-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KILN 201909
AFDILN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON OH
309 PM EDT MON MAY 20 2013

.SYNOPSIS...
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A WARM AND HUMID AIRMASS WILL REMAIN IN PLACE BEFORE A COLD FRONT
ARRIVES ON THURSDAY. MID LEVEL RIDGING WILL SLIDE EAST OF OUR AREA
TONIGHT AS LOW PRESSURE SLOWLY MOVES SOUTH AND EAST ACROSS THE
NORTHERN PLAINS. CHANCES FOR PRECIPITATION WILL INCREASE AS THIS
LOW APPROACHES OUR AREA OVER THE NEXT COUPLE OF DAYS.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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MID LEVEL RIDGE EXTENDING ACROSS THE SOUTHEASTERN CONUS AND INTO
OUR FORECAST AREA IS KEEPING CONVECTION OUT OF OUR AREA THIS
AFTERNOON DESPITE AN UNSTABLE AIRMASS. A CU DECK WILL THIN LATE
THIS AFTERNOON AND EVENING AS WE BEGIN TO LOSE THE PEAK HEATING OF
THE DAY. TONIGHT...MOST CONVECTIVE MODELS ARE INDICATING
DEVELOPMENT OF THUNDERSTORMS WELL WEST OF OUR AREA ASSOCIATED WITH
A DISTURBANCE ROUNDING THE BASE OF A TROUGH EXTENDING SOUTH OF LOW
PRESSURE ACROSS THE NORTHERN PLAINS. THIS CONVECTION IS EXPECTED
TO HEAD EAST TO NORTHEAST THROUGHOUT THE NIGHT AS PLENTY OF
ELEVATED INSTABILITY WILL BE IN PLACE. WHATEVER IS LEFT OF THIS
CONVECTION LATE TONIGHT MAY MAKE IT INTO OUR WESTERN ZONES AFTER
MIDNIGHT. WAS FAIRLY AGGRESSIVE IN THE FORECAST ON BRINGING
SHOWERS AND THUNDERSTORMS INTO THE WESTERN ZONES LATE TONIGHT
WHILE GRADUALLY WEAKENING THEM AS THEY SHIFT EASTWARD ACROSS OUR
AREA TUESDAY MORNING.

ANOTHER MILD NIGHT IS FORECAST FOR TONIGHT WITH OVERNIGHT LOWS
IN THE MID TO UPPER 60S.
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&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
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OVERALL PATTERN FOR THE SHORT TERM TIME PERIOD IS FOR A LOW OVER
THE NORTHERN PLAINS TO SLOWLY SHEAR EASTWARD TUESDAY THROUGH
TUESDAY NIGHT...BEFORE GETTING ABSORBED INTO A DEEPENING TROUGH
ACROSS THE GREAT LAKES. AS THIS SYSTEM BEGINS TO GET SHEARED INTO
SOUTHWESTERLY FLOW ACROSS OUR REGION...TIMING OF INDIVIDUAL PIECES
OF ENERGY AND ASSOCIATED CONVECTION BECOMES UNCERTAIN.

BASED ON THE NEAR TERM FORECAST DECAYING CONVECTION ACROSS OUR
ZONES TUESDAY MORNING...THERE WOULD BE A PORTION OF THE DAY
TUESDAY WHERE THE BOUNDARY LAYER WILL BE WORKED OVER. THEREFORE
THERE MAY BE SEVERAL HOURS DURING THE FIRST PART OF THE DAY
TUESDAY WHERE LITTLE TO NO CONVECTION IS OCCURRING IN OUR FORECAST
AREA. THIS SOLUTION IS BEING INDICATED BY THE MAJORITY OF COMPUTER
MODELS. BY LATE TUESDAY AFTERNOON INSTABILITY WOULD HAVE INCREASED
AND SUFFICIENT RECOVERY OF THE BOUNDARY LAYER IS EXPECTED TO HAVE
OCCURRED. FORCING ASSOCIATED WITH ANY SHORTWAVE ENERGY EJECTING
EAST FROM THE LOW OVER THE PLAINS WILL HELP TO TRIGGER CONVECTIVE
DEVELOP LATE TUESDAY AFTERNOON. ALTHOUGH EXACT TIMING AND
PLACEMENT OF THE CONVECTION IS HIGHLY UNCERTAIN AT THIS TIME...UP
TO 45 KT OF 0-6 KM SHEAR MAY BE PRESENT ACROSS THE NORTHWESTERN
HALF OF OUR FORECAST AREA. THEREFORE...IF CONVECTION DOES GET GOING
TUESDAY AFTERNOON AND EVENING ACROSS OUR NORTHWEST...THERE WILL
BE THE POTENTIAL FOR SOME OF THESE STORMS TO BECOME SEVERE. THE
MAIN THREAT FROM THESE STORMS WOULD BE DAMAGING WIND AND ISOLATED
LARGE HAIL. THIS THREAT IS BEING HIGHLIGHTED IN THE HWO.

