Area Forecast Discussion
Issued by NWS Wilmington, OH

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000
FXUS61 KILN 020617
AFDILN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON OH
217 AM EDT THU APR 2 2015

.SYNOPSIS...
HIGH PRESSURE AND DRY AIRMASS WILL MOVE OFF TO THE EAST TONIGHT. A
FRONTAL ZONE WILL DEVELOP ON THURSDAY AND REMAIN IN THE AREA THROUGH
FRIDAY. SEVERAL WAVES OF LOW PRESSURE TRAVELING ALONG THE FRONT WILL
PROVIDE MULTIPLE ROUNDS OF RAINFALL. HIGH PRESSURE AND DRY AIR
WILL MOVE BACK IN FOR SATURDAY.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
HAVE BEEN TWEAKING VARIOUS PARTS OF THE FORECAST THIS EVENING.
FOR THE REST OF TONIGHT...THIN CIRRUS WILL CONTINUE TO OVERSPREAD
THE AREA AS SURFACE HIGH DRIFTS OFF THE ATLANTIC COAST. KILN VWP
HAS ALREADY RESPONDED ABOVE THE DECOUPLED BOUNDARY LAYER SHOWING
30KTS JUST OFF THE DECK IN RETURN FLOW. AT THE SURFACE THOUGH
WINDS WILL REMAIN LIGHT/SOUTHEAST THROUGH THE NIGHT AND SLOWLY
VEER TO SOUTHERLY AND INCREASE. VERY DRY AIR AT THE SURFACE BEING
HANDLED HORRIBLY BY ALL NWP /A TYPICAL APRIL PROBLEM/ AND THE NEW
02.00Z KILN SOUNDING SHOWS THAT DETERMINISTIC GUIDANCE IS WAY WAY
OFF BELOW 850 MB IN TERMS OF MOISTURE. EVEN NASHVILLE/SPRINGFIELD
ILL HAVE SIMILAR MODEL MOIST BIAS IN COMPARED TO REAL LIFE. THIS
IS A VERY DRY AIRMASS OVER THE AREA SO HAVE DROPPED TEMPS A COUPLE
OF DEGREES EVEN WITH WARM ADVECTION/INCREASING WINDS AS IT WILL
TAKE A LONG TIME FOR BOUNDARY LAYER DWPTS TO COME UP.

LATER IN THE NIGHT /AFTER 09Z/ THERE IS STRONG AGREEMENT THAT LOW
LEVEL JET WILL INDUCE ACCAS AND MID CLOUD ABOVE THE VERY DRY
BOUNDARY LAYER...AND LIFTING A PARCEL AT THE NOSE OF THE LOW LEVEL
JET INDICATES THAT IF SATURATION CAN OCCUR...LAPSE RATES ARE STEEP
AND INSTABILITY WILL LIKELY YIELD HIGH BASED/ELEVATED
SHOWERS/STORMS MOVING QUICKLY FROM SW->NE ACROSS THE AREA EARLY
THURS MORNING. ACTUALLY QUITE IMPRESSED WITH THE INSTBY - BUT HAVE
RESERVATIONS ON THE LARGE QPF COVERAGE GIVEN MOISTURE ERRORS AS
MENTIONED ABOVE. THINK THERE WILL BE ENOUGH ACCAS/ELEVATED INSTBY
TO DRIVE SOME SHOWERS/STORMS QUICKLY THROUGH THE AREA SO INCREASED
RAIN CHANCES IN THE MORNING FOR A QUICK HITTING/BUT LIGHT AMOUNT
BAND OF THERMODYNAMICALLY DRIVEN ACTIVITY ROOTED WAY ABOVE THE
BOUNDARY LAYER. MAY ACTUALLY BE QUITE A BIT OF RADAR ECHO BUT NOT
MUCH MAKING IT TO THE GROUND VIA VERY DRY SUB-CLOUD LAYERS /VIRGA/
THURS MORNING.

TWEAKED THURSDAYS HIGHS DOWN JUST A BIT WITH EVAPORATIVE COOLING
OF SUBSTANTIAL DRY LAYER PERHAPS BEING A LITTLE SLOWER TO WARM
WITH AMPLE CLOUD ON THURSDAY. HAVE ALSO TRIED TO INDICATE A LULL
IN RAIN CHANCES BETWEEN MORNING ACTIVITY AND AFTN/EVENING FRONTAL
ACTIVITY. REMAINDER OF THURSDAY DISCUSSION FOLLOWS BELOW.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY NIGHT/...
SLOW MOVING COLD FRONT TO APPROACH FROM THE WEST THURSDAY AND MOVE
INTO OHIO THURSDAY NIGHT. NRN STREAM ENERGY TO PASS NORTH OF THE
GREAT LAKES WITH SRN STREAM TROF HOLDING BACK OVER THE SRN PLAINS.
THIS KEEPS ILN/S FA IN A MOIST SWRLY FLOW. 50-60 KT LOW LEVEL JET
WITH ENHANCED LOW LEVEL CONVERGENCE DEVELOPING THURSDAY EVENING.

