Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 232005 AFDILN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 405 PM EDT WED JUL 23 2014 .SYNOPSIS...
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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.
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&& .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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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.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
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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.
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&& .LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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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).
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&& .AVIATION /20Z WEDNESDAY THROUGH MONDAY/... AREA OF CONVECTION CONTINUES TO PUSH ERN THRU NRN KY/SW OH. EXPECT REDEVELOPMENT S AND E OF THE TAFS THIS AFTN. MVFR CIGS N OF DAY AND CMH ARE EXPECTED TO WORK INTO THE NRN TAFS LATER THIS AFTN...BEFORE HIGH PRESSURE TO THE NW GRADUALLY SCATTERS THINGS OUT FROM MW TO SE AFTER 00Z. CU DEVELOPMENT IS EXPECTED DURING THE DAY THURSDAY AS THE NORMAL DIURNAL CYCLE KICKS IN. BETTER COVERAGE WILL BE OVER THE NRN TAFS WHERE BKN CIGS ARE EXPECTED. 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...SITES

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