Area Forecast Discussion
Issued by NWS Central Illinois

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736
FXUS63 KILX 092059
AFDILX

AREA FORECAST DISCUSSION
National Weather Service Lincoln IL
259 PM CST TUE FEB 9 2016

.SHORT TERM...(Tonight)
ISSUED AT 250 PM CST TUE FEB 9 2016

Scattered snow-showers persist across the eastern half of the KILX
CWA this afternoon, mainly east of the I-55 corridor.  As deep upper
trough dominating the eastern CONUS begins to slowly shift eastward,
the snow-showers and flurries will taper off from west to east
during the evening.  Based on latest radar trends and Rapid Refresh
forecast, have maintained low chance PoPs for snow-showers
along/east of a Bloomington to Effingham line through mid-evening.
After that, am anticipating dry and cold conditions across the board
for the remainder of the night.  Main short-term challenge will be
potential clearing, as model forecast soundings insist that it will
stay mostly cloudy while latest satellite loops show upstream
clearing across Iowa into northern Missouri.  Am still skeptical
about substantial clearing reaching central Illinois tonight, as
region remains under the influence of cyclonic flow aloft.  Will
therefore maintain mostly cloudy skies, with partial clearing west
of the I-55 corridor overnight.  Main weather story will be the very
cold conditions, as low temperatures drop into the single digits.
With northwesterly winds of 10 to 15 mph continuing through the
night, wind-chill values will bottom out in the -5 to -15 range by
dawn.

&&

.LONG TERM...(Wednesday through Tuesday)
ISSUED AT 250 PM CST TUE FEB 9 2016

Upper trof to hold over the eastern U.S. through the work week
bringing below normal temperatures and several chances for light
snow to parts of the area. Models through about 48 hours are in
reasonable agreement as the cold upper low just to our east will
edge slowly away from the area but the strong northwesterly flow
aloft should hold into at least the start of the weekend. The main
forecast concern will be timing and strength of the fast moving
shortwaves forecast to top the western U.S ridge and race southeast
into the Midwest, one coming Wednesday evening, with another slated
for Friday and then a more significant upper wave expected late next
weekend. Models suggest the better forcing coupled with the deeper
moisture with the first clipper system late tomorrow will be over
southeast Iowa through northeast Missouri and extreme western
Illinois. Will have low chance POPs in our far western counties thru
late evening before that system shifts quickly away from the region.

Another shot of cold air will filter southeast across the Midwest in
the wake of the late Wednesday which will hold over the area through
Friday as the next quick moving wave tracks across the northern
Plains and into the Midwest on Friday. Quite a bit of dry air in
place late Thursday night into Friday as the wave approaches so most
models not showing much QPF in our area with the Canadian model the
most aggressive with the moisture on Friday. With the dry air mass
in place ahead of the weak wave, will only carry 20 and 30 POPs for
some light snow during the day. After the Friday shortwave shifts
off to our southeast, an even colder air mass is slated to push into
central Illinois for the start of the weekend with 850 mb temps
forecast to drop down to between -15 to -20 degrees C Saturday which
will translate to afternoon highs on Saturday only in the teens with
early morning lows near zero in the far northwest and mostly in the
single digits elsewhere.

Further out in time, medium range models indicate the strong
central Pacific jet will shift east and break down, or at least
attempt to break down the amplified ridge over the western U.S.
by late in the weekend or early next week, signaling a pattern
change for later next week. But before that happens, below normal
temperatures will prevail through the weekend with a more
significant wave forecast to track into the Midwest on Sunday with
models trending a bit further north with the surface wave. Despite
the northward shift in the surface low, forecast soundings indicate
the depth of the cold air mass will be sufficient enough to support
mainly light snow Sunday into Sunday night, with the snow chances
decreasing from west to east Monday as the upper trof axis shifts to
our east during the day. With the cold upper trof slowly shifting
away from our area late in this forecast period, the stronger flow
will shift north as well over the east central Pacific into the
western U.S. and start to carve out a longwave trof after the 15th
of the month. This should bring about above normal temperatures but
a return to a more active southwesterly flow pattern for our area.

&&

.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.
&&

$$

SHORT TERM...Barnes
LONG TERM...Smith
AVIATION...Barnes



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