ILN issues Area Forecast Discussion (AFD) at Dec 18, 6:27 PM EST298
FXUS61 KILN 182327
AFDILN
Area Forecast Discussion
National Weather Service Wilmington OH
627 PM EST Wed Dec 18 2024
.SYNOPSIS...
Cooler air will move into the region behind a cold front today
and into Thursday. A low pressure system will bring some light
snow to the region on Friday, with below normal temperatures
continuing through the weekend. Warmer conditions are expected
next week, with rain chances returning by Tuesday morning.
&&
.NEAR TERM /THROUGH THURSDAY/...
An area of surface low pressure that moved through the region
this morning has progressed eastward to roughly Cumberland MD as
of 230 PM. Behind this low, winds through the boundary layer
have switched to the NW, with cold advection occurring. Deeper
moisture is already moving away, and any persisting light
showers should be finished by 21Z. However, as cold advection
continues tonight, some flurries will be possible -- model
soundings suggest very steep lapse rates into a saturated layer
at about 875mb, though this layer will be a little too warm for
ideal dendritic growth. So, any flurries / light snow will be
mostly negligible and accumulations are not expected. Conditions
will remain cloudy to mostly cloudy tonight, but continued cold
advection will bring min temps down into the middle to upper
20s.
&&
.SHORT TERM /THURSDAY NIGHT/...
On Thursday, an ill-defined area of surface high pressure will
move east through the Great Lakes. This will lead to generally
quiet conditions over the ILN CWA, though the cloud deck will be
very slow to erode, and may only really start to break up in the
southern portions of the forecast area. Highs on Thursday will
be in the middle to upper 30s.
By Thursday night, attention will turn toward a surface low and
shortwave moving ESE through the upper Mississippi Valley
region. Snow will develop ahead of this system, and may begin
moving into the northwestern ILN CWA during the 03Z-06Z time
frame. Some light accumulations (up to a half inch) will be
possible before 12Z Friday morning for Mercer County OH and
nearby areas, with additional snow coming across a wider area
after 12Z -- as discussed in the Long Term section below.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
The clipper system will start to weaken as it pivots across the
upper Ohio Valley on Friday as the energy begins to transfer to
off the mid Atlantic Coast. Still though, as the associated
surface low and attendant cold front move through the area
Friday, low level CAA will develop through the day. Pcpn will
likely already be all snow across our northwest Friday morning,
with more of a rain snow mix elsewhere, transitioning over to
mainly all snow from the west through the day. The best chance
for accumulation will be across our northwest where around an
inch of snow will be possible. Elsewhere across the area, any
accumulations should mainly be a half inch or less. Wind gusts
to around 25 mph or so will also be possible during the day on
Friday in the developing CAA. Temperatures will not recover much
through the day, with readings mainly in the low to mid 30s.
Surface high pressure and a colder airmass will settle into the
region through the weekend. Highs on Saturday and Sunday will
only be in the upper 20s to lower 30s with overnight lows in the
teens to lower 20s. The surface high will move off to the east
on Monday with southwesterly low level flow developing ahead of
the next system moving out of the Mississippi Valley. This will
lead to a gradual moderation in temperatures with readings
trending back to near normal through mid week.
There are some timing differences with the system as it moves
into the Ohio Valley, but we will generally see an increasing
chance for pcpn Monday night into Tuesday, with a chance of pcpn
then lingering into Christmas Day. In the developing WAA, pcpn
will be mainly liquid, but depending on the exact timing,
thermal profiles may support a period of mixed pcpn across the
north on Tuesday night. We will also be coming out of an
extending cold period, so ground/pavement temperatures may still
be below freezing at pcpn onset time Tuesday night. This could
lead to the potential for some of the rain to freeze on contact
with the surface Tuesday night, especially across our northern
areas.
&&
.AVIATION /23Z WEDNESDAY THROUGH MONDAY/...
MVFR CIGs continue to overspread the region. MVFR CIGs expected
to persist through the overnight hours, but there may be minor
improvement with CIGs lifting above 2000 ft AGL after 06z. Not
expecting any vsby reductions, but there will be a few spotty
snow flurries/light snow showers that will develop overnight. A
very brief vsby reduction could be possible from this snow, but
should remain a low potential for any categorical reduction
given the lighter intensity/coverage.
Winds remain light overnight but will make a notable shift on
Thursday towards the southeast. Improvement to VFR CIGs are
expected on Thursday by the late morning/early afternoon hours
based on latest guidance.
OUTLOOK... MVFR ceilings and MVFR to IFR visibilities likely on
Friday with snow. The MVFR ceilings may persist into Friday
night and Saturday.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.
&&
$$
SYNOPSIS...Hatzos
NEAR TERM...Hatzos
SHORT TERM...Hatzos
LONG TERM...JGL
AVIATION...Clark
Source:
ILN issues Area Forecast Discussion (AFD) at Dec 18, 6:27 PM EST---------------
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