Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 230026 AFDILN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 726 PM EST MON DEC 22 2014 .SYNOPSIS... AS A LARGE TROUGH OF LOW PRESSURE MOVES TOWARD THE OHIO VALLEY...CHANCES FOR RAIN WILL INCREASE TONIGHT...AS WARM AND MOIST AIR MOVES INTO THE REGION. A COLD FRONT WILL MOVE INTO INDIANA BY WEDNESDAY MORNING...BEFORE MOVING ACROSS THE REGION LATE WEDNESDAY. AHEAD OF THE FRONT...ADDITIONAL RAIN IS EXPECTED ON WEDNESDAY. COOLER TEMPERATURES ARE EXPECTED FOR THE END OF THE WEEK. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... A LARGE UPPER TROUGH OVER THE CENTRAL STATES IS VERY SLOWLY MOVING EASTWARD...WITH DEEP SOUTHWESTERLY FLOW NOW IN PLACE ACROSS THE OHIO VALLEY. AT THE SURFACE...THE PRESSURE GRADIENT HAS STRENGTHENED TODAY...AS A RESULT OF HIGH PRESSURE OFF THE NORTHEAST COAST AND LOW PRESSURE DEVELOPING IN THE OMAHA / KANSAS CITY AREA. THE KILN VWP SHOWS A CLASSIC WARM ADVECTION PATTERN...THOUGH SURFACE WINDS REMAIN SOMEWHAT BACKED...AS A RESULT OF AN INVERSION NEAR 925MB THAT HAS NOT BEEN COMPLETELY BROKEN. MOISTURE TRANSPORT INTO THE OHIO VALLEY IS FORECAST TO INCREASE SIGNIFICANTLY THIS EVENING AND INTO THE OVERNIGHT HOURS. AT THE SAME TIME...A LEAD SHORTWAVE WILL ROTATE NORTHEAST AROUND THE LARGE MID-LEVEL TROUGH...PROVIDING ASCENT IN A FAVORABLE AREA OF DIFFLUENT UPPER FLOW. PRECIPITATION IS EXPECTED TO BECOME FAIRLY WIDESPREAD (THOUGH NOT PARTICULARLY HEAVY) BETWEEN 00Z AND 06Z...GRADUALLY SPREADING NORTHEAST THROUGH THE NWS ILN FORECAST AREA BY WEDNESDAY MORNING. BECAUSE OF THE EXPECTED SCATTERED NATURE OF THE SHOWERS...AND SOME SLIGHT TIMING DIFFERENCES AMONG EVEN THE HIGHER-RESOLUTION MODELS...POPS WERE KEPT IN THE 70-90 PERCENT RANGE. ONCE RADAR TRENDS CAN BE MONITORED...100-PERCENT CHANCES WILL PROBABLY HAVE TO BE INTRODUCED. THE MOST LIKELY CHANCES FOR RAIN APPEAR TO BE IN THE 06Z-09Z TIME FRAME IN THE NORTHERN AND NORTHWESTERN PORTIONS OF THE CWA. AS WAS OBSERVED YESTERDAY...TEMPERATURES ARE LIKELY TO DROP AT SUNSET. HOWEVER...WITH THICKENING LOW-LEVEL MOISTURE AND A SHIFT IN THE NEAR-SURFACE FLOW TO THE SSE...TEMPERATURES ARE LIKELY TO BEGIN RISING AGAIN BEFORE SUNRISE. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/... AFTER AN INITIAL SHORTWAVE PASSES NORTHEAST OF THE OHIO VALLEY ON TUESDAY MORNING...SEVERAL MODELS INDICATE THAT CONDITIONS TUESDAY MID-DAY AND AFTERNOON WILL BE RATHER DRY. THE ILN CWA WILL BE IN AN AREA WITH POOR UPPER SUPPORT FOR ASCENT (CONVERGENCE ALOFT) AND LITTLE IN THE WAY OF LOW-LEVEL FORCING. FOLLOWING THE LEAD OF THE WRF-ARW / WRF-NMM MODELS...POPS WERE REDUCED TO 20-30 PERCENT UNTIL LATE TUESDAY AFTERNOON. AS SURFACE CYCLOGENESIS BEGINS SW OF THE REGION ON TUESDAY EVENING...A STRENGTHENING LOW-LEVEL JET WILL BEGIN A PUSH TOWARD THE MIDDLE OHIO VALLEY. AS THIS LOW-LEVEL CONVERGENCE INCREASES...THE MID-LEVEL TROUGH WILL ALSO BE REALIGNING ITSELF AND BEGINNING TO MOVE EAST...WITH CONDITIONS AGAIN BECOMING SUPPORTIVE FOR ASCENT AS VORTICITY ADVECTION INCREASES. WIDESPREAD PRECIPITATION IS EXPECTED TO OVERSPREAD THE ILN FORECAST AREA