Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 140140
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
840 PM CDT Sat Sep 13 2014

.UPDATE...
ISSUED AT 840 PM CDT SAT SEP 13 2014

Surface high pressure crossing central Illinois tonight will
result in very light winds and clear skies. 00Z sounding shows
pronounced subsidence inversion based just below 850 mb which will
keep skies clear with very little water vapor content allowing for
strong radiational cooling. Lingering low level moisture combined
with rapid temperature drops will cause fog formation overnight.
Forecast sounding profiles indicate the fog should generally be
shallow and patchy, although this could allow for it to be locally
dense. Have continued patchy fog in forecast from 3-8 a.m. north
of I-70 with only minor updates to grids/forecasts. Low
temperatures tonight in the upper 30s/low 40s across central
Illinois look good and no changes made there. Any fog should clear
rapidly in the morning resulting scattered cloud cover gradually
clearing.

&&

.SHORT TERM...(Tonight)
ISSUED AT 220 PM CDT SAT SEP 13 2014

By mid-afternoon, MSAS surface analysis shows high center over
extreme southeast IA/northeast MO. Models continue to drift the
center slowly east tonight over forecast area. As a result, clear
skies and very light winds will allow temperatures to fall
overnight. Dropped current low temp grids a degree or two. Surface
dew points will change little with low level moisture trapped below
inversion. Though moisture is shallow, still should be enough for
patchy fog development over many sections of region so added that to
grids for few hours around sunrise on Sunday.

&&

.LONG TERM...(Sunday through Saturday)
ISSUED AT 220 PM CDT SAT SEP 13 2014

Surface high pressure will begin to slide east of IL on Sunday,
allowing a southerly flow to develop across IL. Coupling that with
another day of full sun should help provide a brief warm-up, as
highs climb into the upper 60s. Lows Sunday night will likely be
8-10F warmer than tonight as well.

An upper level disturbance will eject from the central Plains across
Nebraska Sun night, reaching Illinois on Monday. Showers will become
likely W of I-55 in the morning, with rain expanding toward the I-72
corridor in the afternoon. The progressive nature of the system
should allow the rain to come to an end by Monday evening west of
I-55, and by midnight in the remainder of eastern IL. High temps
will struggle to climb into the 60s on Monday with the cloud cover
and rain, so went below guidance numbers at least NW of I-72.

Starting on Tuesday, the upper trough over the eastern CONUS will
gradually shift eastward as an upper level ridge builds toward
Illinois. So after another chilly night Monday night with low 40s in
the north, we expect moderating temperatures the remainder of the
week. Northwest flow aloft during that time could send a few weak
shortwaves across IL, but dry high pressure entrenched across the
Great Lakes and extending over toward southern IL should keep our
rain chances at a minimum. The next chance of rain looks to hold off
until later next weekend. The warming trend will help our high temps
reach the mid 70s on Friday and upper 70s on Saturday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
ISSUED AT 611 PM CDT SAT SEP 13 2014

Surface high pressure crossing central Illinois tonight will
result in very light winds and clear skies. Low level moisture
combined with clear skies allowing rapid temperatures drops will
cause fog formation overnight. Forecast sounding profiles indicate
the fog should generally be shallow and patchy, although this
could allow for it to be locally dense. 00Z TAFs include tempo
group for 2 mile visibility in fog, but potential adjustments will
need to be made later based on late evening trends. Potential for
local LIFR/VLIFR vis exists for early morning Sunday. Any fog
should clear rapidly in the morning resulting in a scattered
lifting cumulus deck.


&&

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

$$

UPDATE...ONTON
SHORT TERM...GOETSCH
LONG TERM...SHIMON
AVIATION...ONTON






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