Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 310600 AFDILN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 100 AM EST SAT JAN 31 2015 .SYNOPSIS... HIGH PRESSURE WILL BUILD INTO THE AREA TONIGHT THROUGH SATURDAY. A DEVELOPING LOW PRESSURE SYSTEM WILL MOVE THROUGH THE OHIO VALLEY SUNDAY INTO MONDAY BRINGING WIDESPREAD SNOW AND RAIN TO THE REGION. A MUCH COLDER AIR MASS WILL MOVE IN BEHIND THE LOW PRESSURE SYSTEM FOR MONDAY. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... WINDS ARE LIGHT AND VARIABLE AS SURFACE HIGH PRESSURE BUILDS INTO THE REGION. SKIES HAVE BECOME MAINLY CLEAR AFTER CUMULUS DISSIPATED WITH LOSS OF DAYTIME HEATING...WHILE CIRRUS BEGINS TO INVADE FROM THE WEST AHEAD OF DEVELOPING LOW PRESSURE. LOWS TONIGHT WILL GENERALLY BE IN THE TEENS...ALTHOUGH SINGLE DIGITS WILL BE POSSIBLE ACROSS THE NORTH IN AREAS THAT STILL HAVE SOME SNOW COVER. && .SHORT TERM /6 AM THIS MORNING THROUGH SUNDAY NIGHT/... FOCUS IN THE SHORT TERM PERIOD IS ON THE DEVELOPING LOW PRESSURE SYSTEM FORECAST TO MOVE THROUGH THE OHIO VALLEY SUNDAY INTO SUNDAY NIGHT. THE 06Z AND 12Z NAM HAVE TRENDED CONSIDERABLY FARTHER NORTH WITH THE LOW TRACK AND AS A RESULT ARE NOW PULLING QUITE A BIT OF MORE WARM AIR UP AHEAD OF IT INTO OUR AREA. MEANWHILE...BOTH THE 12Z GFS AND 12Z ECMWF ARE STILL FARTHER SOUTH BUT BOTH HAVE BEEN NUDGING SLIGHTLY NORTHWARD WITH EACH RUN OVER THE LAST COUPLE OF DAYS. THE MODELS TEND TO HAVE A NORTHWEST SHIFT WITH TIME IN THE SURFACE LOW TRACK IN THESE DIGGING MID/UPPER LEVEL SHORT WAVE SITUATIONS. AS A RESULT...THINK THE NAM MAY VERY WELL BE LATCHING ON TO SOMETHING...BUT AM HESITANT TO COMPLETELY IGNORE THE ECMWF AND GFS WHICH HAVE BEEN MORE CONSISTENT. AS A RESULT...HAVE TAKEN MORE OF A BLEND OF THE NAM AND GFS/ECMWF BUT WOULD NOT BE SURPRISED IF THE NAM ENDS UP VERIFYING BETTER. AHEAD OF THE SYSTEM...DEVELOPING ISENTROPIC LIFT WILL ALLOW FOR SNOW TO OVERSPREAD THE AREA SATURDAY EVENING...CONTINUING INTO SATURDAY NIGHT. WITH THE MORE NORTHWARD SHIFT...IT LOOKS LIKE THE BEST SNOW SATURDAY NIGHT WILL LIKELY SET UP ACROSS NORTHERN PORTIONS OF OUR FA. AS THE LOW APPROACHES AND BETTER FRONTOGENESIS FORCING DEVELOPS...EXPECT PCPN TO INCREASE IN INTENSITY SUNDAY AFTERNOON INTO SUNDAY EVENING. HOWEVER...THERMAL FIELDS OFF THE NAM ARE SUPPORTING A CHANGE OVER TO RAIN UP TO AT LEAST I-70 THROUGH THE AFTERNOON...WHILE COOLER ECMWF/GFS KEEPS THE RAIN SNOW LINE DOWN CLOSER TO THE OHIO RIVER THROUGH MUCH OF THE DAY. TAKING MORE OF A BLEND OF THE NAM/GFS/ECMWF...WILL ALLOW FOR JUST A LITTLE BIT OF A MIX THROUGH THE I-70 CORRIDOR AND KEEP IT ALL SNOW ACROSS OUR FAR NORTHERN AREAS. AS A RESULT...WILL GO WITH 6-8 INCHES ALONG AND NORTH OF THE I-70 CORRIDOR WITH UP TO AROUND 10 INCHES NOT OUT OF THE QUESTION ACROSS OUR FAR NORTHERN COUNTIES. MOVING SOUTH...SNOW AMOUNTS/HEADLINE DECISIONS BECOME MORE PROBLEMATIC DUE TO THE RAIN MIXING IN/CHANGEOVER AND THE FACT THAT OUR WATCH/WARNING CRITERIA DROPS OFF TO 4 INCHES RIGHT ABOUT WHERE THE RAIN/SNOW TRANSITION LINE IS EXPECTED TO SET UP. SINCE IT IS JUST A WATCH AND WE ARE STILL A WAYS OUT...HAVE OPTED TO ERR ON THE SIDE OF CAUTION AND INCLUDE THE NORTHERN TIER OF OUR LOWER CRITERIA COUNTIES IN THE WATCH...RUNNING FROM FRANKLIN COUNTY INDIANA TO FAIRFIELD COUNTY OHIO. CONFIDENCE IS NOT ALL THAT HIGH THAT WE WILL ACTUALLY REACH