BETWEEN 00Z AND 12Z...AS PRECIPITABLE WATER VALUES MAX OUT ABOVE 1.25 INCHES IN THE SOUTHEASTERN SECTION OF THE CWA...OVER 300 PERCENT OF NORMAL FOR DECEMBER. ANY CHANCES FOR HEAVY RAIN APPEAR TO BE MORE SHOWERY THAN PROLONGED...AND RAINFALL AMOUNTS SHOULD GENERALLY STAY UNDER AN INCH...LEAVING LITTLE POTENTIAL FOR FLOODING. BECAUSE THERE ARE STILL SEVERAL DIFFERING SOLUTIONS WITH REGARDS TO THE EXACT TIMING AND PLACEMENT OF PRECIPITATION...CONFIDENCE IS NOT PARTICULARLY HIGH IN THE EXACT ARRANGEMENT OF THE POP/WEATHER GRIDS. ON WEDNESDAY MORNING...A COLD FRONT WILL BE STALLED OVER INDIANA...ORIENTED IN A NNE-TO-SSW DIRECTION. AS THE DEVELOPING SURFACE LOW MOVES NORTH...THE FRONT WILL BEGIN TO MOVE...PASSING THROUGH THE ILN FORECAST AREA LATE IN THE DAY. AHEAD OF THE FRONT...AND MAINLY FOCUSED IN THE SOUTHEASTERN CWA...SOME WEAK INSTABILITY IS EXPECTED TO DEVELOP. ALTHOUGH A VERY SMALL INVERSION IS LIKELY TO REMAIN IN PLACE FOR MOST OF THE CWA...THE BOUNDARY LAYER MAY WARM UP ENOUGH TO SUPPORT A MOIST-ADIABATIC PROFILE IN NORTHEAST KENTUCKY AND SOUTHERN OHIO. FOR JUST A FEW HOURS AHEAD OF THE FRONT LATE WEDNESDAY AFTERNOON AND EARLY EVENING...A CHANCE OF THUNDER WAS INCLUDED IN THE FORECAST. AFTER THE SURFACE COLD FRONT PASSES THROUGH ON WEDNESDAY EVENING...THE BASE OF THE MID-LEVEL TROUGH IS EXPECTED TO MOVE EAST ACROSS THE OHIO VALLEY THROUGH THURSDAY MORNING. IN A COOLING AIR MASS...RAIN SHOWERS WILL EVENTUALLY CHANGE TO SNOW SHOWERS...AND THE POSSIBILITY FOR VERY LIGHT ACCUMULATIONS DOES EXIST (MAINLY IN THE NORTHERN HALF OF THE FORECAST AREA). HOWEVER...WITH SURFACE TEMPERATURES ONLY EXPECTED TO GET INTO THE LOWER TO MID 30S...AND GROUND CONDITIONS WILL BE WET. THUS...THE SNOW MAY NOT BE ABLE TO STICK OR ACCUMULATE APPRECIABLY...AND CONCERNS FOR HAZARDOUS WEATHER ARE RATHER UNLIKELY. RUNNING THE MATH ON THE FORECAST QPF/POPS/TEMPERATURES...A FEW TENTHS OF AN INCH OF SNOW WERE GENERATED ALONG AND NORTH OF INTERSTATE 70...AND INCLUDED IN THE 06Z-12Z FORECAST BLOCK. TEMPERATURES THROUGH THE SHORT TERM FORECAST PERIOD ARE GOING TO BE HEAVILY DRIVEN BY ADVECTION...REQUIRING NON-DIURNAL TEMPERATURE CURVES THROUGH THURSDAY MORNING. WITH A LITTLE MORE CONFIDENCE IN THE WARM ADVECTION PATTERN...TEMPERATURES WERE INCREASED SLIGHTLY FOR WEDNESDAY...WITH LOWER 60S NOW IN THE FORECAST IN THE PORTSMOUTH AREA. FINALLY...THERE DOES APPEAR TO BE A POTENTIAL FOR SOME GUSTY WINDS ON WEDNESDAY...PRIMARILY BEHIND THE COLD FRONT. THE PRESSURE GRADIENT WILL BE VERY TIGHT...AND THE EVENTUAL STRENGTH OF THE SURFACE LOW WILL CERTAINLY PLAY A ROLE IN HOW STRONG THE WINDS CAN GET. BASED ON 12Z NAM / 12Z GFS BUFKIT SOUNDINGS...GUSTS OF AROUND 30 KNOTS HAVE BEEN INCLUDED IN THE FORECAST. && .LONG TERM /THURSDAY THROUGH MONDAY/... SCATTERED RAIN AND/OR SNOW SHOWERS WILL QUICKLY EXIT OFF TO THE EAST/NORTHEAST CHRISTMAS MORNING AS AFOREMENTIONED LOW PRESSURE SYSTEM MOVES OFF TO THE NORTHEAST. IT NOW APPEARS PER MODEL SOUNDINGS/RH FIELDS THAT POST SYSTEM STRATOCUMULUS DECK WILL HANG IN LONGER THROUGH THE DAY DESPITE SURFACE RIDGING BUILDING TO THE OHIO VALLEY FAIRLY