Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 270446

Area Forecast Discussion
National Weather Service Lincoln IL
1146 PM CDT MON SEP 26 2016

Issued at 852 PM CDT Mon Sep 26 2016

Forecast looks good tonight and only update needed was to remove
the early evening wind gusts wording. Otherwise clear skies
tonight with sw winds less than 10 mph. Cooler lows in the mid to
upper upper 40s by dawn.

Breezy west winds that were gusting 15-25 mph at 6 pm quickly
diminished to 5-10 mph by 7 pm as winds decoupled at sunset. Winds
have also now veered more in a southwest direction. Low dewpoints
in the mid 30s to mid 40s will keep fog from forming despite clear
skies and lighter winds. Latest surface map shows 1026 mb high
pressure over the central Rockies and was ridging eastward into
the Ozarks, while 995 mb surface low pressure was just north of
Lake Superior. Aloft a strong 544 dm 500 mb low was spinning just
north of Lake Superior too. Low pressure system to track into
northeastern part of Lake Superior by Tue morning with its clouds
staying over the Great Lakes region into Tue. Breezy west winds
expected again by late Tue morning and Tue afternoon with gusts
back into the 20s with a fair amount of sunshine. Highs of 70-75F
on Tue, so tomorrow looks like a repeat of todays weather.


.SHORT TERM...(This evening through Tuesday)
ISSUED AT 250 PM CDT Mon Sep 26 2016

A cold front has moved through the Midwest and cooler and drier air
has settled in behind the front.  As a result, quiet weather and
cooler temperatures will continue through the overnight.  Tonights
lows will drop into the 40s...chilly by comparison to the weather of
late. Tomorrow will climb back into the upper 60s and low to mid
70s. Skies should remain clear as dry air and subsidence generally
rules.  The pressure gradient should keep the winds relatively
breezy out of the WNW.

.LONG TERM...(Tuesday night through Monday)
ISSUED AT 250 PM CDT Mon Sep 26 2016

Cooler than normal conditions will dominate the extended forecast,
as an occluded low pressure system drifts from the western Great
Lakes south toward Indiana/Ohio. The trend in the last couple of
runs of the models has been a farther west track of the low, closer
to Illinois. The ECMWF was the first to show that trend, and the
others have shifted in that direction. The EC remains the farthest
west with where the low lingers this week. It is also the last to
eject the low to the east next Saturday, although the Canadian and
GFS are not nearly as far behind as previous model runs.

The overall effect of a westward shift in the low placement would
mean much cloudier conditions in Illinois, at the very least. It
could also mean more days with the potential for periodic showers as
spokes of energy rotate around the cut-off low. We previously just
had slight chance PoPs on Tuesday night into Wednesday. However, the
influence of the EC model on the blended extended has prompted
additional slight chances for rain east of Bloomington to Decatur,
from Thursday night through Saturday. Friday shows the farthest west
expansion of rain chances, reaching all the way to Peoria and
Springfield. The forecast soundings are minimally supportive of rain
at any point this week, with a narrow layer of moisture in the lower
levels the primary moisture source. So rainfall amounts would be
trace amounts to a few hundredths of an inch for any areas that do
get rain this week and next weekend.

As mentioned previously, temps will linger below normal for the
first time in months. Morning lows on Wednesday will dip into the
upper 40s to low 50s. Mostly cloudy conditions on Wednesday will
keep highs that day limited to the mid to upper 60s, our coolest day
of the next week. The lingering proximity of the low just to the
east of Illinois the rest of the week will allow the chilly air mass
to linger. Highs Thursday through Saturday should remain in the
lower 70s, with lows in the lower 50s. At this point, more sunshine
is expected on Thursday, with increasing clouds Friday and Saturday.
With the forecast eastward departure of the low by Sunday, high
temps should climb a few degrees toward the mid 70s Sunday, with mid
to upper 70s next Monday.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1145 PM CDT Mon Sep 26 2016

Very dry air in place across central IL overnight into Tuesday
with dewpoints in the upper 30s/lower 40s. 1025 mb high pressure
over the central Rockies and ridging eastward into the mid MS
valley and KY and providing the fair wx. This will continue VFR
conditions with clear skies across central IL through Tue. Any
patchy shallow fog that develops later tonight will stay focused
along major rivers like the MS and Ohio, and south of I-70 where
higher dewpoints in the upper 40s/lower 50s. SW winds of 4-8 kts
overnight will veer WSW and increase to 10-15 kts with gusts of
17-24 kts between 15-16Z Tue, then diminish to 4-7 kts around
00Z/Wed. Scattered mid/high clouds to arrive from the north after
sunset Tue evening while lower clouds should not arrive along I-74
until after 06Z Wed. This due to strong 543 dm 500 mb low spinning
just north of Lake Superior tracking southward across Lake MI and
far eastern WI during Tue evening.


.ILX Watches/Warnings/Advisories...



LONG TERM...Shimon
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