Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 260832 AFDILN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 432 AM EDT TUE MAY 26 2015 .SYNOPSIS...
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WARM AND HUMID AIR WILL REMAIN IN PLACE OVER THE MIDDLE OHIO VALLEY THROUGH THE REST OF THE WEEK. AS UPPER LEVEL DISTURBANCES MOVE THROUGH THE AREA...THERE WILL BE OCCASIONAL CHANCES FOR SHOWERS AND THUNDERSTORMS TODAY AND WEDNESDAY...AND THEN AGAIN OVER THE WEEKEND.
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&& .NEAR TERM /THROUGH TONIGHT/...
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A DEVELOPING SURFACE LOW AND UPPER TROUGH WILL MOVE ENE INTO WISCONSIN THIS EVENING. MID-LEVEL RIDGING OFF THE SOUTH CAROLINA COAST WILL REMAIN PARKED IN PLACE TODAY...WITH SURFACE HIGH PRESSURE CENTERED A BIT FURTHER TO THE NORTHEAST OVER THE ATLANTIC. ALL OF THESE FACTORS PLACE THE OHIO VALLEY FIRMLY IN A REGIME OF DEEP SOUTHWESTERLY FLOW...BUT THE SLIGHTLY-NORTHWARD POSITION OF THE SURFACE HIGH WILL HELP KEEP SURFACE FLOW AT A LITTLE MORE OF A SOUTHERLY DIRECTION. THIS WILL HELP PROVIDE A REGIME OF CONVERGENCE NEAR THE SURFACE...WITH FAVORABLE UPPER CONDITIONS FOR LIFT FROM AN APPROACHING JET STREAK (ENTRANCE REGION) AND POSITIVE VORTICITY ADVECTION. COMBINED WITH THE DIURNAL CYCLE...SHOWERS AND THUNDERSTORMS WILL DEVELOP AND INCREASE IN COVERAGE OVER INDIANA / CENTRAL KENTUCKY / SW OHIO DURING THE AFTERNOON HOURS...CROSSING THROUGH THE ILN CWA THROUGH EARLY TO MID EVENING. POPS HAVE BEEN RAISED TO 70 PERCENT FOR THE ENTIRE FORECAST AREA...AND ONCE STORM TIMING IS NAILED DOWN WITH HIGH-RES MODEL RUNS LATER TODAY...CATEGORICAL POPS MAY BE ADDED IN. AS TEMPERATURES CLIMB INTO THE LOWER 80S...AND DEWPOINTS HOLD FAIRLY STEADY IN THE MID 60S...INSTABILITY WILL BUILD DURING THE LATE MORNING AND INTO THE AFTERNOON. AS IS TYPICAL...MODEL AGREEMENT ON EXACT INSTABILITY VALUES IS HARD TO COME BY. ONE THING THAT APPEARS CERTAIN IS THAT THE POOR MID-LEVEL LAPSE RATES SAMPLED BY THE 00Z KILN SOUNDING WILL NOT BE GOING ANYWHERE ANY TIME SOON...WHICH WILL SIGNIFICANTLY LIMIT BUOYANCY DESPITE THE OTHERWISE FAVORABLE NEAR-SURFACE THERMODYNAMIC CONDITIONS. BLENDING SOME OF THE MODEL SOLUTIONS...MLCAPE VALUES OF 800-1400 J/KG CAN BE EXPECTED (ADMITTEDLY