Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 250247
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
947 PM CDT SUN JUL 24 2016

.UPDATE...
Issued at 942 PM CDT Sun Jul 24 2016

Cluster of storms over central Illinois continues to produce
torrential rainfall, frequent cloud to ground lightning and
wind gusts in the 50 to 55 mph range. One storm in Fulton
county as an inbound velocity around 60 mph and was just warned
on. Storms will slowly make their way east and southeast tonight
as the cold front slips into the area with the concern shifting
mainly over to a flash flood threat overnight. Updated zones out
soon.

&&

.SHORT TERM...(This evening through Monday)
ISSUED AT 302 PM CDT Sun Jul 24 2016

Oppressive heat and humidity has returned to central and southeast
IL this afternoon, similar conditions to what we had 3 days ago on
Thursday July 21st. Mid afternoon temperatures were in the upper 80s
and lower 90s, while tropical dewpoints were in the upper 70s and
lower 80s. This was giving heat index readings of 105-115F, and
highest in Peoria. Will continue the excessive heat warning across
CWA through 7 pm cdt this evening. Lows overnight will range from
around 70F over the IL river valley, to muggy mid 70s in southeast
IL. Highs Monday to mostly be in the upper 80s, with southeast IL
near 90F. Heat indices Monday afternoon to reach 98-103F in
southeast IL from I-70 southeast. This is shy of 105F so will not
extend the excessive heat warning beyond 7 pm today.

Aside from the heat, a cool front extending from northeast WI and sw
through southeast IA (nw of the Quad Cities) and nw MO is projected
to track southeast across central IL after sunset tonight and
through southeast IL during Monday. The latest forecast models are
developing scattered convection ahead of this cool front late this
afternoon and evening and shift this into southeast IL on Monday.
SPC day1 outlook has marginal risk of severe storms north of I-70
tonight, with a slight risk of severe storms over northeast IL
including eastern Marshall and northeast Woodford counties. SPC
day2outlook has expanded the marginal risk of severe storms across
southeast IL on Monday afternoon. Very unstable/bouyant airmass over
central IL this afternoon with CAPES of 4-6k J/kg similar to Thu
afternoon levels. As frontal boundary moves into IL river valley
late today, should see convection expand and strengthen especially
over northeast IL.

.LONG TERM...(Monday night through Sunday)
ISSUED AT 302 PM CDT Sun Jul 24 2016

Frontal boundary should be just south of the CWA Monday with
convection still possible along and either side of the boundary.
Will keep a slight chance and small chance of storms in the
southeastern part of the CWA to cover this possibility. Beyond this
any convection should be in southern IL for Tue and Tue night.
Though chance pops will be south of the CWA, a slight chance is
still warranted in southeast IL. High pressure should dominate the
weather of the rest of the CWA with drier dewpoints and slightly
cooler temps. By Wed, the front will begin to lift northward as the
high pressure pushes off to the east. This will also allow the
boundary to lift northward from the west and move into western
Illinois. Southeast IL will see chance pops return for Wed.

With the high pressure east of the area by Wed night, another short
wave will drop into the area from the northwest with an associated
low pressure area and frontal system. This will bring the return of
chance pops to the area beginning Wed night. This shortwave trough
will help to carve out a larger trough that will setup over the Grt
Lks/midwest area, keeping the surface boundary near the CWA for the
rest of the week and into the weekend. Therefore, a chance of precip
will continue for the rest of the forecast period. There will likely
be some periods of dry weather, long term models showing some
differences and hard to forecast brief dry periods this far out.
Expect adjustments/refinements in the forecast to occur as the week
progresses.

Temps will cool some as the front drops through the area tomorrow,
but even cooler weather is expected for the latter part of the week
as cyclonic flow sets up.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 600 PM CDT Sun Jul 24 2016

Main concern this forecast period will be coverage of TSRA
this evening and their affect on cigs/vsbys at the TAF sites.
Scattered TSRA were developing northwest of a PIA to BMI line as a
cold front, still well to our northwest, edges slowly southeast.
Coverage tonight looks to be scattered ahead of the cold front so
will continue to handle with VCTS and then tempo with the best
timing if it appears it is going to affect one of our TAF sites
this evening. Any storm has the capability of producing wind gusts
to 45kts along with torrential rainfall and MVFR to possibly brief
IFR cigs as it moves through.

Most of the storm threat should be south of our TAF sites by 04z,
with the potential for a little MVFR fog by dawn Monday. Any fog
should quickly burn off by 13z with the potential for a narrow
band of low VFR/MVFR cigs around dawn. We are expecting any cigs
to lift with mainly VFR conditions for the rest of the TAF period.
Surface winds will be south to southwest this evening at 5 to 10
kts, and then shift into a northerly direction after FROPA in the
06z-10z time frame. Look for northerly winds at 10 kts or less on
Monday.


&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

UPDATE...Smith
SHORT TERM...07
LONG TERM...Auten
AVIATION...Smith



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