Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 062108 AFDILN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 408 PM EST FRI MAR 6 2015 .SYNOPSIS... A RIDGE OF HIGH PRESSURE WILL DROP SOUTH TOWARD THE SOUTHEAST U.S. OVERNIGHT. LOW PRESSURE AND AN ASSOCIATED WEAK COLD FRONT WILL MOVE THROUGH THE GREAT LAKES AND OHIO VALLEY SATURDAY INTO SATURDAY NIGHT. WEAK HIGH PRESSURE WILL BUILD BACK INTO THE REGION FOR SUNDAY. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... A RIDGE OF HIGH PRESSURE WILL DROP SOUTH TOWARD THE SOUTHEAST U.S. OVERNIGHT. AS IT DOES...LOW PRESSURE WILL MOVE TO THE WESTERN GREAT LAKES. A PRESSURE GRADIENT BETWEEN THESE TWO SYSTEMS SHOULD KEEP WINDS UP ACRS THE NORTHWEST OVERNIGHT. THE SOUTHEAST PART OF THE FORECAST AREA WILL HAVE LIGHTER WINDS...AND WITH A DEEP SNOW PACK...SOME VALLEY LOCATIONS MAY EVEN DECOUPLE AS TEMPERATURES COOL. THE NAM AND GFS HAVE BEEN HAVING ISSUES WITH LOW LEVEL RH LATELY...AND THIS WAS SEEN ON THE KILN 12Z SOUNDING IN WHICH THE GFS HAD A MUCH HIGHER RH THAN REALITY. BELIEVE THE NAM AND GFS ARE GROSSLY OVERDONE ON THE LOW LEVEL MOISTURE OVERNIGHT IN WHICH THEY TRY TO DEVELOP LOW CLOUDS. THIS HAS TEMPERATURE IMPLICATIONS (KEEPING IT WARMER) AS WELL AS THE WINDS AND CURRENT SNOW COVER. THE RAP IS NOT AS MOIST AND IS MORE IN LINE WITH THE ECMWF. AS A RESULT...AM FORECASTING JUST AN INCREASE IN HIGH AND MID LEVEL CLOUDS OVERNIGHT WITH LOWS MORE WEIGHTED TOWARD THE ECMWF. HAVE COOLED LOCATIONS IN OUR EAST/SOUTHEAST INTO THE SINGLE DIGITS AS THESE LOCATIONS TEND TO DECOUPLE...AND EVEN MORE SO WITH SNOW COVER. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/... IN A WEST/NORTHWEST FLOW ALOFT...EMBEDDED S/WV ENERGY WILL MOVE ACROSS THE REGION SATURDAY INTO SATURDAY NIGHT. THIS WILL BE REFLECTED AT THE SFC BY LOW PRESSURE OVER THE GREAT LAKES WITH A WEAK COLD FRONT PUSHING SOUTHEAST THROUGH THE REGION SATURDAY NIGHT. AS STATED IN THE NEAR TERM...BELIEVE THE NAM AND GFS ARE OVERDONE ON THE LOW LEVEL RH AND HAVE LEANED MORE TOWARD THE ECMWF. WE SHOULD STILL SEE AN INCREASE IN CLOUDS IN THE WAA AHEAD OF THE COLD FRONT. BELIEVE THE SYSTEM IS MOISTURE STARVED...AND THE LIGHT QPF BEING GENERATED BY THE GFS AND NAM IS MORE A REFLECTION OF ITS HIGH RH BIAS IN THE LOW LEVELS. HIGH RESOLUTION MODELS CONCUR AND GENERATE WEAK PCPN NORTH OF THE AREA. THUS...WEAK ISENTROPIC LIFT AHEAD OF THE FRONT SHOULD KEEP THE CHANCE OF PCPN NORTH OF THE FORECAST AREA AND OVER THE GREAT LAKES. AGAIN...THE PROSPECTS OF LOW CLOUDS ALONG WITH WIND AND SNOW COVER WILL PLAY A HUGE PART ON HOW WARM IT WILL GET ON SATURDAY. WE WILL BE IN A WAA PATTERN WITH A PRETTY GOOD SOUTH/SOUTHWEST FETCH WITH SOME GUSTINESS. THE GFS AND NAM SEEM TO BE HOLDING TEMPERATURES