Area Forecast Discussion
Issued by NWS Wilmington, OH

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643
FXUS61 KILN 192357
AFDILN

Area Forecast Discussion
National Weather Service Wilmington OH
657 PM EST Thu Jan 19 2017

.SYNOPSIS...
Low pressure and a warm front will lift north across the Ohio
Valley and the southern Great Lakes tonight and Friday. Warm,
moist flow will then continue into the first part of the weekend.
A stronger weather system will pass by to our south and southeast
Sunday into Monday.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Widespread showers are still forecast to pass north and northeast
across the region tonight. This precipitation will be associated
with a warm, moist, low level convergent jet axis. Temperatures
will bottom out early, then slowly climb overnight as a surface
warm front approaches the Ohio River Valley.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
A blend of high resolution models, along withe the 12Z GFS and 12Z
ECMWF, have been used to compose the short term forecast.

Widespread showers will taper off from southwest to northeast
Friday as the low level warm, moist convergent jet axis shifts
northward into the Great Lakes. Rainfall amounts will generally
range between 0.50 and 1.00 inches. A surface warm front will
lift north across the area during the day. Considerable low level
moisture will remain, so not much is expected in terms of
sunshine. High temperatures will be much above normal, ranging
from the mid 50s to the lower 60s.

For the period Friday night into Saturday night, broad, warm,
moist flow will continue. Models suggest a few embedded impulses
within a southwest flow aloft will trigger a few showers Friday
night, and then again Saturday afternoon and Saturday night. There
could be enough instability along and south of the Ohio River and
across our western zones for a rumble of thunder Saturday
afternoon and evening. The chance appears to be very low at this
point, so will persist with just showers for now. A somewhat non-
diurnal trend in temperatures have been employed. Highs in the
upper 50s to the lower 60s on Saturday will only drop into the
upper 40s and lower 50s by Sunday morning. These values will
continue to be much above normal for what is considered the
climatological coldest time of the year

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
On Sunday, a fast-moving upper level low pressure system is expected
to move across the southern tier of states. After a day of southerly
flow on Saturday, antecedent conditions will be warm and moist in
the Ohio Valley, but a shift in winds to easterly will put an end to
any further warm advection. However, temperatures are only expected
to drop slightly from Saturday to Sunday, especially as the day now
looks slightly drier than previously thought. Both the ECMWF/GFS
suggest that the ILN forecast area will be well north of the
widespread rainfall developing across the Tennessee Valley region.
As the low moves ENE going into Monday, and with precipitable water
values continuing to remain high for January (near or just under an
inch), an increase in rain chances will eventually occur through
Monday and Monday night -- especially in the eastern half of the
forecast area. Overall model differences with respect to timing are
small (when considering longitudinal position) but placement of the
low / forcing / precipitation remain a little less clear.

Once the low has moved from south of the region to southeast of the
region, a switch to northerly flow will allow for a gradual drop in
temperatures through Monday and Tuesday. Generally dry conditions
are expected on Tuesday, as a narrow ridge arrives into the area.
Forecast specifics become less certain by Monday night and Tuesday,
with GEFS 500mb height plots showing a wide range in both amplitude
and timing of the ridge (and the next wave following behind it).
What appears fairly certain is that warmer-than-normal conditions
will continue through Wednesday, before a cold front moves through
the area at some point on that day, helping to bring in some colder
air for the end of the week. Confidence is low with regards to
precipitation chances with this front, as GFS/ECMWF suggest it will
be lacking in deep moisture.

With broad troughing over the Great Lakes and Ohio Valley on
Thursday, some light precipitation may develop -- and temperatures
during the low end of the diurnal cycle may be cool enough to
support some snow.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
A weak area of surface low pressure will move north into the Ohio
Valley overnight through the first part of the day Friday. -RA/RA
is approaching from the southwest and will overspread the
terminals from southwest to northeast late this evening through
the overnight period.

As the low levels moisten within steadier areas of RA, expect
that MVFR VSBYs and CIGs will eventually develop for all sites.
As the surface low tracks into the local area past 09z, CIGs are
expected to go IFR for all sites. There is the potential for LIFR
CIGs between 12-15z area-wide, but confidence on exact location
inhibited inclusion in the TAFs at this time.

Shield of pcpn will eventually lift north of the TAF sites past
15z as the low tracks north of the area. However, IFR CIGs will
persist through most of the day, with a return to MVFR CIGs
anticipated toward the end of the period.

Easterly winds this evening will go more southwesterly after the
low tracks through the region.

OUTLOOK...MVFR/IFR ceilings possible into Saturday, and then late
Sunday into Tuesday.

&&

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

&&

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



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