Area Forecast Discussion
Issued by NWS Central Illinois

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554
FXUS63 KILX 240119
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
819 PM CDT Tue Apr 23 2019

.UPDATE...
Issued at 818 PM CDT Tue Apr 23 2019

See little need to make changes to forecast for tonight. Precip
just to our south associated with the stationary front along the
Ohio River will gradually move into the southwetern portions of
the forecast area overnight. Clouds will keep temps from falling
any lower than the mid to upper 40s.

&&

.SHORT TERM...(This evening through Wednesday)
ISSUED AT 253 PM CDT Tue Apr 23 2019

Early this afternoon, a cold front continues to sag south across
southern Illinois and Indiana towards the Ohio River Valley. In
its wake, most of central Illinois has been blanketed in low
stratus and cooler temperatures. While there has been steady
clearing of low clouds from the north today, high clouds have been
overspreading the area from the southwest. There may be a few
peaks of sun, especially near and north of the I-74 corridor late
this afternoon or early evening, and partly cloudy conditions will
continue south of I-70. The remainder of the area should remain
cloudy the rest of today and tonight.

Meanwhile, surface low is analyzed over the far southwest corner
of Missouri this afternoon and is progged to lift northeast to
along the I-70 corridor in the southern CWA late Wednesday
evening. Frontal boundary will begin to shift north again
Wednesday. Low to mid 60s are favored north of the front/I-70
corridor Wednesday afternoon, while mid to upper 70s are expected
south. Precip chances will increase in response to low/mid level
isentropic ascent overspreading portions of the area. The highest
PoPs are located along and south of the I-72 corridor Wednesday.
Modest MUCAPE of 200-500 J/kg will be in place near the warm
front allowing for the possibility of a few thunderstorms as well.

.LONG TERM...(Wednesday night through Tuesday)
ISSUED AT 253 PM CDT Tue Apr 23 2019

Area of low pressure will shift east of the region Wednesday
night with precip chances at least briefly diminishing early on
Thursday behind the low. Attention turns back to the northwest as
a northern stream shortwave trough is the progged to dig across
portions of the Upper Midwest and Midwest later Thursday with
attendant surface trough making its way across the forecast area
Thursday afternoon and evening. Weak diurnal instability and
modest forcing associated with the upper wave may support a few
scattered showers, but the bulk of the day should be dry with
afternoon highs in the lower 70s. Northwest flow will bring drier
and slightly cooler conditions on Friday with highs generally in
the mid to upper 60s.

A dynamic system is poised to sweep across the region this
weekend bringing widespread showers along with a chance for
thunderstorms Saturday. Moisture overall is expected to remain on
the more modest side, though both the GFS and ECMWF pool upper 50s
to low 60s dew points immediately along the front. There remain
small but important timing and track differences between the
models which make pinning down convective details difficult.
Strong mid level flow over the region will result in a high shear
environment; however, instability is expected to remain confined
to within a narrow corridor near the cold front. The GFS runs
slightly faster than the ECMWF and brings the front into the
forecast area late afternoon/early evening, but still during a
favorable diurnal time frame. The slower ECMWF, meanwhile comes in
slower and misses this window and the more southerly low track
would not be as favorable for surface based instability over much
if any of the area. If the faster timing were to verify, the high
shear/low CAPE environment could pose at least a conditional risk
for severe weather, so will need to keep a close eye on trends in
the coming days to see if ingredients can come together.

Temperatures briefly turn cooler again behind the low on Sunday
with breezy north winds possible before high pressure translates
east across the region later in the day. Baroclinic zone is
progged to inch back northward setting up over portions of the
Midwest and resulting in a potentially active period of weather.
early through the middle of next week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 632 PM CDT Tue Apr 23 2019

Central Illinois terminal all MVFR this evening as stalled
boundary across southern Illinois continues to push abundant
cloud cover into the area. The northern edge of clouds is
oscillating as waves moving along the front provide pockets of
enhanced lift and then move by. Followed LAMP closely which
suggestd we may have a brief period of VFR late tonight before
the next wave approaches. This stronger wave will likely push the
boundary northward ahead of it and bring a significant possibility
of rain to the terminals by mid-morning at southern terminals and
early afternoon at I-74 sites. CIGs should fall as precip moves in
and may drop to IFR at KSPI and KDEC as they remain just north of
the front.


&&

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

$$

UPDATE...Barker
SHORT TERM...Deubelbeiss
LONG TERM...Deubelbeiss
AVIATION...Barker



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