638
FXUS61 KILN 201737
AFDILN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON OH
1237 PM EST FRI DEC 20 2024
SYNOPSIS
LOW PRESSURE WILL MOVE SOUTHEAST ACROSS THE MIDDLE OHIO VALLEY
TODAY, BRINGING RAIN AND SNOW. COLDER AIR ASSOCIATED WITH A HIGH
PRESSURE SYSTEM WILL MOVE IN BEHIND THE LOW FOR THE WEEKEND,
RESULTING IN BELOW THAN NORMAL TEMPERATURES. WARMER CONDITIONS
ARE EXPECTED NEXT WEEK, WITH PRECIPITATION CHANCES RETURNING BY
MONDAY NIGHT.
NEAR TERM /UNTIL 6 PM THIS EVENING/
RAIN HAS BEEN THE DOMINANT PRECIPITATION TYPE ACROSS THE ILN CWA
SO FAR THIS MORNING, BUT OVER THE PAST HOUR OR SO, ACCUMULATING
SNOW HAS BEGUN FOR PORTIONS OF WEST-CENTRAL OHIO AND EASTERN
INDIANA. IN PARTICULAR, TRAFFIC CAMERAS NEAR THE I-70 / US-40
CORRIDOR IN WAYNE COUNTY IN AND PREBLE COUNTY OH ARE SHOWING
ACCUMULATIONS ON GRASSY AREAS (WITH LITTLE TO NOTHING ON THE
PAVEMENT). AT THE NWS OFFICE IN WILMINGTON, A GENTLE TRANSITION
TO VERY LIGHT SNOW BEGAN AT ABOUT 915 AM.
THE MAIN CONCERN WILL BE FOR THE NEXT 4-6 HOURS, AS THE PRIMARY
FORCING ASSOCIATED WITH THE SURFACE LOW AND 500MB WAVE WILL BE
PIVOTING THROUGH THE ILN FORECAST AREA. THE STRONGEST FORCING
WILL EXTEND ON A NW-TO-SE AXIS FROM WAYNE COUNTY IN / PREBLE
COUNTY OH THROUGH ROUGHLY ADAMS COUNTY OH, AND MAYBE A COUPLE
COUNTIES ON EITHER SIDE OF THAT LINE. HOWEVER, WITH
SOUTHEASTWARD EXTENT, THE DOMINANT PRECIPITATION TYPE THROUGH
THE EVENT WILL BE MORE AND MORE FAVORABLE FOR RAIN. AS SUCH,
SNOW ACCUMULATIONS ARE EXPECTED TO BE MORE PREVALENT TO THE
NORTHWEST, WITH ACCUMULATIONS OF AROUND AN INCH EXTENDING
THROUGH SOUTHWESTERN OHIO. THERE REMAINS A LOW-END CHANCE OF
SOME HIGHER TOTALS NEAR 2 INCHES IF A PERSISTENT BAND SETS UP,
BUT THERE IS ALSO A CHANCE THAT THE FORCING DOES NOT OVERCOME
THE THERMODYNAMICS IN MANY LOCATIONS, LEADING TO ONLY LIGHT
ACCUMULATIONS WITH A DECENT AMOUNT OF RAIN MIXING IN FOR A
SOLID PORTION OF THE AREA. NO SIGNIFICANT CHANGES WERE MADE TO
THE GOING FORECAST.
PREVIOUS DISCUSSION >
LOW PRESSURE NEAR NORTHWEST INDIANA EARLY THIS MORNING IS
FORECAST TO TRACK SOUTHEAST ACROSS THE MIDDLE OHIO VALLEY TODAY.
DYNAMIC LIFT WITH AN UPPER LEVEL SHORT WAVE WILL COMBINE WITH
LOW LEVEL CONVERGENCE ASSOCIATED WITH THE ATTENDENT COLD FRONT
TO PRODUCE A SHIELD OF PRECIPITATION.
