Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 021956
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
256 PM CDT Tue Sep 2 2014

.SHORT TERM...(This evening through Wednesday)
ISSUED AT 254 PM CDT TUE SEP 2 2014

18z/1pm surface analysis shows slow-moving cold front extending from
Chicago to just east of Quincy.  Ahead of the front, central
Illinois remains partly to mostly cloudy and there have even been a
few showers E/NE of Bloomington over the past hour.  Will continue
to carry slight chance PoPs across the eastern KILX CWA through the
afternoon accordingly.  Frontal boundary will continue to push
slowly eastward tonight, eventually washing out across central
Illinois.  Winds will go light/variable due to the weak pressure
gradient and with skies expected to clear, fog will likely develop
overnight.  NAM forecast soundings suggest the most widespread fog
will form across east-central Illinois where skies will clear the
slowest this afternoon.  Have therefore included areas of fog after
midnight along/east of I-57, with patchy fog further west across the
remainder of the area.  After early morning fog dissipates, skies
will initially be mostly sunny before clouds begin to increase in
advance of an approaching warm front on Wednesday.  Based on 12z
NAM/GFS, have slowed the introduction of PoPs until afternoon.


&&

.LONG TERM...(Wednesday night through Tuesday)
ISSUED AT 254 PM CDT TUE SEP 2 2014

Low pressure moving from the Plains toward the western Great Lakes
on Wed night will begin a significant push of warm air from the
southern Plains into Illinois. A shortwave clipping N IL in the
could trigger a few storms from Peoria and northward overnight. By
Thursday, the warm front will re-define north of Illinois, as 850mb
temps of 20-24C surge into our counties. Gusty south winds will aid
in moisture transport pushing humidity levels up, as surface
dewpoints climb into the mid 70s. Mixing that warm air to the ground
supports high temps into the upper 80s and lower 90s, depending on
the amount of sunshine we get into the afternoon. The 12z guidance
are slowing down the advance of storms into IL on Thursday, except
for the GFS, so sunshine could prevail for much of the day. Peak
heat index readings could reach between 100-105F.

Storm chances increase later Thursday night as the cold front
approaches NW IL. Rain chances become widespread across the KILX
forecast area for Friday and Friday night, as the cold front
progresses across IL. Severe potential is hard to pin-point this
early, but very heavy rainfall will be possible as PWAT values climb
toward 2". Friday will be another warm and muggy day ahead of the
cold front, but not quite as hot due to increasing cloud cover and
showers/storms.

The cold front will begin to slow down Friday night, allowing
scattered storms to linger across our southeast counties into
Saturday.

A significant airmass change will follow that frontal passage, as
cool and dry Canadian high pressure builds southeast into the
western Great Lakes. Highs from Saturday through Tuesday will be
mainly in the 70s, with lows mainly in the 50s, with Sunday night
the coldest night.

Storm chances increase next week Tuesday as a cold front arrives
from the west.


&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
ISSUED AT 1256 PM CDT TUE SEP 2 2014

MVFR ceilings persist across much of central Illinois east of the
Illinois River early this afternoon. Cloud cover is beginning to
dissipate and this trend will continue for the next couple of hours.
Will scatter the clouds after 20z at all terminals accordingly.
With weak high pressure building in from the west and winds
becoming light/variable, fog may become an issue overnight. Due
to persistent cloud cover today, minimal mixing of the low-level
moist airmass has occurred. As a result, plenty of surface-based
moisture will be available tonight. Forecast soundings and numeric
guidance both suggest fog may become most widespread across
east-central Illinois since that will be the last area to clear
this afternoon. Have included reduced visbys down to around 3sm at
most sites and 2sm at both KDEC and KCMI between 09z and 13z.
After that, mostly clear skies with light S/SE winds will prevail
Wednesday morning.


&&

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

$$

SHORT TERM...BARNES
LONG TERM...SHIMON
AVIATION...BARNES





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