Area Forecast Discussion
Issued by NWS Wilmington, OH

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FXUS61 KILN 201854
AFDILN

Area Forecast Discussion
National Weather Service Wilmington OH
254 PM EDT Wed Sep 20 2017

.SYNOPSIS...
A weak mid level trough will move east of the area today. Over
the next several days, a stagnant weather pattern will set up,
with mid-level ridging and high pressure near the surface.
Temperatures will remain above normal through the weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
With the KILN sounding measuring a precipitable water amount of
1.53 inches -- roughly 90th percentile for mid-September -- the
area remains in a moist and somewhat stagnant section of the
weather pattern. Model soundings for this afternoon and early
evening suggested that with surface dewpoints in the mid 60s to
around 70, surface based instability would eventually develop.
As expected, some convective showers have indeed popped up,
mainly in the northeastern quarter of the ILN CWA. With very
light flow and just some last-minute support from the departing
mid-level wave, coverage and movement will be very low. PoPs
will be maintained, mainly in the eastern half of the CWA, for
the next several hours.

Fog potential is the greatest concern for tonight, with a
favorable setup in the wind and pressure pattern (overall light
flow with the main axis of the boundary-layer ridging just to
the east). Where skies clear out, conditions will be favorable
for fog to become locally dense, especially in river valleys or
more broadly in the eastern half of the forecast area.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/...
The stagnant weather pattern will essentially remain in place on
Thursday, with broad mid-level ridging extending from the Great
Lakes into the middle Mississippi Valley, and an elongated
surface high centered well northeast of the Ohio Valley region.
Thursday appears to set up as another day with light wind flow
and some chance of afternoon instability, which has resulted in
some inconsistent/weak QPF output across the suite of models.
Looking at soundings, there will be some warming of temperatures
in the 800mb-750mb layer between Wednesday and Thursday, which
will make it less likely for any precipitation to develop. The
chance certainly isn`t zero percent, but appears small or
isolated enough to not include in the main forecast.

Temperatures should be able to rise by a few degrees for both
Thursday and Thursday night.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Strong H5 ridge will be the dominant feature for much of the
forecast period. The ridge will keep Jose off the East Coast and
away from the Ohio Valley, and later on Maria. Meanwhile at the
surface, a surface high centered over the St. Lawrence Valley will
extend southwest into the fa.

The combination of these two features will bring dry condition and
above normal temperatures through the weekend and into early next
week. High temperatures will be about 10 degrees above normal
values through Tuesday as they push into the mid and upper 80s.
Morning lows be around 60.

By Wednesday a cold front will be moving east up the Ohio Valley. It
will bring some scattered convection. The GFS is a little quicker
than the ECMWF and Canadian with the front. Have included 20 PoPs in
the wrn half of the fa for Wednesday. Highs Wednesday will still be
around 80 degrees.

&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
The only real concern for this TAF period is the potential for
more fog overnight and early Thursday morning.

First, while there is a slight chance of a shower at KCMH/KLCK
this afternoon, it appears too low to include in the TAFs.
Amendments will be used if showers develop and move near the
airports.

Overnight, fog is expected to develop again. Tempo IFR
conditions are expected for most of the TAF sites, with likely
LIFR fog at KLUK. The bigger question is at KCMH/KLCK, where IFR
is in the forecast, but there is the potential for a period of
dense fog as well.

There is a chance that some brief MVFR ceilings may form on
Thursday morning, but otherwise, VFR conditions are expected
going into the day.

Winds will be generally light and variable through the entire
TAF period.

OUTLOOK...No significant weather is expected at this time.

&&

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

&&

$$
SYNOPSIS...Hatzos
NEAR TERM...Hatzos
SHORT TERM...Hatzos
LONG TERM...Sites
AVIATION...Hatzos



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