A LITTLE WIDER OF A FORECAST RANGE THAN IS IDEAL). THE POSITION OF THE ILN CWA BETWEEN THE AREAS OF HIGH AND LOW PRESSURE WILL MEAN THAT DEEP-LAYER FLOW WILL BE AT LEAST SOMEWHAT FAVORABLE FOR STRONG STORM POTENTIAL...WITH 0-6KM SOUTHWESTERLY SHEAR OF 25-35 KNOTS. WHILE LOW-LEVEL WIND CONDITIONS NEAR THE SURFACE LOW (IN THE VICINITY OF LAKE MICHIGAN) COULD CAUSE SOME CONCERN FOR TORNADO POTENTIAL OFF TO THE NORTHWEST...0-1KM SHEAR MAY NOT BE SUFFICIENT (IN TERMS OF EITHER DIRECTION OR SPEED) TO PRESENT AN APPRECIABLE TORNADO RISK OVER THE MIDDLE OHIO VALLEY. TAKEN AT A SLIGHTLY DEEPER LAYER (0-3KM)...THE SHEAR IS A LITTLE BIT MORE IMPRESSIVE...WITH A SHIFT OF AROUND 30-40 DEGREES AND A CHANGE OF 20-30 KNOTS IN MAGNITUDE. COMBINING THIS ALL TOGETHER...THE SHEAR PROFILES SUGGEST THAT WHILE LARGE-SCALE ORGANIZATION MAY BE A LITTLE BIT LACKING...INDIVIDUAL CELLS AND CLUSTERS MAY BECOME ORGANIZED AND POTENT...CAPABLE OF PRODUCING STRONG TO SEVERE WINDS. THIS WILL BE ESPECIALLY TRUE IF SURFACE TEMPERATURES ARE ABLE TO MEET OR EXCEED THE FORECAST HIGHS...WHICH COULD INCREASE THE POTENTIAL INTENSITY OF NEGATIVELY BUOYANT DOWNDRAFTS. BASED ON THE SOMEWHAT-NARROW CAPE PROFILE...HIGH FREEZING (14KFT) AND -20C (25KFT) LEVELS...AND A LACK OF EXPECTED DISCRETE/ROTATING STORMS...THE HAIL THREAT APPEARS TO BE A LOWER-END RISK. AS ALLUDED TO ABOVE...THE TORNADO THREAT IS ALSO NOT ESPECIALLY HIGH. AREAS OF LOCALLY BACKED SURFACE WINDS OR BOUNDARY INTERACTIONS COULD BRIEFLY INCREASE THE RISK...BUT THE OVERALL CONDITIONS POINT SIGNIFICANTLY TO A STRAIGHT-LINE WIND EVENT ON THE MESOSCALE. NCAR ENSEMBLE PLOTS SUPPORT THIS AS WELL...WITH VARIOUS ENSEMBLE MEMBERS INDICATING DOWNDRAFT POTENTIAL OVER THE FORECAST AREA...BUT VIRTUALLY NO INDICATION OF UPDRAFT HELICITY OR LARGE HAIL POTENTIAL. COMBINING EVERYTHING TOGETHER...THE GREATEST SEVERE CHANCES APPEAR LIKELY TO OCCUR BETWEEN 4PM AND 9PM (THOUGH WEAKENING CONVECTION MAY PERSIST A LITTLE LONGER THAN THAT). NONE OF THE OVERALL PARAMETERS LOOK PARTICULARLY MORE FAVORABLE IN ONE SECTION OF THE CWA OVER ANOTHER...AND SIMULATED REFLECTIVITY PROJECTIONS FROM CONVECTIVE-ALLOWING MODELS ARE SOMEWHAT SCATTERSHOT IN TERMS OF EXACT TIMING AND PLACEMENT. THUS...THE THREAT WILL BE HANDLED UNIFORMLY IN THE HWO THIS MORNING.
