387 
FXUS61 KILN 061405
AFDILN

AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
1005 AM EDT Mon Sep 6 2021

.SYNOPSIS...
High pressure will continue to move eastward across the Ohio and
Tennessee valley regions today, providing generally quiet
weather through Tuesday. A cold front will move through the area
late Tuesday into Wednesday, bringing a chance of rain, and some
slightly cooler temperatures for the rest of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As a high pressure ridge gradually drifts eastward today, a 
poorly-defined cold front will move southward out of the Great 
Lakes and into the northern sections of the ILN forecast area. 
Ahead of this feature, there will be an area of enhanced 
westerly theta-e advection. Combined with the boundary layer 
convergence from the front, which is the only obvious forcing 
mechanism, some sprinkles are expected to develop (along with an
enhanced cumulus field). Given the extremely weak QPF returns 
across the model suite, and the relatively dry boundary layer 
conditions (dewpoints in the upper 50s), measurable 
precipitation seems unlikely. Will maintain sprinkle forecast,
but will make another assessment later this afternoon should
CAMs dictate otherwise. 

The westerly winds today may provide some gusts up to 15-20 MPH,
especially as the boundary layer mixes in the mid to late 
afternoon. Lower 80s are in the max temp forecast -- very close
to normal.

&&

.SHORT TERM /TUESDAY/...
The surface high will be passing off to the east / southeast of
the region tonight, with winds becoming light once again, but a
different scenario aloft -- as 850mb theta-e continues to
increase across the region on WSW flow. This will keep
conditions a little cloudier and a little warmer than the
previous night, with min temps in the upper 50s to around 60.

On Tuesday morning, deep-layer southwesterly flow will be
increasing significantly over the Ohio Valley and Great Lakes,
as the gradient tightens between the departing high and a
developing stacked low pressure system near Lake Superior. This
southwesterly flow will quickly push the frontal boundary
northward, clearing the ILN CWA into the warm sector for all of
Tuesday. As moisture will still be somewhat lacking, this
pattern favors deep mixing, gusty winds (25-30 MPH in the
northern part of the CWA), and warm temperatures. This forecast
(mid 80s) is a degree or so above the model blend, but it
probably still has room to grow by another degree or two.

As the model trend has continued to be for a slower frontal
passage, precipitation now appears likely to hold off until
after 6PM on Tuesday evening.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Long wave trough will develop over the region early in the 
period. Initial short wave carving out this trough will pass 
north of the area but give the initial push to a cold front that
will be approaching at the beginning of the period. Additional 
energy will follow later Tuesday night into Wednesday. This will
push the front all of the way through the area. Related to the 
timing of the mid level support, at least some of the 00Z 
guidance is suggesting that showers and thunderstorms that 
develop northwest of the area on Tuesday will be in a slow 
weakening state as they move into the forecast area Tuesday 
evening, but then the line of showers (instability will be 
negligible by this point) will become better defined later in 
the night and continuing into Wednesday. Looks like a high 
coverage-low QPF event. So have increased PoPs to likely.

The rest of the long term is forecast to be dry. The long wave 
trough will slowly translate east through the rest of the week 
and deamplify heading into the weekend. This will allow heights 
to start rising and flow will become more zonal by late in the 
period. A short wave passing well north of the area over the 
weekend may push a front into the area on Sunday. There is 
uncertainty whether it will make it this far south, and if it 
does there does not appear to be enough moisture or lift to 
result in a chance of precipitation at this point. 

Temperatures will continue to be a bit below normal until the 
weekend when a warming trend will occur.

&&

.AVIATION /14Z MONDAY THROUGH FRIDAY/...
Aside from valley fog at KLUK this morning -- and maybe again 
tomorrow morning -- VFR conditions are expected through the TAF 
period.

After a period of light winds to start the morning, westerly 
winds will pick up by noon, with gusts to around 16-18 knots. 
Cumulus clouds will increase through the day, and there appears 
to be a very small chance of a sprinkle or a light shower after 
18Z. This chance is too small to include in the TAFs, and would 
have little to no aviation impact if it occurred.

A few clouds may stick around overnight tonight, but VFR
conditions should prevail, as winds become light heading into
Tuesday morning.

OUTLOOK...MVFR conditions will be possible with showers on 
Wednesday morning.

&&

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

&&

$$
SYNOPSIS...Hatzos/Hickman
NEAR TERM...Hatzos/Hickman
SHORT TERM...Hatzos
LONG TERM...
AVIATION...Hatzos