Area Forecast Discussion
Issued by NWS Central Illinois

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911
FXUS63 KILX 180550
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1150 PM CST Sat Feb 17 2018

.UPDATE...
Issued at 917 PM CST Sat Feb 17 2018

Snow is out of the area and clouds are continuing to clear in the
east/northeast out of the CWA. Clear skies will continue
overnight. With winds getting lighter and fresh snow cover in the
north part of the CWA, looks like temps will fall again, like last
night. So will be making some small adjustments to overnight lows
in the north where they still have snow cover. New GOES-16
night-time images helping to see where snow cover still is so
looking at adjustments in about 5 counties...including Galesburg
and Peoria areas. Since temps have already fallen to below
freezing over good portion of the area, not thinking that fog will
be much of an issue, though hires models still show some
development in extreme north. Already mentioned in grids so no
need for adjustment there. Update coming shortly.

&&

.SHORT TERM...(This evening through Sunday)
ISSUED AT 222 PM CST Sat Feb 17 2018

Vigorous upper wave, approaching the Illinois/Iowa border early
this afternoon, has produced some decent snow across the northern
part of the CWA. Have received a report of 2.5 inches of snow
over far northern Knox County, with 1/4 mile visibilities as far
south as Peoria. Lightning data suggested a bit of thundersnow in
northeast Knox County shortly before noon, which could explain the
higher snow amounts there. Areas south have had more of a
snow/rain mix over the last couple hours. Radar mosaics showing
the back edge of the precipitation approaching Galesburg, and
extrapolation has it east of I-39/US-51 by mid afternoon and
largely out of the CWA by sunset.

High pressure will move over the area tonight, with a nice warmup
starting Sunday as southerly winds kick in behind the high. Highs
still look to be in the upper 40s to lower 50s.

.LONG TERM...(Sunday night through Saturday)
ISSUED AT 222 PM CST Sat Feb 17 2018

Not a lot of changes with the timing of rain with the early week
system. Bulk of it should start coming in Sunday night after
midnight, and will go with categorical PoP`s most of the time
through Tuesday night. Heaviest rain axis continues to shift
slightly to the northwest, with areas currently in moderate
drought conditions getting a good soaking. As for the timing of
the frontal passage, the models are coming into better alignment,
with generally late Tuesday afternoon and evening the favored
time.

Some concerns with the tail end of the precipitation Tuesday
night. Forecast soundings off the GFS and ECMWF models show a warm
nose of air lingering around 850 mb, as the colder air comes in at
the surface. This signal has been seen for a few model runs now,
so will go ahead and add a mention of freezing rain Tuesday night,
mainly from about I-55 west.

Models diverge quite a bit in regards to the late week storm
system. The ECMWF model is about 24 hours slower than the GFS and
Canadian models in bringing the precipitation back into the area.
With that model being a bit of an outlier at the moment, will go
with high PoP`s for Friday and Friday night.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1150 PM CST Sat Feb 17 2018

VFR cigs will continue overnight and through most of tomorrow.
There is still the possibility of some light fog at the TAF sites,
though lower vis could be north of PIA overnight. Temp/dwpt
spreads look ok for light fog, but only SPI has gone there with
3sm br. So will add TEMPO group for tomorrow morning for all sites
of 3sm, but back to p6sm by 14z. Some high cirrus is possible
tomorrow afternoon and into the evening. Winds will be light and
variable overnight as high pressure ridge moves east, then
southerly winds return for tomorrow. Wind speeds will increase
tomorrow with gusts around 22-24kts possible tomorrow afternoon.
Should loose the gusts tomorrow evening, but thinking LLWS could
be possible at about 45kts.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Auten
SHORT TERM...Geelhart
LONG TERM...Geelhart
AVIATION...Auten



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