Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 270021 AFDILN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 721 PM EST MON JAN 26 2015 .SYNOPSIS... SURFACE HIGH PRESSURE WILL BUILD INTO THE OHIO VALLEY THROUGH THE MIDDLE OF THE WEEK. AN AREA OF LOW PRESSURE AND A COLD FRONT WILL MOVE ACROSS THE REGION ON THURSDAY...BRINGING A CHANCE OF MIXED PRECIPITATION. COLD HIGH PRESSURE WILL MOVE IN AGAIN ON FRIDAY. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... A TROUGH OF LOW PRESSURE IS MOVING AWAY FROM THE REGION TO THE EAST. UPSTREAM...A WEAK AND FURTHER WEAKENING SHORTWAVE IS MOVING RAPIDLY SOUTHEAST OUT OF THE NORTHERN MISSISSIPPI VALLEY. A SURFACE LOW IS WEAKENING JUST AS QUICKLY...AND IS FORECAST TO ESSENTIALLY DISSIPATE AS IT MOVES ACROSS THE OHIO VALLEY TONIGHT. THERE WILL BE A SHORT PERIOD OF TIME IN WHICH SOMEWHAT-FAVORABLE JET DYNAMICS HELP SUPPORT SOME LIGHT SNOW TO THE SOUTHWEST OF THE ILN FORECAST AREA...WITH POSSIBLE ACCUMULATIONS OVER PARTS OF SOUTHERN INDIANA AND CENTRAL KENTUCKY. HOWEVER...THE ILN CWA APPEARS UNLIKELY TO RECEIVE MUCH PRECIPITATION. A CHANCE OF FLURRIES WAS INSERTED INTO THE GRIDS...MAINLY SOUTH AND WEST OF CINCINNATI. ALONG THE PATH OF THIS WEAK SYSTEM...CLOUD COVER SHOULD REMAIN AT THE HIGH END OF THE SCALE. HOWEVER...925MB/850MB MOISTURE IS NOT EXPECTED TO BE AS PREVALENT ACROSS THE REST OF THE FORECAST AREA...PARTICULARLY IN THE NORTHERN AND NORTHEASTERN AREAS. WITH A SNOW PACK IN PLACE...AND WITH WINDS THAT WILL BECOME LIGHTER THROUGH THE NIGHT...A SOLID AMOUNT OF RADIATIONAL COOLING SHOULD OCCUR. THIS WILL ALLOW TEMPERATURES TO DROP TO AROUND 10 DEGREES...AND OUTLYING OR LOW AREAS MAY GET WELL INTO THE SINGLE DIGITS. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY/... THE SHORT TERM FORECAST PERIOD SHOULD BE FAIRLY QUIET...WITH NO CHANCES FOR PRECIPITATION. TEMPERATURES WILL BE THE BIGGEST CHALLENGE...WITH SURFACE HIGH PRESSURE SITTING OVER THE OHIO VALLEY...AND GENERALLY WEAK ADVECTION PATTERNS SETTING UP THROUGH WEDNESDAY. WITH GRADUALLY CLEARING SKIES...TUESDAY MAY END UP A DEGREE OR TWO WARMER THAN MONDAY...BUT THERE IS NO REASON TO FORECAST A BIG SWING IN TEMPERATURES. FOR TUESDAY NIGHT...CLEARING SKIES AND LIGHT WINDS WILL SET UP SOME VERY FAVORABLE RADIATIONAL COOLING CONDITIONS...AND THE ENTIRE MODEL SUITE HAS TAKEN A DOWNWARD TREND WITH TEMPERATURES. THIS FORECAST REPRESENTS A DROP OF SEVERAL DEGREES FROM THE PREVIOUS MIN TEMP GRID...BUT EVEN A SIMPLE GFS/NAM CONSENSUS BLEND WOULD RESULT IN COOLER CONDITIONS...SO THIS FORECAST STILL HAS ROOM FOR ADDITIONAL DOWNWARD ADJUSTMENT. ON WEDNESDAY...THERE ARE SIGNS THAT SOME WARM ADVECTION COULD BEGIN...THOUGH MAINLY JUST OFF THE SURFACE (AT LEAST THROUGH THE DAYTIME HOURS). AT 925MB...A RIDGE AXIS WILL HAVE TO CROSS EAST THROUGH THE REGION...BEFORE THE LOW-LEVEL FLOW TURNS FROM NNE TO SSW. THOUGH DIURNAL TEMPERATURES WERE USED IN THE FORECAST...IT IS POSSIBLE THAT MAX TEMPS COULD BE SLIGHTLY LATER THAN ON A TYPICAL DAY. WITH THE BOUNDARY BETWEEN SNOW PACK AND SNOW-LACK CUTTING ACROSS THE CWA...IF ANY WARM ADVECTION CAN COMBINE WITH THE PLENTIFUL INSOLATION ON WEDNESDAY...IT COULD HAVE A BIG IMPACT ON THE FINAL NUMBERS. THIS IS A LOW-CONFIDENCE TEMPERATURE FORECAST...ESPECIALLY WITH A FAIRLY TIGHT GRADIENT IN THE GRIDS...AND A MODEL BLEND WAS USED TO GET THE NUMBERS INTO REASONABLE POSITION. HOWEVER...THE EXTREMELY COLD VALUES IN THE CANADIAN MODEL WERE DISCARDED. