Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 271752
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1252 PM CDT Sat Sep 27 2014

.UPDATE...
ISSUED AT 1045 AM CDT SAT SEP 27 2014

Forecast looks on track today and no update planned. Patchy fog
near the Wabash River and locally dense at Robinson dissipate by
830 am. A repeat of yesterdays weather with mostly sunny skies and
light east winds with warm highs in the low to mid 80s. 581 dm 500
mb low over sw IA will meander across western IA this weekend
keeping its isolated convection nw of IL. 1028 mb surface high
pressure sprawled across the Great Lakes will remain in place and
ridge into IL through Monday keeping this nice weather going
through early next week. Temps currently in the low to mid 70s to
warm another 10 degrees with highs in the low to mid 80s with
coolest readings over east central IL.

&&

.SHORT TERM...(Today)
ISSUED AT 313 AM CDT SAT SEP 27 2014

Weak low pressure centered over south-central Iowa will retrograde
slow to the northwest today, but upper level moisture streaming
around the south side of the low will push varying amounts of cirrus
clouds into central Illinois today. Sunshine should still prevail
for the most part, as the overall air mass remains nearly unchanged
from yesterday. That will mean another day of lower 80s for highs
with light east to southeast winds, generally less than 10 mph.

Patchy ground fog early this morning near the Wabash River should
dissipate quickly after sunrise.

&&

.LONG TERM...(Tonight through Friday)
ISSUED AT 313 AM CDT SAT SEP 27 2014

Upper low expected to weaken into a broad wave by Sunday before
dropping southeast across the state. Looks to be a dry passage,
because although moisture will be spreading northeast out of the
southeast states, the wave should be past us before the moisture
gets this far north.

Main challenge for this part of the forecast is with the midweek
system. Latest ECMWF and GFS are in reasonable agreement with the
evolution of the upper low currently near San Francisco, lifting it
into South Dakota by Tuesday evening. Main surface cyclone will be
drawn northward into Manitoba on Wednesday, with its trailing front
hanging up to our northwest. Have mentioned some token 20% PoP`s
northwest of the Illinois River on Wednesday, but rain chances will
more likely hold off until late Wednesday night as a deep long wave
trough emerges on the Plains and forms a surface low over the
Oklahoma area at the trail end of the stationary front. The models
start to diverge with respect to this low, with the GFS much deeper,
but the general trend on both models is to slow the passage of the
front down a bit. Areas east of I-57 may remain dry through most of
Thursday afternoon, with the main daytime threat west of I-55 and
everywhere Thursday night with the passage of the front. Bulk of the
rain should be out of the area by late Friday morning, but we may
see some wraparound showers as a strong secondary shortwave moves
into the region.

Temperatures expected to stay above normal into early next week with
highs lower-mid 80s, before cooling off a bit. As the late week
shortwave arrives, a more prominent surge of cooler air will arrive
for Friday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
ISSUED AT 1250 PM CDT SAT SEP 27 2014

VFR conditions expected to continue across the central IL airports
through Sunday. The exception will be possible patchy shallow
ground fog producing possible MVFR vsbys from 09-13Z especially
along IL river at PIA with a bit higher dewpoints in the mid to
upper 50s with SPI dewpoint currently at 62F. Few to scattered
cumulus clouds 5-6k ft this afternoon mainly at western TAF sites
of PIA and SPI will dissipate by sunset and redevelop by midday
Sunday. Otherwise patches of mid/high clouds to drift northward
across central IL the rest of the weekend. A 580 dm 500 mb low
over western IA to keep its isolated convection nw of IL as it
meanders over western IA through Sunday morning then begins to
drift se thereafter. Large 1027 mb surface high pressure to remain
over the Great Lakes this weekend, keeping light east winds close
to 5 kts during daytime hours and light to calm at night.

&&

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

$$

UPDATE...07
SHORT TERM...SHIMON
LONG TERM...GEELHART
AVIATION...07





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