Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 162357 AFDILN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 757 PM EDT TUE SEP 16 2014 .SYNOPSIS... HIGH PRESSURE IS EXPECTED TO KEEP DRY CONDITIONS ACROSS THE AREA THROUGH SATURDAY. A COLD FRONT WILL APPROACH THE AREA ON SUNDAY BRINGING SHOWERS AND THUNDERSTORMS TO THE REGION. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... MOST OF THE FA REMAINS CLOUDY THIS AFTERNOON. BELIEVE THAT MOST OF THE MODELS ARE TOO QUICK TO CLEAR OUT THE CLOUDS THIS EVENING AND INTO THE NIGHT TONIGHT. WENT MORE PESSIMISTIC WITH THE CLOUDS ESPECIALLY ACROSS THE SOUTH HOWEVER MIGHT NOT HAVE GONE PESSIMISTIC ENOUGH. NEXT FEW HOURS WILL BE KEY FOR WHAT WILL HAPPEN OVERNIGHT. IF THE DRIER AIR ALOFT CAN MIX DOWN BEFORE SUNSET THEN CLEARING WILL TAKE PLACE QUICKER. IF THIS DOES NOT OCCUR BEFORE SUNSET THEN EXPECT SOME CLOUD COVER TO STICK AROUND THROUGH THE NIGHT...ESPECIALLY ACROSS THE SOUTH. CURRENT THOUGHT IS THAT EXTREME NORTHERN AND NORTHEASTERN PORTIONS OF THE FA WILL SEE MORE CLEARING BEFORE SUNSET AND THAT OTHER AREAS WILL TAKE LONGER TO SEE A DECREASE IN CLOUD COVER. AS THE CLOUD COVER DOES SLOWLY EXIT OR DECREASE ACROSS THE FA OVERNIGHT...WITH THE RESIDUAL LOW LEVEL MOISTURE EXPECT FOG TO QUICKLY DEVELOP IN THOSE LOCATIONS. WITH SOME UNCERTAINTY ON HOW QUICKLY THE CLOUDS WILL CLEAR OUT WENT WITH PATCHY FOG EVERYWHERE ACROSS THE FA AND PATCHY DENSE FOG IN THE MORE PRONE LOCATIONS. THIS WILL BE WATCHED CLOSELY HOWEVER TO SEE IF ADDITIONAL FOG WORDING MAY BE NEEDED...ESPECIALLY ACROSS NORTHERN PORTIONS OF THE FA. WITH REGARDS TO TEMPERATURES WENT CLOSER TO THE WARM SIDE OF GUIDANCE OVERNIGHT WITH HAVING THE CLOUD COVER STICKING AROUND LONGER. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... SURFACE HIGH PRESSURE WILL BE IN PLACE FOR WEDNESDAY. A VERY WEAK UPPER LEVEL DISTURBANCE WILL MOVE ACROSS PRIMARILY SOUTHERN PORTIONS OF THE AREA WEDNESDAY EVENING HOWEVER DO NOT EXPECT ANY PRECIPITATION. HAVE A SLIGHT INCREASE IN CLOUDS WITH THIS FEATURE. DRY CONDITIONS ARE EXPECTED THROUGH THE SHORT TERM TIME PERIOD. TEMPERATURES WILL CONTINUE TO BE BELOW NORMAL THROUGH THE SHORT TERM TIME PERIOD WITH HIGH TEMPERATURES GENERALLY IN THE UPPER 60S TO LOWER 70S. LOW TEMPERATURES ARE EXPECTED TO BE IN THE MIDDLE 40S TO AROUND 50. WENT CLOSE TO GUIDANCE FOR TEMPERATURES WEDNESDAY THROUGH THURSDAY NIGHT. && .LONG TERM /FRIDAY THROUGH TUESDAY/... SURFACE HIGH PRESSURE WILL CENTERED OVER SOUTHERN ONTARIO AND QUEBEC ON FRIDAY MORNING...MOVING OFF THE EAST COAST BY SATURDAY MORNING. ALONG WITH A SHORT-TERM FLATTENING OF THE MID-LEVEL PATTERN...LEADING TO HEIGHT RISES OVER THE OHIO VALLEY AS THE EAST COAST TROUGHING DISSIPATES...THIS WILL SIGNAL A PATTERN CHANGE HEADING INTO THE WEEKEND. AS A RESULT...SURFACE WINDS WILL TAKE A SOUTHERLY COMPONENT...LEADING TO A WARM ADVECTION PATTERN FOR FRIDAY AND SATURDAY. THE REMAINING INFLUENCE OF THE SURFACE HIGH WILL PROVIDE FOR A DRY STARTING POINT...AND MOSTLY SUNNY CONDITIONS. THE WARM ADVECTION PATTERN WILL STRENGTHEN ON SATURDAY...WITH SURFACE WINDS TURNING TO THE SSW...AND A TROUGH OVER THE NORTHERN PLAINS BEGINNING TO GET A LITTLE CLOSER TO THE AREA. FRIDAY TEMPERATURES WILL LIKELY STILL REMAIN JUST BELOW NORMAL...BUT NEAR TO SLIGHTLY ABOVE NORMAL TEMPERATURES ARE EXPECTED WITH THE WARMER