Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 290932

Area Forecast Discussion
National Weather Service Lincoln IL
332 AM CST Tue Nov 29 2016

.SHORT TERM...(Today and tonight)
ISSUED AT 332 AM CST Tue Nov 29 2016

Central and southeast Illinois will continue to be under the
influence of a large storm system through the period. The center of
the vertically stacked system currently resides over the northern
Plains/upper Midwest, which is about where it was located 24 hours
ago. The cold front associated with the system extends south into
the southern Plains. Expect the cold front to clear the area
tonight, with temperatures returning to where they should be for late
November by tomorrow.

The front is expected to come through the area dry for the most
part. A short wave that will be helping to drive the front east
today is currently centered near the Texas & Oklahoma panhandles.
This wave is progged to track along/south of the Ohio River Valley,
and most of the associated rainfall should miss our area. However,
far southeast Illinois may be brushed by showers later tonight.
Also, an evening shower can`t be ruled out in far northern portions
of the forecast area as steep lapse rates from diurnal heating and
mid-level cooling move through.

Lowered today`s highs a little from previous forecast as cloud cover
is likely to be more substantial than expected. Most areas should
top out in the 50s.


.LONG TERM...(Wednesday through Monday)
ISSUED AT 332 AM CST Tue Nov 29 2016

After a relatively mild day today, much cooler temperatures are in
store the rest of the week across central and southeast IL. Strong
521 dm 500 mb low pressure along the eastern Dakotas border, is
forecast to track east and weaken to 530 dm over the upper MS river
valley by 12Z/Wed, move across the northern Great Lakes Wed night,
and into western/sw Quebec by 12Z/Thu. A large short wave trof will
push southeast across late Tue night and Wed morning and increase
low clouds from the nw to se during the day Wed, and bring cooler
temperatures on WSW breezes. Highs Wed will range from the lower 40s
nw of the IL river, to the lower 50s near the Wabash river. Some
light rain/snow showers will skirt across northern IL, staying
mainly along and north of I-80 Wed afternoon/evening, but could get
close to Stark and Marshall counties. Lows Wed night projected to be

Large low pressure system moves east across southern Quebec and
northern New England on Thu and Thu night, taking its snow/rain
showers ne of IL, though low clouds likely linger especially north
of I-70. Highs Thu in the lower 40s over most areas, with
Lawrenceville near 45F. Lows Thu night around freezing, in the lower
30s. Not much change on Friday with partly to mostly cloudy skies,
more low clouds over northeast CWA, with highs 39-44F, coolest from
I-74 ne. Lows Fri night in the upper 20s to near 30F as Canadian
high pressure noses into IL Fri night and Sat. This will keep dry
conditions thru Sat evening over central/se IL along with seasonably
cool temperatures. Highs Sat in the upper 30s from I-74 ne and lower
40s sw of I-74.

Still some fairly big differences between the extended forecast
models with the forecast of southern stream system early next week
for Sun/Mon. GFS continues to be further south with storm system on
Sunday, waiting until Monday and Monday night to eject low pressure
northeast into the Ohio river valley. ECMWF model spread
precipitation quickly northeast across IL on Sunday with a stronger
surface low ejecting northeast into the Ohio river valley, and dry
by Monday. GEM model somewhere in between. Most models have trended
a bit milder with their temperature fields which would support more
liquid than frozen precipitation. Followed a blend for now until
models settle their differences. Have slight chance of light
rain/snow into southeast IL south of I-70 late Sat night. Then 20-
30% chance of mix of rain/snow Sunday morning (30% in southeast IL)
then just 20-30% chance of rain Sunday afternoon. Have 20-30% chance
of light rain/snow Sunday night in central IL and just 30% chance of
light rain in southeast IL. Carried a dry forecast on Monday. Lows
Sat night and Sunday night in the lower 30s. Highs Sunday of 40-45F
and low to mid 40s Monday.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1153 PM CST Mon Nov 28 2016

One initial concern is for LLWS conditions as winds diminish in
our NW counties. PIA may see 3 hours of LLWS conditions before the
winds in the 2K Ft level diminish. The other terminal sites have
stronger winds lingering longer, and will diminish at the surface
in concert with the low level jet winds.

The rains and MVFR clouds have departed to the northeast of all
our terminal sites, with CMI just clearing in the last 30 mins.
VFR conditions should prevail for the remainder of the TAF period,
with help from steady winds the rest of tonight preventing much in
the way of fog to form under mostly clear skies.

The forecast soundings are indicating we could see a wave of mid-
level clouds progress across Illinois tomorrow, but there will be
little affect on aviation.

Winds will remain gusty for a few more hours for our eastern
terminals. Gusts will become less strong later tonight. Winds
tomorrow will sustain in the 12-15kt range from the south.




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