Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 240623 AFDILN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 223 AM EDT THU JUL 24 2014 .SYNOPSIS... A COLD FRONT SHIFTING SOUTHEAST THROUGH THE OHIO VALLEY THIS AFTERNOON WILL CONTINUE TO BRING A THREAT FOR SHOWERS AND A FEW THUNDERSTORMS ALONG AND AHEAD OF IT...MAINLY NEAR AND SOUTH OF THE OHIO RIVER TONIGHT...BEFORE COOL AND DRY HIGH PRESSURE BUILDS IN FOR THURSDAY. THIS FEATURE WILL PROMISE SEVERAL DAYS OF COMFORTABLE HUMIDITY AND BELOW NORMAL TEMPERATURES BEFORE LOW PRESSURE AND A DEVELOPING WARM FRONT APPROACH AND PASS THROUGH THE AREA SATURDAY AND SUNDAY...WITH A RETURN OF A WARM AND HUMID AIRMASS...AND THE THREAT FOR SHOWERS AND THUNDERSTORMS. ONCE THIS SYSTEM PASSES...YET ANOTHER PLUNGE OF COOLER AIR WILL RETURN TO THE OHIO VALLEY FOR THE FIRST PART NEXT WEEK...WITH BELOW NORMAL TEMPERATURES. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... OBJECTIVE MESOANALYSIS AT 23.19Z INDICATES THAT OUTFLOW FROM DECAYING MCS FROM THIS MORNING HAD PUSHED THROUGH MOST IF NOT ALL OF THE WFO ILN FORECAST AREA...WITH WNWLY FLOW AT MOST SITES. THIS HAS SCOURED DEEPER INSTABILITY OUT OF THE AREA...THOUGH THE COLD FRONT AT 18Z WAS STILL ANALYZED FROM NEAR CINCINNATI TO JUST SOUTH OF COLUMBUS. BOUNDARY LAYER MOISTURE LAGGED A BIT BEHIND THE FRONT...BUT DEW POINTS IN NORTHERN INDIANA/OHIO WERE FALLING INTO THE LOWER 60S ON SLIGHTLY STRONGER NORTHERLY FLOW. THE BEST SURFACE-BASED INSTBY AT 19Z RESIDED SOUTH OF THE OHIO RIVER WHERE MLCAPE FROM 1000 TO 1500 J/KG REMAINED. HOWEVER...OBSERVATION- DERIVED SHEAR VALUES IN THIS MODEST INSTBY REGION WERE WEAK...WITH 0-6KM BULK SHEAR < 20 KTS...AND VERY WEAK LOW LEVEL FLOW. THUS...THINK THE SEVERE THREAT IS PRETTY NEGLIGIBLE GIVEN THE PRESENCE OF MID/UPPER LEVEL CIRRUS THAT CONTINUES TO TEMPER THE HEATING POTENTIAL...AND INABILITY FOR ANY RENEWED CONVECTIVE DEVELOPMENT /CNTL INDIANA/ TO MAINTAIN ITSELF. WITH A COUPLE OF VERY WEAK RIPPLES OF LOW PRESSURE POTENTIALLY DEVELOPING ALONG FRONT /ONE ALREADY ANALYZED NEAR CVG AND ANOTHER IN SERN MO/...WILL HANG ONTO RAIN CHANCES IN THE EVENING MAINLY ALONG/SOUTH OF THE OHIO RIVER WHERE THE ADVANCING COLD FRONT AND ANY OF THESE WEAK RIPPLES MAY INDUCE A FEW UPDRAFTS OR SHOWER AREAS THROUGH THE NIGHT. THIS IS SUPPORTED BY DECENT HEIGHT FALLS THROUGH THE NIGHT AND A MORE FAVORABLE MID/UPPER LEVEL JET DEVELOPMENT OVER THE UPPER GREAT LAKES AS THE NIGHT WEARS ON...SUGGESTING AT LEAST A LITTLE REDEVELOPMENT IS POSSIBLE THIS EVENING OR OVERNIGHT IN NRN KY/SCNTL OH NEAR OR BEHIND THE FRONT. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM FRIDAY/... A COOL/DRY THURSDAY IS EXPECTED AS HIGH PRESSURE BUILDS IN FROM THE NORTH. 925MB TEMPS DURING PEAK HEATING AROUND 16C WILL SUPPORT MAINLY TEMPS IN THE 70S DURING THE DAY WITH LIGHT NELY FLOW AS HIGH PRESSURE WILL BE SITUATED OVER WESTERN ILLINOIS. PWAT WILL DROP SIGNIFICANTLY THROUGH THE DAY TO 0.60" OR SO...AND SHOULD SEE A MIX OF CLOUDS AND SUN WITH AFTERNOON CUMULUS. SURFACE DEWPOINTS SHOULD MIX OUT/FALL INTO THE LOWER-MID 50S DURING THE AFTERNOON. THIS SETS UP ANOTHER COOL NIGHT /FOR LATE JULY STANDARDS/ ACROSS THE AREA WITH WIDESPREAD LOWER/MID 50S ON THURSDAY NIGHT. