Area Forecast Discussion
Issued by NWS Wilmington, OH

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988
FXUS61 KILN 061311
AFDILN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON OH
911 AM EDT FRI MAY 6 2016

.SYNOPSIS...
DRIER CONDITIONS ARE EXPECTED TODAY...WITH TEMPERATURES RISING TO
VALUES NEAR NORMAL. SHOWERS AND THUNDERSTORMS ARE EXPECTED ON
SATURDAY...AS A COLD FRONT MOVES INTO THE AREA FROM THE NORTH.
THIS FRONT WILL REMAIN IN PLACE ACROSS THE OHIO VALLEY THROUGH THE
FOLLOWING SEVERAL DAYS...WITH CONTINUED CHANCES FOR OCCASIONAL
RAIN THROUGH AT LEAST THE MIDDLE OF THE WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A WEAK AXIS OF SURFACE HIGH PRESSURE WILL SAG SLOWLY SOUTHEAST
INTO THE AREA THROUGH THIS AFTERNOON. AHEAD OF THIS...WEAK
NORTHERLY LOW LEVEL FLOW MAY ALLOW FOR SOME CU
DEVELOPMENT...ESPECIALLY ACROSS EASTERN PORTIONS OF THE AREA. WITH
A FAIR AMOUNT OF SUNSHINE THOUGH...EXPECT TEMPERATURES TO PUSH
INTO THE MID TO UPPER 60S THIS AFTERNOON.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/...
A NARROW 500MB RIDGE...WITH ITS AXIS ORIENTED IN A
SOUTHWEST-TO-NORTHEAST DIRECTION...WILL BRIEFLY MOVE INTO THE
MIDDLE OHIO VALLEY TONIGHT. A DEEP TROUGH MOVING SOUTH FROM
NORTHERN ONTARIO WILL THEN MOVE CLOSER TO THE OHIO
VALLEY...HELPING TO KICK THE CLOSED UPPER LOW OUT OF THE COASTAL
STATES...AND ALSO HELPING TO DRIVE A COLD FRONT THROUGH THE UPPER
MIDWEST AND INTO THE GREAT LAKES / OHIO VALLEY REGION.

AN INTERESTING NOTE REGARDING THE WEATHER SYSTEM FORECAST TO
AFFECT THE REGION THROUGH THE WEEKEND IS THE SOMEWHAT UNUSUAL
ORIENTATION OF THE KEY FEATURES...THANKS TO THE OVERALL NORTHWEST
FLOW PATTERN THAT THE SYSTEM EXISTS WITHIN. THE WARM FRONT THAT
WILL MOVE THROUGH THE REGION EARLY SATURDAY WILL DO SO BY MOVING
EASTWARD...WITH THE FRONT ALONG A NEARLY DUE NORTH-TO-SOUTH AXIS.
THE COLD FRONT...COMING IN LATER IN THE DAY ON SATURDAY...IS
FORECAST TO BE MOVING NEARLY DUE SOUTH. IN TERMS OF
TEMPERATURES...THIS SHOULD ALLOW A PERIOD OF RELATIVELY STRONG
WARMING IN THE WARM SECTOR FOR THE SOUTHERN HALF OF THE FORECAST
AREA ON SATURDAY. TEMPERATURES NEAR 80 ARE NOW IN THE
FORECAST...WITH MID TO UPPER 70S FURTHER NORTH.

AS WARM FRONTAL PROCESSES BEGIN EARLY SATURDAY MORNING...MID-
LEVEL CLOUDS WILL BEGIN TO INCREASE...AND SOME VERY LIGHT
PRECIPITATION WILL BE POSSIBLE. THOUGH MORE LIKELY TO BE
VIRGA...SOME SPRINKLES MAY REACH THE GROUND...AND THIS HAS BEEN
ADDED TO THE FORECAST (MAINLY FROM 09Z TO 15Z). WITH THE TRIPLE
POINT WELL NORTH OF THE ILN FORECAST AREA...THERE SHOULD BE A
SHORT BREAK BETWEEN THE PRIMARY FORCING MECHANISMS...BEFORE A MORE
ACTIVE PERIOD BEGINS ON SATURDAY AFTERNOON ALONG AND AHEAD OF THE
COLD FRONT. BASED ON FAIRLY STRONG MODEL TIMING AGREEMENT...LIKELY
POPS HAVE BEEN USED...PASSING SOUTHWARD ACROSS THE CWA FROM 20Z-
02Z.

