Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 172347
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
547 PM CST Fri Nov 17 2017

.SHORT TERM...(This evening through Saturday)
ISSUED AT 247 PM CST Fri Nov 17 2017

Overall, not many changes to the forecast with the exception of
the details in timing. Main issues in the forecast are
intermittent showers and nondiurnal trends in the temperatures in
through the overnight. Tomorrow, a cold frontal passage, potential
for thunderstorms in the morning hours, and blustery winds behind
the boundary as the cold air settles into the region. Models are
in pretty good agreement with the trends, just some minor issues
with timing.

Strong southerly winds today will continue through the night,
ushering warmer air into Central IL ahead of a developing low to
the west. Within the developing warm sector, temperatures will be
slowly rising through most of the overnight into the upper
40s/low 50s before a cold front drops into the area. Moisture and
the general ascent of the WAA will contribute to ongoing
intermittent showers. Thunder chances will start this evening and
continue into the morning hours ahead of the developing storm
system. Stronger storms should be confined to the morning hours
before noon. With the slower progression of the cold front, SPC
has expanded the marginal risk (mainly for hail in elevated
storms) back slightly to the north. Similar area in the marginal
risk will also see some of the stronger gusts from mid morning on.
Winds just ahead of the boundary will still have the potential to
see gusts with the storms and showers, but the stronger gusts will
be behind the front with the shift to the NW. Increases pressure
gradient will bring stronger sustained winds out of the NW as well.
With the subtle timing differences in the frontal passage, the
stronger winds should be after noon. 30-40kts off the surface will
be subject to turbulent mixing down with any showers, and general
subsidence of the air behind the boundary. A lack of significant
inversion through the overnight will continue the gusts into the
early evening. Wind advisory criteria is borderline, but have
issued for the southern half of the CWA.

.LONG TERM...(Saturday night through Friday)
ISSUED AT 247 PM CST Fri Nov 17 2017

Temps plummet into the 20s again for Sat night and Sun night with
colder air moving into the Midwest. A period of quiet weather sets
up through the remainder of the forecast. Temps warm briefly with
southerly flow and the western ridge shifts eastward slightly for
Monday. Next system moves into the Upper Midwest/Great Lakes for
Tuesday. Cold front remains dry, but lows dropping into the 20s
Tues night and Wed night in response to the airmass shift. GFS
starting to come around to a more northerly track of the wave,
lessening the depth of the cold air into Central IL.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 545 PM CST Fri Nov 17 2017

MVFR ceilings prevail from KSPI-KBMI westward with lower VFR
conditions to the east, although a few pockets of VFR conditions
are possible area wide early this evening. Increasing shower
activity and lowering ceilings will take place this evening, along
with a threat for thunderstorms developing mainly after 05Z. By
early morning, most ceilings should be IFR to LIFR category with
visibility in MVFR to IFR categories. Slowly improving cigs/vsbys
will take place after 18Z behind a cold front. Winds S around 15
kts with gusts to around 25 kts overnight, decreasing along a cold
front passing through the area Saturday morning. Behind the cold
front, strong gusty NW winds 15-25 kts with gusts 30 to 35 kts
from around 18Z to 00Z.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 8 AM to 9 PM CST Saturday for ILZ049>057-
061>063-066>068-071>073.

&&

$$

SHORT TERM...HJS
LONG TERM...HJS
AVIATION...37


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