Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 221754

Area Forecast Discussion
National Weather Service Lincoln IL
1254 PM CDT MON AUG 22 2016

Issued at 1047 AM CDT Mon Aug 22 2016

High pressure centered over the region will keep winds generally
light and somewhat variable...becoming more southerly as the day
progresses into this evening. Mostly sunny skies could end up
dotted with some afternoon cu around 4000-5000 ft. There is some
moisture at 850mb this morning on ILX sounding...but not much in
the way of cloud cover anticipated overall. Forecast is doing
well, and no updates are expected at this time.


.SHORT TERM...(Today and tonight)
ISSUED AT 256 AM CDT Mon Aug 22 2016

High pressure area centered over the CWA will slowly move east
through tonight. Dry weather, mostly sunny skies and light winds
will be the forecast for today through tonight, with winds becoming
south then southwest through the period. After a cool morning, temps
should rebound and reach to around 80 across most of the CWA with
lower 80s in the west. Temps tonight will decrease again with the
coolest temps, upper 50s, being in eastern IL, closer to the high
pressure area and lighter winds. Slight warmer temps, around 60 will
be seen in western IL.

.LONG TERM...(Tuesday through Sunday)
ISSUED AT 256 AM CDT Mon Aug 22 2016

Primary focus remains with the midweek storm system. Upper low
currently seen in water vapor imagery spinning over central British
Columbia is progged by the models to reach southern Manitoba by
midday Wednesday. As the primary wave tracks along the international
border, the mid-Mississippi Valley will be along the northern edge
of an upper high over the southeast U.S. With that particular
feature progged to remain anchored over that region into late week,
the frontal boundary with the northern system will slow down as it
starts to parallel the upper flow. The building MCS over Iowa
continues to favor the late Tuesday night period for arrival in our
area, with the ECMWF suggesting areas east of I-57 should remain
fairly dry overnight. However, have not changed PoP`s too much from
the previous forecast, and kept around a 30% chance over eastern
Illinois after midnight. With the front not expected to reach the
northwest CWA until early Thursday, high rain chances of 60-70%
still look good over most of the forecast area Wednesday and
Wednesday night, with around 40% chance PoP`s south of I-70 closer
to the southern high. Both the NAM and GFS indicate precipitable
waters near or over 2 inches arriving early Wednesday and sticking
around into evening, so heavier rain bands appear likely with the
stronger storms. While CAPE`s are progged by both models to reach
over 3000 J/kg on Wednesday, the bulk shear maximum doesn`t arrive
until later Wednesday evening, so the severe weather threat
continues to appear marginal.

Passage of the front on Thursday doesn`t break any speed records, so
rain chances continue into early evening across the southeast third
of the forecast area. Once this system finally exits, high pressure
will drift eastward across the Midwest through Saturday. The
strength of the southeast upper high will keep the cooler air mass
from penetrating too far south, so temperatures will not be as cool
as the current air mass. on Saturday, a significant wave will be
moving across the northern Plains and lifting into the upper
Mississippi Valley on Sunday. The GFS and ECMWF disagree in how much
of an influence the surface high remains into the weekend, with the
latter model holding tighter and keeping the rain threat off until
late Saturday night. Right now will keep rain chances low on
Saturday but bump them up a bit across areas west of I-55, mainly to
around 30%.

Temperature-wise, warmer and more humid air will advect into the
area Tuesday and especially on Wednesday, with heat index values on
Wednesday back into the low-mid 90s area-wide and lingering south of
I-70 into Thursday afternoon. A brief shot of less humid air will
accompany the surface high late week, before 70 degree dew points
return later on Saturday.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1251 PM CDT Mon Aug 22 2016

High pressure, light and variable winds becoming increasingly
southerly through the overnight. A few cu expected, and starting
to blossom on vis sat imagery this afternoon. ILX sounding had a
little moisture around 850mb, and TAFs reflect that. Going to more
SKC overnight with southerly winds. Patchy fog may be an issue,
but the vis looks pretty decent so far with the light winds.
Eastern areas may be a different story closer to the ridge axis
and will have to watch the afternoon trends. Until then,
maintaining VFR through the forecast period.


.ILX Watches/Warnings/Advisories...


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