Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 210013
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
613 PM CST Tue Feb 20 2018

.SHORT TERM...(This evening through Wednesday)
ISSUED AT 259 PM CST Tue Feb 20 2018

Cold front has recently passed through Decatur, and will arrive
soon in Champaign. Temperatures initially behind it fell 22
degrees in Peoria in 5 minutes, but more recently the drop has
been more in the order of a slower 15 degree fall. With a steady
fall through the evening, most areas west of I-55 should be in the
mid 30s or colder by midnight. Unfortunately, the rain won`t be
done by this point, as more precipitation continues to surge
northeast out of Missouri. Forecast soundings show a prominent
warm nose around 2,000 feet lingering much of the night, so a
changeover to freezing rain and some sleet remains likely. This
should begin this evening west of the Illinois River, and near
I-55 toward the midnight-2 am time frame. Accumulations of around
a tenth inch appear likely on elevated surfaces. Road conditions
may be a bit of a question mark, with the warm pavement from
today, but some travel impacts are still expected. As a result, a
Winter Weather Advisory will be issued for most of the forecast
area. Exception is from about Danville-Effingham southeast, where
the precipitation should be ending around the time temperatures
get cold enough.

In terms of the flooding potential, the Flood Watch will be
expanded into the southeast CWA through tonight. Areas along and
south of I-70 have been missing out on the heaviest rain so far,
but 1-2 inches appear reasonable as precipitable waters remain
around 1.5 inches past midnight. The flood threat west of I-55
will be diminishing, but will leave that part for now and let the
next shift continue to monitor for several more hours.

For Wednesday, the cold front will be hanging up across the
Tennessee Valley into southern Arkansas, with another surge of
moisture coming northeast with a shortwave. Thus, will keep PoP`s
going through the day south of I-70.

.LONG TERM...(Wednesday night through Tuesday)
ISSUED AT 259 PM CST Tue Feb 20 2018

Some variation among the models among exactly how far north this
next moisture surge moves up, but they continue to suggest a
west-east corridor of some freezing rain Wednesday night into
Thursday. Currently this is more favored between I-72 and I-70,
but could reach as far north as Peoria by early Thursday before
transitioning to rain.

With the southwest upper flow persisting through late week, the
next storm system still on track to arrive Thursday night. Waves
of low pressure will continue to ride northeast, until the final
passage of the system Saturday night. Latest ECMWF was not
available for comparison, but the new GFS was much stronger than
the old European run, though timing was in reasonable agreement.
The southeast CWA is more on track for any significant rainfall at
this time, and with the ground saturated from the current system,
another round of flooding will be possible.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 610 PM CST Tue Feb 20 2018

The cold front has pushed east of all the TAF sites, with NW wind
gusts to 25KT developing. Moderate to heavy rain is mainly east of
I-55 as of 00Z/6 pm, with some IFR ceilings at BMI and IFR vis at
CMI. Otherwise, flight categories have improved to MVFR at PIA,
SPI, and DEC. Potential for periods of IFR due to low clouds and
vis will continue for all TAF sites until after midnight, when
MVFR and possibly VFR clouds develop. Freezing rain and icing will
be the other main concern the rest of the night. Temps will drop
below freezing at all terminal sites overnight, with some light
freezing rain and sleet/snow possible for several hours before
precipitation ends from NW to SE between 07z (PIA) and 11Z (CMI).
Despite how much freezing rain/icing occurs during the
precipitation, travel surfaces could still re-freeze due to
residual water on the ground. Slippery travel is expected as the
night progresses.

NW winds should diminish below 10kt tomorrow morning, with clouds
improving to VFR.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Flood Watch through late tonight for ILZ029>031-036>038-040>057-
061>063-066>068-071>073.

Winter Weather Advisory until 6 AM CST Wednesday for ILZ027>031-
036-037-040-041-047-049-050.

Flood Watch until 6 PM CST this evening for ILZ027-028.

Winter Weather Advisory from midnight tonight to 6 AM CST
Wednesday for ILZ038-042>045-048-051>055-061.

&&

$$

SHORT TERM...Geelhart
LONG TERM...Geelhart
AVIATION...Shimon


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