-- Discussion containing changed information from previous version are highlighted. --
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...