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&& .SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
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CONVECTION IS EXPECTED TO BE ON A GENERAL WEAKENING/DISSIPATING TREND LATE TUESDAY EVENING INTO EARLY WEDNESDAY MORNING...ON THE BACK SIDE OF THE NORTHEASTWARD-MOVING SHORTWAVE AND IN A REGIME OF DIURNALLY WEAKENING INSTABILITY. STILL...THE PATTERN OF GENERAL MOIST FLOW WILL SUPPORT A CHANCE OF SOME SHOWERS (OR POSSIBLY A THUNDERSTORM) THROUGH THE OVERNIGHT HOURS. ON WEDNESDAY...AN UPPER TROUGH WILL BE MOVING EAST INTO THE GREAT LAKES REGION. INITIALLY FAIRLY WELL-DEFINED OVER THE UPPER MISSISSIPPI VALLEY (AND HELPING TO DRIVE THE MORE ACTIVE WEATHER ON TUESDAY)...THIS TROUGH WILL BE WASHING OUT AS IT PROGRESSES AHEAD. STILL...IT WILL LEAVE THE MIDDLE OHIO VALLEY IN A FAVORABLE AREA OF LIFT...THOUGH SURFACE FEATURES WILL BE LACKING AND THUS FORCING MAY NOT BE PARTICULARLY WELL FOCUSED. WHILE SHEAR WILL CONTINUE TO BE MODEST...INSTABILITY SHOULD ACTUALLY INCREASE SLIGHTLY FROM TUESDAY...WITH MLCAPE VALUES PERHAPS APPROACHING 2000 J/KG IN THE SOUTHWESTERN SECTIONS OF THE CWA (AND UP TO 1500 J/KG ELSEWHERE). THUS...AMONG THE SCATTERED THUNDERSTORMS THAT DEVELOP...A FEW STRONG TO POSSIBLY SEVERE STORMS MAY OCCUR. AS THE AFOREMENTIONED TROUGH CONTINUES TO WEAKEN AND MOVE EAST...THE ILN FORECAST AREA WILL END UP IN A REGIME OF BUILDING RIDGING ALOFT...AND A WEAK/NEBULOUS AREA OF HIGH PRESSURE AT THE SURFACE. BY THURSDAY...THIS WILL BEGIN TO LIMIT THE CHANCES FOR CONVECTION...WITH DIURNAL DEVELOPMENT ONLY APPEARING TO BE A POSSIBILITY IN THE SOUTHERN HALF OF THE FORECAST AREA. FRIDAY WILL LIKELY BEGIN DRY AS WELL...THOUGH THE FLOW WILL BE SWITCHING BACK TO THE SOUTH IN THE SECOND HALF OF THE DAY...LEAVING A POSSIBILITY FOR SOME DEVELOPMENT (ESPECIALLY FOR THE SOUTHWESTERN HALF OF THE FORECAST AREA) BY LATE AFTERNOON AND EVENING. TO NOTE...THE GFS HAS BEEN A LITTLE MORE AGGRESSIVE THAN OTHER MODELS WITH THE SOUTHWARD PUSH OF THE AREA OF HIGH PRESSURE INTO THE OHIO VALLEY...AND WOULD SUPPORT AN EVEN DRIER FORECAST FOR THURSDAY AND THE FIRST HALF OF FRIDAY. TEMPERATURES AND DEWPOINTS ARE EXPECTED TO CHANGE VERY LITTLE OVER THE COURSE OF THE WEEK. A VERY SLIGHTLY DRIER AIR MASS WILL BE SETTLING IN ON THURSDAY AND INTO FRIDAY...WHICH MAY ALLOW SOME SLIGHTLY COOLER MIN TEMPS ON FRIDAY MORNING. OTHERWISE...MIN TEMPS WILL LIKELY NOT DROP BELOW THE MID 60S. MAX TEMPS SHOULD REMAIN AROUND 80 DEGREES...BUT CONVECTION AND CLOUDS (OR A LACK THEREOF) COULD HAVE AN IMPACT IN EITHER DIRECTION...ESPECIALLY TODAY (TUESDAY) AND WEDNESDAY. FRIDAY MAY BE THE WARMEST DAY OF THE WEEK...WITH DRY AND SUNNY CONDITIONS TO BEGIN THE DAY...WITH WARM ADVECTION KICKING IN.
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&& .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
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MID/UPPER LEVEL FLOW WILL BECOME MORE AMPLIFIED THROUGH THE WEEKEND AS SHORT WAVE ENERGY MOVES OUT OF THE ROCKIES AND INTO THE CENTRAL PLAINS. THIS WILL EVENTUALLY LEAD TO A FRONTAL BOUNDARY PUSHING DOWN TOWARD AND POSSIBLY THROUGH OUR FA THROUGH EARLY NEXT WEEK. HOWEVER...THERE REMAINS QUITE A BIT OF DIFFERENCE BETWEEN THE ECMWF/GFS/CMC WITH HOW FAST AND HOW FAR SOUTH TO PUSH THE FRONT AND WHETHER OR NOT TO STALL IT OUT ACROSS OUR AREA TOWARD THE END OF THE PERIOD. THIS WILL LEAD TO THE POTENTIAL FOR A FAIRLY WET/MORE ACTIVE PERIOD THROUGH THE END OF THE LONG TERM BUT DUE TO THE TIMING UNCERTAINTIES...WILL JUST KEEP POPS IN THE HIGH CHANCE CATEGORY. FRIDAY WILL BE SEASONABLY WARM WITH HIGHS IN THE MID 80S. MORE SEASONABLE TEMPERATURES WILL THEN BEGIN TO PUSH DOWN FROM THE NORTH OVER THE WEEKEND...BUT THEY WILL ULTIMATELY BE DICTATED BY THE PLACEMENT/TIMING OF THE FRONTAL BOUNDARY. FOR THAT REASON...HAVE GENERALLY GONE WITH A MODEL BLEND FOR TEMPERATURES SATURDAY THROUGH MONDAY.