FAVORABLE MOISTURE TRANSPORT FOR A PROLONGED PERIOD. PRECIPITABLE
WATER VALUES INCREASE TO CLOSE TO AROUND 250 PERCENT OF NORMAL OR 2
TO 3 STD DEVIATIONS ABOVE NORMAL THURSDAY NIGHT. WILL CONTINUE
LKLY POPS ACRS THE WEST THURSDAY AFTN AND CATEGORICAL THURSDAY
NIGHT. MARGINAL INSTBY DEVELOPS THU AFTN/THU EVE. WITH THE FRONT
STILL TO OUR WEST...STORMS WILL HAVE TO BE COLD POOL DRIVEN. EXPECT
MARGINAL INSTBY WITH BOUNDARY LAYER CAPES LESS THAN 1000 J/KG.
ALTHOUGH WIND FLOW WILL BE FAVORABLE THE INSTBY WILL BE LIMITING
FACTOR AND EXPECT ONGOING STORMS TO WEAKEN AS THEY TRACK NE AWAY
FROM MORE FAVORABLE INSTBY AXIS. WILL CONTINUE TO MENTION THIS
MARGINAL POTENTIAL IN THE HWO PRODUCT.

IN STRONG WAA PATTERN TEMPERATURES TO BE 20-25 DEGREES ABOVE NORMAL
THURSDAY WITH HIGHS FROM THE UPPER 60S NORTHWEST TO THE LOWER/MID 70S
SOUTHEAST.

EMBEDDED MID LEVEL S/W IN THE SOUTHWESTERLY FLOW WILL INDUCE A SFC
WAVE ON THE FRONTAL BOUNDARY. THIS WAVE TO RIPPLE NE THRU THE OHIO
VALLEY LATE THURSDAY NIGHT/EARLY FRIDAY. THIS WAVE WILL PROVIDE AN
ENHANCED CHANCE OF PCPN WITH FAVORABLE LOW LEVEL FORCING. LOWS
THURSDAY NIGHT FROM THE UPPER 40S NORTHWEST TO THE UPPER 50S
SOUTHEAST. WITH SFC WAVE/FRONT BISECTING THE AREA...THERE WILL BE
A LARGE GRADIENT IN TEMPERATURES ON FRIDAY. FRIDAYS HIGHS ARE EXPECTED
TO RANGE FROM THE MID 50S NW TO UPPER 60S SE.

FLOWS MERGE WITH MEAN TROF OVER THE GREAT LAKES BY SAT MORNING.
NUMERICAL MODEL SOLNS DIFFER SOME ON PLACEMENT BUT ALL HAVE A FINAL
SFC WAVE PASSING THRU THE OHIO VALLEY FRIDAY NIGHT.

DUE TO THE PROLONGED PERIOD OF PRECIPITATION AND THE MOIST
ENVIRONMENT THE POTENTIAL FOR HEAVY RAIN WILL EXIST. NUMERICAL MODEL
SOLNS SUGGEST 1 TO 3+ INCHES OF RAIN BUT DIFFER ON AMOUNTS AND
PLACEMENT. AT THIS TIME WILL CONTINUE TO HIGHLIGHT HEAVY RAIN AND
THE POTENTIAL FOR FLOODING IN THE HWO PRODUCT.

IN CAA ON BACKSIDE OF DEPARTING LOW PRESSURE TEMPERATURES DROP TO
LOWS FROM NEAR 30 NW TO THE UPPER 30S SE BY SATURDAY MORNING.
A BRIEF PERIOD OF SNOW IS POSSIBLE PRIOR TO ENDING LATE FRIDAY
NIGHT BUT DEEP MOISTURE AND BEST LIFT EXITS QUICKLY SO DO NOT
EXPECT SIGNIFICANT SNOW. AT THIS TIME ONLY HAVE ONE TO TWO TENTHS
IN THE N-NE.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
PRECIPITATION WILL BE EXITING THE EASTERN CWA EARLY SATURDAY
MORNING AS SURFACE HIGH PRESSURE AND MUCH DRIER AIR BUILDS IN FROM
THE WEST. DESPITE MOSTLY SUNNY SKIES...A BROAD UPPER TROUGH AND
850 TEMPS AROUND MINUS 5 C WILL MAKE FOR A CHILLY DAY WITH HIGHS
RANGING FROM THE MID 40S NORTH TO LOWER 50S SOUTH. LOWS SATURDAY
NIGHT WILL AGAIN DROP INTO THE 30S ACROSS THE AREA...BEFORE WAA
KICKS IN ON SUNDAY ALLOWING TEMPS TO RETURN BACK TO NEAR NORMAL. A
FRONTAL BOUNDARY STALLED NORTH OF OHIO WILL KEEP CHANCES FOR
SHOWERS NORTH OF THE CWA ON SUNDAY. CLOUD COVER WILL CONSEQUENTLY
BE MORE PREVALENT ACROSS THE NORTHERN HALF OF THE CWA.

