Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 010137

Area Forecast Discussion
National Weather Service Lincoln IL
837 PM CDT Thu Jul 31 2014

ISSUED 837 PM CDT Thu Jul 31 2014

Most of the diurnal cumulus has faded off, leaving behind a smoky
but mostly clear sky. Have recently had some isolated showers
forming along I-70, near a weak boundary that was evident on the 7
pm observation plot. Not expecting these to stay around too long,
but have added some 20% PoP`s in that area for the rest of the
evening. Larger area of rain in central Iowa on radar mosaics and
moving southeast, but this is likely mid-level clouds as
observations in that area mainly have ceilings of 10,000 feet or
higher. Have also maintained the slight chance PoP`s across the
northwest half of the CWA after midnight, as high-resolution
models continue to show some splotchy precipitation with the upper
trough still overhead.

Made some adjustments to the sky cover to reflect a period of
mostly clear skies this evening, before increasing again after
midnight. Temperatures largely on track and required little
change. Updated grids have been sent, and will update the worded
forecasts shortly.



ISSUED 631 PM CDT Thu Jul 31 2014

Thick smoke layer visible high up, but otherwise diurnal cumulus
is fading. Am watching an area of cloudiness tracking southeast
from central and western Iowa, which will start moving into
central Illinois after about 07-08Z, but these should be at or
above 4000 feet. Some of the high-res models hinting at some
showers accompanying it, but have left it out for now as upstream
surface obs not showing anything for the most part. May see some
MVFR light fog late in the night, fading after sunrise. Have added
VCTS at all sites for the afternoon, as instability increases
ahead of an upper wave moving into the area.



ISSUED 238 PM CDT Thu Jul 31 2014

Low pressure will remain stalled in eastern Canada through the end
of the week...keeping scattered showers and isolated storms in the
forecast through Saturday. A dry period is indicated for Sun and
Monday before a frontal boundary moves south into IL and
stalls out across the area. Rain chances will gradually expand
southward beginning Tuesday and extending through Thursday night.

SHORT TERM...Tonight through Saturday night.

Diurnally driven showers are still possible the rest of the
afternoon. Towering cumulus at 2 pm have been developing in small
areas across central and southeast IL. Showers do not appear
imminent in most of our forecast area, but we will keep a 20 pct
chance in our NE areas through 6-7pm. Diurnal stabilization should
bring any of our showers to an end by that time, with clearing
developing by mid-evening. Weak high pressure over C IL will keep
winds light, and radiational cooling will help lows dip into the
upper 50s to around 60 again tonight.

Friday will bring an eastward shift of the upper low in eastern
Canada, but an increased chance of showers for our forecast area
due to a shortwave diving into the back side of the low across
IL. We kept the chance PoPs Friday afternoon across all but SW
of Springfield to Effingham. A few showers could develop already
in the morning, but forecast soundings show the better instability
will hold off until afternoon. SPC discussions indicate that a few
of the storms north of Peoria to Bloomington could contain some
hail, but most of the area should just see rain.

A few showers could linger into Friday evening before dissipating
with diurnal subsidence. Saturday will see additional isolated
shower chances due to another shortwave and a pocket of cold air
in the upper trough axis passing across IL. Instability will be
slightly less than Friday, but a few rumbles of thunder will still
be possible.

Additional cloud cover Friday and Saturday may keep highs a
little cooler in some locations, but areas with more sun could
still climb just over the 80 degree mark for highs. Lows will
continue to drop back into the upper 50s to around 60s into early

LONG TERM...Sunday through Thursday.

Drier conditions are forecast for Sunday and Monday as upper level
ridging diminishes afternoon instability and a warming trend
develops. Highs should be firmly in the lower 80s Sunday with mid
80s more common on Monday. A frontal boundary will approach
central IL from the north on Tuesday and Tuesday night. That will
bring an increase in rain chances north of Peoria, with slight
chance PoPs extending as far south as Lincoln to Champaign. Precip
chances will expand southward on Wednesday as the front pushes
south into central IL. Rain chances will remain primarily north of
a the front from Rushville to Lincoln to Bloomington. A wave of
surface low pressure is forecast to move east along the front Wed
night and Thursday, passing across Illinois. That will increase
rain chances across all of our area during that time.

High temps will climb into the upper 80s south of I-72 Tues
through Thursday, south of the front. North of the front on Wed
and Thur, highs may remain a little cooler in the low 80s.




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