Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 221754
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1254 PM CDT Sat Apr 22 2017

.UPDATE...
Issued at 1055 AM CDT Sat Apr 22 2017

Satellite imagery showing an extensive swath of clouds from the
Southern Plains up into the Northeastern US behind the cold front.
Same clouds are keeping the southern tier of Illinois in cloud
cover and some showers along and south of I-70. Cooler highs are
also expected to the south while the northern half of the state
sees some more sunshine. Only a few degrees difference expected,
however, as northeasterly winds keep the diurnal swings moderate.
Minor updates to the forecast are all that are expected at this
time.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 255 AM CDT Sat Apr 22 2017

Main issue in the short term is with the PoP`s. Our Friday evening
balloon sounding showed a very large dry area below 15,000 feet,
which the NAM and GFS keep in place over the central and northern
parts of the CWA through the day. Batch of rain tracking through
southern Illinois about to enter the parts of our CWA south of
I-70, but areas north of there have very high ceilings, far above
normal rain-making range. The dry northeast flow will persist
through the day, and the high-res models keep a fairly sharp
northern edge of the rain along and south of I-70. Have made some
adjustments to the PoP`s and went dry north of a Jacksonville to
Paris line for today, while maintaining the likely PoP`s south of
I-70. That area will see temperatures confined to the lower 50s
for highs, while areas further northwest near Peoria and Galesburg
reach near 60 degrees due to some periodic sunshine.

The rain will pull away from the forecast area early this evening,
as an upper low currently near Kansas City swings into the
Missouri bootheel overnight. Clearing trend will work its way
southeast across the forecast area, allowing most areas to dip
into the upper 30s (lower 40s south of I-70 where clouds hold on
longer).

.LONG TERM...(Sunday through Friday)
ISSUED AT 255 AM CDT Sat Apr 22 2017

The upper low will only slowly drift through the southeast U.S.
the next couple days, as a zonal flow starts to set up to its
north. This will result in significantly warmer weather to start
the new week, with upper 60s Sunday and low-mid 70s Monday.

Main concern for this period will be with the rain chances. Mid-
week storm system a bit more straight-forward, with both the GFS
and ECMWF showing a frontal passage around midday or early
afternoon Wednesday. Most rain chances moving in after midnight
and should be out of the forecast area by late afternoon or early
evening. However, the longer range models are divergent with the
disposition of this system, which impacts the depth of the upper
trough digging across the southwest U.S. early Thursday. The ECMWF
is the slower model and focuses a much further south track of the
surface system, from about St. Louis northeast into northern
Indiana early Friday. The GFS is much further northwest across
Iowa, with a more widespread and dry warm sector over our area
after the initial rain exits late Thursday night or early Friday.
Leaning more toward the slower solution at the moment and focused
Friday PoP`s north of I-72. Pulled back on the thunder mention
Thursday and Thursday evening as a result.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1252 PM CDT Sat Apr 22 2017

VFR throughout. Northeasterly winds and cirrus...bkn/ovc over
DEC/CMI/SPI... more scattered to the north. High pressure will
remain anchored over the Plains states...and NErly flow will
continue through end of TAF pd.

&&

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

$$

UPDATE...HJS
SHORT TERM...Geelhart
LONG TERM...Geelhart
AVIATION...HJS



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