DOWN TOO MUCH GIVEN THE HIGH RH BIAS AND THE NAM/S TENDENCY TO KEEP SKIN TEMPERATURES CLOSE TO FREEZING WHEN THEIR IS A SNOW COVER DESPITE GOOD WAA. SO...HAVE TAKEN A BLEND OF THE PREVIOUS FORECAST AND THE ECMWF WHICH YIELDS HIGHS IN THE UPPER 30S NORTH TO THE LOWER 40S SOUTH. AS THE FRONT PUSHES THROUGH SATURDAY NIGHT...WINDS WILL SHIFT TO THE WEST AND SKIES SHOULD EVENTUALLY BECOME PARTLY CLOUDY. HAVE USED A BLEND OF MODELS/MOS GUIDANCE FOR OVERNIGHT LOWS. FOR SUNDAY INTO SUNDAY NIGHT...WEAK SURFACE HIGH PRESSURE WILL SETTLE OVER THE OHIO VALLEY. WE WILL REMAIN IN A WEST/NORTHWEST FLOW ALOFT WITH EMBEDDED DISTURBANCES BRINGING CLOUDS TO REGION FROM TIME TO TIME. NAM/GFS ARE A LITTLE STRONGER WITH POST FRONTAL CAA ON SUNDAY WHILE THE ECMWF SHOWS LITTLE CAA. HAVE TAKEN A BLEND OF MODELS SO AS NOT TO BIAS FROM ONE END OF THE SPECTRUM TO THE OTHER END OF THE SPECTRUM. THIS RESULTS IN SLIGHT COOLING IN THE NORTH WITH TEMPERATURES SIMILAR TO SATURDAYS HIGHS IN THE SOUTH. LOWS SUNDAY NIGHT WILL RANGE FROM THE MID 20S NORTH TO NEAR 30 SOUTH. && .LONG TERM /MONDAY THROUGH FRIDAY/... FAIRLY BENIGN EXTENDED PATTERN WITH THE AREA. THOUGH SOME MODEL DIFFERENCES IN A SOUTHERN STREAM SYSTEM LIFTING THROUGH THE KY/TN AREA...WHICH MAY BRING SHOWERS FOR TUE/TUE NIGHT. FOR NOW HAVE BROUGHT SHOWERS UP TO FCST AREA AND AFFECTING THE FAR SOUTH...BUT GENERALLY WENT WITH A GFS/ECMWF BLEND WITH THE ECMWF BEING FURTHER NORTH WITH THIS SYSTEM...SO SUBSEQUENT SHIFTS MAY NEED TO TWEAK UPWARD. STARTED OUT WITH BELOW NORMAL TEMPERATURES WITH THE ANTICIPATION OF LINGERING SNOW COVER...THOUGH SOME WARMING AS THIS SYSTEM APPROACHES BRINGING AMPLE WAA. DRY CONDITIONS THROUGH THE REMAINDER OF THE PERIOD...BUT AHEAD OF A SYSTEM WHICH COULD BRING A WARM/WET PATTERN FOR NEXT WEEKEND. && .AVIATION /21Z FRIDAY THROUGH WEDNESDAY/... TAF SITES CURRENTLY VFR ACROSS THE REGION AS SURFACE HIGH PRESSURE REMAINS IN CONTROL. FORECAST SOUNDINGS FROM THE NAM AND GFS ALL SHOW IFR CONDITIONS TOMORROW MORNING BUT THE GFS AND NAM HAVE ALL PERFORMED POORLY WITH LOW LEVEL MOISTURE THE LAST COUPLE OF WEEKS. THE SREF CIG PROBABILITIES DON`T LOOK TO PROMISING FOR IFR TOMORROW MORNING BUT DO SHOW SOME MVFR CIGS. AN UPPER LEVEL DISTURBANCE WILL MOVE OVERHEAD TOMORROW AFTERNOON BUT WITH ONLY AVERAGE MOISTURE LEVELS AND LIMITED LIFT HAVE LEFT THE MENTION OF PRECIP OUT OF THE TAFS. THE UPPER LEVEL DISTURBANCE WILL PROVIDE STRONGER WINDS ACROSS THE AREA THOUGH. OUTLOOK...MVFR CIGS AND VSBYS POSSIBLE INTO SUNDAY. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...NONE. KY...NONE. IN...NONE. && $$ SYNOPSIS...HICKMAN NEAR TERM...HICKMAN SHORT TERM...HICKMAN LONG TERM...JDR AVIATION...HAINES

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