Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 210406

Area Forecast Discussion
National Weather Service Lincoln IL
1106 PM CDT Sun Jul 20 2014

ISSUED 830 PM CDT Sun Jul 20 2014

Our quiet weather is expected to continue over the next 36 hours
as high pressure off to our east will be slow to move away. The
southerly winds associated with the departing high will increase
over the next day or so allowing warmer temperatures to filter
into our area along with increasing humidity levels. Already seeing
dew points about 3 to 5 degrees higher than what was observed at
this time yesterday with most areas in the low to mid 60s early
this evening. This will allow for warmer overnight lows and bring
the threat for at least some patchy fog again, especially across the
east by dawn Monday. Latest surface analysis showing the real surge
of 70 to 75 degree dew points still well west of our area this
evening with that type of oppressive humidity pushing into the
region just ahead of a cold front late Tuesday. Forecast in good
shape this evening, so no ZFP update will be needed.



ISSUED 1105 PM CDT Sun Jul 20 2014

A brief period of MVFR vsbys will be possible late tonight,
especially along and east of I-55 in the 09z-13z time frame,
otherwise VFR conditions are expected for the remainder of this
forecast period (06z Tue). Little change from previous forecast
issuance, we still see the possibility for some ground fog
formation early Monday morning and whatever does develop should
be gone by 13z. Cumulus clouds will form again between 15z and
16z with bases in the 3500-4500 foot range before dissipating
by 00z. Surface winds will be light southeasterly tonight and
then become south at around 10 kts on Monday.


ISSUED 327 PM CDT Sun Jul 20 2014

SHORT TERM...Tonight through Wednesday

Scattered cumulus covers much of Illinois again this afternoon,
generally based around 4000 to 6000 feet. 24 hour change in
temperatures and dewpoint generally up a few degrees since
yesterday as expected with a warm high pressure ridge building
into the region. Overnight, some fog is possible again as clear
skies combine with increased low-level moisture. West of I-57
pressure gradients start to increase overnight indicating some
light wind which will likely prevent any substantial fog, however
from around I-57 east have placed patchy fog in the forecast
again from around midnight to 7 a.m.

Monday into Tuesday a strong 500 mb ridge will continue to develop
over the West and extend into the Midwest. This will bring a warm
and stable air mass over Illinois. Southerly low level flow will
bring an increase in moisture yielding dewpoints over 70 by Monday
and Tuesday and heat index values approaching 100 by Tuesday

An upper level trough will move over the top of the ridge and
southeastward through the Midwest Tuesday night, along with a
surface cold front. Most model solutions feature fairly similar
timing of a progressive system moving into northwest Illinois
Tuesday evening and exiting Illinois Wednesday afternoon. Have
only slightly increased probability of precipitation with this
feature to bring likely category (60% or greater) to most of the
central IL forecast area at some point as the feature moves
through. Not expecting a significant severe threat given the
arrival time at night, but don`t think the possibility can be
ruled out at this point given uncertainty with the timing and
CAPE/shear values expected to accompany the system. Some lingering
showers/storms will continue through Wednesday across the
southeast CWA, but areas I-72 north will likely be dry by
afternoon as high pressure begins to build from the north.

LONG TERM...Thursday through Sunday

Cooler conditions are expected Thursday and Friday as cool dry
northerly flow pushes into the region following the Tuesday night
shortwave. Past there, focus shifts to potential MCS activity
Friday night sliding down the upper ridge, which will be re-
establishing itself along and west of the Rockies. For Sunday, a
deep trough is progged by both the GFS and European models over
the Midwest, hence cooler than climatological temperatures and a
chance for precipitation are in the forecast.




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