Area Forecast Discussion
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FXUS63 KILX 260814
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
314 AM CDT Tue Aug 26 2014

.SHORT TERM...(Today and tonight)
ISSUED AT 312 AM CDT TUE AUG 26 2014

One more hot and humid day is on tap for at least the southern half
of the KILX CWA, as heat index readings climb into the 105 to 110F
range during peak heating. The heat warning will continue from
Lincoln and south, with the heat advisory east to Champaign/Danville
through early evening.

Last evening some cooler air was pushed out from a line of storms
that clipped our north from Stark County to Champaign/Vermilion
counties and south along the Indiana border. That worked to lower
dew points across the north, which should help to keep the heat
indices a bit lower during the afternoon, but still hot in the
upper 90s.

Once again the high-res models are having a hard time with current
convection and are all over the board with respect to storm
development over the next 24 hours. When merged with the lower
resolution models, the general theme is for a line of storms to
eventually develop across our northern counties as a cold front
slowly moves south into our forecast area. A few storm cells
developing in eastern Iowa over the last hour has increased some
confidence that a few storms could affect our northwestern counties
by mid-morning, so will keep at least chance PoPs NW of Peoria this
morning. The daytime storms are projected to drift south as they
dissipate toward I-72 later this afternoon. The next complex of
storms is projected for later tonight, when a stronger MCS is
forecast to roll out of Iowa. Under that scenario, storms would
affect areas north of Peoria after 08z/2am CDT, where we have likely
PoPs.

There remains a high level of elevated instability, with plenty of
precipitable water, so any storms that can overcome the mid-level
warming could produce some very heavy rainfall and strong winds over
the next 24 hours.


&&

.LONG TERM...(Wednesday through Labor Day)
ISSUED AT 312 AM CDT TUE AUG 26 2014

Upper ridge will be breaking down on Wednesday as a wave moves
through the upper Great Lakes region. Still watching the deep trough
seen on water vapor imagery across the western U.S. this morning.
Last couple model runs had some reasonable agreement with tracking
this feature into the Plains by early Saturday, but have some
disagreements resolving the split flow over the central U.S. as a
trough digs over the Pacific Northwest. The ECMWF largely dampen out
the Plains wave, while the GFS keeps it somewhat intact and lifts it
into Wisconsin on Sunday, possibly due to some feedback issues. Have
leaned the holiday weekend forecast more toward the ECMWF as a
result.

In the nearer term, the 00Z models largely bring the front through
most of the forecast area by Wednesday evening, with the NAM
furthest north and the GEM/GFS furthest south. Best shower/storm
threat will be during the morning before the precipitation is
shunted into what`s left of the ridge. After that, focus shifts to
our northwest as the front lifts back northward in response to the
wave moving onto the Plains. Frequent MCS activity will lead to
potential flooding concerns across Iowa/Wisconsin, with mainly
scattered activity in our area from the remnants of said activity or
other development along the boundary.

Rather humid conditions expected to continue on Wednesday, until
drier air spreads in from a high pressure building into the Great
Lakes. However, the humidity will return on Thursday as the front
lifts back north. Temperatures across the southeast CWA may still
reach the lower 90s Wednesday and Thursday, but highs in the 80s
will prevail through the period.


&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
ISSUED AT 1100 PM CDT MON AUG 25 2014

Little change from previous discussion with the main concern
overnight being from lower vsbys due to fog and the threat
for more showers and storms, especially across the west and
northwest. Outflow boundary from this afternoon`s storms has
shifted well south of the forecast area this evening with an
east to southeast component to the surface winds thanks to a
meso-high that developed along the rear of the thunderstorm
complex. What affect this outflow boundary will have on our
fog chances is not clear as a few nights ago we saw the same
thing happen during the late afternoon/early evening hours
with very little in the way of fog due to somewhat lower dew
points brought in with the outflow boundary. However, with
the rain we received with the storms, the low levels of the
atmosphere are saturated so any decrease in wind speeds overnight
should lead to at least patchy fog, which should lift across the
area by 13z.

A cool front will then push across the area during the day Tuesday
bringing a switch in winds and the threat for additional showers
and storms, which may push into our west as early as the 12z-15z
time frame. Outside any lower vsbys in fog early in the morning, it
still appears we should see mainly VFR conditions during the day.
Surface winds will be turning more into the southeast and then south
overnight with speeds of less than 10kts. Winds should then become
light northerly during the morning across the west and over the
east in the afternoon with speeds of 5 to 10 kts.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
EXCESSIVE HEAT WARNING until 7 PM CDT this evening FOR ILZ042-
047>054-056-061>063-066>068-071>073.

HEAT ADVISORY until 7 PM CDT this evening FOR ILZ043>046-055-057.

&&

$$

SHORT TERM...SHIMON
LONG TERM...GEELHART
AVIATION...SMITH




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