Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 301725

Area Forecast Discussion
National Weather Service Lincoln IL
1225 PM CDT FRI SEP 30 2016

Issued at 1002 AM CDT Fri Sep 30 2016

Upper low continues to spin near Louisville this morning, with
periodic showers pushing westward into Illinois. No real change
expected in this pattern expected through this evening, before the
low finally starts to move northward after midnight. Main updates
to the forecast generally involved massaging the PoP trends into
Saturday, with little change needed to temperatures.


.SHORT TERM...(Today and tonight)
ISSUED AT 308 AM CDT Fri Sep 30 2016

07z/2am water vapor imagery shows center of persistent upper low
centered over central Kentucky.  Scattered showers continue to pivot
around the low, with the most concentrated area of rain immediately
to the north of the center over southern Indiana/far northern
Kentucky.  Based on recent radar loops, have opted to go with likely
PoPs along/south of a Paris to Effingham line early this
morning...with rain chances steadily decreasing further west toward
the Illinois River Valley.  As the day progresses, additional
showers will develop further west, resulting in increasing PoPs
across the remainder of the KILX CWA.  With upper low slowly lifting
back northward and lapse rates steepening, MUCAPE values are progged
to reach the 600-1000J/kg range across the east later today.  As
a result, have mentioned isolated thunder along/east of I-55 this
afternoon.  Given extensive cloud cover and scattered showers,
high temperatures will once again remain in the middle to upper
60s.  Showery weather will continue tonight, although areal
coverage will decrease due to loss of daytime instability.  Will
carry chance PoPs everywhere, with lows dropping into the middle

.LONG TERM...(Saturday through Thursday)
ISSUED AT 308 AM CDT Fri Sep 30 2016

Upper low will continue to lift northward into northern Indiana by
Saturday evening.  With this feature still in the vicinity, am
expecting scattered showers and cool conditions to persist through
Saturday.  After that, all model solutions track the low into the
Great Lakes by Sunday, resulting in rising heights across the
Midwest and a return to warmer/drier conditions for early next week.
With increasing amounts of sunshine, high temperatures will reach
the lower 70s on Sunday, then the middle 70s by Monday.

The next big weather question will revolve around how quickly a
western CONUS trough can translate eastward next week.  The speed of
this system will likely be impacted by Hurricane Matthew as it
tracks northward off the North Carolina coast by the middle of next
week.  Given the expected track/intensity of Matthew, think a slower
eastward progression of the trough is prudent.  As a result, have
maintained dry conditions through Tuesday night, with only low
chance PoPs arriving across the western CWA by Wednesday.  Wednesday
night into Thursday appears to be the primary time frame for precip
chances as the trough and its associated cold front gradually make
their way eastward into Illinois.  Before the precip arrives
however, a couple of very warm days with temperatures well into the
70s and perhaps to around 80 degrees will be on tap for Tuesday and


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1224 PM CDT Fri Sep 30 2016

Windows for VFR conditions are small and limited to only this
afternoon, as a fairly widespread area of ceilings 2000 feet or
less cover most of Illinois. While some modest increase in
ceilings is possible this afternoon, they should begin tanking
again this evening and widespread IFR/LIFR conditions are likely
by 06Z. Showers continue to be widely scattered and this trend
will continue tonight, making it tough to go more any more
specific than VCSH most of the time. Have added a VCTS mention for
KCMI this afternoon, as some lines of storms track west out of
central Indiana. By late in the period, MVFR conditions should
start to prevail, as the pesky upper low finally starts to lift
out of the region.


.ILX Watches/Warnings/Advisories...


LONG TERM...Barnes
AVIATION...Geelhart is the U.S. government's official web portal to all federal, state and local government web resources and services.