Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 200729
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
229 AM CDT Mon Oct 20 2014

.SHORT TERM...(Today)
ISSUED AT 229 AM CDT MON OCT 20 2014

Latest surface analysis had low pressure centered over eastern Lake
Superior, with the trailing cold front extending southwest into the
central Plains. This low/front is being driven by a potent short
wave diving southeast across the upper Midwest/western Great Lakes.
However, despite the good forcing these features should provide, the
air mass the system is moving through is very dry. In fact, at the
moment, there is little/no cloud cover along the cold front once you
move away from the immediate vicinity of the surface low. There is
respectable WAA/isentropic lift over the southeast 1/3 of Illinois
ahead of the cold front, and this is resulting in a few sprinkles
breaking through from time to time from an AC deck around 10k feet.
This enhanced warm advection regime should shift south/east of the
forecast area by shortly after sunrise. So, do not expect measurable
rainfall ahead of the front today, although a few sprinkles will be
possible south of I-70 into the mid-morning hours.

The cold front should have cleared the forecast area by early
afternoon, with temperatures staying steady or slowly falling in its
wake. A strong low level inversion that is currently in place should
quickly erode in the post frontal cold advection. This may result in
a few hours of gusty northwest winds this afternoon.


&&

.LONG TERM...(Tonight through Sunday)
ISSUED AT 229 AM CDT MON OCT 20 2014

Once the current system passes, the remainder of the week looks to
be fairly quiet. The upper ridge currently along the east slopes of
the Rockies will shift eastward into the Mississippi Valley by mid
week, with dry weather prevailing. The main forecast issue involves
Thursday, as the ridge erodes between an incoming wave from the
northern Plains, and a large upper low that will slowly wobble
through the mid-Atlantic states. The general consensus over the last
few model runs was that the associated shower activity would have
difficulty crossing the Mississippi River into Illinois, but the
latest GFS and ECMWF do bring some diminishing showers across the
north half of the state Thursday afternoon/evening as an upper low
develops and slides into northern Wisconsin. Have kept the forecast
dry for now, but will monitor to see if this is a persistent trend
before introducing into the forecast.

A nice warming trend is on tap toward late week, as thermal ridging
extends east from the central Plains. 850 mb temperatures progged to
rise to around 16C by Saturday afternoon, which would bring surface
temperatures to around 70 degrees in many areas.


&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
ISSUED AT 1157 PM CDT SUN OCT 19 2014

VFR conditions are expected over the next 24 hours despite a
surface trough forecast to move across the area tomorrow. The rest
of the night, a band of AC and cirrus will continue to advance
ESE across the area. PIA should be north of the clouds for the
most part, while BMI/SPI will be on the northern periphery.
DEC/CMI will be closer to some possible sprinkles as the first of
two shortwaves enhances lift across our southeast area. There
remains some potential for cloud heights to approach MVFR for DEC
and CMI late tonight and early tomorrow morning ahead of the
second trough, but the lowest cloud heights in that time frame
should be around 3500-4000 FT. Forecast soundings show an increase
of moisture in the 3.5-5K ft level tomorrow afternoon, so periodic
lower clouds will be possible tomorrow afternoon and evening.

Winds will start out SW from 7-9KT, then become W-NW tomorrow
morning behind the surface trough while increasing to 10-12kt.


&&

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

$$

SHORT TERM...Bak
LONG TERM...Geelhart
AVIATION...Shimon





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