Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 201022

Area Forecast Discussion
National Weather Service Lincoln IL
522 AM CDT Tue Jun 20 2017

.SHORT TERM...(Today and tonight)
ISSUED AT 258 AM CDT Tue Jun 20 2017

Main issue for this part of the forecast involves potential for
scattered convection once again. Shortwave across northwest
Minnesota will be dropping southeast today as the upper ridge
persists across the Rockies. Strong lapse rates below about 600 mb are
expected to help trigger storms similar to yesterday, with
high-resolution models focusing on the 3-6 pm time frame over the
northern CWA and around 5-8 pm from about Jacksonville northeast
to Danville. Have bumped up PoP`s a fair amount from the going
forecast, mainly to around 30-40% late afternoon through about mid
evening. Forecast soundings still show quite a bit of dry air
below about 750 mb, so evaporative cooling will bring the
potential for some gusts over 40 mph in the stronger storms. The
storms will fade off with loss of daytime heating, and will go
with a dry forecast by midnight.

Temperatures should reach the mid 80s over the forecast area
today, although with the drier dew points and a decent southwest
breeze, it should feel a bit cooler.

.LONG TERM...(Wednesday through Monday)
ISSUED AT 258 AM CDT Tue Jun 20 2017

Longer range continues to feature a breakdown of the western ridge
by mid week, with zonal flow settling southward from Canada. Fast
moving waves will help bring precipitation to our north as a
frontal boundary sets up, but with this boundary parallel to the
upper flow, a southward push will wait until a stronger wave drops
from Canada late in the week. Complicating factor with this
scenario is with the developing tropical cyclone over the Gulf of
Mexico. Longer range models draw some of the remnant moisture
northeast into the Ohio Valley by Friday, which would enhance
the rainfall along the boundary. The GFS/ECMWF models largely have
the boundary south of the CWA by the time this occurs, but areas
south of I-70 may potentially see some of this heavier rain.

Over the weekend, a broad trough will set up over the Mississippi
Valley, with some model discrepancies on how strong the next
shortwave will be during the weekend. The ECMWF is much more
robust in this regard, with fairly high rain chances Saturday
night and Sunday morning, while the GFS remains weaker. Both
models suggest a cooling trend though, with highs mainly in the
70s for Sunday and Monday.


.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 521 AM CDT Tue Jun 20 2017

Main TAF issue will be the development of scattered convection
this afternoon. Much of the high-resolution guidance suggests
this arriving in KPIA/KBMI in the 20-22Z time frame, and from
KSPI-KCMI closer to 00Z. Have continued the VCTS mention at all
sites. Some of the heavier showers may produce gusty winds and
brief MVFR/IFR visibility reductions, but uncertainty in coverage
precludes trying to pin down details in the TAF`s this far out.
Remaining convection should be diminishing south of the TAF sites
by about 02Z with loss of daytime heating.




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