Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 242342 AFDILN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 642 PM EST TUE FEB 24 2015 .SYNOPSIS... 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. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... 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. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... 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). && .LONG TERM /FRIDAY THROUGH TUESDAY/... HIGH PRESSURE WILL KEEP DRY CONDITIONS ACROSS THE FA FOR THE START OF THE LONG TERM THROUGH MOST OF SATURDAY NIGHT. TEMPERATURES WILL START OUT WELL BELOW NORMAL FOR THE LONG TERM. SKIES WILL BE MOSTLY CLEAR AND WINDS WILL BE LIGHT ACROSS MOST OF THE AREA FRIDAY NIGHT. SNOW WILL STILL BE ON THE GROUND ACROSS MANY LOCATIONS AS WELL AND A COLD AIRMASS WILL BE IN PLACE. ALL OF THESE FACTORS WILL LEAD TO MOST LOCATIONS BEING BELOW ZERO FRIDAY NIGHT. WAA WILL ALLOW FOR TEMPERATURES TO RISE INTO THE UPPER TEENS TO AROUND 30 ACROSS THE AREA ON SATURDAY. AN UNSETTLED PATTERN BEGINS LATE SATURDAY NIGHT THROUGH THE REMAINDER OF THE LONG TERM. WENT CLOSE TO THE GFS FOR THIS TIME PERIOD. A SYSTEM BEGINS TO APPROACH AND MOVE INTO THE AREA LATE SATURDAY NIGHT INTO SUNDAY. MODELS ARE TRENDING COLDER WITH THIS SYSTEM AND WENT PRIMARILY SNOW ACROSS THE NORTHERN HALF OF THE FA AND A MIX OF RAIN AND SNOW ACROSS THE SOUTH. A COLD FRONT WILL MOVE THROUGH SUNDAY NIGHT INTO MONDAY MORNING AND PRECIPITATION WILL GENERALLY BE LIMITED TO SOUTH OF THE FA ON MONDAY HOWEVER SOME PRECIPITATION MAY LINGER ACROSS SOUTHERN PORTIONS OF THE FA. A LOW PRESSURE SYSTEM WILL BEGIN TO BRING PRECIPITATION BACK INTO THE AREA MONDAY NIGHT INTO TUESDAY. THIS SYSTEM BRINGS WARMER AIR TO THE REGION AND A POTENTIAL HEAVY RAIN THREAT. INCREASED PRECIPITATION CHANCES SIGNIFICANTLY WITH THIS SYSTEM. IF CURRENT TRENDS CONTINUE FLOODING WILL BE A CONCERN WITH THIS SYSTEM DUE TO A DECENT AMOUNT OF RAIN...SNOW ON THE GROUND...AND FROZEN GROUND. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... VFR CEILINGS AHEAD OF A COLD FRONT WILL SPREAD ACROSS THE TERMINALS EARLY IN THE PERIOD. A TEMPORARY LOWERING TO MVFR IS NOT OUT OF THE QUESTION. CANNOT RULE OUT A FEW FLURRIES FROM KDAY TO KCMH/KLCK. CEILINGS WILL CLEAR OUT AFTER THE FRONT MOVES THROUGH BETWEEN 07Z AND 11Z. THEREAFTER ONLY EXPECT HIGH AND PERHAPS SOME MID CLOUDS. WINDS WILL WEAKEN AND BECOME VARIABLE BEFORE SWITCHING AROUND TO THE NORTHEAST AS WEAK HIGH PRESSURE BUILDS IN. OUTLOOK...MVFR CEILINGS LIKELY 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...NOVAK AVIATION...

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