Area Forecast Discussion
Issued by NWS Wilmington, OH

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000
FXUS61 KILN 260832
AFDILN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON OH
432 AM EDT TUE MAY 26 2015

.SYNOPSIS...
WARM AND HUMID AIR WILL REMAIN IN PLACE OVER THE MIDDLE OHIO VALLEY
THROUGH THE REST OF THE WEEK. AS UPPER LEVEL DISTURBANCES MOVE
THROUGH THE AREA...THERE WILL BE OCCASIONAL CHANCES FOR SHOWERS AND
THUNDERSTORMS TODAY AND WEDNESDAY...AND THEN AGAIN OVER THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
A DEVELOPING SURFACE LOW AND UPPER TROUGH WILL MOVE ENE INTO
WISCONSIN THIS EVENING. MID-LEVEL RIDGING OFF THE SOUTH CAROLINA
COAST WILL REMAIN PARKED IN PLACE TODAY...WITH SURFACE HIGH
PRESSURE CENTERED A BIT FURTHER TO THE NORTHEAST OVER THE
ATLANTIC. ALL OF THESE FACTORS PLACE THE OHIO VALLEY FIRMLY IN A
REGIME OF DEEP SOUTHWESTERLY FLOW...BUT THE SLIGHTLY-NORTHWARD
POSITION OF THE SURFACE HIGH WILL HELP KEEP SURFACE FLOW AT A
LITTLE MORE OF A SOUTHERLY DIRECTION. THIS WILL HELP PROVIDE A
REGIME OF CONVERGENCE NEAR THE SURFACE...WITH FAVORABLE UPPER
CONDITIONS FOR LIFT FROM AN APPROACHING JET STREAK (ENTRANCE
REGION) AND POSITIVE VORTICITY ADVECTION. COMBINED WITH THE
DIURNAL CYCLE...SHOWERS AND THUNDERSTORMS WILL DEVELOP AND
INCREASE IN COVERAGE OVER INDIANA / CENTRAL KENTUCKY / SW OHIO
DURING THE AFTERNOON HOURS...CROSSING THROUGH THE ILN CWA THROUGH
EARLY TO MID EVENING. POPS HAVE BEEN RAISED TO 70 PERCENT FOR THE
ENTIRE FORECAST AREA...AND ONCE STORM TIMING IS NAILED DOWN WITH
HIGH-RES MODEL RUNS LATER TODAY...CATEGORICAL POPS MAY BE
ADDED IN.

AS TEMPERATURES CLIMB INTO THE LOWER 80S...AND DEWPOINTS HOLD
FAIRLY STEADY IN THE MID 60S...INSTABILITY WILL BUILD DURING THE
LATE MORNING AND INTO THE AFTERNOON. AS IS TYPICAL...MODEL
AGREEMENT ON EXACT INSTABILITY VALUES IS HARD TO COME BY. ONE
THING THAT APPEARS CERTAIN IS THAT THE POOR MID-LEVEL LAPSE RATES
SAMPLED BY THE 00Z KILN SOUNDING WILL NOT BE GOING ANYWHERE ANY
TIME SOON...WHICH WILL SIGNIFICANTLY LIMIT BUOYANCY DESPITE THE
OTHERWISE FAVORABLE NEAR-SURFACE THERMODYNAMIC CONDITIONS.
BLENDING SOME OF THE MODEL SOLUTIONS...MLCAPE VALUES OF 800-1400
J/KG CAN BE EXPECTED (ADMITTEDLY A LITTLE WIDER OF A FORECAST
RANGE THAN IS IDEAL).

