES QUESTIONABLE IF COVERAGE OF DAYTIME/EVE STORMS WARRANTS MENTION. RIGHT NOW HAVE RUN 15-25% RAIN CHANCES BOTH OF THESE DAYS...AND THAT MAY BE TOO HIGH. INTO WEDNESDAY...SOME HINTS OF HEIGHT FALLS WHICH MAY ALLOW A LITTLE STRONGER FLOW OR A WEAK SHORTWAVE TROUGH TO CROSS THE GREAT LAKES. SO A BETTER STORM THREAT THEN...HOWEVER AT THIS TIME RANGE THIS IS A VERY LOW CONFIDENCE FORECAST GIVEN CONDITIONAL NATURE OF THE RIDGE BUCKLING. SO ALL IN ALL...HAVE TENDED TO FOCUS RAIN CHANCES NEAR PEAK HEATING INTO THE EVENING AND ALLOW FOR SOME DRY NIGHTS/EARLY MORNINGS. FLY IN OINTMENT WILL BE ANY FORWARD PROPAGATING MCS THAT SURVIVES THROUGH THE NIGHT...ORIGINATING TO OUR NORTHWEST AND FALLING DOWN NNWLY FLOW EITHER SATURDAY MORNING OR SUNDAY MORNING. LOW CONFIDENCE STORM CHANCE...BUT HIGH CONFIDENCE WARM/HUMID PATTERN IS THE STORY FOR THE SAT-WED TIMEFRAME.
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&& .AVIATION /08Z THURSDAY THROUGH MONDAY/... THE REGION WILL BE WEDGED BETWEEN TWO SYNOPTIC SCALE SYSTEMS OVER THE NEXT 24 HOURS. A MID LEVEL CLOSED LOW SLOWLY MOVING FROM THE EASTERN GREAT LAKES TO NEW ENGLAND AREA. MEANWHILE...A MID LEVEL RIDGE WILL TRY TO NUDGE ITS WAY NORTHWARD INTO THE MIDDLE MISSISSIPPI VALLEY. OUR AREA WILL BE INFLUENCED BY THE NORTHWEST FLOW ALOFT BETWEEN THESE TWO SYSTEMS ALONG WITH EMBEDDED DISTURBANCES RIDING SOUTHEAST ON THE EAST SIDE OF THE RIDGE AXIS FROM TIME TO TIME. AT THE SAME TIME...A WEAK TO MODEST LOW LEVEL JET WILL BRING SOME LOW LEVEL MOIST ASCENT. MANY MODEL SOLUTIONS...INCLUDING THE CONVECTION ALLOWING MODELS...CONTINUE TO STRUGGLE WITH TIMING AND PLACEMENT OF CONVECTION OVER THE NEXT 24 HOURS. THERE IS SOME CONSENSUS IN AT LEAST THE FIRST 12 HOURS. A WEAK DISTURBANCE OVER NRN INDIANA IS EXPECTED TO MOVE SOUTHEAST ACROSS NRN OHIO THIS MORNING. ALSO...A LOW LEVEL JET IS FORECAST TO IMPINGE ON THE REGION FROM THE WEST. WE SHOULD SEE AN INCREASE IN SHOWERS AND THUNDERSTORMS THIS MORNING...ESPECIALLY BETWEEN 12Z AND 18Z. HAVE PLACED TEMPO MVFR CONDITIONS AT ALL THE TAF SITES. FOR THIS AFTERNOON...SOME MODELS SUGGEST WE COULD BE IN A RELATIVE LULL AS THE LOW LEVEL JET DIURNALLY WEAKENS AND THE DISTURBANCE MOVES AWAY. HAVE LEFT A VCSH DESCRIPTOR AT THE TAF SITES FOR LOW CHANCES FOR SHOWERS OR A STORM. FOR TONIGHT...ANOTHER EMBEDDED DISTURBANCE IS FORECAST TO ROTATE SOUTHEAST INTO THE REGION. THERE CONTINUES TO BE DIFFERENCES IN THE EVOLUTION OF NOCTURNAL CONVECTION. RIGHT NOW..THE BEST CHANCE FOR SHOWERS/STORMS SHOULD OCCUR AFTER 06Z AND BE MORE WEIGHTED TOWARDS THE NORTHERN TAF SITES OF KDAY...KCMH...AND KLCK. HOWEVER...IT SHOULD BE NOTED THAT SOME MODELS HAVE CONVECTION AFFECTING THE ENTIRE REGION IN THE FORM OF A MESOSCALE CONVECTIVE SYSTEM. WILL CONTINUE TO MONITOR MODEL TRENDS FOR TIMING AND SPATIAL COVERAGE. OUTLOOK...THUNDERSTORMS POSSIBLE FRIDAY EVENING THROUGH SUNDAY. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...NONE. KY...NONE. IN...NONE. && $$ SYNOPSIS...SNYDER NEAR TERM...SNYDER SHORT TERM...SNYDER LONG TERM...BINAU AVIATION...HICKMAN

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