Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 241146
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
646 AM CDT SAT SEP 24 2016

.SHORT TERM...(Today and tonight)
ISSUED AT 325 AM CDT Sat Sep 24 2016

A weak boundary will located from west central IL into southeast IL
this morning. Most of the CWA is north of this boundary where winds
are primarily out of the east-northeast. Patchy fog has developed
north of this boundary over a good portion of the CWA, as well as in
southeast IL. In addition, stratus is spreading west into northern
parts of the CWA and is forecast to ooze south some early this
morning. Do not expect this area of clouds to remain the whole day,
but could take several hours before it dissipates/burns off/lifts
north out of the CWA. So will have to have some mostly cloudy skies
in the north and northeast this morning, then becoming partly sunny
this afternoon. Temps will be a little cooler as well, probably only
reaching into the lower 80s by this afternoon. Other areas of the
CWA where there will be much more sunshine will see afternoon
highs reaching the mid to upper 80s, and around 90 in some areas.

Late tonight there should be an influx of more moisture and clouds
into the CWA as the next weather system approaches the area. Trend
in the models is for a little slower timing of the onset of precip.
So, any chance of precip will be very late tonight, well after
midnight. Clouds will keep temps up some, but still expecting mid to
upper 60s for overnight lows. In addition, patchy fog should be an
issue across the CWA late tonight.

.LONG TERM...(Sunday through Friday)
ISSUED AT 325 AM CDT Sat Sep 24 2016

Only real precipitation issue in the longer range will be the timing
of the front Sunday afternoon and evening. Most of the model
guidance has it roughly along the I-55 corridor by around 7 pm and
exiting the forecast area toward midnight. While an isolated severe
storm can`t be ruled out, both the GFS and NAM are indicating very
weak bulk shear values where the higher CAPE`s are progged, although
the GFS has the higher CAPE`s more along the front near the edge of
where the shear increases. By evening, the instability quickly
wanes, and any thunderstorms will mainly be east of I-55 and during
the early evening. A few storms may linger past midnight east of I-
57, though.

Welcome shot of more fall-like weather is on tap early next week, as
upper low currently over southwest Wyoming lifts northeast and
reforms near the Minnesota/Ontario border. As the low drifts north
of the Great Lakes, it will draw down a slug of cooler air into the
Midwest, with 850 mb temperatures as low as 3C over central Illinois
by late Monday evening. Temperatures Monday night and Tuesday night
likely to dip into the upper 40s, with daytime highs Monday-Tuesday
in the upper 60s to lower 70s. The strength of the low will also
result in fairly windy conditions on Monday, with Bufkit guidance
indicating some potential for 25-30 mph gusts across the northern
CWA.

The upper low will be a bit slow to depart, with the latest ECMWF
gradually sinking it into the eastern Tennessee Valley late in the
week. That solution would result in a more extended period of cooler
conditions most of the week. This is a fairly substantial change
from the previous run, which was much closer to the evening GFS
solution that builds modest ridging eastward late in the week.
Thus, will follow more of a blend of the current GFS and yesterday
morning`s ECMWF, indicating a gradual warming trend toward the
upper 70s late next week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 646 AM CDT Sat Sep 24 2016

IFR cig/vis category or worse is present at all sites this
morning. Fog and low stratus present but should begin to dissipate
in next couple of hours at most sites. Timing of this
clearing/dissipation is based on model consensus for this
morning. CU will also develop later this morning but then
dissipate early this evening after loss of heating. Various models
and satellite simulations indicate that fog will occur again at
all sites. Unsure as to exact timing and how low it will get, so
will just show trend of reducing vis into MVFR category around
midnight. Winds through the period will be mainly east to
southeast.

&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

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



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