MAIN CONCERN THIS MORNING IS THE POTENTIAL FOR A PERIOD OF SNOW
TO AFFECT PARTS OF EAST CENTRAL INDIANA AND
WESTERN/SOUTHWESTERN OHIO AND NORTHERN KENTUCKY (THIS INCLUDES
THE CINCINNATI AND DAYTON METRO AREAS). MODELS CONTINUE TO SHOW
THAT PRECIPITATION MAY FORM INTO A BAND DUE TO STRONG LOW LEVEL
CONVERGENCE. PRECIPITATION MAY INITIALLY MIX WITH RAIN AT THE
ONSET, THEN WITH FAIRLY STRONG VERTICAL MOTION, SURFACE
TEMPERATURES WILL COOL TO NEAR FREEZING, AND THE ATMOSPHERIC
SOUNDING WILL BE COLD ENOUGH TO PRODUCE A PERIOD OF SNOW. SNOW
IS EXPECTED TO ACCUMULATE MAINLY ON ELEVATED AND GRASSY
SURFACES. HOWEVER, WITH TEMPERATURES HOVERING NEAR FREEZING AND
PAVEMENT TEMPERATURES HOVERING NEAR FREEZING AS WELL, A PERIOD
OF MODERATE SNOW COULD RESULT IN A QUICK COVERING ON ROADS,
PRODUCING SLICK SPOTS, ESPECIALLY THE VULNERABLE BRIDGES AND
OVERPASSES. SNOW ACCUMULATIONS WILL VARY BETWEEN A HALF INCH TO
UP TO 2 INCHES IN THIS REGION. ELSEWHERE, FORCING WILL BE
WEAKER, AND WITH SOME SLIGHT WARMING OCCURRING AHEAD OF THE
FRONT, PRECIPITATION SHOULD FALL AS RAIN/SNOW OR JUST PLAIN
RAIN. A SPECIAL WEATHER STATEMENT WILL BE ISSUED TO COVER THE
POTENTIAL IMPACTS THIS MORNING IN THE AFOREMENTIONED REGION.
FOR THIS AFTERNOON, THE LOW WILL EXIT TO THE SOUTHEAST TOWARD
WEST VIRGINIA. SOME WRAP AROUND PRECIPITATION IS EXPECTED, BUT
THIS WILL BE LIGHTER IN NATURE THAN THIS MORNINGS ACTIVITY.
SLIGHTLY WARMER AIR WILL WRAP AROUND THE LOW BEFORE MUCH COLDER
AIR ARRIVES TONIGHT. THUS, RAIN/SNOW OR JUST PLAIN RAIN, ARE
FORECAST FOR THE REMAINDER OF THE AFTERNOON HOURS. HIGHS WILL
RANGE FROM THE LOWER TO MID 30S WEST TO THE UPPER 30S EAST.
SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/
FOR TONIGHT, IN THE CAA PATTERN, CLOUDS WILL LINGER, ESPECIALLY
SOUTH AND EAST. SOME PATCHES OF LIGHT SNOW MAY ALSO LINGER IN
THE EAST, BUT SHOULD EXIT OUT AFTER MIDNIGHT. IT WILL BE COLDER
AS LOCALLY GUSTY NORTH WINDS FUNNEL THE COLDER AIR SOUTHWARD.
LOWS WILL RANGE FROM NEAR 20 NORTH TO THE UPPER 20S ALONG AND
SOUTH OF THE OHIO RIVER.
ON SATURDAY, SURFACE HIGH PRESSURE CENTERED OVER THE UPPER
MISSISSIPPI RIVER VALLEY/WESTERN GREAT LAKES, WILL BUILD
SOUTHEAST TOWARD OUR REGION. IT WILL REMAIN COLD UNDER PARTLY
CLOUDY SKIES. HIGHS WILL RANGE FROM THE UPPER 20S NORTH TO THE
LOWER 30S SOUTH.
LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/
DEEP NORTHWEST FLOW WILL PULL IN THE COLDEST AIR OF THE
FORECAST WITH SUNDAY MORNING LOWS GENERALLY BETWEEN 15 AND 20
DEGREES AS A RIDGE OF HIGH PRESSURE SETTLES OVER THE CWA. AS THE
AXIS OF THE RIDGE MOVES EAST, RETURN FLOW WILL SET UP ON
SUNDAY. TEMPERATURES WILL ONLY BE MARGINALLY WARMER THAN
SATURDAY'S WITH A CONTINUATION OF THE DEEP AND COOL NORTHWEST
FLOW ALOFT.
A WEAK MID-LEVEL RIDGE WILL PASS OVER SUNDAY NIGHT AND LOWS
MONDAY MORNING WILL BE MARGINALLY WARMER IN THE LOWER 20S. ON
MONDAY, SOUTHERLY FLOW WILL PICK UP AHEAD OF AN APPROACHING COLD
FRONT BEHIND A MID-LEVEL SHORTWAVE. WINDS WILL TURN MORE
SOUTHWEST AND USHER IN WARMER TEMPERATURES IN THE LOW TO MID
40S.
AS THE FRONT CONTINUES TO APPROACH, RAIN IS EXPECTED TO BEGIN
IN THE NORTHWEST IN THE LATE DAY, SPREAD SOUTHWARD IN THE
EVENING, AND END OVERNIGHT FOR MOST IF NOT ALL OF THE CWA. THE
COLD FRONT IS EXPECTED TO STRETCH OUT OVER THE CWA AND WEAKEN
DURING THE DAY TUESDAY.
MODELS DIVERGE FROM THIS POINT ONWARD, WITH THE GFS SHOWING A
RETURNING WARM FRONT LIFTING NE, FOLLOWED BY S/W ENERGY
TRIGGERING SHOWERS THURSDAY AND OVERNIGHT. FRIDAY SHOWS DEEP SW
FLOW AND A SW- NE AREA OF RAIN IMPACTING THE CWA FROM S-N. THE
FOOTPRINT OF THIS RAIN POTENTIAL DOES NOT SEEM TO BE PLAUSIBLE
WITHOUT A SURFACE LOW/FRONT THAT IS NOT INDICATED AT THIS TIME.
THE EUROPEAN AND CANADIAN MODELS ALSO DIVERGE SIGNIFICANTLY,
MOST NOTABLY WITH A DRY FORECAST BEYOND TUESDAY.
AVIATION /18Z FRIDAY THROUGH WEDNESDAY/
A MIX OF RAIN AND SNOW IS STILL OCCURRING ACROSS THE AREA.
STEADY PRECIPITATION IS EXPECTED TO END IN THE NEXT FEW HOURS,
WITH LIGHTER AND MORE INTERMITTENT PRECIPITATION EXPECTED TO
CONTINUE INTO THE EVENING. MVFR TO IFR VISIBILITIES ARE EXPECTED
WHERE IT IS SNOWING, WITH MVFR VISIBILITIES WHERE IT IS RAINING.
CEILINGS REMAIN GENERALLY IFR ACROSS THE AREA. VFR VISIBILITIES
ARE EXPECTED BY EVENING, THOUGH LOWER-END MVFR CEILINGS WILL
PERSIST INTO THE OVERNIGHT HOURS. FOR WINDS, WESTERLY WINDS WILL
EVENTUALLY SHIFT TO THE NNW, WITH A FEW GUSTS INTO THE LOWER 20
KNOT RANGE POSSIBLE THROUGH AROUND 04Z.
CEILINGS ARE EXPECTED TO GRADUALLY LIFT OR SCATTER OUT INTO THE
VFR RANGE EARLY SATURDAY MORNING, WITH NNW FLOW SETTLING IN AT
AROUND 10 KNOTS THROUGH THE DAY ON SATURDAY.
OUTLOOK...MVFR/IFR CONDITIONS LIKELY AT TIMES TUESDAY MORNING
THROUGH WEDNESDAY.
ILN WATCHES/WARNINGS/ADVISORIES
OH...NONE.
KY...NONE.
IN...NONE.
SYNOPSIS...HICKMAN
NEAR TERM...HATZOS/HICKMAN
SHORT TERM...HICKMAN
LONG TERM...FRANKS
AVIATION...HATZOS
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