Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 222059 AFDILN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 359 PM EST MON DEC 22 2014 .SYNOPSIS...
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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.
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&& .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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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.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/...
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THE SHORT TERM FORECAST DISCUSSION WILL BE UPDATED SHORTLY. PREVIOUS DISCUSSION > WARM FRONT WILL LIFT NORTH ACROSS THE REGION TONIGHT. SHOWERS WILL OCCUR ALONG THIS BOUNDARY AS IT LIFTS THROUGH. CANNOT COMPLETELY RULE OUT A THUNDERSTORM BUT THAT CHANCE LOOKS TOO LOW TO INCLUDE IN THE FORECAST AT THIS POINT. TEMPERATURES MAY DROP OFF SOME IN THE EVENING BUT THEN READINGS WILL BE STEADY OR RISE THROUGH THE NIGHT. SHOWERS MAY LINGER INTO TUESDAY MORNING BUT THEN THE FORCING BECOMES WEAK. SO THE CHANCE OF PRECIPITATION WILL DIMINISH TUESDAY AFTERNOON WITH A COMPLETE LULL IN ACTIVITY POSSIBLE. STAYED NEAR MODEL CONSENSUS FOR HIGHS. A WEAK COLD FRONT WITH LITTLE IF ANY CONVERGENCE WILL MOVE TOWARDS THE INDIANA-OHIO LINE LATE TUESDAY INTO TUESDAY EVENING BEFORE STALLING. THIS BOUNDARY BECOMES IMPORTANT BECAUSE LOW PRESSURE WILL TRACK NORTH NORTHEAST ALONG IT TUESDAY NIGHT INTO WEDNESDAY AS A SHORT WAVE LIFTS OUT OF THE SOUTHERN PLAINS. THE 00Z NAM WAS AN OUTLIER IN THIS REGARD AND SEEMS UNLIKELY TO VERIFY AT THIS POINT. AS FORCING INCREASES TUESDAY NIGHT SHOWERS WILL REDEVELOP AND SPREAD ACROSS THE REGION. THE PRECIPITATION SHOULD BE WIDESPREAD BY LATE TUESDAY NIGHT AND CONTINUE INTO WEDNESDAY. AGAIN THERE IS THE POTENTIAL FOR SOME THUNDERSTORMS AHEAD OF THE LOW BUT CONFIDENCE WAS NOT HIGH ENOUGH TO INCLUDE IN THE GRIDS. TEMPERATURE FORECAST BECOMES QUITE A CHALLENGE WITH A WIDE VARIETY OF POSSIBILITIES OFFERED BY BOTH MODELS AND MOS. SEEMS MOST LIKELY THAT IT WILL REMAIN QUITE MILD TUESDAY NIGHT EXCEPT FOR PERHAPS THE FAR WESTERN COUNTIES WHERE THE STALLED BOUNDARY WILL SET UP. HAVE USED A BLEND OF SREF AND ECMWF 2 METER TEMPERATURES WHICH ENDS UP FALLING BETWEEN GFS MOS AND PARALLEL GFS MOS. NOT EXPECTING MUCH RISE IN READINGS ON WEDNESDAY BEFORE THE LOW PASSES AND TEMPERATURES START FALLING OFF. SYSTEM GETS PRETTY DYNAMIC SO THERE COULD BE SOME GUSTY SOUTHERLY WINDS IN THE WARM SECTOR AS THE LOW MOVES THROUGH ON WEDNESDAY.
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&& .LONG TERM /THURSDAY THROUGH MONDAY/...
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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.
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&& .AVIATION /20Z MONDAY THROUGH SATURDAY/... PRECIP WILL START IN THE 0-6Z TIME FRAME TONIGHT AND THEN INCREASE IN COVERAGE THROUGH 12Z. NAM MODEL IS NOTORIOUSLY DRY AFTER AN INITIAL WAVE THIS EVENING. WILL OPT TO KEEP THE PREVAILING SHOWERS THAT ARE IN THE FORECAST TONIGHT BUT TRY TO HEDGE SLIGHTLY TO THE DRIER SOLUTION WHICH HAS SUPPORT FROM THE REGIONAL CANADIAN MODEL. THE NEWD EJECTING INITIAL LOBE OF RAIN WITH THE WEAKENING SFC LOW IN WI WILL OCCUR WHERE WINDS ARE STILL SE. THE SW-NE BAND OF RAIN INDICATED OVER I-71 CORRIDOR EARLY TUESDAY APPEARS OFF FOR SOME REASON. THINK THAT YOU WOULD WANT MORE STREAMWISE CONVERGENCE IN THE LOWER ATMOSPHERE TO WRING OUT RAIN IN THIS AREA FOR THE 12-18Z TIME FRAME THAT IS BEING PROGGED BY THE GFS AND EURO AND TO A LESSER EXTEND HEMISPHERIC CANADIAN MODEL. EVEN IF POPS DO HOLD OFF...CIGS SHOULD STILL STAND A BETTER CHANCE OF DROPPING TO MVFR CATEGORY TONIGHT AND THROUGH TOMORROW. OUTLOOK...MVFR CIGS AND VSBYS ARE POSSIBLE THRU THURS AND COULD DROP TO IFR AT TIMES. WINDS WILL PICK UP WED INTO THURS. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...NONE. KY...NONE. IN...NONE. && $$ SYNOPSIS...HATZOS NEAR TERM...HATZOS SHORT TERM... LONG TERM...HICKMAN AVIATION...FRANKS

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