Area Forecast Discussion
Issued by NWS Wilmington, OH

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000
FXUS61 KILN 281813
AFDILN

Area Forecast Discussion
National Weather Service Wilmington OH
213 PM EDT Fri Apr 28 2017

.SYNOPSIS...
High pressure will move east early today. A frontal boundary will
develop into the region this afternoon and linger near the area
into Sunday, causing unsettled weather through the weekend. Cooler
temperatures will filter in behind the front next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A developing warm front will lift north across the Tennessee
Valley through this afternoon, possibly pushing north into
southern portions of our fa through this evening. There remains
some uncertainty among the models as to how far north this
boundary will make it and as a result where the heavy rain and
severe threat will set up later today into tonight.

Along and south of the boundary, good instability will develop
through this afternoon. A weak mid level short wave will move
east across the Ohio Valley this afternoon and this may help
initiate convection along the boundary. With good shear
profiles along the boundary, severe storms with some rotators
would be possible later this afternoon into this evening along
and south of the boundary with training storms and potential
flash flooding too. Farther to the north of the boundary, the
storms will be more elevated, leading to primarily a hail
threat heading into this evening.

The synoptic models are generally farther north than the
higher-res cams, with the last several runs of the HRRR keeping
the focus generally south of our FA. It does appear the the
highest severe threat will be south of the Ohio River, possibly
over into far south central Ohio. This is also the area that
would seem most prone to flash flooding but with the synoptic
models much farther north with their swath of heavy rain later
tonight, there remains quite a bit of uncertainty as to where
the heaviest rain threat will be. We may eventually need a
flash flood watch across parts of the area but prefer to see
what the 12Z runs show to see if the flood threat can be more
fine tuned.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
Warm front nearly parallel to the upper flow will remain in the
region tonight, lifting to Northwest Ohio. As isentropic lift
intensifies under a strengthening upper jet, showers will become
widespread in northwestern locations, while showers will be
much less prevalent in the southeast farther from the boundary.
Convective development will be enhanced by ample short wave
energy and moisture advection traveling along the slow moving
boundary. Thunderstorms will be possible in a zone of elevated
CAPE near the front, and some storms may reach severe limits.
Models indicate favorable wind shear profiles above an
inversion layer that suggest large hail as the main threat.

Showers and a few thunderstorms will continue mainly across
northern locations on Saturday. Activity should show a
diminishing trend by Saturday evening when the frontal forcing
is forecast to lift toward Lake Erie.

With the area mainly in the warm sector, temperatures will
exhibit a warming trend. Highs will range from the upper 60s
north, up to the mid 80s south.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Warm and moist southwest flow aloft will lead to an active weather
pattern this weekend into early next week. Surface warm front to
lift north through ILN/s FA Saturday night. Best forcing associated
with low level jet/instability and moisture to our west. Therefore,
will limit pops to chance category with the best chance northwest.

Upper level low to develop over the Central Plains and then lift
northeast into the Upper MS Vly Monday. On Sunday the best forcing
and lift to our west with ILN/s FA in the warm sector. Will limit
pops to chance across the western counties. Temperatures look to be
10 to 15 degrees above normal, with highs Sunday ranging from 80
northwest to the upper 80s southeast.

Model solutions generally similar with strong cold front pushing
east into ILN/s western counties by 12Z Monday and then sweeping
east across the FA early. Due to strong front expect widespread
convection to develop but instability is marginal. PW/s increase to
above 1.5 inches, so heavy rain rates will be likely but
precipitation will be progressive with front east of ILN/s by early
afternoon. 850 mb winds of 45-50 kts will persist in the wake of the
front in CAA pattern. Momentum transfer technique suggest surface
wind gusts of 40 mph likely. Will continue to highlight this threat
in the HWO product. Temperatures will be turn cooler with highs
Monday from the mid 60s west to the mid 70s east.

Deep upper level low to track ene through the Great Lakes Monday
into Tuesday. Will keep chance pops of a shower across the north
into early Tuesday. Temperatures will be a little below normal, with
highs ranging from near 60 northwest to the upper 60s southeast.

Mid/upper level flow backs with moisture increasing Wednesday acrs
the far south and then across the entire FA Thursday. Model
solutions differ on moisture placement Thursday with GFS keeping
main moisture east. Have favored a Canadian/Ecmwf blend with best
pops in the east Thursday but spreading pcpn chances across the
entire area. Wednesday`s highs look to range from the lower 60s
northwest to the upper 60s southeast. Thursday looks even cooler
with highs of 60 to 65.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
Showers and thunderstorms are expected to develop through the
late afternoon and into the overnight hours as a warm front
lifts north into the Ohio Valley. There remains quite a bit of
uncertainty as to the timing and placement of these storms
though which leads to a low confidence forecast, especially
into tonight. Will trend the TAFs toward the general consensus
of the higher res models, allowing for thunder at the terminals
mainly in the 23-03Z time frame, with the best chance at the
southern sites. This will lead to some MVFR vsbys along with
the potential for IFR or lower in any thunderstorms, as locally
heavy rainfall will be possible. Cigs will start off VFR but
should trend to MVFR as the low levels moisten up overnight,
especially along and north of the boundary. MVFR cigs will then
likely linger through the morning hours along and north of the
boundary, mainly affecting the northern TAF sites. The threat
for showers will persist through much of the night and possibly
into Saturday morning, but this will be somewhat dependent on
the exact placement of the frontal boundary.

OUTLOOK...MVFR ceilings and visibilities with a chance of thunderstorms
are possible Saturday, Sunday night and Monday. Wind gusts to 35
kt possible Sunday into Tuesday.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...Flash Flood Watch from 7 PM EDT this evening through Saturday
     morning for OHZ070>072-077>081.
KY...Flash Flood Watch from 7 PM EDT this evening through Saturday
     morning for KYZ089>099.
IN...Flash Flood Watch from 7 PM EDT this evening through Saturday
     morning for INZ066-073>075-080.

&&

$$
SYNOPSIS...Coniglio
NEAR TERM...JGL
SHORT TERM...Coniglio
LONG TERM...AR
AVIATION...JGL


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