-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KILN 211422
AFDILN

Area Forecast Discussion
National Weather Service Wilmington OH
1022 AM EDT Thu Sep 21 2017

.SYNOPSIS...
A mid level ridge of high pressure will set up over the Great
Lakes and remain stagnant into early next week. This high will
offer dry weather and very warm temperatures. Daytime highs are
expected to be 10 to 15 degrees above normal through the
weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Very few changes were needed to the forecast this morning, but
the main concern for today involves the very slight chance of
showers. The previous forecast decided to hold off on including
showers, owing to an expected lack in coverage and some capping.
None of this has changed, but a few showers have already
developed (and dissipated) this morning near Dayton. Again, the
best course of action appears to keep a silent 10% chance, with
the expectation that almost all locations will remain dry today.

With almost full sun over the ILN CWA, max temps were increased
by a degree or so for this afternoon.

Previous discussion >
Mid level ridge to build from the lower MS VLY into the Eastern
Great Lakes. Surface high pressure to remain centered over the
Upper Ohio Valley today. High level debris clouds from upstream
convection will spill over the ridge into the region today.

Latest nighttime microphysics satellite channel depicts fog in
the river valleys. Clouds spilling into the nw should mitigate
widespread fog over West Central Ohio. Have issued a special
weather statement for the southeast, highlighting reduced
visibilities in valley locations.

Some of the earlier model solutions and the latest GFS soln
continues to generate some light qpf over our western counties.
Upon inspection of the forecast soundings, expect a cap in
place and without significant forcing do not expect widespread
convection. Therefore, have maintained a dry forecast today.

850mb thermal ridge to our west nudges a little east today.
Based on this slight warming expect highs a little warmer than
yesterday. Expect highs 10 to 13 degrees above normal today and
generally in the mid and upper 80s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
Given a quasi-steady state weather pattern tonight should be
close to this morning. Temperatures will drop to lows from the
lower 60s east to the mid 60s west. Valley fog, especially in
eastern locations is again likely tonight.

With placement of the mid level ridge and 8H temperatures,
Friday/Saturday look to the be the warmest days during this
warm weather period. Therefore, expect highs on Friday to be a
little warmer than today with most locations topping out in the
upper 80s under mostly sunny sky conditions.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Ridge building at the surface and aloft will dictate weather
conditions through most of this period. Latest models continue to
indicate 1020 mb surface high pressure over New England in
conjunction with a 5900 meter 500mb high extending from the Gulf
Coast to Southern Canada. The surface high is shown to retrograde
under the upper high to the Great Lakes and Ohio Valley by Sunday,
with the system then exhibiting modest height and pressure falls by
Tuesday. A large, high amplitude upper trough pushing a surface cold
front toward the area on Wednesday will bring additional height
falls, signaling a change in pattern for late next week.

The absence of forcing and deep moisture in the anticyclonic
circulation around the high will allow dry weather and mostly clear
skies to persist from Friday night through Tuesday. Cooler air aloft
riding above the surface cold front will produce enough instability
for increasing clouds and a chance of showers and thunderstorms
Wednesday afternoon and evening.

Under anomalously high geopotential heights, temperatures will be up
to 15 degrees above normal for late September. High temperatures
reaching the middle and upper 80s Friday through Tuesday are
forecast to slip to around 80 on Wednesday under clouds and cold
advection.

&&

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
Mid level ridge to build from the Lower MS VLY through the
Eastern Great Lakes. Surface high pressure will remain centered
just to our east over the Upper Ohio Valley. Subsidence over the
area has led to clear skies through the first part of the
night. The clear skies, light winds and a moist boundary layer
created favorable conditions for fog development mainly in the
river valleys

Latest IR satellite imagery shows high level debris clouds from
upstream convection spilling over the ridge into western Ohio.

Have IFR VSBY restrictions at favored KLUK and KILN sites with
mainly MVFR restrictions at remainder of the TAF sites.

Moisture is shallow, so the fog will burn off quickly after
sunrise. Expect some scattered cu development along with
continued high level clouds from upstream convection.

Radiation fog development likely again tonight with IFR
restrictions limited to the favored valley location at KLUK.
Through 06Z have limited the restriction to the MVFR category.


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

&&

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

&&

$$
SYNOPSIS...AR
NEAR TERM...Hatzos/AR
SHORT TERM...AR
LONG TERM...Coniglio
AVIATION...AR