Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 092046 AFDILN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 346 PM EST TUE FEB 9 2016 .SYNOPSIS...
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A LARGE UPPER TROUGH WILL SLOWLY MOVE EAST OF THE OHIO VALLEY OVER THE NEXT FEW DAYS. THIS WILL KEEP A CHANCE OF SNOW SHOWERS THROUGH WEDNESDAY...AND BELOW NORMAL TEMPERATURES (WITH DRIER CONDITIONS) THROUGH THE REST OF THE WEEK.
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&& .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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WINTER WEATHER ADVISORY HEADLINES HAVE BEEN EXTENDED SLIGHTLY INTO WEDNESDAY...PRIMARILY DUE TO THE PROLONGED AND CONTINUED CHANCE OF SNOW SHOWERS OVER THE NEXT 24 HOURS. CHANCES FOR SNOW ON WEDNESDAY WILL BE DISCUSSED IN THE SHORT TERM SECTION BELOW. LARGE-SCALE TROUGHING CONTINUES TO ENVELOP THE ENTIRE EASTERN HALF OF THE COUNTRY...WITH THE AXIS OF THE TROUGH STILL IN PLACE OVER THE GREAT LAKES AND OHIO VALLEY. ORIGINALLY A CLOSED LOW...THE TROUGH IS GRADUALLY WEAKENING AS IT MOVES TO THE EAST. WATER VAPOR IMAGERY SHOWS THE COMPLEXITIES OF THE SYSTEM...WITH AN OBVIOUS LARGE-SCALE CIRCULATION ACROSS HUNDREDS OF MILES...BUT SEVERAL INDIVIDUAL GYRES EMBEDDED WITHIN THE BROADER FLOW. AT THE SURFACE...A CLOSED LOW IS CURRENTLY LOCATED NORTH OF LONDON ONTARIO. THIS LOW HAS SEVERAL TROUGHS ROTATING AROUND IT...WITH ONE TROUGH ENTERING THE FORECAST AREA FROM THE NORTHWEST AS OF THIS WRITING. WITH A NOTED WIND SHIFT...AND SOME ENHANCED CONVERGENCE...SNOW SHOWERS HAVE DEVELOPED ACROSS THE ILN FORECAST AREA THIS AFTERNOON. ADDITIONAL SNOW SHOWER DEVELOPMENT IS EXPECTED AS THIS FEATURE MOVES THROUGH THE REGION...WITH THE POTENTIAL FOR AROUND A HALF INCH OF SNOWFALL. FORCING BECOMES WEAKER GOING THROUGH THE REST OF THE EVENING AND OVERNIGHT...BUT MODEL SOUNDINGS SUGGEST THAT THE BOUNDARY LAYER WILL REMAIN WELL MIXED...WITH MOISTURE EXTENDING A LITTLE BIT INTO THE DENDRITIC GROWTH ZONE FROM THE BOTTOM OF THE INVERSION. THUS...SOME LIGHT SNOW SHOWERS OR FLURRIES WILL REMAIN LIKELY THROUGH THE NIGHT. TEMPERATURES WILL CONTINUE TO FALL IN THE COLD ADVECTION TONIGHT...AND TEMPERATURES WILL LIKELY REACH THE MIDDLE TO UPPER TEENS ACROSS THE FORECAST AREA. FOR THE AREA WHERE SNOW WAS HEAVIEST THIS MORNING (HAMILTON COUNTY TO HOCKING COUNTY)...TEMPERATURES WERE DROPPED A FEW DEGREES BELOW THE OTHERWISE-EXPECTED FORECAST NUMBERS FOR THE REST OF THE CWA.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
