Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 242028 AFDILN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 328 PM EST TUE FEB 24 2015 .SYNOPSIS...
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A FEW SNOW SHOWERS WILL BE POSSIBLE TONIGHT AS A COLD FRONT MOVES SOUTHEAST THROUGH THE REGION. ANOTHER CHANCE OF SNOW WILL OCCUR WEDNESDAY NIGHT INTO THURSDAY. THE NEXT ROUND OF VERY COLD AIR WILL MOVE IN BEHIND THIS SYSTEM FOR FRIDAY...WITH A WARMING TREND EXPECTED FOR THE WEEKEND.
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&& .NEAR TERM /THROUGH TONIGHT/...
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THE FOCUS FOR THE FORECAST TONIGHT IS ON A WEAK COLD FRONT MOVING IN FROM THE NORTHWEST...WHICH (AT LEAST AT THE SURFACE) IS FORECAST TO STALL AND WASH OUT OVER THE NORTHERN SECTIONS OF THE ILN FORECAST AREA. HOWEVER...AT 850MB...12Z NAM12 AND 18Z RAP13 FORECASTS SUGGEST THAT THE COLD AIR WILL SPREAD FURTHER OVER THE OHIO VALLEY. AS THIS OCCURS...A SMALL AMOUNT OF INSTABILITY IS EXPECTED TO DEVELOP IN THE 3000-5000 FOOT LAYER. THIS LAYER SHOULD MOISTEN AS IT OVERLAPS WITH THE DENDRITIC GROWTH ZONE...ESPECIALLY IN THE NORTHERN SECTIONS OF THE ILN FORECAST AREA. THIS IS FAVORABLE FOR THE DEVELOPMENT OF A FEW SNOW SHOWERS...AND HRRR SIMULATED REFLECTIVITY SUPPORTS THIS...WITH LIGHT ECHOES ENTERING THE CWA AFTER 02Z. WITH WEAK FORCING AND A WHOLE LOT OF DRY AIR TO OVERCOME (SEE THE 12Z KILN SOUNDING FOR REFERENCE)...NO SIGNIFICANT ISSUES OR ACCUMULATIONS ARE EXPECTED. PERHAPS SOME OF THE SNOW SHOWERS COULD PUT DOWN A FEW TENTHS OF AN INCH. THE FORECAST WILL CALL ONLY FOR FLURRIES IN THE SOUTHERN SECTIONS OF THE ILN FORECAST AREA...WHERE THE THERMODYNAMIC CONDITIONS WILL NOT BE AS WELL ALIGNED AS FURTHER NORTH (AND NEAR-SURFACE FORCING WILL BE NEXT TO NOTHING). AHEAD OF THE SURFACE FRONT...WIND FLOW WILL REMAIN OUT OF THE WSW...THOUGH IT WILL WEAKEN AS THE NIGHT GOES ON. WITH CLOUDS ALSO INCREASING...ANOTHER NIGHT OF BOTTOM-FALLING-OUT TEMPERATURES WILL NOT OCCUR. THE COLDEST TEMPERATURES (SINGLE DIGITS) ARE FORECAST IN THE NORTHWESTERN CWA...WHERE SOME COLD ADVECTION SHOULD BEGIN BEFORE DAYBREAK. ELSEWHERE...TEMPERATURES IN THE TEENS CAN BE EXPECTED OVERNIGHT...WITH ONLY VERY SLOWLY FALLING TEMPERATURES (OR EVEN STEADY TEMPERATURES) AFTER MIDNIGHT.
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
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A NARROW WEDGE OF HIGH PRESSURE WILL NOSE INTO THE REGION FROM THE NORTHWEST ON WEDNESDAY...LEADING TO A WEAK SURFACE PRESSURE PATTERN AND LIGHT WINDS ACROSS THE MIDDLE OHIO VALLEY. EVENTUALLY...BY WEDNESDAY NIGHT...THIS WILL BEGIN TO CHANGE. HIGH PRESSURE WILL STRENGTHEN OVER THE NORTHERN PLAINS...AS LOW PRESSURE DEVELOPS IN THE SOUTHEASTERN STATES. THIS WILL SHIFT FLOW TO THE NNE AT THE SURFACE...WHILE FLOW ALOFT WILL BE OUT OF THE WSW...AS THE NEXT LOBE OF THE LARGE UPPER TROUGH WILL KEEP ITS AXIS WEST OF THE AREA THROUGH THE SHORT TERM OF THE FORECAST. AFTER A CALM DAY ON WEDNESDAY...WITH TEMPERATURES PERHAPS A DEGREE OR TWO WARMER THAN TUESDAY...A COMPLICATED BUT FAIRLY LOW-IMPACT WEATHER SITUATION WILL DEVELOP FOR WEDNESDAY NIGHT AND EARLY THURSDAY. THE CHALLENGE IS IN THE ALIGNMENT OF WEATHER SYSTEMS FROM SEPARATE STREAMS...AND THEIR INEVITABLE INTERACTION OVER THE OHIO VALLEY. BASED ON 12Z MODEL RUNS...IT APPEARS LIKELY THAT THE PRIMARY AREAS OF PRECIPITATION ASSOCIATED WITH THESE SYSTEMS WILL NOT JOIN UP OVER THE ILN FORECAST AREA...BUT THERE IS ENOUGH UNCERTAINTY WITH THE TRACKS TO KEEP THE WHOLE CWA IN A SIMILAR REGIME FOR POPS. THE 12Z NAM12 IS AN OUTLIER WITH A WEAKER SYSTEM FROM THE NORTHERN STREAM. GREATER CHANCES FOR SNOW ARE MORE LIKELY TO BE NEEDED IN THE NORTHERN CWA AS A RESULT OF THIS WAVE...WHILE SNOW FROM THE SOUTHERN WAVE IS MOST LIKELY TO AFFECT THE FAR SOUTHEASTERN CWA (IF IT EVEN GETS THAT FAR NORTH). NONE OF THE MODELS ARE SUPPORTING MORE THAN AN INCH OR TWO AT ANY LOCATION...NOT ENOUGH TO PRESENT VERY MUCH CONCERN...SO THERE IS STILL TIME TO ASSESS HOW THIS SCENARIO IS GOING TO UNFOLD BEFORE WORRYING ABOUT POTENTIAL HAZARDS. CHANCES FOR SNOW WILL TAPER OFF FROM NORTHWEST TO SOUTHEAST ON THURSDAY...BUT AS NORTHERLY FLOW INCREASES OVER THE AREA...ANOTHER ROUND OF COLDER AIR WILL BEGIN TO SETTLE INTO THE REGION. WITH CLEARING SKIES BY EARLY FRIDAY MORNING...TEMPERATURES ARE LIKELY TO DROP TO NEAR OR BELOW ZERO YET AGAIN (WITH THE COLDEST VALUES IN THE NORTHWESTERN CWA).
