255
FXUS61 KILN 200005
AFDILN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON OH
705 PM EST THU DEC 19 2024
SYNOPSIS
SURFACE HIGH PRESSURE WILL CONTINUE MOVING EAST THROUGH THE
GREAT LAKES TODAY. ON FRIDAY MORNING, AN AREA OF LOW PRESSURE
WILL MOVE INTO THE REGION, BRINGING SNOW AND RAIN TO THE AREA.
COLD AIR WILL MOVE IN BEHIND THIS SYSTEM, WITH COOLER THAN
NORMAL TEMPERATURES EXPECTED THROUGH THE WEEKEND. WARMER
CONDITIONS ARE EXPECTED NEXT WEEK, WITH PRECIPITATION CHANCES
RETURNING BY MONDAY NIGHT.
NEAR TERM /UNTIL 6 AM FRIDAY MORNING/
QUIET WEATHER CONDITIONS WILL CONTINUE INTO THE OVERNIGHT HOURS.
A PERSISTENT STRATOCUMULUS CLOUD LAYER REMAINS IN PLACE ACROSS
THE AREA, WITH MODEL SOUNDINGS SHOWING THICK MOISTURE ATOP A
MIXED LAYER AT AROUND 900MB-875MB. ANY HOLES IN THE CLOUDS HAVE
FILLED BACK IN FAIRLY QUICKLY, THOUGH A FEW BREAKS -- MAINLY IN
THE SOUTHERN PART OF THE FORECAST AREA -- MIGHT OCCUR THROUGH
EVENING.
CLOUDS WILL BEGIN TO INCREASE IN COVERAGE AND DEPTH OVERNIGHT,
IN ADVANCE OF THE NEXT WEATHER SYSTEM MOVING INTO THE AREA. A
SWIRL IN THE CLOUDS IS VERY EVIDENT ON SATELLITE IMAGERY OVER
WISCONSIN, ASSOCIATED WITH A LEAD SHORTWAVE MOVING EASTWARD. THE
MAIN SHORTWAVE, AND AN ASSOCIATED SURFACE LOW, WILL MOVE INTO
THE OHIO VALLEY AFTER 12Z.
WITH SOUTHERLY FLOW OVERNIGHT, MIN TEMPS WILL ONLY FALL A FEW
DEGREES FROM CURRENT AFTERNOON VALUES -- WITH LOWS EXPECTED TO
BE IN THE LOWER 30S.
SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/
THE MAIN CONCERN FOR FRIDAY IS A LOW PRESSURE SYSTEM MOVING ESE
THROUGH THE AREA, ASSOCIATED WITH A SLIGHTLY-SHARPENING 500MB
TROUGH. AT 12Z FRIDAY, THESE FEATURES WILL BE LOCATED JUST
UPSTREAM OF THE ILN CWA, THOUGH AN INITIAL BAND OF PRECIPITATION
(FORCED BY WARM ADVECTION ALOFT) WILL ALREADY BE IN THE PROCESS
OF SPREADING INTO THE AREA. A SECOND BLOSSOMING OF
PRECIPITATION, MORE DIRECTLY ASSOCIATED WITH THE TRACK OF THE
SURFACE LOW AND THE AXIS OF THE 500MB TROUGH, WILL OCCUR DURING
THE 13Z-18Z TIME FRAME. 12Z MODELS TODAY HAVE TRENDED TOWARD A
SLIGHT SOUTHWESTWARD SHIFT WITH THE AXIS OF HEAVIEST
PRECIPITATION, PERHAPS FOCUSING A LITTLE LESS QPF ON CENTRAL
OHIO AND A LITTLE MORE ON WEST-CENTRAL AND SOUTHWEST OHIO.
ONE OF THE MAIN FORECAST CHALLENGES WITH THIS SYSTEM IS THE VERY
MARGINAL BOUNDARY LAYER THERMODYNAMIC CONDITIONS. SOME OF THE
SNOW WILL MIX WITH RAIN -- PARTICULARLY IN THE SOUTHERN PART OF
THE FORECAST AREA EARLY IN THE EVENT, AND IN THE SOUTHERN AND
EASTERN PARTS OF THE FORECAST AREA LATER IN THE EVENT. THIS MIX
WITH RAIN WILL CUT DOWN ON SNOW TOTALS, AS WILL THE MEAGER SNOW
RATIOS (8:1 TO 10:1). FINALLY, EVEN WHERE SNOW FALLS, SURFACE
TEMPERATURES AND GROUND CONDITIONS SUGGEST THAT ACCUMULATIONS
WILL BE MORE LIKELY ON GRASSY AND RAISED SURFACES. THIS IS AN
EVENT WITH A QPF FOOTPRINT THAT COULD OTHERWISE SUPPORT A SOLID
1-2 INCHES WITH EVEN MARGINALLY COOLER BOUNDARY LAYER
CONDITIONS, BUT INSTEAD WILL LIKELY COME IN AT THE LOWER END OF
THAT RANGE, WITH IMPACTS REMAINING SOMEWHAT LIMITED. THE TIMING
OF THE FIRST ROUND OF SNOW WILL IMPACT THE MORNING RUSH, WITH
ADDITIONAL ACCUMULATIONS CONTINUING THROUGH AROUND 18Z.