DETERMINISTIC MODELS AND ENSEMBLE GUIDANCE THEN DIVERGE
SIGNIFICANTLY FOR THE REMAINDER OF THE EXTENDED PERIOD. GENERALLY
USED AN EQUAL BLEND OF WPC GUIDANCE...GFS AND ECMWF FOR MONDAY
THROUGH WEDNESDAY. GFS IS QUICKER THAN ECMWF TO BRING THE NEXT
SYSTEM INTO THE GREAT LAKES REGION LATE MONDAY INTO TUESDAY. THE ILN
CWA WILL BE IN THE WARM SECTOR BOTH DAYS WITH PERSISTENT WAA
ALLOWING TEMPS TO WARM INTO THE UPPER 50S TO MID 60S ON MONDAY AND
INTO THE MID 60S TO NEAR 70 ON TUESDAY. ISENTROPIC LIFT WILL PROVIDE
A CHANCE OF SHOWERS DURING THE DAY ON MONDAY. A DEVELOPING LLJ
MONDAY NIGHT WILL THEN TRANSPORT AMPLE GULF MOISTURE INTO THE OHIO
VALLEY WITH PWATS AROUND 1 TO 1.5 INCHES (OVER 200 PERCENT OF
NORMAL) ON TUESDAY. PRECIP CHANCES WILL BE HIGHEST MONDAY NIGHT INTO
TUESDAY AND HAVE INCLUDED THUNDER IN THE GRIDS ON TUESDAY AS
FAVORABLE INSTABILITY DEVELOPS THANKS TO THE INCREASING WARMTH AND
LOW LEVEL MOISTURE.

CHANCES FOR SHOWERS AND ISOLATED THUNDER WILL CONTINUE INTO
WEDNESDAY AS A COLD FRONT DROPS SOUTHEAST ACROSS THE AREA. LOW
CONFIDENCE IN TIMING OF FROPA HOWEVER AS GFS IS QUICK TO PUSH IT
THROUGH TUESDAY NIGHT AND ECMWF DOES NOT PUSH IT THROUGH UNTIL LATER
WEDNESDAY.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
HIGH LEVEL CLOUDINESS WILL BE ON THE INCREASE THROUGH THE PRE DAWN
HOURS AHEAD OF A LEAD MID LEVEL SHORT WAVE CURRENTLY MOVING
THROUGH THE MID MISSISSIPPI VALLEY. THIS SHORT WAVE IS FORECAST TO
SLOWLY WEAKEN AS IT PUSHES EASTWARD INTO THE MID OHIO VALLEY
THROUGH MID MORNING. AS A RESULT...EXPECT TO SEE A GRADUAL
WEAKENING TREND IN THE CONVECTION CURRENTLY MOVING INTO WESTERN
KENTUCKY/SOUTHERN ILLINOIS AS IT WORKS ITS WAY EAST TOWARD OUR FA.
BASED ON THE CURRENT TIMING...WOULD EXPECT PCPN FROM THIS TO
OVERSPREAD THE TAF SITES THROUGH MID MORNING. GIVEN THE RELATIVELY
DRY LOW LEVELS...WILL KEEP CIGS VFR WITH THIS FIRST BATCH AND ONLY
ALLOW FOR AN OCCASIONAL MVFR VSBY WITH ANY HEAVIER SHOWER. WITH THE
EXPECTED WEAKENING TREND...WILL ALSO HOLD OFF ON MENTIONING ANY
THUNDER WITH THIS INITIAL BATCH OF PCPN.

EXPECT TO SEE A LULL IN THE PCPN FROM LATE MORNING INTO MID
AFTERNOON AS WE GET ON THE BACK SIDE OF THE INITIAL SHORTWAVE. THE
COMBINATION OF SOME POSSIBLE BREAKS IN THE CLOUDS ALONG WITH
CONTINUED LOW LEVEL WAA WILL ALLOW US TO DESTABILIZE THROUGH THE
AFTERNOON HOURS. THIS WILL LEAD TO SHOWER AND THUNDERSTORM REDEVELOPMENT
FROM WEST TO EAST ACROSS THE AREA LATE THIS AFTERNOON AND
CONTINUING INTO THIS EVENING. SHOWERS AND OCCASIONAL
THUNDERSTORMS WILL THEN CONTINUE THROUGH THE REMAINDER OF THE TAF
PERIOD AS A COLD FRONT SAGS VERY SLOWLY SOUTHEAST TOWARD THE AREA.

SOUTHERLY WINDS WILL BE ON THE INCREASE AND BECOME GUSTY LATER
THIS MORNING AND CONTINUE INTO THE AFTERNOON HOURS.

OUTLOOK...MVFR AND POSSIBLY IFR CEILINGS AND VISIBILITIES ARE
POSSIBLE INTO FRIDAY NIGHT...ESPECIALLY IN PERIODS OF HIGHER
INTENSITY SHOWERS/STORMS.

&&

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

&&

$$
SYNOPSIS...AR
NEAR TERM...BINAU
SHORT TERM...BINAU/AR
LONG TERM...KURZ
AVIATION...JGL






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