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... AT 12Z FRIDAY...SURFACE HIGH PRESSURE WILL BE CENTERED DIRECTLY OVER THE OHIO VALLEY...FULLY ENCOMPASSING THE ILN CWA WITH A FAIRLY DRY AIR MASS. VERY TRANQUIL CONDITIONS ARE EXPECTED FOR FRIDAY...WITH MAX TEMPS FORECAST WITHIN A FEW DEGREES OF 80. ONE LARGE MID-LEVEL TROUGH OVER THE EASTERN HALF OF THE COUNTRY WILL BEGIN TO MOVE AWAY BY FRIDAY NIGHT...AS THE PATTERN BEGINS TO FLATTEN ACROSS THE OHIO VALLEY FOR MOST OF THE WEEKEND. THIS WILL ACTUALLY PUT THE REGION MORE INTO THE STRONGER FLOW ALOFT...BRINGING THE POSSIBILITY FOR CONVECTIVE SYSTEMS TO MOVE EAST OR SOUTHEAST THROUGH THE AREA. THERE REMAINS SOME UNCERTAINTY IN TIMING OF THESE SMALLER FEATURES THROUGH THE WEEKEND...PRECLUDING USING HIGHER POPS IN THE FORECAST QUITE YET. SEVERAL MODELS ALLOW FOR SOME LIGHT QPF TO MOVE INTO THE REGION FRIDAY NIGHT...THOUGH RH VALUES IN THE LOW LEVELS ARE NOT VERY HIGH. THIS SUGGESTS PERHAPS SOME SPRINKLES OR DISSIPATING SHOWERS AS WARM ADVECTION BEGINS OVER THE REGION...WITH A SHARP INCREASE IN THETA-E NOTED ALOFT...AND GENERALLY MOVING WNW-TO-ESE. FORCING ON SATURDAY APPEARS NEBULOUS...SO POPS HAVE BEEN KEPT IN THE LOW CHANCE CATEGORY...THOUGH THE AIR MASS WILL BECOME HOT AND HUMID. ON SUNDAY...A MORE PRONOUNCED FRONT WILL BE MOVING EASTWARD THROUGH THE REGION. BOTH THE GFS AND ECMWF HAVE CONSISTENTLY DEVELOPED ONE OR SEVERAL CONVECTIVE COMPLEXES TO THE WEST OF THE ILN CWA ON SATURDAY NIGHT...DRIVING THEM THROUGH THE REGION IN THE WESTERLY FLOW...WITH FAIRLY WET CONDITIONS EXPECTED THROUGH THE DAY. POPS FOR SUNDAY HAVE BEEN INCREASED SLIGHTLY AS A RESULT OF THIS CONFIDENCE...AND IT IS LIKELY THAT CHANCES WILL HAVE TO BE INCREASED FURTHER AS SOON AS THE EXACT TIMING OF THE CONVECTION BECOMES MORE CERTAIN. A RATHER SHARP UPPER TROUGH WILL BE MOVING SOUTH THROUGH THE GREAT LAKES ON SUNDAY AND INTO MONDAY...DRIVING THE AFOREMENTIONED COLD FRONT...AND A SURFACE LOW THROUGH SOUTHERN MICHIGAN. THIS TROUGH WILL ESTABLISH ITSELF RATHER ROBUSTLY ACROSS THE EASTERN HALF OF THE COUNTRY...IN A WELL-ADVERTISED PATTERN SHIFT TOWARD ANOTHER ROUND OF BELOW-NORMAL TEMPERATURES. 12Z GFS/ECMWF PROJECTIONS SHOW THE COOLEST AIR OVER THE OHIO VALLEY AT 12Z TUESDAY MORNING. PRECIPITATION CHANCES SEEM MORE LIKELY ON MONDAY RATHER THAN LATER IN THE WEEK...THOUGH STILL ON THE LOWER END OF THE SCALE (AND LIKELY DIURNALLY DRIVEN). && .AVIATION /06Z THURSDAY THROUGH MONDAY/... COLD FRONT HAS PUSHED SOUTH OF THE OHIO RIVER. WAVE OF LOW PRESSURE TRAVELING ALONG THIS FRONT IN NRN KY HAS SLOWED ITS PROGRESSION BUT ALL LINGERING PRECIPITATION SHUD REMAIN SHOULD OF THE TAF SITES. THIS FRONT WILL PUSH SOUTH TODAY WITH HIGH PRESSURE BUILDING INTO THE REGION. LINGERING MVFR CIGS AT THE SRN TAF SITES WILL GIVE WAY TO A PERIOD OF VFR CIGS BETWEEN 3500 AND 5000 FEET. THESE CIGS WILL PARTIALLY CLEAR THE TAF SITES EARLY THIS MORNING. IN LOW LEVEL CAA PATTERN EXPECT A GOOD DEAL OF CUMULUS DEVELOPMENT TODAY. FCST SOUNDINGS BACK THIS UP WITH MOISTURE INDICATED BETWEEN 4000 AND 5000 FEET. WILL ALLOW FOR VFR THESE CIGS INTO THE LATE AFTN WITH CLEARING THIS EVENING AS THE SFC HIGH BUILD IN. NORTHEAST WINDS AROUND 10 KTS WILL PREVAIL THRU THE DAY BEFORE BECOMING LIGHT THIS EVENING. OUTLOOK...THUNDERSTORMS POSSIBLE SATURDAY AND SUNDAY. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...NONE. KY...NONE. IN...NONE. && $$ SYNOPSIS...BINAU NEAR TERM...BINAU SHORT TERM...BINAU LONG TERM...HATZOS AVIATION...AR

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