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&& .AVIATION /07Z TUESDAY THROUGH SATURDAY/... FIRST CONCERN EARLY THIS MORNING IS THE POTENTIAL FOR MVFR CEILINGS AND VISIBILITIES. AM GETTING MIXED SIGNALS FOR MVFR CEILINGS PER LATEST MODELS. HOWEVER...THERE ARE SOME LOWER CLOUDS DEVELOPING NEAR KCVG AND KDAY...AND THESE MAY BECOME A CEILING AROUND 2000 FEET OVER THE NEXT 4 HOURS...ABOUT 2 HOURS LATER AT KCMH AND KLCK. VISIBILITIES SHOULD BE HELD IN CHECK GIVEN SFC PRESSURE GRADIENT...SANS KLUK WHICH MAY DROP INTO THE 3-5SM RANGE. FOR LATER TODAY...OUR REGION WILL BE UNDERNEATH A MOIST SOUTHWEST FLOW ALOFT. MORNING DAYTIME HEATING WILL RESULT IN CUMULUS DEVELOPMENT WITH WINDS PICKING UP FROM THE SOUTH. BY THE AFTERNOON HOURS...A DISTURBANCE WILL ROTATE NORTHEAST INTO THE WESTERN GREAT LAKES. A TRAILING TAIL/INFLECTION IN THE MID LEVELS WILL TEAM UP WITH A POTENTIAL LOW LEVEL CONVERGENT AXIS TO BRING THE LIKELIHOOD OF SHOWERS AND THUNDERSTORMS. THERE CONTINUES TO BE SOME TIMING AND COVERAGE ISSUES WITH THE HIGH RESOLUTION MODELS SO HAVE OPTED TO KEEP VCTS GOING AT THIS TIME. WILL ATTEMPT TO PICK A TEMPO GROUP FOR THE BEST CHANCE AT THE TERMINALS WITH THE NEXT TAF ISSUANCE. OTHERWISE...WITH THE MOIST AIRMASS IN PLACE...MVFR CONDITIONS WILL BE LIKELY WITH STORMS WITH LOCAL POCKETS OF IFR CONDITIONS (MOST LIKELY VISIBILITIES) DUE TO HEAVY RAINFALL IN THE STRONGEST CORES. FOR TONIGHT...DISTURBANCE AND ITS TAIL/INFLECTION WILL PUSH OFF TO THE NORTHEAST THROUGH THE REMAINDER OF OUR REGION. WITH THE LOSS OF DAYTIME HEATING...WE SHOULD SEE A GRADUAL DECREASE IN THUNDERSTORM ACTIVITY...WITH JUST A FEW SHOWERS LINGERING IN THE MOIST FLOW LATE TONIGHT. MODELS SUGGEST THAT SOME MVFR/IFR CEILINGS MAY DEVELOP IN THE 06Z TO 12Z AND WILL TAKE A LOOK AT THIS AGAIN WITH THE NEXT ISSUANCE. .OUTLOOK...MVFR/IFR CEILINGS POSSIBLE WEDNESDAY MORNING. THUNDERSTORMS POSSIBLE WEDNESDAY AFTERNOON AND EVENING...AND AGAIN SATURDAY. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...NONE. KY...NONE. IN...NONE. && $$ SYNOPSIS...HATZOS NEAR TERM...HATZOS SHORT TERM...HATZOS LONG TERM...JGL AVIATION...HICKMAN

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