Area Forecast Discussion
Issued by NWS Wilmington, OH

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000
FXUS61 KILN 172014
AFDILN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON OH
414 PM EDT SUN AUG 17 2014

.SYNOPSIS...
A WEAK LOW PRESSURE SYSTEM OVER SOUTHERN INDIANA WILL BEGIN TO
ACCELERATE A LITTLE AS IT CONTINUES TO WEAKEN FURTHER WHILE MOVING
ALONG AND JUST SOUTH OF THE OHIO RIVER. SHOWERS AND THUNDERSTORMS
WILL GENERALLY STAY FOCUSED SOUTH OF THE OHIO RIVER TONIGHT AND
MONDAY NEAR THE PATH OF THE LOW...THOUGH SCATTERED SHOWERS AND
STORMS WILL BE POSSIBLE OVER CENTRAL AND SOUTHERN OHIO AND INDIANA
AS WELL IN THE VERY HUMID AND MODERATELY UNSTABLE AIRMASS. A BRIEF
PERIOD DRY WEATHER IS EXPECTED MONDAY NIGHT INTO EARLY TUESDAY
BEFORE THE NEXT WEAK COLD FRONT APPROACHES THE REGION WITH A
THREAT FOR SHOWERS AND THUNDERSTORMS. THIS FRONT WILL WASH OUT AND
STALL OVER THE AREA...WITH A WARM AND VERY HUMID AIRMASS TAKING
HOLD FOR THE LAST HALF OF THE WEEK INTO EARLY NEXT WEEKEND...WITH
HIGHS WELL INTO THE 80S AND MILD NIGHTS IN THE 60S AND LOWER 70S.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
THIS AFTERNOON OBJECTIVE RAP ANALYSIS AND OBSERVATIONAL DATA SETS
/SATELLITE AND RADAR LOOPS/ CONFIRM THE WEAKENING MID LEVEL CLOSED
LOW NEARLY STATIONARY OVER SOUTHWESTERN INDIANA. A WEAK COLD FRONT
HAD ALSO STALLED ACROSS NORTHERN OHIO. RADAR TRENDS OVER THE LAST
FEW HOURS SHOW THAT THE BULK OF STRONG FORCING/DEEPER MOISTURE
RESIDED ON THE SRN/SERN FLANK OF THE UPPER LOW...WITH WIDESPREAD
SHOWERS AND THUNDERSTORMS OVER KY/TN. THE NERN FLANK OF A SHIELD
OF LGT/MOD SHOWERS/RAIN HAS STUBBORNLY BEEN ERODED AS IT MAKES
INROADS INTO THE WFO ILN FORECAST AREA. SCT SHRA/TSRA WERE SLOWLY
DEVELOPING ALONG THE STALLED FRONT OVER NORTHERN OHIO.
MESOANALYSIS LATE THIS AFTERNOON INDICATED A PLUME OF HIGH PWAT
REMAINED ATTENDANT TO THE UPPER LOW...WITH PWAT ABOUT 160% OF
NORMAL OVER SRN IND/NRN KY NEAR AND JUST EAST OF THE CENTER OF
CIRCULATION. A LARGE RESERVOIR OF MID 60S TO MID 70S SURFACE
DEWPOINTS EXISTED NEAR THE CIRCULATION AND ESPECIALLY TO THE
SOUTH/WEST. INSTBY WAS RATHER MEAGER OWING TO MOIST LAPSE RATES
AND AMPLE/WIDESPREAD CLOUDS OVER MUCH OF THE AREA...KEEPING
TEMPERATURES IN THE 70S FOR THE MOST PART. ALSO OF IMPORTANCE TO
THE SHORT TERM FORECAST IS A STRONG SHORTWAVE TROUGH ACROSS SASK
MOVING EAST.

