Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 170557 AFDILN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 157 AM EDT WED SEP 17 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 THIS MORNING/... SURFACE HIGH PRESSURE HAS SETTLES INTO THE OHIO VALLEY THIS EVENING PER SURFACE ANALYSIS. STRATOCUMULUS ACROSS THE TRI-STATE REGION THIS EVENING HAS BEEN ERODING/SHRINKING IN COVERAGE PER SATELLITE IMAGERY TRENDS. THIS IS LIKELY BEING CAUSED BY LARGE SCALE SUBSIDENCE AND MUCH DRIER AIR JUST ABOVE THE TOP OF THE CLOUD DECK. AS A RESULT...WILL ALLOW SKIES TO BECOME CLEAR TO MOSTLY CLEAR OVERNIGHT. THE COMBINATION OF LINGERING LOW LEVEL MOISTURE...CLEAR SKIES...AND CALM WINDS WILL SET THE STAGE FOR AREAS OF FOG TO FORM OVERNIGHT. SOME OF THE FOG MAY BECOME LOCALLY DENSE IN SPOTS...ESPECIALLY IN THE FOG PRONE AREAS SUCH AS RIVER VALLEYS. HAVE THIS PLACED IN THE FORECAST ALONG WITH A MENTION IN THE HWO PRODUCT. WILL MONITOR CONDITIONS OVERNIGHT SHOULD DENSE FOG BECOME WIDESPREAD ENOUGH TO WARRANT AN ADVISORY. OVERNIGHT LOWS WILL MAINLY DIP INTO THE 40S. && .SHORT TERM /6 AM THIS MORNING THROUGH THURSDAY NIGHT/... FOG WILL DISSIPATE ACROSS THE REGION BY MID MORNING. OTHERWISE...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 /06Z WEDNESDAY THROUGH SUNDAY/... SC HAS FINALLY DISSIPATED UNDER THE SUBSIDENCE OF BUILDING HIGH PRESSURE. WITH LIGHT WINDS AND LINGERING LOW LEVEL MOISTURE... EXPECT FOG FORMATION EARLY THIS MORNING. BROUGHT IN MVFR VSBYS AT THE CVG/DAY/CMH. AT THE OTHER 3 TAFS WENT WITH IFR VSBYS AND/OR CEILINGS. AFT 12Z...THE FOG WILL BURN OFF. THE HIGH WILL REMAIN OVER THE REGION....BUT DIURNAL CU WILL DEVELOP AFT 14Z. AN H5 S/WV IS FORECAST TO PUSH INTO THE AREA AFT 18Z. EXPECT SOME MID LEVEL CLOUDS WITH THE PASSAGE OF THE S/W. OUTLOOK...THUNDERSTORMS POSSIBLE SUNDAY. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...NONE. KY...NONE. IN...NONE. && $$ SYNOPSIS...HICKMAN/NOVAK NEAR TERM...NOVAK SHORT TERM...NOVAK LONG TERM...HATZOS AVIATION...SITES

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