THE AFOREMENTIONED NORTHWESTERLY FLOW PATTERN IS ONE THAT WILL
PROVIDE A FAIR AMOUNT OF WIND SHEAR FOR THE COLD FRONT TO INTERACT
WITH. IT IS INTERESTING TO NOTE THAT SREF WIND SHEAR
PROBABILITIES ACTUALLY INDICATE A LOCAL MINIMUM OF DEEP-LAYER
SHEAR OVER THE ILN FORECAST AREA ON SATURDAY AFTERNOON...PERHAPS
SUGGESTING THAT THE STRONGER SHEAR WILL BE SLIGHTLY OUT OF PHASE
WITH THE EXPECTED DIURNAL HEATING AND EVENTUAL COLD FRONTAL
TIMING. NONETHELESS...COMBINED WITH THE STRONG FRONTAL
FORCING...THERE SHOULD BE ENOUGH SHEAR TO SUPPORT A DEGREE OF
THUNDERSTORM ORGANIZATION. THE DIRECTIONAL SHEAR IS NOT OVERLY
STRONG EITHER...BUT THROUGH THE 0-3KM LAYER...WINDS SHOULD SHIFT
FROM ABOUT 260 DEGREES AT THE SURFACE TO AROUND 300 DEGREES AT
3KM. INSTABILITY IS ANOTHER FACTOR THAT APPEARS SUFFICIENT THOUGH
NOT OVERLY IMPRESSIVE...WITH MLCAPE VALUES OF AROUND 1000-1200
J/KG AS A FAIR MODEL CONSENSUS. THE WARM ADVECTION PATTERN THROUGH
THE BOUNDARY LAYER IS ESSENTIALLY DUE WESTERLY...NOT A FAVORABLE
PATTERN AT ALL FOR SIGNIFICANT MOISTURE FLOW INTO THE OHIO VALLEY.
THIS WILL LIMIT INSTABILITY FROM BECOMING STRONGER...AND WILL ALSO
KEEP CLOUD BASES AT AROUND 4000-5000 FEET. THE END RESULT IS THAT
THE CHANCE OF SEVERE WEATHER CERTAINLY EXISTS...WITH THE POTENTIAL
FOR SOME ORGANIZED SEGMENTS AND POSSIBLY SUPERCELLS...WITH A
CHANCE OF PRODUCING LARGE HAIL AND DAMAGING WINDS.
HOWEVER...CONFIDENCE IN A MORE SIGNIFICANT SEVERE EVENT IS
LIMITED BY THE QUESTIONS ABOUT THE SHEAR TIMING AND QUALITY
(WIDENESS) OF THE INSTABILITY PROFILE. FURTHERMORE...THE TORNADO
THREAT APPEARS VERY LOW...WITH UNFAVORABLE NEAR-SURFACE
THERMODYNAMICS AND MARGINAL 0-1KM SHEAR.

THE COLD FRONT IS NOT EXPECTED TO GET TOO FAR BEYOND THE SOUTHERN
ILN FORECAST AREA ON SATURDAY NIGHT...STALLING OUT SOMEWHERE IN
THE VICINITY...AND POSSIBLY CONTINUING TO ACT AS A FOCUS FOR SOME
SHOWERS GOING INTO SUNDAY. THOUGH THERE APPEARS TO BE A BREAK IN
THE FORCING ON SUNDAY AFTERNOON...WHEN THE FRONT STARTS A
NORTHWARD MOTION AS A WARM FRONT AGAIN SUNDAY
NIGHT...PRECIPITATION CHANCES WILL INCREASE FROM THE SOUTH AND
WEST. THOUGH BOUNDARY LAYER CONDITIONS WILL BE SOMEWHAT
STABLE...SOME ELEVATED CONVECTION COULD OCCUR GOING INTO MONDAY
MORNING. AGAIN IN THE WARM SECTOR (AND WITH A BRIEF PERIOD OF
MID-LEVEL RIDGING MOVING IN)...CHANCES FOR PRECIPITATION WILL BE
MARGINAL FOR MONDAY AFTERNOON...BUT APPEAR LIKELY TO INCREASE
SIGNIFICANTLY GOING INTO MONDAY NIGHT AND TUESDAY.

