Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 051644
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1044 AM CST Tue Dec 5 2017

.UPDATE...
Issued at 1035 AM CST Tue Dec 5 2017

Gusty westerly winds expected across the area this afternoon
bringing in much colder air to the region. Forecast soundings
and the last few runs of the HRRR model indicates gusts up
to 45 mph in a few locations along and especially north of
the I-72 corridor. The winds should quickly diminish late
this afternoon into the early evening hours. Latest satellite
data and surface observations indicate a patch of clouds tracking
east across east central Iowa with a track that suggests our
northern counties will be affected by that this afternoon. A weak
weather disturbance further to our northwest will track southeast
into our area later tonight into Wednesday and bring another round
of clouds and possibly some flurries or sprinkles during the day
Wednesday. Have made some minor adjustments to sky condition and
temperature trends for this afternoon. We should have the updated
ZFP out by 11 am.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 233 AM CST Tue Dec 5 2017

Cold front has exited the southeast tip of the forecast area early
this morning, with the rain recently ending at Lawrenceville.
Still have had some significant winds behind the front, with
Bloomington gusting to 49 mph shortly before 1 am. Winds across
the southern CWA have started to diminish a bit, and a bit of a
lull will occur early this morning. However, there`s still a tight
pressure gradient behind the storm system, and a trend toward some
clearing later this morning should help mix down additional wind
gusts. Gusts 30-35 mph likely this afternoon as far south as I-70.

The cold air advection will continue today, as a large upper wave
swings across the upper Mississippi Valley. 850 mb temperatures
should be as low as -9C by midday. While the southwest half of the
forecast area may eke out some lower 40s this afternoon,
temperatures will fall well below freezing tonight.

.LONG TERM...(Wednesday through Monday)
ISSUED AT 233 AM CST Tue Dec 5 2017

A fast moving upper wave will be swinging through the area early
Wednesday morning. Not a lot of moisture upstairs with this wave,
so the impact will be little more than flurries, and skies should
be mostly sunny by afternoon.

Impressive surge of Arctic air will be quickly dropping southward
mid week, with 850 mb temps in our area down to near -15C by early
Thursday morning. Blended guidance is continuing to struggle some
with the depth of the cold, with a high bias occurring due to the
warmer weather of the last couple weeks. Have had to make some
downward adjustments in late week temperatures, especially on
Saturday, when a stronger upper low plunges another lobe of very
cold air southward. Some moderation in temperatures will occur
Sunday into Monday, before the Arctic express reloads for another
surge.

The clipper exhibited by the longer range models for late week
continues to be a challenge. Little moisture advection will be
able to take place. The European model is the driest of the bunch,
and features a dry frontal passage Friday evening. The GFS is
furthest south with the upper low, all the way down to southern
Lake Michigan by early Saturday morning, and thus brings a much
further south shot of light snow. For now, PoP`s with this
feature were scaled back to around 30%, in a nod toward the drier
trend seen on recent model runs.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 522 AM CST Tue Dec 5 2017

Areas of high MVFR ceilings (2500-3000 feet) currently moving
through central Illinois. Back side has recently pushed just east
of KPIA, and will be clearing out over the next couple hours. Have
included a TEMPO period for these ceilings from KBMI-KDEC eastward
for the first couple hours. Otherwise, VFR conditions expected.

West winds will be gusting 25-30 knots a good portion of the day,
especially mid morning through mid afternoon.


&&

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

$$

UPDATE...Smith
SHORT TERM...Geelhart
LONG TERM...Geelhart
AVIATION...Geelhart



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