THE POSITION OF THE ILN CWA BETWEEN THE AREAS OF HIGH AND LOW
PRESSURE WILL MEAN THAT DEEP-LAYER FLOW WILL BE AT LEAST SOMEWHAT
FAVORABLE FOR STRONG STORM POTENTIAL...WITH 0-6KM SOUTHWESTERLY
SHEAR OF 25-35 KNOTS. WHILE LOW-LEVEL WIND CONDITIONS NEAR THE
SURFACE LOW (IN THE VICINITY OF LAKE MICHIGAN) COULD CAUSE SOME
CONCERN FOR TORNADO POTENTIAL OFF TO THE NORTHWEST...0-1KM SHEAR
MAY NOT BE SUFFICIENT (IN TERMS OF EITHER DIRECTION OR SPEED) TO
PRESENT AN APPRECIABLE TORNADO RISK OVER THE MIDDLE OHIO VALLEY.
TAKEN AT A SLIGHTLY DEEPER LAYER (0-3KM)...THE SHEAR IS A LITTLE
BIT MORE IMPRESSIVE...WITH A SHIFT OF AROUND 30-40 DEGREES AND A
CHANGE OF 20-30 KNOTS IN MAGNITUDE. COMBINING THIS ALL
TOGETHER...THE SHEAR PROFILES SUGGEST THAT WHILE LARGE-SCALE
ORGANIZATION MAY BE A LITTLE BIT LACKING...INDIVIDUAL CELLS AND
CLUSTERS MAY BECOME ORGANIZED AND POTENT...CAPABLE OF PRODUCING
STRONG TO SEVERE WINDS. THIS WILL BE ESPECIALLY TRUE IF SURFACE
TEMPERATURES ARE ABLE TO MEET OR EXCEED THE FORECAST HIGHS...WHICH
COULD INCREASE THE POTENTIAL INTENSITY OF NEGATIVELY BUOYANT
DOWNDRAFTS. BASED ON THE SOMEWHAT-NARROW CAPE PROFILE...HIGH
FREEZING (14KFT) AND -20C (25KFT) LEVELS...AND A LACK OF EXPECTED
DISCRETE/ROTATING STORMS...THE HAIL THREAT APPEARS TO BE A
LOWER-END RISK. AS ALLUDED TO ABOVE...THE TORNADO THREAT IS ALSO
NOT ESPECIALLY HIGH. AREAS OF LOCALLY BACKED SURFACE WINDS OR
BOUNDARY INTERACTIONS COULD BRIEFLY INCREASE THE RISK...BUT THE
OVERALL CONDITIONS POINT SIGNIFICANTLY TO A STRAIGHT-LINE WIND
EVENT ON THE MESOSCALE. NCAR ENSEMBLE PLOTS SUPPORT THIS AS
WELL...WITH VARIOUS ENSEMBLE MEMBERS INDICATING DOWNDRAFT
POTENTIAL OVER THE FORECAST AREA...BUT VIRTUALLY NO INDICATION OF
UPDRAFT HELICITY OR LARGE HAIL POTENTIAL.

COMBINING EVERYTHING TOGETHER...THE GREATEST SEVERE CHANCES APPEAR
LIKELY TO OCCUR BETWEEN 4PM AND 9PM (THOUGH WEAKENING CONVECTION
MAY PERSIST A LITTLE LONGER THAN THAT). NONE OF THE OVERALL
PARAMETERS LOOK PARTICULARLY MORE FAVORABLE IN ONE SECTION OF THE
CWA OVER ANOTHER...AND SIMULATED REFLECTIVITY PROJECTIONS FROM
CONVECTIVE-ALLOWING MODELS ARE SOMEWHAT SCATTERSHOT IN TERMS OF
EXACT TIMING AND PLACEMENT. THUS...THE THREAT WILL BE HANDLED
UNIFORMLY IN THE HWO THIS MORNING.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
CONVECTION IS EXPECTED TO BE ON A GENERAL WEAKENING/DISSIPATING
TREND LATE TUESDAY EVENING INTO EARLY WEDNESDAY MORNING...ON THE
BACK SIDE OF THE NORTHEASTWARD-MOVING SHORTWAVE AND IN A REGIME OF
DIURNALLY WEAKENING INSTABILITY. STILL...THE PATTERN OF GENERAL
MOIST FLOW WILL SUPPORT A CHANCE OF SOME SHOWERS (OR POSSIBLY A
THUNDERSTORM) THROUGH THE OVERNIGHT HOURS.

