Area Forecast Discussion
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FXUS63 KILX 012045

National Weather Service Lincoln IL
245 PM CST TUE DEC 1 2015

.SHORT TERM...(Tonight)

Large upper low spinning over north central Iowa early this
afternoon, with various shortwaves rotating counter-clockwise around
it. Snow showers have been advancing eastward across Iowa through
the day with some mixed precipitation being reported as far east as
Cedar Rapids by 2 pm. Cirrus clouds over the southeast parts of the
forecast area have been thinning the last few hours, and earlier
stratocumulus over the northwest corner has moved away, but a large
shield of lower clouds is advancing across the Illinois/Iowa border.

Main concern for tonight remains with precipitation timing. HRRR
model has been suggesting some increase in precipitation further
south across Missouri this afternoon, ahead of an upper wave near
Kansas City, and some echoes are starting to be seen in northern
Missouri with light rain as close as Kirksville. A surface boundary
ahead of it is progged to sharpen a bit as it moves into central
Illinois this evening, with PoP`s gradually increasing as the
boundary arrives. Currently thinking most areas east of I-55 should
remain dry until after midnight, until a second wave currently over
southeast Nebraska swings into the area. Have increased PoP`s a bit
and went likely (60%) for a couple hours north of Bloomington after
about 3 am. With temperatures near or just above freezing, a
rain/snow mix should gradually change to snow, but accumulations
still expected to be mainly a quarter inch or less with slightly
higher totals north of I-74. Mainly sprinkles/flurries are expected
south of I-72, and areas south of I-70 likely to remain dry until
early Wednesday morning.


.LONG TERM...(Wednesday through Tuesday)

The large 500 mb low we have watched inch its way out of the
Rockies late in the weekend and early this week will be edging east
across far southern Wisconsin Wednesday and into extreme northwest
Indiana by early evening. This system will bringing cooler
conditions to the forecast area along with scattered snow showers,
especially across the north, which may mix or change to light rain
or sprinkles in the south during the afternoon. The stronger lift is
forecast to push in early Wednesday morning and gradually shift east
of the area during the afternoon. If we are going to see any
accumulation along and north of I-74, it would be in the morning, as
surface temperatures are expected to rise into the mid and upper 30s
by mid-afternoon. The snowfall should total less than one inch
across the north, with little, if any accumulations further
south. The precip threat should shift east of the forecast area by
late afternoon or early evening as the 500 mb trof axis edges east
into Indiana by then.

Upper level heights will gradually build across the Midwest by the
end of the work week as a trof moves into the western part of the
country. This will bring unseasonably mild weather back into the
region starting on Friday and holding into at least the first few
days of next week with afternoon temperatures closing in on 50
degrees far north and well into the 50s elsewhere. Models continue
to show their differences, at least compared to 24 hours ago, with
respect to shortwave energy coming out of the southwest portion of
the country late this weekend and especially into early next week.
The latest ECMWF indicated a closed 500 mb low pushing across
south-central Illinois on Monday, whereas the GFS was much further
south. The Euro solution puts rain back into at least the southern
half of the forecast area, where the GFS track keeps us dry. No
reason to make any significant changes early next week based on
what we saw today with the 12z runs, so will continue to keep
only slights going in the southerly quarter of the forecast area
on Monday with the above normal temperature regime holding into a
good portion of next week.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)

Main concern will be with development of MVFR conditions
overnight. A fast moving disturbance, associated with an upper
level low tracking slowly east across Iowa, will bring a period
of snow showers to central Illinois. Greatest potential for a
significant reduction in visibility will be closer to KPIA/KBMI
and northward, but ceilings expected to lower below 3000 feet at
all TAF sites during the 06-12Z period. With the low expected to
begin tracking southeast during the day Wednesday, the lower
clouds and periodic show showers will persist the remainder of the
TAF period.


.ILX Watches/Warnings/Advisories...


SHORT TERM...Geelhart
AVIATION...Geelhart is the U.S. government's official web portal to all federal, state and local government web resources and services.