COLD ADVECTION WILL KICK IN BEHIND THE SURFACE LOW, FIRST OUT OF
THE WEST, AND THEN OUT OF THE NNW. THIS WILL BRING TEMPERATURES
WELL BELOW FREEZING HEADING INTO SATURDAY MORNING. THERE MAY BE
SOME REFREEZE POTENTIAL ON ROADS, THOUGH GENERALLY DRY
CONDITIONS (WITH INCREASING WINDS) MAY NOT KEEP ENOUGH MOISTURE
ON SURFACES FOR IT TO BE A LARGER CONCERN.
LONG TERM /SATURDAY THROUGH THURSDAY/
SURFACE HIGH PRESSURE AND A SEASONABLY COLD AIRMASS WILL SHIFT
EAST ACROSS THE REGION THROUGH THE WEEKEND. TEMPERATURES WILL BE
ABOUT 10 DEGREES BELOW NORMAL WITH HIGHS BOTH DAYS IN THE UPPER
20S TO LOWER 30S AND OVERNIGHT LOWS IN THE TEENS TO LOWER 20S.
MID LEVEL SHORT WAVE ENERGY WILL MOVE OUT OF THE NORTHERN
PLAINS SUNDAY NIGHT AND ACROSS THE GREAT LAKES MONDAY INTO
TUESDAY. AS IT DOES, AN ASSOCIATED FRONTAL BOUNDARY WILL SAG
SOUTHEAST INTO OUR AREA THROUGH TUESDAY. INCREASING SOUTHWEST
FLOW AND MOISTURE ADVECTION AHEAD OF THIS WILL LEAD TO A
DEVELOPING CHANCE FOR PCPN MONDAY NIGHT WITH PCPN CHANCES THEN
CONTINUING INTO TUESDAY. IN THE SOUTHWEST FLOW, THERMAL PROFILES
WILL GENERALLY TREND TOWARD MAINLY RAIN, BUT THERE COULD STILL
BE SOME MIX ACROSS OUR NORTH MONDAY NIGHT AS THE PCPN DEVELOPS.
HIGHS ON MONDAY WILL RANGE FROM THE MID TO UPPER 30S IN THE
NORTH TO THE MID 40S IN THE SOUTH WITH HIGH SON TUESDAY IN THE
40S.
SOME UNCERTAINTY THEN ARISES THROUGH THE REMAINDER OF THE
PERIOD AS ADDITIONAL MID LEVEL ENERGY/SHORT WAVES MOVE INTO THE
OHIO VALLEY. IT LOOKS LIKE THE BOUNDARY MAY STALL OUT ACROSS OUR
AREA AND THEN POSSIBLY LIFT BACK TO THE NORTH WEDNESDAY INTO
THURSDAY. THIS WILL KEEP A CHANCE OF RAIN ACROSS OUR AREA ON
WEDNESDAY, WITH LOWER CHANCES PERSISTING INTO THURSDAY. WE WILL
ALSO SEE A GRADUAL WARMING TEND WITH HIGHS BY THURSDAY RANGING
FROM THE UPPER 40S NORTH TO THE MID 50S SOUTH.
AVIATION /00Z FRIDAY THROUGH TUESDAY/
BUSY TAF PERIOD WITH SEVERAL CATEGORICAL REDUCTIONS AND A MIX
OF RAIN AND SNOW EXPECTED FOR ALL TERMINALS.
MVFR CIGS BECOME MORE WIDESPREAD TONIGHT, EVENTUALLY LOWERING
TO <2000 FT AGL. SOME LIGHT PRECIP, MAINLY IN THE FORM OF SNOW,
WILL TRAVERSE THE TERMINALS TONIGHT, MAINLY AFTER 06Z. SHORTLY
AFTER SUNRISE, THERE IS EXPECTED TO BE A SLIGHTLY MORE INTENSE
BAND OF PCPN THAT DEVELOPS, LIKELY IMPACTING THE TERMINALS WEST
OF KCMH/KLCK A BIT MORE. WHILE A RAIN-SNOW MIX MAY BE PRESENT
EARLY IN THE MORNING, THE INTENSE PCPN MAY HELP TRANSITION THE
P-TYPE TO SNOW DURING THAT TIME PERIOD. THIS WOULD RESULT IN
LOWER VSBYS TO AT LEAST IFR, PERHAPS SOME LIFR. ADDITIONALLY,
EXPECTING CIGS TO LOWER INTO IFR CATEGORY DURING THIS TIME
PERIOD AS WELL. SOME LIFR CIGS COULD FORM BY LATE MORNING OR
EARLY AFTERNOON.
ONCE THE HEAVIER BAND OF PCPN ENDS, IT IS EXPECTED THAT MORE
RAIN WILL BEGIN TO MIX IN WITH THE LIGHT PCPN THAT LINGERS
FRIDAY AFTERNOON/EVENING.
CONTINUE TO HIGHLIGHT IFR CIGS LINGERING AT KCVG BEYOND THE 24HR
TAF PERIOD.
OUTLOOK...MVFR/IFR CEILINGS WILL CONTINUE INTO FRIDAY NIGHT,
WITH MVFR CONDITIONS POSSIBLE THROUGH SATURDAY. MVFR CONDITIONS
ARE POSSIBLE AGAIN ON TUESDAY.
ILN WATCHES/WARNINGS/ADVISORIES
OH...NONE.
KY...NONE.
IN...NONE.
SYNOPSIS...HATZOS
NEAR TERM...HATZOS
SHORT TERM...HATZOS
LONG TERM...JGL
AVIATION...CLARK
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