WARNING CRITERIA IN THOSE COUNTIES BUT WANTED TO BUILD IN A LITTLE WIGGLE ROOM IN CASE THE GFS/ECMWF END UP BEING CLOSER TO THE FINAL SOLUTION. && .LONG TERM /MONDAY THROUGH FRIDAY/... THE WINTER STORM WILL BE COMING TO AN END ON MONDAY MORNING...WITH SOME LIGHT ADDITIONAL SNOW ACCUMULATIONS POSSIBLE IN THE SCIOTO VALLEY BETWEEN 12Z AND 18Z. ON THE BACK SIDE OF THE STRENGTHENING SURFACE LOW...GUSTY NNW FLOW WILL LEAD TO STRONG COLD ADVECTION THROUGH THE GREAT LAKES AND NORTHERN OHIO VALLEY. THIS WILL LEAD TO A FEW COMPLICATIONS WITH THE FORECAST. FOR ONE...TEMPS WILL BE FALLING RAPIDLY GOING INTO THE EARLY MORNING HOURS. WITH THE POTENTIAL FOR SOME BLOWING SNOW...AND REFREEZING ON ROADS...THIS COULD ALLOW HAZARDOUS CONDITIONS TO CONTINUE THROUGH BEYOND THE END OF THE SNOWFALL. ALSO...THE DIURNAL RANGE FOR MONDAY WILL BE QUITE SMALL...EVEN WITH SOME BREAKS IN THE CLOUDS EXPECTED TO DEVELOP. MAX TEMPS ARE UNLIKELY TO RISE MORE THAN A FEW DEGREES FROM THE MORNING LOWS. COLD AND DRY HIGH PRESSURE WILL MOVE OVER THE REGION BY TUESDAY MORNING. ALTHOUGH SOME CLOUDS MAY STILL PERSIST...RADIATIONAL COOLING CONDITIONS WILL BE OTHERWISE FAVORABLE...ALLOWING FOR TEMPERATURES IN SNOW-COVERED AREAS TO APPROACH OR EVEN DROP BELOW ZERO DEGREES. COMBINED WITH SOME WIND (GENERALLY INCREASING SLIGHTLY BY 12Z)...WIND CHILLS APPEAR LIKELY TO DROP INTO ADVISORY CRITERIA FOR THE NORTHERN SECTIONS OF THE FORECAST AREA. FORECAST SPECIFICS BECOME MUCH MORE UNCERTAIN FOR TUESDAY AND BEYOND. QUICK WNW FLOW ALOFT WILL BE SET UP ACROSS THE NORTHERN TIER OF THE CONUS...WITH SEVERAL WEATHER DISTURBANCES EXPECTED TO MOVE THROUGH. AN INITIAL SHORTWAVE WILL WEAKEN AS IT MOVES INTO THE GREAT LAKES ON TUESDAY...WITH ANOTHER COLD FRONT EXPECTED TO MOVE THROUGH SOMETIME BETWEEN WEDNESDAY NIGHT INTO THURSDAY. IN ADVANCE OF THE FRONT...TEMPERATURES APPEAR LIKELY TO BE SOMEWHAT MILD...AND VALUES WERE RAISED IN THE FORECAST FOR THIS TIME PERIOD. HOWEVER...BEHIND THE FRONT...ANOTHER LENGTHY PERIOD OF COLD CONDITIONS IS EXPECTED TO CONTINUE THROUGH THE WEEKEND. PRECIPITATION WITH THE COLD FRONT WILL LIKELY BE MAINLY SNOW...BUT CURRENT MODEL FORECASTS ARE FAIRLY SUBDUED ON ACCUMULATION POTENTIAL. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... VFR CONDITIONS WILL BE FOUND OVER THE TAF SITES THROUGH MOST OF THE PERIOD. AT THE TAIL END A NOSE OF PRECIPITATION WILL AFFECT WESTERN SITES AFTER ABOUT 3 OR 4Z WHICH WILL LOWER VSBYS AND CIGS TO MVFR RANGE. ATTM...RAIN MAY MIX WITH SNOW AT CVG/LUK BEFORE THE WARMER AIR ON SOUTHERLY WINDS PUSH THE MIX NORTH AND MIX OUT ANY LOWER CEILINGS IN THE 6-12Z TIME FRAME. KDAY AND KILN STAND A BETTER CHANCE OF SEEING PLAIN SNOW AS A START TO THIS WINTER EVENT. KCMH/LCK WILL LIKELY NOT SEE ANY PRECIP UNTIL AFTER 6Z. OUTLOOK...SIGNIFICANT SNOW ACCUMULATIONS...IFR CEILINGS AND VISIBILITIES LIKELY THROUGH SUNDAY NIGHT WITH MVFR CONDITIONS POSSIBLY CONTINUING INTO MONDAY. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...WINTER STORM WATCH FROM LATE TONIGHT THROUGH MONDAY MORNING FOR OHZ026-034-035-042>046-051>056-060>065-070>072. KY...NONE. IN...WINTER STORM WATCH FROM LATE TONIGHT THROUGH MONDAY MORNING FOR INZ050-058-059-066. && $$ SYNOPSIS...JGL NEAR TERM...CONIGLIO/JGL SHORT TERM...JGL LONG TERM...HATZOS AVIATION...FRANKS

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