Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 251138

Area Forecast Discussion
638 AM CDT Sat Oct 25 2014

.SHORT TERM...(Today)

Main concern in the short term will be the dense fog again early
this morning, mainly in the northwestern parts of the CWA. Unlike
last night, the dense fog has not developed yet in the CWA and is
still located along and west of the Mississippi River. However, HRRR
model still forecast dense fog to move into the area. So will
continue the dense fog advisory as is, and will not extend in time or
area. Fog will be in areas east of the Illinois river, but not
dense. After the fog dissipates this morning, mostly clear skies
will be the rule for the area. Should be lots of sunshine to allow
temps to rise into the lower to middle 70s by this afternoon, which
is well above normal for the later part of October. Northwest winds
will only bring in a drier airmass for the day and beyond.


.LONG TERM...(Tonight through Friday)

1020 mb high pressure over over the northern High Plains, near the
eastern MT and western Dakotas border, to settle into IL by
sunrise Sunday and weaken a bit to 1018 mb, then drift into
eastern KY by sunset Sunday. This will continue fair weather
through Sunday night. 850 mb temps cool to 12-14C tonight into
Sunday morning before rising back up to 14-16C by sunset Sunday.
Lows mostly in the middle 40s tonight (fog limited overnight
tonight over central IL with drier air advecting in). Highs
Sunday mostly 70-75F, except upper 60s to near 70F from I-74

Strong low pressure of 1000 mb to eject ne from western KS Sunday
evening into Lake MI Monday night and bring a cold front east across
IL overnight Monday night and across the Wabash river valley in
eastern IL Tue morning. Breezy ssw winds Monday ahead of this storm
system to bring in warm air with highs approaching 80F. Have a
slight chance of showers and thunderstorms late Monday afternoon
far NW CWA by Galesburg. Best chances of showers and isolated
thunderstorms spread east across IL during Monday night (mainly
after midnight Monday night in eastern IL) and Tue morning, then
diminish Tue afternoon from the west. Highs Tue range from lower 60s
from I-55 nw to upper 60s to around 70F from I-70 se. Temperatures
steady or slowly falling Tue afternoon behind the cold front. Slight
chance of showers early Tue evening near the Wabash river, otherwise
dry weather returns Tue night through Wed night as another high
pressure system settles over IL by Wed afternoon. Near normal highs
Wed/Thu in the upper 50s/lower 60s.

A weak northern stream short wave to dive se into upper level trof
over the eastern states and bring another cold front into IL by Thu
afternoon/evening. Have just slight chance of showers Thu due to
limited moisture. ECMWF model shows strong cutoff upper level low
near IL on Halloween along with showers, but other models like GFS
are drier. Models due agree that even colder air arrives on
Halloween with highs in the lower 50s central IL and mid 50s se of
I-70, while low temperatures near freezing next Friday night over
central IL and mid 30s in southeast IL.


.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)

Difficult part of the forecast will be dense fog and lower IFR
clouds this morning and what time it will dissipate. HRRR keeps
the lower vis along the IL river and to the northwest. So, PIA
will be the only site effected by dense fog. However, other sites
will also have some light fog during the first 2-3hrs of the
morning. IFR and MVFR clouds are also advecting into the area from
the northwest and will effect the other sites early this morning,
before the sunshine burns them off. HRRR is keeps lower clouds in
the area til later this morning. Not sure if I agree with this
forecast, so have skies scattering out and then clearing at all
sites between 15 and 17z. Then clear skies will prevail for
remainder of TAF period, as high pressure builds into the area
with lower dewpoints and northwest winds at 5-10kts.


DENSE FOG ADVISORY until 9 AM CDT this morning FOR ILZ027>029-



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