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THE PRIMARY UPPER TROUGH AXIS WILL BE MOVING AWAY FROM THE REGION EARLY WEDNESDAY...BUT CHANCES FOR SNOW WILL INCREASE AGAIN ON WEDNESDAY MORNING. A COMBINATION OF FORCING FROM A SHORTWAVE AND SURFACE TROUGH WILL PIVOT EASTWARD THROUGH THE REGION BETWEEN 09Z AND 18Z. WITH COLDER TEMPERATURES THAN EXPERIENCED TODAY (TUESDAY)...ESPECIALLY ALOFT IN THE 900MB-750MB LAYER...THE POTENTIAL FOR WEAK CONVECTIVE INSTABILITY THROUGH THE DENDRITIC GROWTH ZONE WILL BE INCREASED. THE COMBINATION OF FORCING AND STEEL LAPSE RATES WILL BE GREATEST OVER THE NORTHEASTERN QUADRANT OF THE FORECAST AREA (CENTRAL OHIO) DURING THE 15Z-18Z TIME FRAME...WHERE SOME HEAVY SNOW SHOWERS MAY BE POSSIBLE. IT IS ALWAYS DIFFICULT TO DRAW A UNIFORM SNOW TOTAL FORECAST GRID IN A SNOW SHOWER SITUATION...GIVEN THE INHERENT GEOGRAPHIC UNCERTAINTIES CAUSED BY THE EVENTUAL DEVELOPMENTAL LOCATIONS OF THE HEAVIEST SHOWERS. THAT BEING SAID...ACCUMULATIONS OF AROUND AN INCH WILL NOT BE A SURPRISE AT ALL...WITH THE GREATEST POTENTIAL FOR UP TO TWO INCHES IN THE NORTHEASTERN ILN CWA. POPS RANGE FROM 40-80 PERCENT ACROSS THE FORECAST AREA FROM SOUTHWEST TO NORTHEAST...WITH THESE VALUES KEPT LOWER THAN PREFERRED DUE TO THE AFOREMENTIONED ISSUES AND FOR COLLABORATION PURPOSES. THESE POP NUMBERS WILL LIKELY NEED TO BE RAISED IN FUTURE FORECASTS...AS IT SEEMS QUITE CERTAIN THAT MOST LOCATIONS WILL AT LEAST MEASURE A LITTLE BIT OF ADDITIONAL SNOW ON WEDNESDAY MORNING. AS A FINAL NOTE ABOUT THE SNOW...A FAVORABLY-POSITIONED STRATOCUMULUS DECK WILL LIKELY KEEP THE CHANCE OF FLURRIES IN PLACE THROUGH WEDNESDAY NIGHT...POSSIBLY EVEN INTO THURSDAY MORNING. THE WINTER WEATHER ADVISORY ESSENTIALLY HAS TWO SEGMENTS...THOUGH CODING PURPOSES REQUIRE IT TO BE SPLIT INTO FOUR GROUPS. FOR THE SOUTHERN AND SOUTHWESTERN CWA (CINCINNATI/WILMINGTON/MAYSVILLE) THE ADVISORY WAS EXTENDED THROUGH MORNING. FOR THE EASTERN CWA (PORTSMOUTH/CHILLICOTHE/COLUMBUS) THE ADVISORY WAS CONTINUED THROUGH LATE AFTERNOON. TEMPERATURES ARE EXPECTED TO RISE ONLY VERY SLIGHTLY ON WEDNESDAY...AS CONTINUED COLD ADVECTION (AND A LACK OF INSOLATION) LIMITS THE POTENTIAL FOR DIURNAL HEATING. WEDNESDAY NIGHT WILL BE QUITE COLD...ESPECIALLY WITH SNOW IN PLACE...AND TEMPERATURES IN THE SINGLE DIGITS ARE NOW IN THE FORECAST (DROPPED SEVERAL DEGREES FROM PREVIOUS NUMBERS). LITTLE CHANGE IS EXPECTED TO THE TEMPERATURES ON THURSDAY...WITH A GENERALLY NEUTRAL LOW-LEVEL ADVECTION PATTERN. HOWEVER...WITH TEMPERATURES SLOWLY BEGINNING TO WARM ALOFT...THE CLOUDS ARE EXPECTED TO EVENTUALLY BREAK BY THE END OF THE DAY.
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&& .LONG TERM /FRIDAY THROUGH MONDAY/...
