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Area Forecast Discussion
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000
FXUS61 KILN 170752
AFDILN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON OH
352 AM EDT TUE MAR 17 2015

.SYNOPSIS...
A COLD FRONT WILL MOVE SOUTH ACROSS THE REGION THIS MORNING...WITH 
MUCH COOLER AND DRIER AIR SETTLING IN BEHIND IT. A CHANCE OF RAIN 
WILL OCCUR ON THURSDAY INTO FRIDAY...WITH DRY CONDITIONS AND 
SLIGHTLY WARMER TEMPERATURES FOR THE WEEKEND.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
THE ILN CWA WILL SPEND ANOTHER FEW HOURS IN A WARM AIR MASS AHEAD
OF AN APPROACHING COLD FRONT...BEFORE THIS BRIEF PERIOD OF
WELL-ABOVE-NORMAL TEMPERATURES COMES TO AN END. THE SURFACE COLD
FRONT CURRENTLY EXTENDS FROM AROUND FORT WAYNE TO TOLEDO.
HOWEVER...BASED ON THETA-E AND WIND PLOTS AT VARIOUS LEVELS ON
RECENT NAM/RAP RUNS...THE FRONT IS THE MOST WELL-DEFINED AT 925MB.
UNTIL THE FRONT ARRIVES...TEMPERATURES WILL CONTINUE TO SHOW
ALMOST NO DECREASE...WITH GUSTY WSW FLOW.

THE TEMPERATURE FORECAST FOR TODAY IS A CHALLENGE...BECAUSE THE
FRONT WILL BE COMING THROUGH THE REGION DURING THE TYPICAL TIME
PERIOD OF THE LARGEST DIURNAL SWINGS...BUT WILL BE CLEAR THROUGH
THE AREA BEFORE THE END OF THE AFTERNOON. IT IS OBVIOUS THAT THERE
WILL NOT BE A TYPICAL DIURNAL TRACE FOR TEMPERATURES...BUT THIS
ALSO DOES NOT LOOK LIKE A SITUATION WITH STEADILY FALLING
TEMPERATURES THROUGH THE DAY. RATHER THAN A CURVE...THE
TEMPERATURE TRACE TODAY MAY END UP LIKE MORE OF A ZIG-ZAG...WITH
VALUES THAT MOVE VERY LITTLE DURING THE MORNING (BUT POSSIBLY
INCREASE SLIGHTLY IN THE MID TO LATE AFTERNOON HOURS).

IN TERMS OF PRECIPITATION POTENTIAL...THERE IS VERY LITTLE TO
SPEAK OF. THE PRIMARY AXIS OF DEEP-LAYER MOISTURE (WHICH IS NOT
VERY EXPANSIVE TO BEGIN WITH) IS SITUATED WELL BEHIND THE
LOW-LEVEL FRONT. BASED ON HRRR RUNS AND UPSTREAM CONDITIONS (FROM
RADAR AND OBSERVATIONS)...PRECIPITATION HAS BEEN LIMITED TO A
CHANCE OF SPRINKLES ACROSS CENTRAL OHIO NEAR 12Z-15Z (AND THIS MAY
NOT EVEN OCCUR).

&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/...
BEHIND THE COLD FRONT...TEMPERATURES ARE EXPECTED TO BE NOTABLY
COLDER THROUGH THE REST OF THE WEEK. HOWEVER...THE PRIMARY FOCUS
FOR THE COLD AIR ALOFT WILL BE OVER THE NORTHEASTERN STATES...WITH
THE OHIO VALLEY ON THE SOUTHWESTERN EDGE OF THE LARGE DEVELOPING
MID-LEVEL TROUGH. AT THE SURFACE...DRY HIGH PRESSURE WILL MOVE
INTO PLACE...PROVIDING GENERALLY LIGHT WINDS...AND THUS NO REASON
FOR ANY SIGNIFICANT MODIFICATION OF THE AIR IN THE LOW-LEVELS.
THUS...THE WARMING TREND THROUGH THE END OF THE WEEK WILL BE
GENERALLY SLOW. ALTHOUGH WINDS WILL BECOME MORE FAVORABLE FOR
WARMING BY FRIDAY...CONDITIONS WILL LIKELY ALSO BE WETTER AND
CLOUDIER.