ON WEDNESDAY...AN UPPER TROUGH WILL BE MOVING EAST INTO THE GREAT
LAKES REGION. INITIALLY FAIRLY WELL-DEFINED OVER THE UPPER
MISSISSIPPI VALLEY (AND HELPING TO DRIVE THE MORE ACTIVE WEATHER
ON TUESDAY)...THIS TROUGH WILL BE WASHING OUT AS IT
PROGRESSES AHEAD. STILL...IT WILL LEAVE THE MIDDLE OHIO VALLEY IN
A FAVORABLE AREA OF LIFT...THOUGH SURFACE FEATURES WILL BE LACKING
AND THUS FORCING MAY NOT BE PARTICULARLY WELL FOCUSED. WHILE SHEAR
WILL CONTINUE TO BE MODEST...INSTABILITY SHOULD ACTUALLY INCREASE
SLIGHTLY FROM TUESDAY...WITH MLCAPE VALUES PERHAPS APPROACHING
2000 J/KG IN THE SOUTHWESTERN SECTIONS OF THE CWA (AND UP TO 1500
J/KG ELSEWHERE). THUS...AMONG THE SCATTERED THUNDERSTORMS THAT
DEVELOP...A FEW STRONG TO POSSIBLY SEVERE STORMS MAY OCCUR.

AS THE AFOREMENTIONED TROUGH CONTINUES TO WEAKEN AND MOVE
EAST...THE ILN FORECAST AREA WILL END UP IN A REGIME OF BUILDING
RIDGING ALOFT...AND A WEAK/NEBULOUS AREA OF HIGH PRESSURE AT THE
SURFACE. BY THURSDAY...THIS WILL BEGIN TO LIMIT THE CHANCES FOR
CONVECTION...WITH DIURNAL DEVELOPMENT ONLY APPEARING TO BE A
POSSIBILITY IN THE SOUTHERN HALF OF THE FORECAST AREA. FRIDAY WILL
LIKELY BEGIN DRY AS WELL...THOUGH THE FLOW WILL BE SWITCHING BACK
TO THE SOUTH IN THE SECOND HALF OF THE DAY...LEAVING A POSSIBILITY
FOR SOME DEVELOPMENT (ESPECIALLY FOR THE SOUTHWESTERN HALF OF THE
FORECAST AREA) BY LATE AFTERNOON AND EVENING. TO NOTE...THE GFS
HAS BEEN A LITTLE MORE AGGRESSIVE THAN OTHER MODELS WITH THE
SOUTHWARD PUSH OF THE AREA OF HIGH PRESSURE INTO THE OHIO
VALLEY...AND WOULD SUPPORT AN EVEN DRIER FORECAST FOR THURSDAY AND
THE FIRST HALF OF FRIDAY.

TEMPERATURES AND DEWPOINTS ARE EXPECTED TO CHANGE VERY LITTLE OVER
THE COURSE OF THE WEEK. A VERY SLIGHTLY DRIER AIR MASS WILL BE
SETTLING IN ON THURSDAY AND INTO FRIDAY...WHICH MAY ALLOW SOME
SLIGHTLY COOLER MIN TEMPS ON FRIDAY MORNING. OTHERWISE...MIN TEMPS
WILL LIKELY NOT DROP BELOW THE MID 60S. MAX TEMPS SHOULD REMAIN
AROUND 80 DEGREES...BUT CONVECTION AND CLOUDS (OR A LACK THEREOF)
COULD HAVE AN IMPACT IN EITHER DIRECTION...ESPECIALLY TODAY
(TUESDAY) AND WEDNESDAY. FRIDAY MAY BE THE WARMEST DAY OF THE
WEEK...WITH DRY AND SUNNY CONDITIONS TO BEGIN THE DAY...WITH WARM
ADVECTION KICKING IN.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
MID/UPPER LEVEL FLOW WILL BECOME MORE AMPLIFIED THROUGH THE
WEEKEND AS SHORT WAVE ENERGY MOVES OUT OF THE ROCKIES AND INTO THE
CENTRAL PLAINS. THIS WILL EVENTUALLY LEAD TO A FRONTAL BOUNDARY
PUSHING DOWN TOWARD AND POSSIBLY THROUGH OUR FA THROUGH EARLY NEXT
WEEK. HOWEVER...THERE REMAINS QUITE A BIT OF DIFFERENCE BETWEEN
THE ECMWF/GFS/CMC WITH HOW FAST AND HOW FAR SOUTH TO PUSH THE
FRONT AND WHETHER OR NOT TO STALL IT OUT ACROSS OUR AREA TOWARD
THE END OF THE PERIOD. THIS WILL LEAD TO THE POTENTIAL FOR A
FAIRLY WET/MORE ACTIVE PERIOD THROUGH THE END OF THE LONG TERM BUT
DUE TO THE TIMING UNCERTAINTIES...WILL JUST KEEP POPS IN THE HIGH
CHANCE CATEGORY.