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&& .LONG TERM /FRIDAY THROUGH MONDAY/...
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THE LONG TERM FORECAST DISCUSSION WILL BE UPDATED SHORTLY. PREVIOUS DISCUSSION > AFTER THE H5 ENERGY AND SNOW PUSHES BY...THE MAIN CORE OF THE HIGH DROPS INTO THE REGION FOR THURSDAY NIGHT. GUIDANCE IS INDICATING A GOOD ARCTIC BLAST WITH LOW BELOW ZERO FOR ALL BUT THE EXTREME SE...WHERE IT WILL STILL BE AROUND ZERO. THE HIGH WILL CROSS OVER THE REGION FRIDAY AND SATURDAY. TEMPERATURES WILL REMAIN WELL BELOW NORMAL. SUNSHINE ON FRIDAY WILL ALLOW HIGHS TO REACH 15 TO 25 DEGREES...ABOUT 20 DEGREES BELOW NORMAL. AFTER SINGLE DIGIT LOWS FRIDAY NIGHT TEMPERATURES WILL WORK INTO THE 20S AND LOWER 30S ON SATURDAY. GFS AND ECMWF ARE BOTH PUSHING A SYSTEM OUT THE COUNTRYS MID SECTION SATURDAY NIGHT INTO SUNDAY. THERE ARE SOME SUBTLE TIMING DIFFERENCES BETWEEN THE TWO. PTYPE WILL BE TRICKY. RIGHT NOW WENT WITH SNOW...CHANGING TO RAIN ON SUNDAY...BUT IF WARM AIR COMES IN ALOFT QUICKER...COULD SEE SOME FREEZING RAIN BEFORE THE SFC TEMPERATURES GET ABOVE ZERO. CDFNT PUSHES ACROSS SUNDAY NIGHT. COOLER AIR WILL WORK IN ON BEHIND THE FRONT...CHANGING THE PCPN BACK TO SNOW. TEMPERATURES SHOULD REBOUND BACK ABOVE FREEZING ON MONDAY CHANGING PCPN BACK TO RAIN FOR
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&& .AVIATION /20Z TUESDAY THROUGH SUNDAY/... A WEAK COLD FRONT WILL PASS SOUTHEAST THROUGH THE TAF SITES LATE TONIGHT. AHEAD OF THE FRONT...MID/HIGH LEVEL CLOUDS WILL GIVE WAY TO SOME MVFR CEILINGS. SOME MVFR CEILINGS WILL CONTINUE IN THE CAA BEHIND THE FRONT...MAINLY ACROSS THE NORTHERN TAF SITES. MOISTURE IS LIMITED AND FORCING IS WEAK. HOWEVER...THERE COULD BE A FEW FLURRIES OR SNOW SHOWERS TONIGHT INTO EARLY WEDNESDAY MORNING. DO NOT THINK THE COVERAGE WILL BE SUFFICIENT ENOUGH TO MENTION IN THE TAFS ATTM. WEAK SURFACE RIDGING WILL OCCUR BEHIND THE FRONT ON WEDNESDAY. MID AND HIGH LEVEL CLOUDS WILL INCREASE FROM THE WEST AND SOUTHWEST AHEAD OF TWO WEATHER SYSTEMS TO AFFECT THE REGION WEDNESDAY NIGHT INTO THURSDAY. IT IS UNCLEAR ATTM HOW FAST STRATOCUMULUS MAY SCATTERED BY WEDNESDAY AFTERNOON...SO HAVE KEPT MVFR CEILINGS AT THE NORTHERN TAF SITES THROUGH 18Z. OUTLOOK...MVFR CEILINGS AND MVFR TO IFR VISIBILITIES POSSIBLE THURSDAY AFTERNOON AND NIGHT. MVFR CEILINGS AND VISIBILITIES POSSIBLE SUNDAY. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...NONE. KY...NONE. IN...NONE. && $$ SYNOPSIS...HATZOS NEAR TERM...HATZOS SHORT TERM...HATZOS LONG TERM...SITES AVIATION...HICKMAN

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