TONIGHT...THERE IS STRONG AGREEMENT AMONG 17.12Z DATA THAT THE
WEAKENING CLOSED LOW WILL CONTINUE TO SLOWLY WEAKEN AND BECOME A
LITTLE MORE PROGRESSIVE AS IT OPENS UP AND SHEARS DOWNSTREAM A
BIT. THIS IS OWING TO THE KICKER ENERGY MOVING QUICKLY ACROSS SASK
ATOP THE SUBTROPICAL SWRN CONUS RIDGING. SPECIFICALLY...THE 700MB
CLOSED LOW WILL PLOD SLOWLY ALONG AND JUST SOUTH OF THE OHIO RIVER
THROUGH NORTHERN KENTUCKY REACHING THE CVG AREA BY SUNRISE MONDAY
MORNING. GIVEN THE BULK OF THE FLOW/FORCING WILL BE ON THE
SOUTH/SOUTHEAST SIDE OF THE CIRCULATION...EXPECT THE MOST
WIDESPREAD/HEAVIEST RAIN JUST SOUTH OF THE LOCAL FORECAST AREA.
HOWEVER...WILL NEED TO WATCH ANY ACTIVITY THAT FORMS ACROSS NRN KY
AS MID LVL STEERING FLOW WILL BE LIGHT NEAR THE PATH OF THE MID
LEVEL SYSTEM AND IF A DEFORMATION TYPE RAIN BAND FORMS ACRS OUR
NRN KY COUNTIES THE PWAT/WARM RAIN PROCESSES COULD LEAD TO NARROW
BAND OF HEAVIER RAIN...BUT RIGHT NOW IT SEEMS THE WEAKENING NATURE
OF THE OPENING WAVE AND THE IDEA IT BECOMES MORE PROGRESSIVE WITH
TIME SHOULD MITIGATE THIS POTENTIAL A GREAT DEGREE. MAINTAINED THE
LIKELY RAIN CHANCES ACROSS OUR FAR SOUTH NEAR THE NOSE OF MODEST
NORTHEAST-ORIENTED LOW LEVEL JET THAT POINTS INTO OUR AREA THIS
EVENING INTO THE FIRST PART OF THE OVERNIGHT...ALTHOUGH RECENT
EXPERIMENTAL /ESRL/ AND PARALLEL /NCEP/ HRRR RUNS ARE NOT VERY
BULLISH ON RAIN COVERAGE ACRS NRN KY TONIGHT. ELSEWHERE...AS THERE
HAS BEEN DURING THE DAY...SCT SHRA ON THE PERIPHERY OF THE UPPER
LOW WILL CON/T TO BE POSSIBLE...WITH ACTIVITY REMAINING LIGHT AND
LIKELY NOT CONTAINING THUNDER.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/...
THROUGH THE DAY MONDAY THE UPPER LEVEL WAVE REALLY OPENS
UP/SHEARS OUT/WEAKENS AS DEEPER LAYER NWLY FLOW DRIVING THE KICKER
ENERGY TO OUR NW SPREADS ACROSS THE GREAT LAKES. A SURFACE
TROUGH/INVERTED TROUGH HANGS BACK OVER THE FORECAST AREA IN THE
WAKE OF THE WEAKENING SURFACE LOW...AS DOES THE WEAK/WASHING OUT
STATIONARY FRONT OVER NORTHERN OHIO. A VERY MOIST AND UNCAPPED
AIRMASS REMAINS DURING PEAK HEATING WITH WIDESPREAD CUMULUS
EVENTUALLY CONVECTING DURING DAYTIME HEATING WITH THE SUBTLE
SURFACE FORCING MECHANISMS...AND MLCAPE PER 17.12Z FORECAST
SOUNDINGS /GFS AND NAM/ OF 1000-1500 J/KG. FLOW IS WEAK SO JUST
SOME SLOW MOVING HEAVY RAINERS ALL THAT IS EXPECTED DURING THE
AFTERNOON/EARLY EVENING. GIVEN THE AMPLE MOISTURE...AND NOTING
THIS REGION WEST OF THE UPPER LOW FAILED TO WARM MUCH TODAY...AM
KEEPING HIGHS MOSTLY IN THE 70S TO AROUND 80 ON MONDAY...ON THE
COOLER SIDE OF 17.12Z MOS.