TEMPERATURES ON SUNDAY ARE EXPECTED TO BE COOL...WITH THE ILN CWA
FIRMLY ON THE NORTHERN SIDE OF THE FRONTAL BOUNDARY. THIS WILL
CHANGE WITH THE FRONT MOVING NORTH ON MONDAY...ALLOWING FOR
ANOTHER WARMING TREND TO BEGIN. IN EITHER CASE...THE SWING SHOULD
REMAIN GENERALLY WITHIN AROUND 5 DEGREES OF CLIMATOLOGICAL NORMS.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
SEVERAL DISTURBANCES WILL WORK THROUGH THE REGION FROM MONDAY
THROUGH THURSDAY KEEPING PRECIPITATION CHANCES IN THE FORECAST FOR
MOST OF THIS TIME. WENT WITH A MODEL BLEND DURING THIS TIME.
MODELS ARE IN GENERAL AGREEMENT ON THE MAIN FEATURES THROUGH
WEDNESDAY ALTHOUGH THERE ARE SOME DIFFERENCES IN TIMING AND
STRENGTH OF EACH SYSTEM.

MODELS START TO DIVERGE FOR THURSDAY WITH THE ECMWF KEEPING
PRECIPITATION ACROSS THE REGION WHILE THE GFS IS DRIER.  AT THIS
POINT TRENDED TOWARDS THE ECMWF WITH A CHANCE OF PRECIPITATION FOR
THURSDAY.

HIGH TEMPERATURES THROUGH THE LONG TERM WILL GENERALLY BE IN THE 60S
AND 70S WITH LOWS IN THE 40S AND 50S.  WENT CLOSE TO THE MODEL BLEND
FOR TEMPERATURES DURING THIS TIME.

&&

.AVIATION /13Z FRIDAY THROUGH TUESDAY/...
SKIES HAVE BECOME MOSTLY CLEAR THIS MORNING...AND VFR CONDITIONS
ARE EXPECTED THROUGH THE REST OF THE FORECAST PERIOD. THE ONLY
EXCEPTION WILL BE DURING THE NEXT HOUR OR TWO AT KLUK...WHERE SOME
FOG HAS FINALLY DEVELOPED EARLY THIS MORNING.

SOME VFR CUMULUS MAY DEVELOP TODAY...WITH NORTHWESTERLY WINDS OF
AROUND 10 KNOTS. GOING INTO TONIGHT...WINDS WILL SHIFT TO THE
SOUTHWEST...AND MAY BECOME LIGHT AND VARIABLE FOR A FEW HOURS IN
THE EVENING AND EARLY OVERNIGHT HOURS. WINDS WILL BEGIN TO
INCREASE AGAIN BEFORE SUNRISE...WHICH SHOULD LIMIT THE THREAT OF
FOG.

WITH INCREASING MID AND HIGH CLOUDS TOMORROW MORNING...THERE IS A
SLIGHT CHANCE OF A SPRINKLE AT THE AIRPORTS...BUT NOTHING WORTH
MENTIONING IN THE TAFS.

OUTLOOK...THUNDERSTORMS ARE POSSIBLE ON SATURDAY AFTERNOON AND
EVENING...WITH A CHANCE OF MVFR/IFR CONDITIONS. THUNDERSTORMS ARE
AGAIN POSSIBLE ON MONDAY AND TUESDAY.

&&

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

&&

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



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