Area Forecast Discussion
Issued by NWS Wilmington, OH

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504
FXUS61 KILN 251820
AFDILN

Area Forecast Discussion
National Weather Service Wilmington OH
120 PM EST Sat Feb 25 2017

.SYNOPSIS...
A much cooler airmass will continue to settle into the region
today as a weak upper level disturbance brings a few rain and
snow showers. High pressure will build into the Ohio Valley
tonight into Sunday, leading to mainly clear skies. Seasonable
temperatures will remain in place across the area for Sunday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Shower activity will continue to move east this afternoon and
experience a slow but steady diminishing trend, ending by
evening. This is as the h5 trough is crossing the region and
downward motion with building surface high pressure in the lower
Midwest. Temperatures will slowly drop as the westerly winds
continue through the day.

&&

.SHORT TERM /SUNDAY/...
The trough axis will push off to the east tonight with surface
high pressure building into the region later tonight. This will
lead to decreasing clouds southwest to northeast and overnight
lows in the low to mid 20s. Mostly sunny skies are expected on
Sunday with highs in the low to mid 40s.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Sunday night surface high pressure will be centered near the
coast of NC with southwest flow across the region. At the same
time an upper level disturbance over AZ will eject east and push
towards the forecast area. Both the GFS and ECMWF have come
into fairly good agreement here with this system ejecting east
and spilling vorticity across the area Monday morning. As this
happens high cloud bases will thicken and slowly lower with
precipitation moving in from the west. Initially Monday morning
a rain/snow mix will be supported with the entire sounding below
freezing except right at the surface. Behind the remnant
shortwave Monday afternoon dry mid and upper level air will work
into the area helping to cut off the precip a bit.

Monday night into Tuesday morning there will be a brief break as the
next upper level disturbance over the Mountain West gets its act
together. Later Tuesday morning into afternoon the upper level
disturbance will push northeast into Minnesota pulling a warm front
north across the area. Widespread overrunning will commence with
PWATs approaching 0.85". Widespread weak lift will also accompany
the WAA which is supported by GFS omega fields. Tuesday afternoon a
surface low will track northeast towards WI allowing temperatures to
rise into the 60s. Shear values Tuesday afternoon will also become
impressive as ILN gets warm sectored with SFC- 3 KM shear 40 + kts
at times. GFS soundings currently show a CAP across the area though
which would limit convection across the region.

Tuesday night into Wednesday morning another upper level disturbance
will swing around the base of the upper level trough axis centered
over the Western United States and push towards the forecast area.
As this happens another surface low will form in the plains and push
northeast along a baroclinic zone. At the same the upper level jet
will begin to strengthen and briefly place ILN in a RRQ. Also a weak
split will occur in the jet. The GFS/ ECMWF/ and CMC all show this
happening. The difference between the three is placement of the
baroclinic zone (e.g., front), and track of eventual surface low as
it heads northeast. The NAEFS shows PWAT anomalies of 2 SD. The GFS
also has a PWAT of 1.35" just south of the region. As mentioned
above though these small differences in track between models has a
big difference on rainfall distribution. The ECMWF is furthest north
with the second surface low and has heavier rainfall totals across
our northwestern zones while the GFS is furthest south with the
track and has the heaviest totals across central KY. The CMC is a
compromise between the two and have trended the forecast this
direction. Given the RRQ, splitting upper level jet, abundant
moisture and lift have raised PoPs for Wednesday.

Wednesday evening into Thursday morning a stronger upper level
disturbance will push east over the area finally pushing the surface
cold front through the area. Thursday afternoon into Friday another
upper level disturbance will head southeast out of southwestern
Canada and bring a chance of snow and rain to the area Friday
morning. GFS soundings completely saturate Friday morning with almost
the entire forecast sounding below freezing. As of now mostly snow
Friday morning would be expected given the thermal profile of the
GFS. Eventual track and strength of this disturbance remains in
question though as the ECMWF is weaker with the disturbance so have
kept PoPs at chance for now. Friday night into Saturday surface high
pressure will dip south into the area from Canada and bring below
normal temperatures to the area. Saturday afternoon the surface high
pressure will already be east of the forecast area as the upper
level trough axis heads east.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
Significant cloud cover with mvfr cigs and passing snow showers
will lift later this afternoon and break up this evening, latest
in the eastern TAF sites of KCMH and KLCK. Winds will lose any
gustiness by nightfall, and then skies will clear for the
overnight period.

A surface high will be south of the area at daybreak Sunday and
winds will switch to the south as it passes. High clouds will
stream in from the west later in the day.

OUTLOOK...MVFR ceilings and visibilities possible Monday,
Tuesday night, and Wednesday.

&&

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

&&

$$
SYNOPSIS...JGL
NEAR TERM...Franks
SHORT TERM...JGL
LONG TERM...Haines
AVIATION...Franks



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