ON TUESDAY...THE AFOREMENTIONED SHORTWAVE OVER SASK WILL BE
ARRIVING WITH A COLD FRONT AT PEAK HEATING WILL ACTUALLY ENCOUNTER
A SOMEWHAT FAVORABLE AIRMASS FOR ROBUST CONVECTION. BOUNDARY LAYER
FLOW WILL HAVE TURNED TO THE SOUTHWEST WHILE MID LEVEL WNWLY FLOW
WILL BE INCREASING AS RIDGING BEGINS TO BUILD A MODEST HEIGHT
GRADIENT TO OUR WEST/SOUTH. 17.12Z NAM/GFS FORECAST BUFR SOUNDINGS
FOR ILN/CVG/DAY/CMH ALL EXHIBIT MLCAPE FROM 1500 TO 2000 J/KG WITH
A STEEPER MID LEVEL LAPSE RATE WITH BOUNDARY LAYER DWPTS STILL IN
THE 60S. 0-6KM BULK SHEAR VALUES AROUND 30-35KTS COULD PROMOTE A
LITTLE MORE ORGANIZATION TO THE STORMS COMPARED TO MONDAY.
UPCOMING SHIFTS MAY NEED TO MOVE TO HIGHER RAIN CHANCES IF CURRENT
SIGNALS PERSIST..ESPECIALLY LATER IN THE DAY TUES INTO TUESDAY EVENING.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
UPPER LEVEL RIDGE OVER THE GULF COAST REGION WILL BUILD SLOWLY NORTH
INTO THE MID MISSISSIPPI VALLEY THROUGH THE END OF THE WEEK. THIS
WILL RESULT IN A NORTHWEST FLOW PATTERN ALOFT THROUGH AT LEAST
FRIDAY. BOTH THE 12Z GFS AND 12Z ECMWF CONTINUE TO INDICATE THE
POSSIBILITY OF SEVERAL SHORT WAVES RIDING DOWN THROUGH THE AREA IN
THIS PATTERN. WITH DEWPOINTS PUSHING UP INTO THE UPPER 60S TO LOWER
70S...THERE SHOULD BE SUFFICIENT INSTABILITY TO CREATE THE POTENTIAL
FOR A RATHER ACTIVE PATTERN THROUGH THE END OF THE WEEK. TIMING
REMAINS DIFFICULT THOUGH SO WILL KEEP POPS IN THE CHANCE CATEGORY.
TEMPERATURES ALSO REMAIN SOMEWHAT PROBLEMATIC AS WE WILL REMAIN IN
THE TRANSITION ZONE BETWEEN WARMER TEMPERATURES TO OUR
SOUTHWEST/COOLER TO THE NORTHEAST. WILL CONTINUE WITH FAIRLY
SEASONABLE HIGHS...BUT OVERNIGHT LOWS MAY REMAIN A LITTLE ON THE
WARM SIDE...UPPER 60S TO NEAR 70...GIVEN THE HIGHER DEWPOINTS.

SOME UNCERTAINTY EXIST BETWEEN THE 12Z GFS AND 12Z ECMWF OVER THE
WEEKEND AS THE GFS IS TRYING TO BUILD THE UPPER LEVEL RIDGE MORE
EAST TOWARD OUR AREA...WHILE THE ECMWF BEGINS TO FLATTEN OUT THE
RIDGE AS SHORT WAVE ENERGY MOVES ACROSS THE UPPER GREAT LAKES. HAVE
TRENDED MORE TOWARD THE GFS...DECREASING POPS THROUGH THE WEEKEND
AND ALLOWING FOR A CONTINUED SLOW WARMUP IN TEMPS THROUGH SUNDAY.

&&

.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
LOW PRESSURE TRAVELING THROUGH KENTUCKY WILL HAVE VARYING EFFECTS
ON TAF SITES. SOUTHERN SITES CVG AND LUK WILL HAVE SHOWERS IN THE
VICINITY THROUGH MUCH OF THE PERIOD AS THE LOW SPINS NEARBY TO THE
SOUTH. CEILINGS BELOW 2000 FT WILL BE POSSIBLE THERE LATE TONIGHT
IN A MOIST BOUNDARY LAYER...AND BR AND HZ WILL REDUCE VISIBILITIES
TONIGHT INTO MONDAY. CONDITIONS COULD IMPROVE MONDAY AFTERNOON AS
THE LOW MOVES EAST.

FARTHER NORTH AT ILN DAY CMH AND LCK...THE SYSTEM IS FORECAST TO
PRODUCE MUCH LESS PRECIPITATION. WENT WITH VCSH THIS AFTERNOON
INTO THIS EVENING...WITH NO PRECIP IN THE FORECAST THEREAFTER.
CEILINGS MAY FALL INTO THE MVFR RANGE AT DAY AND ILN WHILE
REMAINING VFR AT CMH AND LCK. BR WILL BE POSSIBLE AT DAY ILN AND
LCK...WITH THE TYPICALLY WARMER CMH REMAINING FREE FROM SURFACE
OBSCURATION.

WIND DIRECTION WILL VARY WITH RESPECT TO THE POSITION OF THE LOW
AND A WEAK FRONT THAT IS WASHING OUT OVER CENTRAL OHIO. WIND
SPEEDS ARE EXPECTED TO REMAIN BELOW 10 KNOTS.

OUTLOOK...THUNDERSTORMS POSSIBLE TUESDAY THROUGH THURSDAY.

&&

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

&&

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






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