Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 130808 AFDILN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 408 AM EDT SUN JUL 13 2014 .SYNOPSIS... A COLD FRONT WILL SLOWLY SAG SOUTHEAST INTO THE REGION THROUGH TONIGHT. SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE AHEAD OF THIS FRONT. ON MONDAY...THIS FRONT WEAKENS AND MOVES SOUTHEAST WHILE ANOTHER COLD FRONT APPROACHES FROM THE NORTHWEST. THE SECONDARY COLD FRONT IS EXPECTED TO PASS EAST THROUGH THE AREA MONDAY NIGHT. AN UNSEASONABLY COOL AIRMASS WILL THEN FOLLOW IN THE WAKE OF THIS FRONT INTO MID WEEK. && .NEAR TERM /THROUGH TONIGHT/... MOSAIC RADAR THIS MORNING DEPICTED A SWATH OF SHOWERS AND EMBEDDED THUNDERSTORMS EXTENDING FROM SOUTHERN ONTARIO...SOUTHWEST THROUGH NRN INDIANA...NRN ILLINOIS...THEN INTO THE CENTRAL PLAINS. HIGH RESOLUTION MODELS INDICATE THAT THE MAIN BULK OF PCPN OVER THE GREAT LIKES WILL SHIFT EAST/NORTHEAST WITH ITS ASSOCIATED LOW LEVEL JET AND UPR LVL S/WV THIS MORNING. IN THE MEANTIME...THE PCPN TO THE WEST WILL TRY TO SAG SOUTHEAST INTO OUR NW/NRN COUNTIES THROUGH THE MORNING HOURS...LIKELY WEAKENING AS THIS OCCURS. THE MAIN FORECAST DILEMMA FOR LATER TODAY INTO TONIGHT WILL BE THE POTENTIAL FOR ADDITIONAL SHOWER/THUNDERSTORM DEVELOPMENT AND SUBSEQUENT SEVERE WEATHER/HEAVY RAINFALL. A WEAK COLD FRONT WILL SLOWLY SAG SOUTHEAST INTO OUR NW CWFA THIS AFTERNOON. VARIOUS HIGH RESOLUTION MODELS OFFER DIFFER SCENARIOS ON TIMING AND COVERAGE OF THE SHOWER/THUNDERSTORM DEVELOPMENT IN ASSOCIATION WITH THIS FRONT. SOME PREVIOUS RUNS INDICATED THAT PERHAPS CONVECTION WOULD START ALONG THE FRONT AND THEN PROPAGATE SLOWLY SOUTHEAST ACROSS THE CWFA TOWARD BETTER INSTABILITY. LATER RUNS NOW SUGGEST THAT IF CURRENT DEBRIS CLOUDS CAN THIN SOME BY THIS AFTERNOON...SHOWERS/STORMS SHOULD DEVELOP IN PERHAPS A PREFRONTAL CONVERGENT AXIS WHERE DIFFERENTIAL HEATING MAY ACT AS A PSEUDO FRONT. THIS SEEMS MOST LIKELY IN THE VICINITY OF THE I-71 CORRIDOR AND POINTS SE. ONCE THIS OCCURS...THE CONVECTION SHOULD GROW IN COVERAGE AS IT SAGS SOUTHEAST INTO THE BETTER/HIGHER INSTABILITY. RIGHT NOW...IT LOOKS LIKE WE SHOULD BE ABLE TO ACHIEVE AT LEAST MODERATE INSTABILITY... 1500 J/KG FOR STORMS TO FEED ON. ALSO...WITH AT LEAST LOW END MODERATE BULK 0-6KM/0-3KM SHEAR VALUES...THE STORMS SHOULD BE ABLE TO ORGANIZE IN LINEAR SEGMENTS. AS SUCH...THE MAIN SEVERE WEATHER THREAT WOULD BE DAMAGING WINDS WITH PERHAPS AN ISOLATED LARGE HAIL THREAT. THE OTHER POTENTIAL ISSUE WILL BE HEAVY RAIN. PWATS ARE FORECAST TO CLIMB TO 2.00 TO 2.25 THIS AFTERNOON...WHICH IS 150 PERCENT ABOVE NORMAL FOR MID JULY. THIS VERY MOIST AIRMASS...ALONG WITH THE EXPECTED SLOW PROGRESSION OF THE CONVECTION TO THE EAST/SOUTHEAST WILL CERTAINLY POSE A FLOOD THREAT AS THUNDERSTORMS MAY TRAIN OVER THE SAME AREAS. HOWEVER...GIVEN CURRENT HIGH FFG VALUES...AND WITH STILL SOME UNCERTAINTY AS TO WHERE THE CONVECTION WILL START AND THEN PROPAGATE FROM ITS SOURCE REGION...HAVE DECIDED TO JUST MENTION HEAVY RAIN IN THE ZONES AND HIGHLIGHT THE THREAT IN THE HWO. THE DAYSHIFT MAY HAVE A BETTER HANDLE ON THE GREATEST THREAT AREA AND PERHAPS A SHORT TERM FLASH FLOOD WATCH MAY BE ISSUED. FOR TONIGHT...THE FRONT WILL BECOME MORE ILL DEFINED AS IT SAGS SOUTHEAST INTO THE HEART OF THE CWFA. DO NOT LIKE THE NAM/GFS GRID SCALE FEEDBACK WHICH BLOW UP HIGH QPF VALUES ACRS THE SRN ZONES TOWARD MORNING. AS SUCH...HAVE GONE WITH THE CONVECTION ALLOWING MODELS WHICH SUGGEST THAT CONVECTION SHOULD DIMINISH IN COVERAGE TOWARD MONDAY MORNING ACROSS THE SOUTHERN ZONES. THE NORTHERN ZONES ARE EXPECTED TO REMAIN DRY OVERNIGHT. HIGHS TODAY WILL BE TRICKY DUE TO CLOUDS/PCPN. THIS CALLS FOR A BIAS CORRECTED BLEND WHICH YIELDS HIGHS FROM THE LOWER 80S NW TO NEAR 90 SE. OVERNIGHT LOWS WILL RANGE FROM THE MID 60S NW TO THE LOWER 70S ALONG AND SOUTH OF THE OHIO RIVER. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... A LARGE SCALE ANOMALOUS MID LEVEL CLOSED LOW IS STILL FORECAST TO DIG SOUTHEAST INTO THE WESTERN GREAT LAKES ON MONDAY. THIS PROCESS SHOULD SHIFT FIRST AREA OF CONVECTION/CONVERGENT AXIS SOUTHEAST OF THE REGION WHILE A SECONDARY COLD FRONT APPROACHES THE REGION FROM THE NW. THERE STILL REMAINS UNCERTAINTY ON THE AMOUNT OF LOW LEVEL CONVERGENCE THAT IS EXPECTED WITH THE SECONDARY FRONT AS IT ENTERS OUR WRN CWFA LATE IN THE DAY OR EARLY EVENING. AS SUCH...HAVE KEPT POPS IN THE CHANCE CATEGORY ON MONDAY WITH 50 PERCENT EMPLOYED ACRS THE WEST FOR SHOWERS/STORMS. HIGHS ON MONDAY WILL BE A LITTLE COOLER IN MOST SPOTS...RANGING FROM THE LOWER TO MID 80S. FOR MONDAY NIGHT INTO TUESDAY...AFOREMENTIONED UPPER LEVEL CLOSED LOW WILL TRAVERSE SLOWLY ACROSS THE GREAT LAKES. THE COLD FRONT WILL PUSH EAST THROUGH THE REGION MONDAY NIGHT AND SHOULD BE OUT OF THE AREA BY TUESDAY MORNING. WILL CONTINUE THE CHANCE FOR SHOWERS/STORMS UNTIL FRONTAL PASSAGE. AFTER THAT...WE SHOULD BE IN THE DRY SLOT BEHIND THE FRONT WITH PARTLY CLOUDY SKIES EXPECTED ON TUESDAY. THE COOL DOWN WILL BEGIN ON TUESDAY WITH HIGHS RANGING FROM THE LOWER 70S NW TO THE MID 70S SOUTHEAST. FOR TUESDAY NIGHT...PARTLY CLOUDY SKIES ARE EXPECTED AS WEAK SFC RIDGING MOVES INTO THE AREA. LOWS WILL BE COOL AND WILL APPROACH RECORD LOWS FOR JULY 16. LOWS WILL BOTTOM OUT INTO THE LOWER AND MID 50S. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... HIGH PRESSURE AND AN UNSEASONABLY COOL AIRMASS WILL SETTLE INTO THE REGION THROUGH MIDWEEK. THE COOL AIRMASS COULD ALLOW FOR A FEW DIURNAL SHOWERS DURING THE AFTERNOON/EARLY EVENING WEDNESDAY AND POSSIBLY EVEN THURSDAY. HOWEVER...CHANCE AND COVERAGE APPEARS LOW ENOUGH AT THIS POINT TO LEAVE OUT OF FORECAST. THE AIRMASS WILL REMAIN ON THE COOL SIDE WEDNESDAY INTO THURSDAY AS IT GRADUALLY MODIFIES WITH HIGHS INTO THE MID TO POSSIBLY UPPER 70S BY THURSDAY. HIGH PRESSURE WILL THEN SLIDE OFF TO THE EAST THROUGH THE END OF THE WEEK. AS WE TRANSITION INTO RETURN FLOW...HIGHS BY SATURDAY WILL SLOWLY MODERATE BACK INTO THE LOWER 80S. && .AVIATION /08Z SUNDAY THROUGH THURSDAY/... WHILE GENERALLY TRANQUIL CONDITIONS ARE EXPECTED OVERNIGHT...SOUTHWESTERLY WINDS WILL BEGIN TO INCREASE IN INTENSITY BY SUNRISE. SHOWERS AND THUNDERSTORMS CURRENTLY STRETCHING FROM SOUTHERN MICHIGAN TO NORTHERN ILLINOIS WILL GRADUALLY WEAKEN AS THEY MOVE INTO THE AREA. HOWEVER...SCATTERED WEAK SHOWERS WILL CONTINUE TO BE POSSIBLE ALONG A BOUNDARY THAT IS MOVING SLOWLY TO THE SOUTH. THE FOCUS FOR ADDITIONAL CONVECTIVE DEVELOPMENT WILL ALSO MOVE SOUTH THROUGH THE DAY...WITH SHOWERS AND THUNDERSTORMS LIKELY TO OCCUR AT OR NEAR ALL OF THE TAF SITES. THERE ARE STILL SEVERAL POSSIBLE SCENARIOS REGARDING THE TIMING OF STORMS...THOUGH MID-DAY THROUGH EVENING SEEMS THE MOST LIKELY POSSIBILITY. BY SUNDAY NIGHT...WINDS WILL BEGIN TO SHIFT TO THE WEST AND THEN WEST-NORTHWEST. THERE WILL CONTINUE TO BE A CHANCE OF OCCASIONAL SHOWERS...ALTHOUGH STRONGER CONVECTION WILL BE LESS LIKELY AFTER 00Z. OUTLOOK...THUNDERSTORMS ARE POSSIBLE FROM SUNDAY NIGHT INTO MONDAY. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...NONE. KY...NONE. IN...NONE. && $$ SYNOPSIS...HICKMAN NEAR TERM...HICKMAN SHORT TERM...HICKMAN LONG TERM...JGL AVIATION...HATZOS

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