FRIDAY WILL BE SEASONABLY WARM WITH HIGHS IN THE MID 80S. MORE
SEASONABLE TEMPERATURES WILL THEN BEGIN TO PUSH DOWN FROM THE NORTH
OVER THE WEEKEND...BUT THEY WILL ULTIMATELY BE DICTATED BY THE
PLACEMENT/TIMING OF THE FRONTAL BOUNDARY. FOR THAT REASON...HAVE
GENERALLY GONE WITH A MODEL BLEND FOR TEMPERATURES SATURDAY THROUGH
MONDAY.

&&

.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
FIRST CONCERN EARLY THIS MORNING IS THE POTENTIAL FOR MVFR
CEILINGS AND VISIBILITIES. AM GETTING MIXED SIGNALS FOR MVFR
CEILINGS PER LATEST MODELS. HOWEVER...THERE ARE SOME LOWER CLOUDS
DEVELOPING NEAR KCVG AND KDAY...AND THESE MAY BECOME A CEILING
AROUND 2000 FEET OVER THE NEXT 4 HOURS...ABOUT 2 HOURS LATER AT
KCMH AND KLCK. VISIBILITIES SHOULD BE HELD IN CHECK GIVEN SFC
PRESSURE GRADIENT...SANS KLUK WHICH MAY DROP INTO THE 3-5SM RANGE.

FOR LATER TODAY...OUR REGION WILL BE UNDERNEATH A MOIST SOUTHWEST
FLOW ALOFT. MORNING DAYTIME HEATING WILL RESULT IN CUMULUS
DEVELOPMENT WITH WINDS PICKING UP FROM THE SOUTH. BY THE
AFTERNOON HOURS...A DISTURBANCE WILL ROTATE NORTHEAST INTO THE
WESTERN GREAT LAKES. A TRAILING TAIL/INFLECTION IN THE MID LEVELS
WILL TEAM UP WITH A POTENTIAL LOW LEVEL CONVERGENT AXIS TO BRING
THE LIKELIHOOD OF SHOWERS AND THUNDERSTORMS. THERE CONTINUES TO BE
SOME TIMING AND COVERAGE ISSUES WITH THE HIGH RESOLUTION MODELS SO
HAVE OPTED TO KEEP VCTS GOING AT THIS TIME. WILL ATTEMPT TO PICK
A TEMPO GROUP FOR THE BEST CHANCE AT THE TERMINALS WITH THE NEXT
TAF ISSUANCE. OTHERWISE...WITH THE MOIST AIRMASS IN PLACE...MVFR
CONDITIONS WILL BE LIKELY WITH STORMS WITH LOCAL POCKETS OF IFR
CONDITIONS (MOST LIKELY VISIBILITIES) DUE TO HEAVY RAINFALL IN THE
STRONGEST CORES.

FOR TONIGHT...DISTURBANCE AND ITS TAIL/INFLECTION WILL PUSH OFF TO
THE NORTHEAST THROUGH THE REMAINDER OF OUR REGION. WITH THE LOSS
OF DAYTIME HEATING...WE SHOULD SEE A GRADUAL DECREASE IN
THUNDERSTORM ACTIVITY...WITH JUST A FEW SHOWERS LINGERING IN THE
MOIST FLOW LATE TONIGHT. MODELS SUGGEST THAT SOME MVFR/IFR CEILINGS
MAY DEVELOP IN THE 06Z TO 12Z AND WILL TAKE A LOOK AT THIS AGAIN
WITH THE NEXT ISSUANCE.

.OUTLOOK...MVFR/IFR CEILINGS POSSIBLE WEDNESDAY MORNING. THUNDERSTORMS
POSSIBLE WEDNESDAY AFTERNOON AND EVENING...AND AGAIN SATURDAY.

&&

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

&&

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






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