Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 181456
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
956 AM CDT Sat Mar 18 2017

.UPDATE...
Issued at 956 AM CDT Sat Mar 18 2017

Forecast was recently updated mainly for the latest cloud trends.
Large expanse of stratocumulus has covered pretty much all of the
forecast area now, but we remain on the fringes. 925 mb humidity
plots off the RAP suggest this should be about as far as it makes
it westward, with some slow clearing edging east early this
afternoon. Temperatures will be highly dependent on this, as an
earlier clearing trend would bring highs up several degrees
similar to yesterday. This would mainly be a risk across the
western CWA, as it appears the east should stay fairly cloudy into
early evening.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 335 AM CDT Sat Mar 18 2017

Cold front has pushed through the CWA overnight and this is allowing
cooler air to advect into the area, along with gusty winds out of
the northwest. Based on HiRes models, the gusty winds will continue
in the morning and then begin to wane during the afternoon hours as
the high pressure ridge gets closer to the area...loosening the
gradient. The high pressure area will continue to build into the
area tonight with lighter and more variable winds. This will allow
temps to cool and should drop to below freezing across the whole
area. Temps in the southeast do get down to 30-32 F, but this is
borderline enough, and not a hard freeze. So believe freeze warning
not warranted at this time. Highs today will be cooler than
yesterday ranging from the mid 40s in the east to the lower 50s in
the southwest.

.LONG TERM...(Sunday through Friday)
ISSUED AT 335 AM CDT Sat Mar 18 2017

Upper level ridge over the Rockies will shift east into IL on Sunday
as surface high pressure ridge over the Dakotas shifts east into the
Ohio river valley on Sunday. This will provide a nice day to central
and southeast IL, with mostly sunny skies and fairly light SSE winds
of 5-10 mph with highs in the mid to upper 50s.

Increasing warm air advection and low level jet will set up over
IA/MO and western IL later Sunday evening and develop showers and a
chance of thunderstorms, that shifts east into central and eastern
IL during overnight Sunday night. SPC day2 outlook shows marginal
risk of severe thunderstorms along and west of I-55 overnight Sunday
night, for marginal severe hail.  A cold front pushes southward into
the IL river valley late Sunday night/early Mon morning, south of I-
72 by 18Z/1 pm Mon and south of I-70 by sunset Mon. This will likely
keep a chance of showers going along with thunderstorms south of a
Rushville to Bloomington line per SPC day3 outlook. Milder highs
Monday in the low to mid 60s, with upper 60s in sw CWA as Winchester
and Flora in far SW CWA will be approaching 70F.

00Z forecast models shift frontal boundary south of the Ohio river
overnight Monday night while keeping chances of showers and isolated
thunderstorms around in southeast IL Monday night. A disturbance
moving out of the central plains and into the mid MS river valley
Tue afternoon/evening returns chances of showers to mainly southern
half of CWA. Cooler highs in the low to mid 50s on Tuesday.

1038 mb high pressure settles southeast into the Great Lakes region
on Wed evening and into the mid Atlantic states on Thu. This will
provide dry weather to central IL from overnight Tue night through
Wed evening. Highs Wed of 45-50F. Warm air advection begins again
overnight Wed night into Thu and spreads light precipitation back ne
into central Il, with a mix of precipitation Wed night and early Thu
morning (lows in the lower 30s) before changing to all rain by
mid/late Thu morning. Highs Thu of 50-55F.

Stronger storm system ejects ne from the TX/OK panhandle friday
morning into the sw Great Lakes Sat morning. This will likely spread
a better chance of showers and thunderstorms ne over central IL Fri
and especially Fri night, then continued likely chances of showers
on Sat. Milder highs Fri in the 60s, then cools into the 50s on Sat
with southeast IL near 60F.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 629 AM CDT Sat Mar 18 2017

Clouds are currently VFR at all TAF sites this morning, but
expecting cigs to drop to MVFR in an hour or so as lower clouds
slowly advect into the area from the northwest. Observation trends
to the northwest support this forecast as well. Only site
remaining VFR would be SPI, but have included TEMPO group for few
hours as HiRes models show some MVFR clouds getting to SPI for an
hour or two...but remaining VFR through the period. Remainder of
the sites will eventually rise into the VFR category during the
afternoon and then continue into the late afternoon/early evening
hours. HiRes models support clearing taking place from west to
east through the evening and see no reason this will not occur,
given the high pressure ridge forecast to build into the area.
Gusty northwest winds expected today at all sites with tight
gradient, but then decrease in speed this evening. As high
pressure builds in, winds will become light and variable over most
sites, but north at BMI and northwest at CMI.


&&

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

$$

UPDATE...Geelhart
SHORT TERM...Auten
LONG TERM...07
AVIATION...Auten



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