Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 291449
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
949 AM CDT THU SEP 29 2016

.UPDATE...
Issued at 949 AM CDT Thu Sep 29 2016

Upper low currently centered near Louisville KY and will continue
to drift southward through the afternoon. Bands of showers
continue to rotate southwestward into the CWA around this low,
with earlier showers mainly along I-55 and the next band to target
areas between I-55 and I-57. Some sharper mid-level lapse rates
may contribute to a few thunderstorms at times, but mostly general
rain showers will be the rule. Areas near and west of the Illinois
River will remain dry most of the time.

Recent updates were mainly to reflect PoP trends, increasing them
in some areas. Temperatures are largely on track.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 300 AM CDT Thu Sep 29 2016

07z/2am water vapor imagery shows center of unseasonably deep upper
low over southern Indiana, with primary mid-level moisture plume
wrapping around the system from the Carolinas N/NW into southern
Michigan.  As this slug of moisture continues to pivot around the
low, it is expected to spill into east-central Illinois today.
Latest radar imagery is showing numerous showers across northern
Indiana into northeast Illinois, and these should continue to spread
southwestward across the eastern half of the KILX CWA this morning.
Based on latest radar trends and HRRR forecast, have gone with
scattered showers everywhere east of the Illinois River today.  Due
to the cloud cover and showers, temperatures will once again be held
below normal for this time of year, with readings mainly in the
middle to upper 60s.  Showery conditions will continue tonight as
another vorticity max rotates around the parent upper low.  Models
suggest showers will become more numerous after midnight,
particularly across the E/NE CWA.  Overnight lows will be in the
middle 50s.

.LONG TERM...(Friday through Wednesday)
ISSUED AT 300 AM CDT Thu Sep 29 2016

As has been advertised by the last few model runs, the upper low is
expected to drop southward into Kentucky today, then begin lifting
back northward on Friday.  With the system expected to reach eastern
Illinois by late in the day, Friday appears to be the wettest day of
the forecast period with numerous showers across nearly the entire
CWA.  Thanks to steepening lapse rates beneath the cold core aloft,
GFS MUCAPE values are forecast to reach the 800-1000J/kg range
across the eastern half of Illinois Friday afternoon.  Have
therefore gone with likely PoPs for showers and isolated thunder
everywhere east of the Illinois River at that time.  Scattered
showers will continue Friday night into Saturday as the low makes
only slow progress northward: however, 00z Sep 29 models agree that
the system will finally get shunted further northeast into the Great
Lakes by Sunday as a pronounced upper trough digs across the
western CONUS.

With the upper low departing and heights climbing substantially,
warming conditions are anticipated early next week.  Temperatures
will reach the lower to middle 70s by Sunday, then will peak in the
upper 70s to lower 80s by Monday and Tuesday.  As the western trough
approaches, it will eventually push a cold front into Illinois later
next week: however, the timing of the front is still in question due
to the evolution of Tropical Storm Matthew.  GFS/ECMWF differ on the
speed of Matthew, with the ECMWF being considerably slower and
nearly stalling the system over the southern Bahamas late next week.
Trending toward the faster GFS, Matthew should track from Cuba N/NE
off the coast of North Carolina by Wed/Thu.  This will tend to slow
the eastward progress of the approaching trough/surface front...and
delay rain chances in central Illinois.  As a result, have gone with
dry condtions through Wednesday, with showers holding off until
Thursday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 651 AM CDT Thu Sep 29 2016

Lower clouds and scattered showers continue to rotate around the
upper level system sitting over IN. Unfortunately do not see this
flow pattern changing very much, so scattered shower will continue
to impact flyers outside. Some cig heights are VFR, while other
sites are already below that level. Believe all sites will be MVFR
or less during the day. Winds will be northerly with gusts already
occurring. Gusts will increase more during the afternoon, and I do
believe I saw of picture of one earlier today.


&&

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

$$

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


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