Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 031701

Area Forecast Discussion
National Weather Service Lincoln IL
1201 PM CDT TUE MAY 3 2016

Issued at 1022 AM CDT Tue May 3 2016

No significant forecast changes anticipated this morning. With
significant low-level lapse rates expect cumulus field to quickly
develop by midday which should slow warming in line with current
package. Clouds should diminish late this afternoon but then
increase again with the approaching cold front tonight. Still
appears best rain chances should be confined to after midnight.


.SHORT TERM...(Today)
ISSUED AT 304 AM CDT Tue May 3 2016

Another mostly quiet day is anticipated today across central and
southeast Illinois. Main concern revolves around cloud cover and if
there will be any precipitation.

Forecast area remains under the influence of a sheared trof axis
aloft, and weakly cyclonic flow at the surface. This scenario will
change little during the day today. A piece of energy within the
sheared trof is coming through the area at the moment with little
fanfare, although there are a few very weak/spotty radar returns.
However, have not seen recent reports of any of these returns
reaching the ground. Some additional sheared energy will impact the
area later today, but it will have very little instability to work
with. So think this feature should come through dry, but have
maintained a very low PoP in extreme SE IL where the instability may
be a bit better. Ultimately, based on forecast soundings & the items
mentioned above, think most of what we will see this afternoon is an
enhanced diurnal CU field and little more than a few sprinkles.

.LONG TERM...(Tonight through Monday)
ISSUED AT 304 AM CDT Tue May 3 2016

Latest models show little change in the projected upper air pattern
over the next several days. Current upper ridge already in place
with high pressure centered over southern Alberta. As the current
system over the central Plains and mid-Mississippi Valley drops
southward today, it will yield to an upper low that is now in
northwest Ontario and is projected to reach Lake Michigan on
Wednesday morning. Cooler conditions are expected for a few days as
a broad trough covers the eastern CONUS, but as the ridge shifts
eastward on Friday, significantly warmer conditions expected. Latest
blended guidance brings highs into the mid 70s over the western CWA
as early as Friday, and 80 degree readings over much of the forecast
area on Saturday.

Surface boundary associated with the Ontario system appears to be
picking up speed, and have increased PoP`s quite a bit and somewhat
faster than earlier, with likely PoP`s over areas north of Peoria as
early as late evening. Also went with a period of 60% PoP`s over
east central Illinois after midnight. The window for rain looks to
only last about a couple hours at any given location, given the
speed of this system. Some steeper mid-level lapse rates favor a few
rumbles of thunder as well. Have maintained some chance PoP`s over
the eastern half of the forecast area as well on Wednesday due to
the arrival of the upper low.

Weekend system starting to come into a little better agreement in
the longer range models. Both the GFS and ECMWF settle a quasi-
stationary front over central Illinois by Saturday afternoon,
lingering in the general area through Sunday. How fast this boundary
retreats northward is more in question, with our region caught
between the southern jet stream being steered south of the upper low
over the 4-corners region, and the northern jet stream coming
through the Great Lakes. Thus, once precipitation chances develop
through the day Saturday, chance PoP`s will remain in the forecast
into Monday.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1138 AM CDT Tue May 3 2016

Strong low-level lapse rates are combining with daytime heating to
develop cumulus field at midday. Most terminals in central
Illinois will likely have broken VFR ceilings by early this
afternoon. As heating diminishes so will the cumulus field.

A fast moving system over western ontario will race south pushing
a cold front through the state late tonight. Dynamics are
relatively strong, but moisture - particularly in boundary layer -
is somewhat limited. Will introduce a tempo group of MVFR precip for
the period suggested by NAM.


.ILX Watches/Warnings/Advisories...


LONG TERM...Geelhart
AVIATION...Barker is the U.S. government's official web portal to all federal, state and local government web resources and services.