CHANCES FOR SHOWER AND THUNDERSTORMS WILL CONTINUE INTO TUESDAY
NIGHT AND INTO THE DAY ON WEDNESDAY AS THE LOW PROGRESSES NEARER
TO OUR AREA. SHEAR AND INSTABILITY WILL DECREASE ON TUESDAY NIGHT
AND WEDNESDAY....WHICH SHOULD LESSEN THE OVERALL SEVERE THREAT.
HOWEVER...ON WEDNESDAY THERE MAY STILL BE SUFFICIENT INSTABILITY
TO COMBINE WITH ABOUT 35 KT OF 0-6 KM SHEAR TO PRODUCE ISOLATED
CHANCES FOR DAMAGING WINDS AND LARGE HAIL SHOULD STORMS GET
ORGANIZED.

BY WEDNESDAY EVENING THE BEST CHANCES FOR PRECIPITATION WILL SHIFT
EAST OF OUR AREA ALONG WITH THE BEST FORCING.

TEMPERATURES WILL BE ON A DOWNWARD TREND THROUGHOUT THE SHORT TERM
TIME PERIOD. ON TUESDAY EXPECT UPPER 80S ACROSS THE EAST TO LOWER
80S ACROSS THE WEST. BY WEDNESDAY...CLOUD COVER AND PRECIPITATION
WILL KEEP TEMPERATURES LOWER THAN TUESDAY. OVERNIGHT LOWS WILL
CONTINUE TO BE MILD BOTH TUESDAY AND WEDNESDAY NIGHT AS WE REMAIN
IN THIS WARM AND HUMID AIRMASS.
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&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
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THE UPPER LEVEL TROUGH WILL PIVOT EAST ACROSS OUR AREA THROUGH THE
DAY ON THURSDAY. THIS COMBINED WITH SOME LINGERING
INSTABILITIES...WILL KEEP THE THREAT OF SHOWERS AND A FEW
THUNDERSTORMS GOING THROUGH THE AFTERNOON. AS THE TROUGH BEGINS TO
SHIFT EAST AND WE LOSE THE INSTABILITY...PCPN SHOULD TAPER OFF TO A
FEW SHOWERS THURSDAY NIGHT. COOLER AIR WILL BEGIN FILTERING INTO THE
AREA THROUGH THE DAY ON THURSDAY WITH HIGHS RANGING FROM THE UPPER
60S NORTHWEST TO LOW TO MID 70S SOUTHEAST.

SURFACE HIGH PRESSURE WILL BUILD DOWN FROM THE NORTH AND INTO OUR
AREA FRIDAY INTO SATURDAY...KEEPING A SEASONABLY COOL AIRMASS IN
PLACE THROUGH THE START OF THE WEEKEND. HIGHS ON FRIDAY WILL BE IN
THE MID TO UPPER 60S AND WITH THE SURFACE HIGH OVERHEAD...LOWS
SATURDAY MORNING WILL DIP INTO THE LOW TO MID 40S. THE SURFACE HIGH
WILL BEGIN TO SHIFT OFF TO THE EAST THROUGH THE REMAINDER OF THE
WEEKEND AS MID LEVEL RIDGING BEGINS TO ESTABLISH ITSELF ALOFT. THIS
WILL RESULT IN A GRADUAL RETURN TO WARMER TEMPERATURES THROUGH THE
REST OF THE HOLIDAY WEEKEND. MODELS ARE STILL TRYING TO SUGGEST THE
POSSIBILITY OF SOME ENERGY DROPPING DOWN FROM THE NORTHWEST LATE IN
THE WEEKEND. HOWEVER...TIMING AND PLACEMENT ARE HIGHLY VARIABLE SO
WILL MAINTAIN A DRY FORECAST AT THIS POINT.
-- End Changed Discussion --

&&

.AVIATION /19Z MONDAY THROUGH SATURDAY/...
MVFR CEILINGS WILL PERSIST FOR A FEW MORE HOURS UNTIL MIXING
RAISES CLOUD HEIGHTS AND VISIBILITIES LATER THIS AFTERNOON. WINDS
WILL GUST CLOSE TO 20 KNOTS DURING THIS TIME AS WELL. BR MAY FORM
AGAIN TONIGHT AT LUK AND ILN UNDER LIGHT WINDS AND A HUMID AIRMASS.
DAY MAY SEE A FEW SHOWERS TONIGHT IF ACTIVITY TO THE WEST HOLDS
TOGETHER AS INDICATED ON THE NAM AND RAP MODELS. CONVECTION MAY
DEVELOP AT ALL SITES ON TUESDAY AS FORCING INCREASES AHEAD OF A
FRONTAL ZONE...WITH WIND GUSTS OVER 20 KNOTS EXPECTED.

OUTLOOK...THUNDERSTORMS WILL BE POSSIBLE FROM TUESDAY NIGHT THROUGH
THURSDAY.

&&

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

&&

$$
SYNOPSIS...LATTO
NEAR TERM...LATTO
SHORT TERM...LATTO
LONG TERM...JGL
AVIATION...CONIGLIO