THE ONLY CONCERN FOR PRECIPITATION THROUGH THE REST OF THE WEEK
WILL BE WITH A SOUTHERN STREAM SYSTEM APPROACHING THE SOUTHERN
OHIO VALLEY ON THURSDAY. THE INITIAL SHOT OF MOISTURE WILL RIDE
INTO THE AREA ON THURSDAY MORNING...PERHAPS A SLIGHT DELAY FROM
WHAT PREVIOUS FORECASTS AND MODEL RUNS HAD INDICATED. THE BIGGEST
CONCERN WITH THE PROGRESSION OF THIS MOISTURE IS THE NORTHWARD
EXTENT...WHICH STILL REMAINS VARIABLE FROM MODEL TO MODEL. IN
GENERAL...THE ECMWF HAS ALLOWED FOR THE GREATEST NORTHWARD
PROGRESSION (COVERING A MUCH WIDER SWATH OF THE ILN FORECAST AREA)
AND THE NAM HAS BEEN FURTHEST TO THE SOUTH (LEAVING CONDITIONS
MAINLY DRY). A GFS SOLUTION IS NOT A BAD COMPROMISE...FOCUSING
PRECIPITATION MAINLY ALONG AND SOUTH OF THE OHIO RIVER WITH THE
INITIAL BATCH OF PRECIPITATION. THINGS GET SLIGHTLY MORE
COMPLICATED GOING INTO THURSDAY NIGHT...AS A SHORTWAVE IN THE
NORTHERN STREAM BEGINS TO INTERACT WITH THE SYSTEM...PIVOTING
THINGS INTO A DIRECTION OF NORTHEASTERLY TRAVEL. AS THIS
OCCURS...THE 00Z MODEL RUNS HAVE BEEN FAIRLY UNANIMOUS IN ALLOWING
FOR A MUCH HIGHER CHANCE OF PRECIPITATION IN THE SOUTHEASTERN ILN
FORECAST AREA.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
WE WILL TRANSITION INTO MORE OF A NORTHWEST FLOW PATTERN ALOFT
THROUGH THE WEEKEND. SHORT WAVE ENERGY DROPPING DOWN THROUGH THE
GREAT LAKES WILL HELP DRIVE A COLD FRONT SOUTH THROUGH OUR AREA
SATURDAY INTO SATURDAY NIGHT. IT LOOKS LIKE THE BEST FORCING AND
DEEPEST MOISTURE WILL PRIMARILY REMAIN OFF TO OUR NORTH AND
EAST...BUT WILL GO AHEAD AND INTRODUCE AT LEAST SOME SLIGHT CHANCE
POPS WITH THIS ACROSS OUR EAST THROUGH THE DAY ON SATURDAY. HIGHS
ON SATURDAY SHOULD PUSH UP INTO THE 50S AHEAD OF THE FRONT. COOL
HIGH PRESSURE WILL BUILD INTO THE AREA FOR THE FIRST PART OF NEXT
WEEK WITH HIGHS GENERALLY IN THE 40S SUNDAY AND MONDAY.

&&

.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
A COLD FRONT WILL DROP SOUTH ACROSS THE TAF SITES BETWEEN 11Z AND
13Z. IN TERMS OF PRECIPITATION...LITTLE IF ANY IS EXPECTED.
BIGGEST CONCERN ASSOCIATED WITH THE FRONT WILL BE THE POTENTIAL
FOR LOWER CEILINGS AND GUSTY NORTHERLY WINDS IN THE WAKE OF
FRONTAL PASSAGE. MODELS CONTINUE TO INDICATE THAT PERHAPS
CEILINGS MAY DEVELOP AS LOW AS IFR. I AM NOT CONFIDENT ON THIS
GIVEN THE PAST HISTORY OF THE MODELS OVERDOING THE LOW LEVEL
RELATIVE HUMIDITY FIELDS. FEEL MORE CONFIDENT THAT CEILINGS WILL
DROP INTO THE MVFR CATEGORY AND WILL LIKELY FALL BELOW 2000
FEET. THE EXCEPTION WOULD BE KLUK WHICH IS A LOWER ELEVATION AIRPORT.
THUS...WILL FORECAST A PERIOD OF MVFR CEILINGS THIS MORNING INTO
EARLY AFTERNOON. DRIER AIR FILTERING SOUTHWARD IN THE LATER PART
OF THE AFTERNOON SHOULD ALLOW CEILINGS TO SCATTERED AND RETURN TO
VFR. GUSTY NORTHERLY WINDS OF 12-15 KNOTS WITH GUSTS AROUND 25
KNOTS CAN BE EXPECTED.

FOR TONIGHT...AN EXPANSIVE SURFACE RIDGE OF HIGH PRESSURE WILL
BUILD SOUTHEAST INTO THE OHIO VALLEY. A RELAXING PRESSURE GRADIENT
AND NIGHTFALL DECOUPLING WILL ALLOW WINDS TO DIMINISH OVER TIME.
SOME HIGHER LEVEL CLOUDS MAY SPILL EAST/SOUTHEAST INTO THE REGION
AFTER 06Z. 

OUTLOOK...NO SIGNIFICANT WEATHER IS EXPECTED.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...NONE.
KY...NONE.
IN...NONE.

&&

$$
SYNOPSIS...HATZOS
NEAR TERM...HATZOS
SHORT TERM...HATZOS
LONG TERM...JGL
AVIATION...HICKMAN






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