Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 170218
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
918 PM CDT Mon Apr 16 2018

.UPDATE...
Issued at 910 PM CDT Mon Apr 16 2018

The storm system that brought the rain and snow to the area over
the past 24 hours has finally shifted far enough to our east this
evening to allow winds to gradually subside. However, latest cloud
trends are suggesting a slower clearing trend aross the forecast
area tonight with the latest HRRR indicating the backedge of the
cloud shield out to our northwest rotating across parts of central
Illinois during the early morning hours. Will make some minor timing
adjustments to the sky condition for the early morning hours through
at least the mid-morning hours of Tuesday.

Surface high pressure will drift across the area on Tuesday bringing
some sunshine to the area and as a result, warmer temperatures.
Everyone should be back into the 50s Tuesday afternoon and that
will feel good compared with what he have had to deal with over
the past couple of days. But evening with the improvement in
temperatures tomorrow, we will still be around 10 degrees below
normal for the middle of April.

One concern related to the discussion above is with the HRRR forecast
soundings indicating some moisture getting trapped underneath a
developing subsidence inversion tomorrow resulting in more cloud
cover than currently forecast. The RAP soundings also hinting at
that possibility while the 3km NAM soundings indicated our eastern
counties may be in line for more cloud cover, at least through
the morning before the inversion starts to break down by afternoon.
Otherwise, the rest of the forecast looks to be doing fine with
very few changes made. An updated ZFP should be out soon with
adjustments to the overnight portion of the forecast, dealing
with the expected cloud trends across the forecast area.

&&

.SHORT TERM...(This evening through Tuesday)
ISSUED AT 309 PM CDT Mon Apr 16 2018

Upper low continues to pull away to the east with light rain/snow
showers diminishing from was to east. As showers are partially
diurnally driven, any lingering showers should end by sunset.
Currently this activity looks to be from around Bloomington to
Shelbyville eastward. Cold air will continue to advect into the area
in brisk northwest winds, with lows tonight from 25 to 30 degrees.
Winds will decrease and clouds will diminish as a high pressure
ridge axis to the west edges into the area. Will continue the freeze
warning for tonight along and south of I-70 where the growing season
has started, although even colder temperatures will be to the north.

Temperatures should start to moderate for Tuesday as high pressure
slips east and light or southerly winds begin. Expecting highs
ranging from the low 50s north of I-74 to the mid and upper 50s from
Springfield to Mattoon southward.

.LONG TERM...(Tuesday night through Monday)
ISSUED AT 309 PM CDT Mon Apr 16 2018

The next system of importance comes Wednesday as a fast moving upper
wave and attendant surface low ejects east from the Rockies. Models
are fairly consistent at this point with the surface low crossing
northern IL mid-day Wednesday. With the earlier timing, highs
Wednesday have trended downward as the warmest temperatures will
come early in the day before a cold front pushes east through the
area. Most of the precipitation looks to be north of I-74, although
have slight chances for rain from around Jacksonville to
Martinsville. Highs ranging from 51 in Galesburg to 68 in
Lawrenceville, although any earlier timing could trim those
temperatures down further. A few snow flakes will be possible
Wednesday night north of I-74, but no accumulation is expected with
lows just above freezing.

High pressure and dry Thursday and Friday. Highs low to mid 50s
Thursday then mid and upper 50s Friday. Next low looks to cut off
and move south of central Illinois over the weekend. Therefore,
have slight to no chance of precipitation and highs trending from
around 55 to 60 Saturday up to 60 to 65 Monday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 617 PM CDT Mon Apr 16 2018

The back-edge of the stratocumulus deck was near SPI at this hour
and will continue to slowly push east this evening. Based on the
current speed, it appears the clearing line will get to CMI by
05 to 06z. However, a few of the short term model solutions
suggest as the clearing line advances east late this evening,
additional clouds will develop just to the west and northwest
of the cloud shield after 05z, but confidence on that at this
time is low. Right now it appears if that did occur, it would
affect BMI and CMI by keeping the cloud deck (3000-4000 ft AGL)
in longer than currently anticipated. Will go more optimistic
at this point as high pressure builds into the region late
tonight and on Tuesday with VFR conditions. West to northwest
winds of 10 to 20 kts this evening will quickly diminish after
00z with a northwest wind of 10 to 15 kts expected on Tuesday.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Freeze Warning from midnight tonight to 9 AM CDT Tuesday for
ILZ062-063-066>068-071>073.

&&

$$

UPDATE...Smith
SHORT TERM...37
LONG TERM...37
AVIATION...Smith



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