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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KILN 150613
AFDILN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON OH
213 AM EDT WED MAY 15 2013

.SYNOPSIS...
SOUTHERLY FLOW AT THE SURFACE WILL BE FOUND OVER THE REGION
THROUGH WEDNESDAY...WITH VERY WARM CONDITIONS EXPECTED. AS LOW
PRESSURE IN CANADA MOVES EAST...A FRONTAL BOUNDARY WILL STALL OVER
THE OHIO VALLEY FROM WEDNESDAY NIGHT THROUGH FRIDAY. THIS WILL
PROVIDE A FOCUS FOR SHOWERS AND THUNDERSTORMS.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
RIDGING IS HOLDING STEADY...WITH THE CWA ON THE NORTHEASTERN EDGE
OF THE POSITIVE 500MB HEIGHT AXIS. SATELLITE AND MODELS CONTINUE
TO SUGGEST THAT SOME MID LEVEL CLOUDS WILL SPILL SOUTHEAST ACROSS
THE REGION...MOST NUMEROUS OVER THE NORTH. SOME SPRINKLES ARE
OCCURRING WITHIN THE 12 KFT-15 KFT DECK ACRS NW OHIO. IT IS
CONCEIVABLE THAT SOME SPRINKLES MAY SKIM OR FAR NE OVERNIGHT...BUT
HAVE LEFT THE FORECAST DRY.

OVERNIGHT LOW FORECAST IS COMPLICATED GIVEN INCREASING DEWPOINTS
FROM THE WEST...THE CURRENT LULL IN THE WINDS...BUT AN INCREASE IN
THE WINDS/PRESSURE GRADIENT TOWARD SUNRISE DUE TO LOW PRESSURE
OVER THE GREAT LAKES. OVERALL...LOWS SHOULD RANGE FROM THE UPPER
50S FAR EAST/SOUTHEAST TO THE MID 60S WEST.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH THURSDAY NIGHT/...
OF GREATEST CONCERN IN THE SHORT TERM IS THE POTENTIAL FOR VERY
WARM TEMPERATURES ON WEDNESDAY...AND CONVECTION THROUGH THE PERIOD.

TODAY (TUESDAY)...THE AIR MASS OVER THE NORTHERN MISSISSIPPI
VALLEY REGION (ESPECIALLY IOWA) IS ANOMALOUSLY WARM...WITH
NUMEROUS RECORDS BEING SET. 850MB TEMPS IN THIS REGION ARE AT
AROUND +25 CELSIUS. THIS AIR MASS IS FORECAST TO ADVECT INTO THE
OHIO VALLEY BY WEDNESDAY...BUT THE MAGNITUDE OF THE ANOMALY WILL
DECREASE. THE DRY/WARM LAYER AT 850MB IS VERY EVIDENT ON MODEL RH
FIELDS...AND SHOWS UP ON ILN-AREA FORECAST SOUNDINGS AS AN
ELEVATED MIXED LAYER ABOVE THE WEDNESDAY MORNING NOCTURNAL
INVERSION / WEDNESDAY MIDDAY LCL. STRONG BOUNDARY LAYER MIXING IS
EXPECTED INTO THIS WARM LAYER...THOUGH IT SHOULD STILL HOLD AS A
CAP GIVEN THE MAGNITUDE OF THE WARMTH AND THE QUESTIONABLE QUALITY
OF THE LOW LEVEL MOISTURE.

SREF 850MB TEMP PLOTS SHOW THAT THE 850MB TEMP ANOMALY IS ABOVE 3
STANDARD DEVIATIONS TODAY OVER IOWA...BUT THIS WILL DECREASE TO
AROUND 2 STANDARD DEVIATIONS OVER THE ILN CWA ON WEDNESDAY. ALMOST
ALL MODEL/GUIDANCE PLOTS APPEAR TOO LOW FOR TEMPS GIVEN THE STRONG
MIXING AND WINDS (GUSTS UP TO 25-35 MPH) WITH 850MB TEMPS AT
AROUND +18 TO +20 CELSIUS. THUS...THE MAX TEMP FORECAST IS ABOVE
MOST OF THE GUIDANCE AND SLIGHTLY HIGHER THAN THE INHERITED
FORECAST. RECORDS OF 92 DEGREES APPEAR TO BE SECURE AT COLUMBUS AND
DAYTON...BUT WITH A FORECAST HIGH OF 87...THE 89 DEGREE RECORD AT
CINCINNATI (1944) IS NOT AS SAFE.

