Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 251725

Area Forecast Discussion
National Weather Service Lincoln IL
1225 PM CDT MON JUL 25 2016

Issued at 1047 AM CDT Mon Jul 25 2016

Cold front is settling slowly southward through central Illinois
this morning...with 15z/10am surface analysis showing the
boundary near the I-72 corridor. Light northerly winds are trying
to bring slightly drier air into the northern KILX CWA, as
evidenced by dewpoints dropping into the upper 60s north of the
Peoria area. While latest radar imagery is clear, most models
suggest widely scattered showers and thunderstorms developing in
the vicinity of the front this afternoon. Based on model
consensus, it appears chance PoPs are warranted mainly along and
south of I-70. Current forecast has a good handle on things, so
other than some minor updates to hourly sky cover and temp grids,
no significant updates are needed at this time.


.SHORT TERM...(Today and tonight)
ISSUED AT 323 AM CDT Mon Jul 25 2016

The weak cold front has slowed down and appears to be nearly
stationary from SW to NE along the Illinois river. The consensus of
short term guidance still project the front to re-gain some forward
momentum today and advance into southeast IL, in response to high
pressure in the Plains pushing east.

At present, showers and storms ahead of the front have become
confined to areas east of I-55 at 3 am. Additional showers and
storms have begun to develop farther southwest of our counties, and
are heading toward Scott, Morgan and Sangamon counties. There should
be enough support for that convection to advance into our forecast
area, with 2500-3000 J/kg of MUCAPES still avail.

Severe potential before sunrise should remain low, but flash
flooding will be a concern due to the very heavy rainfall from
earlier last evening, when many areas along and just east of I-55
picked up 2-3" of rain. Those storms are progressing to the NE along
an axis of precipitable water values of 2.2 to 2.3". Any storm
development this afternoon could approach severe levels southeast of
a line from Shelbyville to Mattoon, where SPC has a Marginal Risk in
the severe outlook. While strong wind and hail may occur in the
stronger storms, flooding will remain a concern with any storm.
Storms will eventually progress SE out of our forecast area tonight,
as high pressure builds into IL from the W-NW.

Temperatures today will warm to near 90 south of I-70, with heat
indices in that area of 100-103 (just below advisory criteria (105).
Will not have any heat headlines today, after the brutally hot day
yesterday. Father north, high temps should only reach the mid 80s,
as dewpoints begin to pull back into the mid 60s.

.LONG TERM...(Tuesday through Sunday)
ISSUED AT 323 AM CDT Mon Jul 25 2016

For tomorrow, some very low pops confined to south of I-70  with the
front settling down into the Ohio River Valley. Remainder of the
area is dry through tomorrow night.  Pops return as early as Wed
afternoon in the ECMWF and the NAM with the front pushing back into
the region from the S/SW as a warm front.  GFS is a little slower
with the development of any rain, but precip spreading across the
CWA through Wed night. Both days slightly cooler than the past few
days, but still well into the 80s, with enough RH to result in heat
indices in the 90s.

On a bigger scale, the western ridge will start to build again after
midweek, ultimately amplifying the flow aloft.  This sets up more
northwesterly regime for the Midwest, and the forecast becomes
dominated by chance pops with a few periods of slights...but rarely
without the risk for any precip. Several waves dive down into
region, with the best chances for precip looking like Thursday
through Friday, with a possible break for Saturday.  Temps in the
extended remain in the 80s in the afternoons...and overnight lows in
the mid to upper 60s.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1225 PM CDT Mon Jul 25 2016

Winds are light and variable at the central Illinois terminals
early this afternoon as a cold front sinks slowly southward into
the area. Boundary is ill-defined by surface obs, but is expected
to drop south of the TAF sites later this afternoon/evening. A
thick layer of mid-level clouds is in place at 12000-15000ft with
visible satellite also showing lower diurnal clouds developing at
around 1500-2500ft. Aside from perhaps a brief MVFR ceiling,
forecast soundings are suggesting the lower clouds will remain
scattered. As the front drops southward and the diurnal clouds
dissipate, skies will become mostly clear this evening. With clear
skies, light winds, and ample low-level moisture in place, think
patchy fog will develop overnight. Have therefore dropped visbys
to 3-5SM between 09z and 14z.


.ILX Watches/Warnings/Advisories...


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