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495
FXUS61 KILN 181018
AFDILN

Area Forecast Discussion
National Weather Service Wilmington OH
618 AM EDT Thu Oct 18 2018

.SYNOPSIS...
High pressure will will result in dry but continued cool
conditions through tonight. A chance of showers will return for
Friday afternoon into Friday night as a cold front moves
through the region. A continued chance of showers will linger
Saturday into Saturday night as an upper level disturbance moves
across the Great Lakes. Temperatures will remain below normal
into early next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Surface high pressure is building east into the area early this
morning and this had allowed for winds to begin to taper off.
However, we are still seeing a fair amount of high level clouds
working across southern portions of the area. These clouds have
been slowly thinning out along the northern edge but we are
still seeing some IR enhancement to the cirrus at times along
and south of the Ohio River. Across the north in areas that have
cleared off, temperatures have fallen to near or below freezing
this morning. Across the south though, temperatures are still
running in the mid to upper 30s. Assuming that the clouds will
continue to thin out, suppose we could get close to freezing
along and north of the Ohio River, but it will likely be tough
to get that low across our far south at this point. Will
nonetheless keep the freeze warning going across the entire
area, just in case the clouds thin out enough to allow for some
frost development across the far south.

Otherwise, high pressure will continue to build into the region
today, resulting in mostly sunny skies. We will start out in
weak CAA this morning before transitioning to more neutral
advection later today. This combined with a fair amount of sun,
should allow for high temperatures this afternoon in the low to
mid 50s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
The surface high will push east across the area tonight. We
will start off mostly clear this evening, but could begin to see
a bit of an increase in high level clouds late tonight. Lows
will drop into the mid to upper 30s which could result in some
areas of frost once again. Southwesterly low level flow will
develop on the back side of the high through the day on Friday.
This will lead to some weak developing isentropic lift through
the afternoon hours and be accompanied by some weak mid level
energy moving into the mid Ohio Valley. This will result in an
increasing chance of rain showers from the southwest, mainly
through the afternoon hours on Friday. In developing low level
WAA, highs on Friday will be in the upper 50s to lower 60s.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Deep and highly-amplified troughing will dig into the eastern
Great Lakes region into the interior northeast this upcoming
weekend. After the initial cold frontal passage overnight
Friday, with increasingly dry conditions from northwest to
southeast during the nighttime, northwest flow will settle into
the the lower/mid levels of the atmosphere. By Saturday
afternoon, another compact vort lobe rounding the southwestern
periphery of the digging/deepening trough will track southeast
through the Great Lakes region. This will provide enough lift to
initiate scattered shower development, especially as fetch off
of the Great Lakes aids in enhancement of activity during the
afternoon and evening time period. The best lift /and therefore
the best time period for scattered rain showers/ will be moving
through the region late Saturday afternoon into the early part
of the evening. Compact/sudden height falls aloft will swing
through Ohio during this time period, with a surface trof
pivoting southeast through the ILN FA. Colder air at the surface
will filter in following the passage of the surface trof/cold
front and there may be a brief period where enuf lift overlaps
with cooling BL conditions to turn some of the raindrops to
snowflakes. At the very least, cold air settling in aloft will
certainly introduce flakes into the column, but whether they
will make it all the way to the ground before melting remains to
be seen.

There are several things that may support a quicker transition to at
least a mix of light rain and snow showers across east-central
Indiana, west-central Ohio and central Ohio during the evening hours
-- most notably of which will be the fact that the pcpn will
initially be falling into relatively dry lower levels. This may
bring on some evaporational cooling within the lower part of the
column, which may act to cool the column slightly faster than is
currently being modeled. Nevertheless, do think that there will be a
several hour period where a mix will be possible, especially where
surface temperatures cool into the upper 30s. However, as the core
of the surface cold air settles in, sinking air on the backside of
the midlevel vort lobe should bring a fairly quick end to the
scattered rain/snow shower activity past midnight. Additionally,
surface high pressure will be building into the western Ohio Valley
during the overnight into early Sunday morning, acting to shunt some
of the moisture off of Lake Michigan a bit to the east -- meaning
that any lingering lake effect or lake enhanced activity will likely
stay north of the local area for the latter overnight period.

The other main item of interest for Saturday will be the breeziness.
Steepening low-level lapse rates, thanks to pre-surface-trof diurnal
warming coincident with colder air settling in aloft, will help
enhance low level mixing during the afternoon and early evening
hours. Current momentum transfer techniques on fcst soundings
suggest that gusts to 35 MPH will be possible between 2 PM and 8 PM
Saturday before the combination of diurnally-driven/frontal cooling
at the surface allows for gusts to subside considerably for the late
evening period.

Mainly clear and unseasonably chilly temperatures are expected
Sunday and Sunday night. Frost and freezing temperatures will
again be possible Sunday night into early Monday morning.

By Tuesday, another system progressing south through the eastern
Great Lakes will begin to impact the local area, although mainly in
wind shift only. With the main forcing/support fcst to remain well
east of the region, combined with relatively meager moisture return
ahead of the front, pcpn chances look to stay fairly low even with
the passage of a front during the Tuesday-early Wednesday time
period. As of right now, this looks to be a dry passage, but the
details will continue to be hammered out in the coming days.

Unseasonably cool temperatures will persist through the entirety of
the long term period, with no significant pattern change expected
within the next week. Abundant sunshine during the day and cool
overnight periods will be the prevailing conditions from Sunday
through Wednesday.

&&

.AVIATION /10Z THURSDAY THROUGH MONDAY/...
High pressure and a dry airmass will remain in place across the
region through tonight. Mostly clear skies are expected trough
the TAF period. Some localized river valley fog may affect KLUK
late tonight...otherwise VFR conditions are expected.

OUTLOOK...MVFR conditions are possible from Friday evening into
Saturday.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...Freeze Warning until 10 AM EDT this morning for OHZ026-034-035-
     042>046-051>056-060>065-070>074-077>082-088.
KY...Freeze Warning until 10 AM EDT this morning for KYZ089>100.
IN...Freeze Warning until 10 AM EDT this morning for INZ050-058-059-
     066-073>075-080.

&&

$$
SYNOPSIS...JGL
NEAR TERM...JGL
SHORT TERM...JGL
LONG TERM...KC
AVIATION...JGL