Information is from the NWS Wilmington, OH Office


ILN Area Forecast Discussion/SKEW-T

FXUS61 KILN 180002
AFDILN

AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
702 PM EST Thu Jan 17 2019

.SYNOPSIS...
A cold front will cross the region this evening and end
precipitation from west to east, with high pressure building
behind it for Friday. The high will exit east Friday night and
the next low pressure system will track from western Kentucky to
northeast Kentucky during the day Saturday. As it does,
moderate rainfall over the Ohio River and significant snow along
the I-70 corridor is expected, followed by an intrusion of
bitterly cold air overnight and through the day Sunday.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Snow around Columbus will transition to some rain. Rain will
start out tonight across southeastern portions of the forecast
area. Expect all this precipitation to transition to drizzle
before tapering off overnight. In the areas with drizzle and
through the early morning hours visibilities will be reduced
significantly. Went ahead and issued a dense fog advisory for
many locations north of the Ohio River. This is also areas where
there is still snow on the ground, which is also a key factor in
the visibility reductions. As drier air works into the region
late in the night visibilities will begin to improve and
precipitation will taper off. Expect extensive cloud cover to
remain however. Although there is the potential for a brief
period of precipitation occurring with temperatures below
freezing, do not expect this to be widespread or for a long
period of time.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Outside of a solid overcast sky with low ceilings and possibly
some persisting morning fog, Friday will be relatively benign as
high pressure builds in briefly. Highs will barely eke out a
2-3 degree rise and reach to within a few degrees of 35, once
again coldest in the nw and warmest in the se.

The surface high will move east overnight. East winds will pick
up through the course of the night and the airmass will increase
in moisture ahead of the next surface low taking aim on the
region. Overnight lows will drop to the mid 20s over the north
to the low and mid 30s in Kentucky and far southeast Indiana.

The beginning of this snow and rain will likely occur west of
the I-75 corridor before daybreak but could spread to the
eastern edges of our forecast area. As of this moment, the mixed
layer between the two precipitation types will contain just
about everything with freezing rain and possibly some sleet
mixed in with both the rain and snow. This will primarily reside
south of a Richmond IN-Wilmington-Chillicothe line and run to
about 10-20 miles south of the Ohio River.

Significant rain or snow will not likely occur until after
daybreak Saturday.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Well-advertised winter storm will affect the area at the
beginning of the period. Precipitation will overspread the rest
of the forecast area Saturday morning and continue into Saturday
evening before tapering off late Saturday night. Warm air will
get drawn north with a stronger surge aloft as is normally the
case. So precipitation will go through numerous phases on
Saturday, except in west central Ohio where it appears that
precipitation will remain all snow. Surface temperatures are
forecast to warm above freezing across about the southern half
of the forecast area, so those locations will change to just
rain during the day. In between these two regions will have a
longer duration of a mixed bag and that is where greater ice
accumulations are possible. Across northern Kentucky into south
central Ohio, there may around an inch of rain which may result
in some minor flood issues.

12Z NAM and GFS indicate a bit of a dry slot pushing into southern
areas Saturday evening but with a rather robust deformation axis on
the back side of the cyclone. Colder air will be pouring into the
area behind the low will cause a sharp change back to snow and an
increase in snow-to-liquid ratios. So the greatest snow
accumulations are expected Saturday night. In addition, winds will
increase, so there is the potential for some blowing and drifting
snow. Based on forecast snow/ice accumulations, a winter storm watch
has been issued from Franklin County Indiana to Licking County
Ohio and area northwards.

Arctic air will invade the region with temperatures steady or even
slowly falling on Sunday. Readings will fall into the single digits
either side of zero Sunday night, and although winds will be
diminishing by that time as high pressure builds in, winds chills
will likely fall into advisory territory for parts of the region.

Very cold air will remain Monday as the Arctic high passes across
the region. Temperatures will likely fall fast Monday evening, but
then strong warm air advection will commence which will stop the
fall and may even lead to some rises before daybreak. It appears
that there will be a pretty quick rebound in temperatures on Tuesday
in advance of approaching low pressure. 12Z guidance still showing
some spread on when this system moves through. So broadbrushed PoPs
a bit from Tuesday into Wednesday to account for the uncertainty.
Temperatures will fall back closer to normal after the mid week
system moves through.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
VLIFR to LIFR conditions expected for most of the night. Expect
conditions to improve slightly to IFR and in some cases MVFR
during the day on Friday.

Snow will start off around KCMH. Elsewhere, expect rain and
drizzle to start off the TAF period. Drizzle will continue
through the evening hours before tapering off overnight.
Visibilities will be reduced significantly where there is the
drizzle and ceilings will be low.

Visibilities will begin to improve later in the overnight hours.
Cigs will start to improve slightly during the day on Friday.

Winds will generally be light and less than 10 knots.

OUTLOOK...MVFR/IFR conditions will continue through Friday. IFR
conditions are likely with precipitation on Saturday and
Saturday night, with MVFR/IFR conditions and gusty winds on
Sunday.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...Dense Fog Advisory until 3 AM EST Friday for OHZ026-034-035-
     042>044-051>053-060>062-070>072-077>079.
     Winter Storm Watch from late Friday night through late
     Saturday night for OHZ026-034-035-042>046-051>056-060>063-
     070>072.
     Dense Fog Advisory until 4 AM EST Friday for OHZ045-046-
     054>056-063>065-073-074-080.
KY...None.
IN...Dense Fog Advisory until 3 AM EST Friday for INZ050-058-059-
     066-073-074.
     Winter Storm Watch from late Friday night through late
     Saturday night for INZ050-058-059-066.

&&

$$
SYNOPSIS...Franks
NEAR TERM...Novak
SHORT TERM...Franks
LONG TERM...
AVIATION...Novak


Skew-T

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