Area Forecast Discussion
Issued by NWS Central Illinois

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855
FXUS63 KILX 190154
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
854 PM CDT Wed Oct 18 2017

.UPDATE...
Issued at 846 PM CDT Wed Oct 18 2017

Quiet weather scene over the region tonight should continue
through the day on Thursday. A weak frontal boundary to our
northwest is not expected to make it through our area with
only a slight wind shift into the southwest or west across
the northern third of the forecast area tomorrow. Some patchy
cirrus associated with the weak boundary but that is about
it. Light southerly winds tonight should stay up enough to
keep temperatures a bit warmer than what we saw in a few
locations early this morning. Current forecast in the mid
40s to around 50 still looks good, although a few adjustments
were made in our far east and southeast counties with our more
favored cold spots like Robinson and Paris already down into the
upper 40s to lower 50s at this hour. Another great day shaping up
for Thursday with sunshine and afternoon temps a few degrees
warmer than today. The updated zones should be out by 9 pm.

&&

.SHORT TERM...(This evening through Thursday)
ISSUED AT 237 PM CDT Wed Oct 18 2017

Quiet weather will persist across central and southeast Illinois
through the short term period. The air mass will remain very dry,
and persistent southerly flow will help cause gradual warming. A
modified persistence forecast is likely to do well, with
temperatures moderating slightly like they have the past couple of
days.

.LONG TERM...(Thursday night through Wednesday)
ISSUED AT 237 PM CDT Wed Oct 18 2017

The quiet and increasingly warm pattern will continue into the
weekend. The upper-level flow is forecast to amplify significantly
over the lower 48 states from the nearly zonal flow that exists
now. The rising heights and persistent southerly low-level flow
may have daytime highs approaching 80 by Friday & Saturday.

A major trof will push a cold front through the forecast area by
late in the weekend, accompanied by showers and thunderstorms.
There are still differences in model timing with the front, but
the consensus has the boundary and best precipitation chances
coming through Saturday night into early Sunday. There does not
appear to be a significant severe storm risk with FROPA at this
time, largely due to the unfavorable time of day of its expected
passage and associated low instability.

The forecast beyond the frontal passage is more problematic. While
the current operational GFS & ECMWF models are progressive with
the upper trof driving the front, the last couple runs of the
Canadian model develop a significant upper low over the southern
Plains. This low is currently progged to slow the progress of the
front, and also lift into the Midwest for the first part of the
week. A lingering front and/or upper low would keep a rain risk
going into at least midweek. While the Canadian solution is not
favored at this time, a similar solution is evident in some GFS
ensemble members and has been seen in prior solutions of other
models. This uncertainty is resulting in an extended period of low
PoPs to start next week. In any event, it will be notably cooler
behind the front next week. Several days of below normal
temperatures appear likely.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 610 PM CDT Wed Oct 18 2017

VFR conditions are expected through this forecast period. Forecast
soundings and model time height cross sections continue to show a
shallow layer from 1200-1500 feet AGL where wind speeds will range
from 30-35 kts through the evening hours. Still below LLWS criteria
but a bit higher than what was seen earlier in the model data so
will need to keep an eye on that, especially for PIA and BMI in
the 00z-06z time frame. Otherwise, a mostly clear sky can be
expected into Thursday. Surface winds will be southerly tonight at
10 kts or less, then light southwesterly flow is expected on
Thursday with speeds again of less than 10 kts.


&&

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

$$

UPDATE...Smith
SHORT TERM...Bak
LONG TERM...Bak
AVIATION...Smith



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