Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 252335
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
535 PM CST Sun Jan 25 2015

.SHORT TERM...(Tonight)
ISSUED AT 239 PM CST SUN JAN 25 2015

Area of low pressure which has brought our precipitation was
centered near Carbondale early this afternoon. Rain/snow transition
line has been struggling to move any further south, and in fact
areas from Macomb to Bloomington which had switched over were
starting to mix with rain again. Temperatures have been above
freezing over most of the snow area and accumulations have been
minor and slushy, but some more substantial 1-2 inch totals have
occurred north of Galesburg where temperatures are now below
freezing. The deformation band of snow has been weakening some the
last few hours, and there is a substantial hole in the precip over
the central 2/3 of the forecast area.

The RAP model shows a further weakening of the the deformation band
over the next few hours, and actually has the entire CWA dry by 6
pm. Have some concerns that may be too quick across the southeast,
as the upper wave continues to dig across southeast Missouri, and
have lingered some likely PoP`s down there slightly beyond that time
frame, but reduced PoP`s to below 20% by 9 pm.

Overnight, models are trying to show some substantial clearing over
most of the forecast area beginning late evening. While there is
some breakup of the clouds upstream across Wisconsin, it is not
completely clear up there and the north/northeast flow is not
especially conducive to rapid clearing. Have gone with partly cloudy
skies overnight across the northwest half of the forecast area, but
clouds will already been increasing ahead of the next clipper which
will be dropping southeast into northern Minnesota overnight.

&&

.LONG TERM...(Monday through Sunday)
ISSUED AT 239 PM CST SUN JAN 25 2015

A couple of cooler days are on tap across central and southeast
Illinois in the wake of today`s clipper. There is still a chance we
may see a few snow flakes or sprinkles on Monday as a shearing
upper-level wave, currently diving across the Canadian Prairies,
passes through the Great Lakes region and parts of the Midwest.
However, looking at forecast soundings, there will be a very small
window of opportunity where ice crystals will be present, suggesting
the chance of measurable precipitation is quite low. So, for now,
will only carry a chance of flurries Monday across the northern
portion of the forecast area as the very sheared wave passes to our
north. It is definitely possible that we will see nothing at all, or
perhaps some light drizzle or freezing drizzle (depending on surface
temperatures) due to the paucity of ice crystals.

Temperatures will warm heading into midweek as the persistent
amplified upper-level flow briefly turns more zonal, and a system
approaches from the Pacific coast. This system will mainly pose a
rain threat as it moves through Wednesday night into Thursday. A
brief period of snow is not out of the question later Thursday as
cold air filters in behind the system, but forecast soundings
currently suggest the moisture depth will be too shallow to support
precipitation (no ice crystals) by the time the thermal profile
would support snow.

Another cool down is expected in the wake of the midweek system, but
temperatures should still be near normal for late January. The
eastern North American mean trof that has been in place will try to
reestablish itself by the weekend. A clipper type wave in the
returning northwest upper-level flow may bring a chance of snow to
the area over the weekend. However, the current storm track keeps
the best snow chances to our north, and have only included a slight
chance of snow at this time.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 525 PM CST SUN JAN 25 2015

Surface low near KSDF at 23z will continue to push away from
terminals this evening. Precip should continue to diminish as weak
ridging moves into area. Ridging also reduces the gradient over
the region early this evening suggesting the ongoing gusty winds
will drop off rather quickly.

Area of clearing between systems is pushing south and is
approaching KMLI at 23z. This area will slow as it pushes south
and low-level winds diminish but will likely move into KPIA later
this evening with at least some scattering of the current ceiling
and then spread more slowly south and east overnight.

Next system is already approaching on Monday as weak channeled
vorticity plunges down deep east coast trough. Mid-level CIGS will
spread across the area during the morning with lowering decks into
MVFR by the end of the TAF valid time. Still some question as to
how far SW light precip can develop during the afternoon so we
leave out of all terminals at this point.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Geelhart
LONG TERM...Bak
AVIATION...Barker






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