Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 241737

Area Forecast Discussion
National Weather Service Lincoln IL
1237 PM CDT Mon Apr 24 2017

Issued at 1100 AM CDT Mon Apr 24 2017

A surface ridge axis will slowly progress from NW to SE across
Illinois today. Easterly winds will eventually shift to the
southeast this afternoon as the axis progresses into Kentucky. The
only clouds of note today will be thin cirrus riding over the
upper level ridge. Ample sunshine and dry low level air will help
temps climb quickly toward afternoon highs of 74 to 78F. Only
minor adjustments were needed to the hourly temps, dewpoints and
winds for today. Therefore, no formal zone update will be needed
this morning. The remainder of the forecast database looked on


.SHORT TERM...(Today and tonight)
ISSUED AT 250 AM CDT Mon Apr 24 2017

Prominent upper low over northern Alabama this morning will
continue to sink southward today, finally loosening its grip on
our area. This will allow winds to gradually turn south/southeast.
With a very dry airmass remaining in place, forecast soundings
would suggest highs in the mid 70s. Went a couple degrees above
this, given the temperature trends from yesterday. Temperatures
tonight should only drop off to the lower 50s as the southerly
flow persists through the night.

.LONG TERM...(Tuesday through Sunday)
ISSUED AT 250 AM CDT Mon Apr 24 2017

Upper low currently off the western tip of Washington will be
dropping southeast into the 4-corners region by Tuesday afternoon,
helping to carve out a significant trough over the Plains. Strong
south-southwest flow to pump warmer and more humid air into our
region Tuesday into Wednesday, ahead of a cold front which will
likely cross the forecast area Wednesday afternoon and evening.
Western parts of the forecast area should see some showers and
thunderstorms moving in before sunrise Wednesday, with them
overspreading the CWA through the day, although areas near the
Indiana border may need to wait until late afternoon. Latest SPC
Day3 outlook indicates a marginal risk of severe weather, as 0-6km
bulk shear increases to 50-60 knots ahead of the front. Main
question here will be the extent of the cloud cover which may
mitigate some of the instability, although both the NAM and GFS
advertise some pockets of MUCAPE around 1000 J/kg in the

Given the slow movement of the front, rain is likely through
Wednesday night in western parts of the forecast area, and until
early Thursday over the east. Not much of a dry period behind it,
as the next system will already be taking shape over the Rockies.
Broad scale upper low is expected to form over the central Rockies
by early Friday, before tightening up and ejecting northeast.
The latest ECMWF is most prominent with this low and track it into
southeast South Dakota by early Sunday, while the GFS keeps it
much further south across the Texas panhandle. Both solutions
would favor an extensive rain shield spreading along a warm front
late Friday night. The GFS would keep this front generally
stationary into early Sunday, while the ECMWF lifts it quicker and
brings us into the warm sector. Anomalously high precipitable
water values reach around 1.8 inches per the GFS with this system,
suggesting the potential for heavier rains through the weekend.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1237 PM CDT Mon Apr 24 2017

High pressure passing across Illinois this afternoon will provide
VFR conditions for the 18z TAF period. The main concern for this
forecast will be the increasing south winds tomorrow morning, as
low pressure in the Plains begins to get organized. Have included
gusts to 20-23kt at all TAF sites after 14-15z tomorrow.
Otherwise, relatively quiet weather will dominate the first 18
hours of this TAF period.


Issued at 250 AM CDT Mon Apr 24 2017

Very dry air mass will result in relative humidities falling below
20% across much of central Illinois this afternoon. 10 hour dead
fuels are below 6% across the northern part of the forecast area,
and mainly 7-8% elsewhere. Main concern for any fire weather
issues would be over the far northwest CWA, where winds increase
to around 10-15 mph northwest of the Illinois River toward
midday, with some gusts to near 20. Winds currently expected to
remain low enough to keep conditions below red flag criteria, but
some fires could start to get out of control.




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