QUICK. WE SHOULD SEE A DECREASE IN CLOUD COVER FROM WEST TO EAST FROM THE AFTERNOON INTO THE EVENING. HIGHS WILL BE NEAR SEASONAL NORMALS RANGING FROM THE UPPER 30S TO THE LOWER 40S. SURFACE RIDGE OF HIGH PRESSURE WILL GRADUALLY MOVE OFF TO THE EAST THURSDAY NIGHT INTO FRIDAY WHILE LOW PRESSURE AND A COLD FRONT APPROACH FROM THE WEST. MODELS HAVE SLOWED DOWN THIS SYSTEM SOME. AS SUCH...WE SHOULD SEE SOME SUNSHINE ON FRIDAY. WITH SOUTHERLY FLOW AND DIABATIC HEATING...TEMPERATURES ARE FORECAST TO WARM INTO THE UPPER 40S TO THE LOWER 50S. FOR FRIDAY NIGHT INTO SATURDAY...COLD FRONT WILL MOVE SLOWLY SOUTHEAST INTO OUR AREA. SYSTEM CONTINUES TO BE MOISTURE STARVED FOR THE MOST PART...RESULTING IN THE CONTINUATION OF LOW CHANCE POPS. WE SHOULD SEE SOME LIGHT RAIN AND/OR LIGHT SNOW DURING THIS PERIOD AS COLDER AIR SLOWER FILTERS INTO THE REGION. FOR THE PERIOD SATURDAY NIGHT INTO SUNDAY...OPERATIONAL 12Z MODELS BEGIN TO DIVERGE SIGNIFICANTLY WITH EACH OTHER. FORECAST SOLUTIONS FROM EACH MODEL ARE DEPENDENT ON WHETHER S/WV ENERGY ASSOCIATED WITH THE SYSTEM ON SATURDAY REMAINS IN TACT AS ONE FEATURE AS IT HEADS NORTHEAST THROUGH THE GREAT LAKES...OR SPLITS INTO TWO DISTINCT PIECES OF ENERGY...WITH ONE HANGING BACK. THE GFS AND ECMWF ARE IN STARK OPPOSITES OF EACH OTHER WITH THE GFS MAINTAINING THE ONE S/WV SOLUTION AND THE ECMWF MAINTAINING TWO DISTINCT S/WVS. THE CMC WAS SPLIT BETWEEN THE TWO WITH A WEAKER SECONDARY HANG BACK S/WV. AS A RESULT...THE GFS FORECASTS HIGH PRESSURE FOR SUNDAY AND COLDER TEMPERATURES WHILE THE ECMWF DEVELOPS A SFC WAVE ALONG STALLED OUT FRONTAL BOUNDARY...PUSHING PCPN NORTH OF THE OHIO RIVER AND EVEN ALL THE WAY TO THE SOUTHERN GREAT LAKES. OBVIOUSLY THIS IS A LOW CONFIDENCE FORECAST ATTM AND HAVE TAKEN A BLEND OF WPC/GFS/CMC WHICH BRINGS LOW CHANCES FOR RAIN/SNOW TO OUR SRN CWFA ON SUNDAY WHILE MAINTAINING A DRY FORECAST FARTHER NORTH. HIGH PRESSURE SHOULD ESTABLISH ITSELF ACROSS THE AREA SUNDAY NIGHT INTO MONDAY. TEMPERATURES WILL BE SLIGHTLY BELOW SEASONAL NORMALS BY THEN. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/...
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SE SFC FLOW HAS KEPT THE LOW LEVELS DRY AND CIGS VFR FOR THE BEGINNING OF THE TAF PERIOD. AS FLOW BECOMES SOUTHERLY TOWARDS 06Z...CIGS WILL DROP TO MVFR AND SCATTERED SHOWERS WILL AFFECT THE TAFS. IT LOOKS LIKE THIS SHOT OF RAIN IS ASSOCIATED WITH VORT LOBE SWINGING NORTH IN THE H5 FLOW. AFTER THIS SHOT OF LIFT...BETWEEN 06-12Z...IT IS LOOKS LIKE THE LIFT IS WEAK AND THAT THE RAIN CHANCES WILL BE PRETTY SCATTERED SO KEPT ONLY VCSH IN THE TAFS. DESPITE THE WEAK LIFT...MODELS ARE BRINGING IN PLENTY OF LOW LEVEL MOISTURE...SO MVFR CIGS ARE EXPECTED THROUGHOUT THE DAY. THEY COULD DROP TO IFR...BUT CONFIDENCE IS NOT HIGH ENOUGH AT THIS TIME TO PUT IN FORECAST. OUTLOOK...MVFR CIGS AND VSBYS ARE POSSIBLE THROUGH THURSDAY AND COULD DROP TO IFR AT TIMES. WINDS WILL PICK UP WEDNESDAY INTO THURSDAY.
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&& .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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