Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 200207
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
907 PM CDT Sun Oct 19 2014

.UPDATE...
ISSUED AT 900 PM CDT SUN OCT 19 2014

A band of mid and high clouds will progress to the ESE across IL
the rest of the evening and just after midnight. The clouds are
associated with a weak shortwave in the 500mb flow. Moisture will
be scarce, so precip will be limited, and mainly confined to areas
southeast of a line from Taylorville to Paris after 08z/2am
tonight. A stronger shortwave arriving with the upper trough axis
tomorrow will help keep slight precip chances in roughly that
same area through 18z/1pm tomorrow. Sprinkles and light showers
will be the main result, with no thunder expected.

As for temps tonight, a continuation of the SW surface winds will
provide slightly warmer conditions, with lows in the upper 40s to
low 50s in most areas. The warm surge will continue through the
morning tomorrow, helping push high temps into the mid to upper
60s, before the cold front passes and winds shift to the WNW and
cooling begins.

Only minor adjustments were needed to the sky and hourly temp
forecasts, so no formal product updates will be needed this eve.

&&

.SHORT TERM...(Tonight)
ISSUED AT 234 PM CDT SUN OCT 19 2014

12z KILX upper air sounding showed a very strong subsidence
inversion around 900mb, with a layer of surface-based moisture
trapped beneath it.  Due to a lack of adequate mixing with the much
drier airmass aloft, low clouds have persisted/developed across the
area today.  18z/1pm visible satellite imagery showed these clouds
along/east of the I-55 corridor.  Surface high pressure has shifted
into the Ohio River Valley, so S/SW winds on its back side are
finally beginning to push the clouds off to the east.  Am expecting
the clouds to gradually dissipate/shift eastward over the next
couple of hours, with mostly clear skies across the board by late
afternoon/early evening.

Next upper short-wave to impact the weather across central Illinois
is evident on water vapor imagery over Manitoba.  As this feature
drops southeastward, it will push a weak frontal boundary into the
region late tonight into early Monday morning.  Forecast soundings
remain quite dry ahead of the front and 12z models have therefore
backed way off on precip development.  Lead short-wave will bring
increasing high clouds to central Illinois this evening, then main
wave may bring lower/thicker clouds into the picture overnight.
Given dry soundings and best lift associated with Manitoba wave
skirting by to the N/NE, will only carry slight chance PoPs across
the southeast CWA after midnight.  May see a few sprinkles further
north, but measurable precip is not expected.

&&

.LONG TERM...(Monday through Sunday)
ISSUED AT 234 PM CDT SUN OCT 19 2014

After the short wave and weak frontal boundary, a mid level ridge
and surface high pressure will build into the region with dry
conditions. This will continue into Thur as the CWA remains in a
somewhat anti-cyclonic flow. Models then begin to bring another wave
toward the region Thursday. Models differ on what happens to this
wave as the ridge gets pinched off between the approaching wave and
the large low sitting over the northeastern US. The GFS takes the
energy north while the ECMWF takes it to the north and south. Either
way, central IL will remain dry through the rest of the week. Then
pushing into the weekend, ridging returns with dry weather.

Warmest temps will be tomorrow ahead of the short wave. Then behind
it, slightly cooler temps are expected. Temps will remain below
normal through the rest of the week, and then warm for the weekend.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 659 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. This
evening, a band of AC and Cirrus will advance across the terminals,
with the lowest clouds around 9K FT. Cloud heights will approach
MVFR later tonight and early tomorrow morning ahead of the trough,
but the lowest cloud heights in that time frame should be around
3500 FT. Forecast soundings show moisture in the 3.5-5K ft level
will linger into the afternoon, so periodic lower clouds will be
possible.

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.
&&

$$

UPDATE...Shimon
SHORT TERM...Barnes
LONG TERM...Auten
AVIATION...Shimon





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