WITH SURFACE LOW PRESSURE MOVING EAST ACROSS MICHIGAN AND INTO
CANADA...AND GRADUALLY FALLING HEIGHTS OVER THE OHIO VALLEY...A
FRONTAL BOUNDARY WILL MOVE INTO THE ILN CWA ON WEDNESDAY
AFTERNOON. PERHAPS INITIALLY DRY...ALL MODELS FORECAST A GRADUAL
ACTIVATION OF THIS FRONT DURING THE DAY. CONVERGENCE WILL INCREASE
TO SOME DEGREE...AND 1000-1500 J/KG OF MIXED LAYER CAPE WILL ALSO
DEVELOP JUST AHEAD OF THE FRONT. THE PRESENCE OF THE FRONT WILL BE
NEEDED TO SPARK CONVECTION...GIVEN THE CAP OUT IN FRONT...BUT THE
AVAILABLE INSTABILITY (NOT UNEXPECTED GIVEN THE ABNORMALLY WARM
TEMPS) WILL CERTAINLY SUPPORT THE DEVELOPMENT OF THUNDERSTORMS.
WITH A LACK OF ADDITIONAL FORCING SUPPORT...THIS ACTIVITY MAY NOT
BE WIDESPREAD...SO POPS WERE KEPT IN THE 50-60 PERCENT RANGE AT
MOST.

AS SHEAR WILL BE VERY WEAK AND MOSTLY UNIDIRECTIONAL (AND
PARALLEL TO THE FRONT)...WELL-ORGANIZED STORMS ARE NOT VERY
LIKELY. HOWEVER...LAPSE RATES WILL BE SOMEWHAT STEEP...EVEN IN THE
MID LEVELS (GREATER THAN 7 DEGREES C/KM). ALSO...A NARROW BAND OF
ENHANCED PW VALUES WILL EXIST NEAR THE FRONT...AND THE SHEAR
VECTOR DOES FAVOR THE POSSIBILITY OF STORM MOTIONS (E TO ESE) THAT
ARE PARALLEL TO THE REGION OF LIFT. SO...THERE MAY BE SOME DEGREE
OF A HAIL OR RAINFALL THREAT.

THE FRONT IS FORECAST TO STALL OUT NEAR THE SOUTHERN PARTS OF THE
CWA BY THURSDAY MORNING...REMAINING IN PLACE UNTIL IT VERY SLOWLY
STARTS LIFTING NORTH AGAIN ON THURSDAY NIGHT. THIS WILL KEEP AN
AXIS OF PRECIPITATION CHANCES ACROSS THE SAME REGION...LEADING TO
COOLER...CLOUDIER AND WETTER CONDITIONS ON THURSDAY. GIVEN A MUCH
LESS FAVORABLE THERMODYNAMIC ENVIRONMENT...STRONG STORMS ARE
UNLIKELY.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
QUASI-STATIONARY FRONT IS EXPECTED TO BE NEAR THE SOUTHERN PART OF
THE FORECAST AREA AT THE BEGINNING OF THE PERIOD. THIS WILL CONTINUE
TO BE A FOCUS FOR PRIMARILY DIURNAL CONVECTION.

APPEARS THAT THIS BOUNDARY WILL WEAKEN AND LIFT NORTH THROUGH THE
WEEKEND. WILL STILL BE AT LEAST A SMALL CHANCE OF SHOWERS AND
THUNDERSTORMS WITH TEMPERATURES SLOWLY WARMING AS UPPER HEIGHTS
RISE. AT THIS POINT EXPECT MONDAY TO BE THE WARMEST DAY OF THE
LONG TERM PERIOD. THEN A SHORT WAVE AND ASSOCIATED COLD FRONT IS
FORECAST TO PUSH INTO THE REGION ON TUESDAY. THIS SHOULD BRING A
GOOD CHANCE OF SHOWERS AND THUNDERSTORMS TO THE AREA.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
MID LEVEL CLOUDS CONTINUE TO SPILL SOUTHEAST ACROSS THE NRN TAF SITES
ATTM AND SHOULD CONTINUE FOR THE FIRST PART OF THE TAF PERIOD.
LOW PRESSURE CENTER MOVG THRU THE GREAT LAKES TODAY WILL PULL A CDFNT
INTO THE REGION. MODEL TIME SERIES ARE INDICATING THAT THE CU
WILL BE LATE TO DEVELOP...WAITING UNTIL AFT 18-20Z WHEN THE
FRONT PUSHES INTO THE REGION. SO HAVE CONTINUED WITH THE VCTS AT
KDAY/KCMH/KLCK AT 21Z. THE FNT WILL SAG FARTHER SOUTH DURING WED
NGT...BUT IN GENERAL WILL LINGER ACROSS THE TAFS...SO HAVE VCTS IN
ALL THE TAFS AFT 00Z.

INCREASING PRESSURE GRADIENT ALONG WITH MIXING OF H8 JET WILL
KEEP WINDS GUSTY TODAY. HAVE GUSTS AROUND 25KTS...BUT A COUPLE
COULD APPROACH 30 KNOTS. PRESSURE GRADIENT WEAKENS BY 00Z SO WINDS
SHOULD SUBSIDE BY SUNSET.

OUTLOOK...THUNDERSTORMS POSSIBLE WEDNESDAY NIGHT THROUGH SUNDAY.
-- End Changed Discussion --

&&

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

&&

$$
SYNOPSIS...HATZOS/HICKMAN
NEAR TERM...HATZOS/HICKMAN
SHORT TERM...HATZOS
LONG TERM...
AVIATION...SITES