Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 291758

Area Forecast Discussion
National Weather Service Lincoln IL
1258 PM CDT Mon May 29 2017

Issued at 1100 AM CDT Mon May 29 2017

A cold front progressing across Illinois today may trigger a few
showers and storms. While some sprinkles could occur late this
morning into early afternoon toward Rushville and Jacksonville,
the better chances for precip will come toward mid afternoon into
early evening, as the forcing for precip focuses southeast of a
line from Springfield to Danville. Most areas will remain dry, but
MUCAPES around 1000 J/kg could be enough instability for a few
thunderstorms. Have continued to include thunder this afternoon
into early eve, mainly in our east-southeast counties. Despite
some increased cloud cover, there should be ample late May
sunshine to push high temps into the upper 70s to low 80s. Areas
along Hwy 50 may even reach the mid 80s.

Overall, only minor changes were needed to the short term forecast
PoPs and weather. Updated forecast info is already available.


.SHORT TERM...(Today and tonight)
ISSUED AT 242 AM CDT Mon May 29 2017

Large upper low clearly seen on water vapor imagery early this
morning just north of the Minnesota arrowhead. As this feature
slowly wobbles northeast through tonight, periodic shortwaves will
rotate around it and swing across the Midwest. While a lot of the
activity will be closer to the low, the arrival of one of the
waves will trigger some isolated convection by mid afternoon from
about I-55 east, where CAPE`s are progged to reach about 1000
J/kg. Chances settle into southeast Illinois by early evening and
should be out of the forecast area by midnight.

As the upper wave should arrive later in the day, the warmer
weather will linger for another day, with highs mainly in the
lower 80s.

.LONG TERM...(Tuesday through Sunday)
ISSUED AT 242 AM CDT Mon May 29 2017

The upper pattern will be slow to transition through mid week, but
the broad trough will slowly shift east as the upper low hangs out
over northern Ontario. Additional isolated convection is possible
Tuesday afternoon and evening as the next wave passes, then dry
weather is on tap through Wednesday night as high pressure slowly
drifts eastward.

Main focus remains with the latter part of the week. The GFS and
ECMWF are starting to get into a little better sync with the
positioning of the frontal boundary on Friday night and Saturday,
generally over the middle of the forecast area. However, the ECMWF
is a bit faster in shutting off the precipitation late Saturday.
Model disagreements return Sunday, with the GFS featuring the
arrival of a shortwave from the northwest, and the ECMWF slowly
building an upper ridge eastward. A slight nudge toward the latter
model is in the forecast for this time frame.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1258 PM CDT Mon May 29 2017

VFR conditions will prevail over the next 24 hours, despite a cold
frontal passage this afternoon into early evening. The lowest
clouds of note will be mid-level at 6-8K ft, along a line of
showers and isolated storms that is projected to develop this
afternoon south of I-72/74 to Danville. Therefore, have only
included a VCTS in the SPI, CMI and DEC 18z TAFs. Instability
peaks around mid-afternoon and then wanes into the evening. Early
evening stabilization of the boundary layer should help shut down
storm potential near any terminal sites.

Gusty west winds will be the other aviation concern, with gusts
around 20kt this afternoon. Winds will remain westerly tonight as
they decouple and remain below 10kt overnight. Winds will increase
again Tuesday morning from the west, but it appears less gusty




SHORT TERM...Geelhart
LONG TERM...Geelhart
AVIATION...Shimon is the U.S. government's official web portal to all federal, state and local government web resources and services.