Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 191935
AFDILX

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

.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 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 1234 PM CDT SUN OCT 19 2014

MVFR ceilings persist at the central Illinois terminals early this
afternoon as low-level moisture remains trapped below a strong
subsidence inversion. Moisture has been very slowly shifting
eastward over the past couple of hours, and latest HRRR continues
this trend through the afternoon. Based on satellite timing tools,
will scatter the ceilings at KSPI by 19z, then further east to KCMI
by around 21z. Once low clouds clear out, quite a bit of high
cirrus clouds will stream across the area this afternoon/evening
in advance of a trough axis currently extending from Minnesota to
Nebraska. Latest satellite and regional obs indicate only mid/high
clouds associated with this boundary: however, as it drops
southeastward later tonight into Monday morning, most models are
showing a marked increase in 1000-850mb RH. Soundings remain
rather dry, so am expecting little more than a few sprinkles early
Monday morning. However, have included low VFR ceilings at all
sites except KPIA and KSPI as the boundary passes. After that,
winds will veer to the W/NW and skies will clear toward midday.


&&

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

$$

SHORT TERM...Barnes
LONG TERM...Auten
AVIATION...Barnes






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