Area Forecast Discussion
Issued by NWS Central Illinois

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400
FXUS63 KILX 091755
AFDILX

AREA FORECAST DISCUSSION
National Weather Service Lincoln IL
1155 AM CST TUE FEB 9 2016

.UPDATE...
ISSUED AT 1043 AM CST TUE FEB 9 2016

16z/10am radar imagery shows snow-showers tracking across much of
the KILX CWA: however, the activity is beginning to come to an end
northwest of the I-55 corridor. Based on radar trends and upstream
obs, have updated forecast to remove PoPs across the NW. Will
continue to carry scattered snow snow-showers along/southeast of
a Bloomington to Jacksonville line, with just a few flurries
further north and west. Have also adjusted PoPs into tonight as
deep upper low over the eastern Great Lakes very slowly shifts
eastward. Rapid Refresh/NAM suggest little or no measurable precip
this evening, so have opted to remove PoPs entirely in favor of
just scattered flurries across the eastern CWA. Flurries will
gradually come to an end east of the I-57 corridor after midnight.

&&

.SHORT TERM...(Today)
ISSUED AT 339 AM CST TUE FEB 9 2016

Cold northwest flow to continue across central IL today with upper
low centered over Ohio slowly moving east. Cyclonic flow with
embedded weak disturbances and portions of the air column near
saturation will produce periods of light snow showers through the
day. Model forecast precipitation generally shifting eastward
through the day in concert with upper low...so trend through the day
will be for a slow diminishment of snow showers from west to east.
Additional snow accumulations expected to be only a few tenths or
less west of I-57 to around one half inch east of I-57. Highs
expected to range from 17 in Galesburg to 26 in Lawrenceville...with
blustery NW winds 15-20 mph and gusts to 25 mph continuing.

.LONG TERM...(Tonight through Monday)
ISSUED AT 339 AM CST TUE FEB 9 2016

Not much of a shift in the overall forecast.  Long wave trof over
the eastern half of the country will dominate the weather pattern
through the week and the first half of next weekend.  Bitterly cold
temps through the week behind the snow, ending tonight.  Some of the
models starting to show some continuity for both the depth of the
cold air as well as the series of quick waves moving through the
region in the northwesterly flow that will remain in place through
Saturday.

Blustery and cold tonight with northwesterly winds remaining in the
15-20 mph range overnight and temps dipping down to the single
digits.  Areas NW of the river will be very close to wind chill
criteria, albeit briefly.  So far, not enough to warrant an
advisory.  Cold air will keep the high temps for Wed and Thur in the
teens and 20s.  Overnight lows will be in the single digits and
lower teens by Friday morning.  Models starting to agree on a couple
waves, one passing to the south of ILX on Wed night, and a slight
chance for snow across the SW is in place for now.  The next quick
moving clipper like system is slated for Friday.  This one the
potential for some light accumulations and have started the trend in
the forecast.  Even though this is on Day 4, the nature of the quick
wave means the confidence in the timing is low overall and could
easily shift slightly in the next couple runs.  By late in the
weekend, an upper level ridge is shifting into the region and the
temperatures are moderating somewhat.  Although the ECMWF is coming
around a little bit from the extremely cold solution of 24 hrs ago,
neither the GFS nor the ECMWF are particularly warm in the extended.
Concerned the guidance may be a bit too high too quickly into the
first part of next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
ISSUED AT 1155 AM CST TUE FEB 9 2016

MVFR conditions will prevail through the entire 18z TAF period.
Scattered snow-showers will continue for the next couple of hours,
before gradually shifting further south and east away from the
central Illinois terminals. The main aviation forecast question
will be whether or not any clearing can occur late tonight into
Wednesday morning. Current satellite imagery shows plenty of low
clouds across Illinois and immediately upstream into Iowa:
however, a large clear area has developed further north across
Minnesota. Both the 12z NAM and the latest Rapid Refresh forecast
soundings keep the low clouds socked in across central Illinois
through midday Wednesday. Whether this is just the typical high
boundary layer RH bias often seen with the models in strong CAA
patterns remains to be seen. Despite clearing well upstream across
Minnesota, am skeptical of any substantial clearing overnight as
region remains in deep cyclonic flow aloft. Have therefore sided
with the more pessimistic models and maintained MVFR ceilings
through 18z Wed.

&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

UPDATE...Barnes
SHORT TERM...Onton
LONG TERM...HJS
AVIATION...Barnes



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