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A WEAK SYSTEM WILL MOVE GENERALLY SOUTH OF THE AREA FRIDAY MORNING. INTRODUCE ONLY A SLIGHT CHANCE OF SNOW SHOWERS TO SOUTHERN PORTIONS OF THE REGION DURING THIS TIME. AN UPPER LEVEL DISTURBANCE MOVES THROUGH FRIDAY AFTERNOON INTO FRIDAY EVENING BRINGING BETTER CHANCES FOR SOME LIGHT SNOW TO THE REGION. WINDS OFF OF LAKE MICHIGAN WILL LINGER SNOW SHOWERS ACROSS PORTIONS OF THE AREA FRIDAY NIGHT INTO SATURDAY. TEMPERATURES WILL STRUGGLE TO RISE ON SATURDAY WITH COLD AIRMASS IN PLACE. ANY REMAINING SNOW SHOWERS WILL TAPER OFF BY SATURDAY EVENING AND CLOUD COVER WILL DECREASE. THE COMBINATION LIGHT WINDS...MOSTLY CLEAR SKIES...AND SNOW ON THE GROUND WILL LEAD TO TEMPERATURES DROPPING INTO THE SINGLE DIGITS TO SINGLE DIGITS BELOW ZERO SATURDAY NIGHT. DRY CONDITIONS WILL BE IN PLACE MOST OF THE DAY ON SUNDAY HOWEVER EXPECT AN INCREASE IN CLOUDS THROUGH THE DAY IN ADVANCE OF THE NEXT SYSTEM. MODELS ARE IN SOME DISAGREEMENT ON HOW QUICKLY PRECIPITATION WILL OVERSPREAD THE AREA. HAVE PRECIPITATION CHANCES BEGINNING TO MOVE INTO THE REGION SUNDAY EVENING INTO SUNDAY NIGHT WITH BETTER CHANCES DURING THE DAY ON MONDAY. ALTHOUGH THERE MAY BE A BRIEF MIX IN PRECIPITATION ACROSS SOUTHERN PORTIONS OF THE REGION GENERALLY EXPECT TEMPERATURE PROFILES TO BE COLD ENOUGH THAT PRECIPITATION WILL BE IN THE FORM OF SNOW. SNOW WILL TAPER OFF MONDAY NIGHT WITH HIGH PRESSURE AND DRY CONDITIONS MOVING INTO THE REGION FOR TUESDAY.
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&& .AVIATION /20Z TUESDAY THROUGH SUNDAY/... A LARGE SCALE UPPER LEVEL TROUGH WILL REMAIN OVER THE GREAT LAKES AND OHIO VALLEY THROUGH THE TAF PERIOD. FOR THIS AFTERNOON INTO EARLY EVENING...A SURFACE TROUGH WILL ROTATE EAST ACROSS THE NORTHERN TAT SITES. THIS FEATURE WILL BRING A PERIOD OF MVFR CEILINGS AND IFR VISIBILITIES TO KDAY...KCMH...AND KLCK. ELSEWHERE...DIURNAL INSTABILITY AND CYCLONIC FLOW WILL RESULT IN MAINLY LIGHT SNOW SHOWERS. MVFR CEILINGS/VISIBILITIES WITH PERHAPS POCKETS OF IFR VISIBILITIES ARE EXPECTED WITH THIS ACTIVITY. FOR TONIGHT...MODELS SUGGEST THAT AN EMBEDDED DISTURBANCE WILL DIG SOUTHEAST TOWARD THE REGION BETWEEN 06Z AND 12Z. BEFORE THEN...FORECAST AREA WILL HAVE A RELATIVE LULL IN SNOW SHOWER ACTIVITY. THEREAFTER...SNOW SHOWER COVERAGE SHOULD INCREASE FROM WEST TO EAST. HAVE TRIED TO TIME THE HIGHER PROBABILITY OF SNOW SHOWERS AT THE TAF SITES. MVFR CONDITIONS WILL PERSIST WITH AN OCCASIONAL LOWER IFR VISIBILITY POSSIBLE. ON WEDNESDAY...EMBEDDED DISTURBANCE WILL MOVE EAST. SNOW SHOWERS WILL TAPER TO FLURRIES WEST. MVFR CONDITIONS WILL PERSIST. OUTLOOK...MVFR CEILINGS POSSIBLE WEDNESDAY NIGHT INTO THURSDAY. MVFR CEILINGS AND VISIBILITIES POSSIBLE FRIDAY AFTERNOON INTO SATURDAY. && .ILN WATCHES/WARNINGS/ADVISORIES...
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OH...WINTER WEATHER ADVISORY UNTIL 10 AM EST WEDNESDAY FOR OHZ053- 060>062-070>072-077>081. WINTER WEATHER ADVISORY UNTIL 6 PM EST WEDNESDAY FOR OHZ046- 054>056-063>065-073-074-082-088. KY...WINTER WEATHER ADVISORY UNTIL 10 AM EST WEDNESDAY FOR KYZ089>100. IN...WINTER WEATHER ADVISORY UNTIL 10 AM EST WEDNESDAY FOR INZ058- 059-066-073>075-080.
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&& $$ SYNOPSIS...HATZOS NEAR TERM...HATZOS SHORT TERM...HATZOS LONG TERM...NOVAK AVIATION...HICKMAN

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