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... FOR THE PERIOD WEDNESDAY NIGHT INTO THURSDAY NIGHT...THE ECMWF AND THE GFS STILL DIFFER A BIT ON THE TIMING OF A TANDEM OF S/WVS TO AFFECT THE REGION...ALONG WITH AN ASSOCIATED LOW PRESSURE/COLD FRONT. THE ECMWF IS SLIGHT SLOWER AND LITTLE MORE SHARPER WITH THE SECOND S/WV WHILE THE GFS IS FASTER. HAVE CONTINUED WITH THE GFS TIMING AT THIS TIME TO KEEP CONTINUITY FROM PREVIOUS FORECAST. WITH RETURN FLOW...TEMPERATURES WILL BEGIN TO WARM SOME LATE WEDNESDAY NIGHT INTO THURSDAY. THERE WILL BE A RACE BETWEEN HOW FAST IT WARMS COMPARED TO WHEN THE ONSET OF PCPN BEGINS. IT LOOKS LIKE THERE WILL BE A THREAT FOR A WINTRY MIX...SNOW...SLEET OR FREEZING RAIN FOR LOCATIONS ALONG AND NORTH OF THE OHIO RIVER LATE WEDNESDAY NIGHT INTO THURSDAY MORNING. BEST CHANCE WILL BE FROM EAST CENTRAL INDIANA INTO CENTRAL OHIO AND POINTS NORTH. MINOR SNOW...SLEET...OR ICE ACCUMULATIONS WILL BE POSSIBLE GIVEN A COLD START...ANY FREEZING RAIN WILL POSE A HAZARD TO TRAVEL SO WE WILL CONTINUE TO MONITOR THIS SYSTEM. HAVE MENTIONED THE THREAT IN THE HWO PRODUCT. PCPN IS EXPECTED TO CHANGE TO ALL RAIN BY THURSDAY AFTERNOON AS IT WARMS ABOVE FREEZING. PCPN SHOULD CHANGE BACK TO SNOW THURSDAY NIGHT IN THE WAKE OF THE COLD FRONT BEFORE ENDING BY FRIDAY MORNING. FOR FRIDAY INTO FRIDAY NIGHT...HIGH PRESSURE WILL ONCE AGAIN BUILD INTO THE REGION. TEMPERATURES WILL COOL BACK DOWN TO BELOW SEASONAL NORMALS. LONG RANGE MODELS DISAGREE ON HOW S/WV ENERGY FROM THE NRN BRANCH OF THE JET STREAM WILL EITHER PHASE OR NOT PHASE WITH SRN STREAM S/WV ENERGY. AS A RESULT...HAVE GONE WITH WPC FORECAST WHICH IS AN ENSEMBLE MEAN OF SOLUTIONS. THIS BRINGS A COLD FRONT THROUGH THE REGION SATURDAY NIGHT INTO SUNDAY WITH A CHANCE OF SNOW. COLDER AIR...OF THE ARCTIC VARIETY...SHOULD PUSH INTO THE REGION SUNDAY INTO MONDAY. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... MID LEVEL MOISTURE WILL STREAM DOWN INTO THE REGION TONIGHT FROM THE WESTERN GREAT LAKES AS UPPER LEVEL ENERGY DIVES DOWN INTO THE H5 TROF OVER THE EAST COAST. THE AXIS OF THE MOISTURE WILL TAKE IT DOWN TO THE SW OF CVG...SO THE BEST CLOUD COVERAGE WILL BE ACROSS THE SW TAFS. THE CONSENSUS OF THE MODELS IS TO KEEP ANY PCPN SW OF CVG...SO LEFT THE TAF DRY. DID TAKE CIGS DOWN TO AROUND 5K FT AT CVG...BUT LEFT A MID DECK AT LUK ALONG WITH ILN AND DAY. AS THE SYSTEM OFF EAST COAST DEEPENS IT COULD THROW SOME LOW CLOUDS BACK INTO THE ERN TAFS ON TUESDAY. BROUGHT MVFR CIGS TO CMH/LCK AROUND 14Z. WASNT AS CONFIDENT IN THE MVFR CIGS REACHING ILN...SO ONLY WENT WITH A TEMPO GROUP AFT 20Z. OUTLOOK...MVFR CIGS AND VSBYS POSSIBLE THURSDAY. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...NONE. KY...NONE. IN...NONE. && $$ SYNOPSIS...HATZOS NEAR TERM...HATZOS SHORT TERM...HATZOS LONG TERM...HICKMAN AVIATION...SITES

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