Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 251514

Area Forecast Discussion
National Weather Service Lincoln IL
1014 AM CDT MON APR 25 2016

Issued at 1014 AM CDT Mon Apr 25 2016

Early morning scattered clouds have been thinning out and moving
east out of the area, with mostly sunny conditions at midday. Wind
gusts starting to reach the 25-30 mph range in several areas as
the low level inversion seen on the morning sounding mixes out.
Temperatures have already reached the 70-75 degree range across
the CWA. While clouds should start to increase later today,
CAPE`s expected to reach over 1500 J/kg by mid afternoon over west
central Illinois, helping to fuel some scattered thunderstorms.

Have done some tweaking to the timing of the convection, starting
the PoP`s northwest of the Illinois River around 2-3 pm and
bringing them about as far as Springfield-Rantoul by late
afternoon. Latest HRRR and the evening run of the NSSL 1km ARW do
suggest some scattered convection more in the Decatur-Champaign
area late afternoon, so have maintained the slight chance PoP`s in
that area but limited them to late afternoon. Greatest convection
still expected more across northern Illinois, shifting southward
as the boundary moves into central Illinois/Indiana tonight.
Northern parts of the CWA should pretty much be dry by midnight,
and have removed the post-midnight PoP`s in that area.


.SHORT TERM...(Today)
ISSUED AT 333 AM CDT Mon Apr 25 2016

Storm system over eastern South Dakota as of 300 am is expected to
track east along a stalled frontal boundary over northern Iowa east
through southern Wisconsin later today. A cold front located from
the low over eastern South Dakota southward through eastern Nebraska
will track slowly east today and not get into our area until first
thing Tuesday morning. Surface dew points in the mid to upper 50s
were noted just east of the cold front and as the boundary shifts
east today, so will the moist axis into our area this afternoon.

As was advertised with most model data, the storms that occurred
last night in Iowa have dissipated with the latest surface analysis
indicating a weak boundary/remnant outflow boundary over east
central Iowa. Most of the high res reflectivity simulations off the
4km NAM along with the WRF-ARW and NMM indicate redevelopment in
west-central Illinois later this afternoon. Surface temperatures in
the lower 80s combined with dew points in the upper 50s will yield
ML capes of around 1800 in a few areas along and west of the
Illinois River later this afternoon. That combined with rather steep
mid level lapse rates and 0-6km shear values of around 40 kts will
bring the threat for scattered thunderstorms after 300 pm, some of
which may produce strong winds and large hail, roughly along and
west of a Springfield to Bloomington line.

.LONG TERM...(Tonight through Sunday)
ISSUED AT 333 AM CDT Mon Apr 25 2016

After another warm day, with showers and thunderstorms chances
through the afternoon and into the evening hours, a series of
weather systems will bring precip for most of this week. The first
wave has slowed on approach overall, delaying the onset of precip.
Also, models are having some consistency issues with the extent of
the southerly progression of the front before the next wave moves
into the Midwest and enhances the precip/storms for Tuesday night
and into Wednesday.  Much of ILX sits in an area with limited severe
weather potential partially due to timing of the system late Tuesday
in the overnight hours. At any rate, the deep low over the southern
Plains ejects out and into the region, spreading best chances for
precipitation Wednesday and Wednesday night. Models still limiting
the progression of the warm front, keeping temperatures not quite as
warm for Tue/Wed ahead of the advancing storm center. By late
Thursday, the winds become more northerly and drier air slowly tries
to build back in for a brief break Thu night through later Friday.
The break looks to be short lived again as another wave moves out of
the long wave trof over the SW and into the region, bringing precip
back for next weekend. Overall, an active pattern, with more wet
than dry.


.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 612 AM CDT Mon Apr 25 2016

VFR conditions are expected this forecast period. Thunderstorms
that occurred to our west last evening have dissipated as they
approached the Mississippi River early this morning. There were
some scattered mid and high clouds that were pushing into the area
from the storms that occurred last evening. Latest sounding data
indicates some higher based cumulus should develop late this
morning with bases in the 4000-5000 foot range. In addition, a
rather gusty south to southwest wind of 15 to 20 kts is expected
later this morning into the afternoon hours with gusts around 25
kts possible. As a frontal boundary slow approaches the area late
tonight and tonight, scattered convection will be possible, but at
this time, it appears coverage will be too limited to include much
more than VCTS. Southwest winds of 10 to 15 kts can be expected
after sunset this evening.


.ILX Watches/Warnings/Advisories...


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