FLOW ON SATURDAY. THROUGH SATURDAY...FORECAST MODEL AGREEMENT IS STRONG. AS THE TROUGH APPROACHES THE OHIO VALLEY ON SUNDAY MORNING...SURFACE LOW PRESSURE IS EXPECTED TO DEVELOP IN THE NORTHERN GREAT LAKES. A COLD FRONT WILL EXTEND SOUTH FROM THIS LOW...AND WILL MOVE THROUGH THE ILN CWA ON SUNDAY. THESE BASIC DETAILS ARE FAIRLY CERTAIN...BUT THERE IS MUCH GREATER MODEL SPREAD IN THE SPECIFICS OF HOW THE TROUGH AND FRONT ARE BEING DEPICTED. THE AMPLITUDE OF THE UPPER TROUGH...IN PARTICULAR...SHOWS MARKED DIFFERENCES BETWEEN THE GFS AND ECMWF (AND EVEN WITHIN THE INDIVIDUAL GFSE MEMBERS). AMONG THE FLATTEST SOLUTIONS IS THE 12Z ECMWF...WHICH PIVOTS THE FRONT IN AN ORIENTATION THAT WOULD PROVIDE LITTLE IN THE WAY OF FORCING OR SHEAR OVER THE OHIO VALLEY. THE 12Z OPERATIONAL GFS IS AMONG THE STRONGEST SOLUTIONS...WITH A CLOSED 500MB LOW THAT IS NOT SUPPORTED BY ITS ENSEMBLE MEMBERS. THUS...IT IS NOT SURPRISING THAT TIMING AND STRENGTH DIFFERENCES WITH THE SURFACE FRONT ARE A FORECAST CHALLENGE. THOUGH PRECIPITATION IS FAIRLY LIKELY TO OCCUR ON SUNDAY FOR THE ILN CWA...POPS HAVE BEEN LIMITED TO 40 PERCENT UNTIL TIMING AGREEMENT IN THE MODELS BECOMES STRONGER. ALSO UNCERTAIN IS THE EVENTUAL MAGNITUDE OF THE FLOW ALOFT AND WARM ADVECTION AT THE SURFACE...WHICH WILL CERTAINLY IMPACT WHETHER OR NOT SHEAR AND INSTABILITY (RESPECTIVELY) ARE ABLE TO BECOME A CONCERN. BEHIND THE FRONT (FROM SUNDAY NIGHT INTO NEXT WEEK)...A COOLER AND DRIER AIR MASS OF CANADIAN ORIGIN WILL MOVE INTO PLACE. THIS LARGE AREA OF HIGH PRESSURE IS FORECAST TO COVER A SIGNIFICANT PORTION OF THE MIDWESTERN STATES AND INTO THE OHIO VALLEY. AFTER A DAY ON SUNDAY THAT IS LIKELY TO FEATURE A TEMPERATURE GRADIENT (WITH WARM CONDITIONS REMAINING IN THE SOUTHEASTERN CWA)...THE FIRST PART OF THE WEEK WILL FEATURE TEMPERATURES FALLING WELL BELOW NORMAL. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... SURFACE HIGH PRESSURE WILL SETTLE INTO THE OHIO VALLEY OVERNIGHT. THE MAIN FORECAST CONCERN OVERNIGHT INTO WEDNESDAY MORNING WILL BE THE POTENTIAL FOR FOG TO FORM. LATEST SATELLITE IMAGERY CONTINUES TO SHOW LINGERING STRATOCUMULUS OVER THE TRI-STATE REGION. MODELS INDICATE THAT THIS CLOUD DECK SHOULD SHIFT SLOWLY SOUTH AND THEN SOUTH/SOUTHWEST OVERNIGHT AND PERHAPS ERODE. IF THIS OCCURS...THEN LOCATIONS LIKE KCVG AND KLUK WILL HAVE THE SAME POTENTIAL FOR FOG AS THE OTHER SITES. THE OTHER SITES ARE EXPECTED TO GO MOSTLY CLEAR SOONER THAN KCVG/KLUK. WITH LIGHT TO CALM WINDS...LINGERING SHALLOW MOISTURE AT THE SURFACE...AND A SOMEWHAT DAMP GROUND...FOG FORMATION SEEMS LIKELY. THUS...HAVE BROUGHT IFR/LIFR/VLIFR VSBYS AND/OR CEILINGS DEPENDING ON WHETHER THE AIRPORT IS MORE FOG PRONE THAN THE OTHERS (KILN...KLCK AND KLUK ARE THE MOST FOG PRONE). ON WEDNESDAY...HIGH PRESSURE WILL REMAIN OVER THE REGION. FOG SHOULD BURN OFF BY 14Z. DIURNALLY DRIVEN CUMULUS WILL DEVELOP BETWEEN 14Z AND 16Z. A WEAK S/WV IS FORECAST TO PUSH INTO THE AREA LATE WEDNESDAY AND WEDNESDAY EVENING. THIS FEATURE WILL BRING A MIX OF MID AND HIGH LEVEL CLOUDS BY THEN. OUTLOOK...THUNDERSTORMS POSSIBLE SUNDAY. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...NONE. KY...NONE. IN...NONE. && $$ SYNOPSIS...NOVAK NEAR TERM...NOVAK SHORT TERM...NOVAK LONG TERM...HATZOS AVIATION...HICKMAN

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