Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 241921

Area Forecast Discussion
National Weather Service Lincoln IL
221 PM CDT Thu Jul 24 2014

ISSUED 210 PM CDT Thu Jul 24 2014

SHORT TERM...Tonight through Sunday

Main forecast concern this period will be timing and coverage of
convection as a series of shortwaves track southeast across the
region. Already seeing a band of elevated storms over parts of
northwest Iowa tracking south-southeast with additional clusters
of storms to the northwest over the Dakotas in a zone of low and
mid level warm advection. Will maintain low chance POPs for our
counties to the west of the Illinois River well after midnight.
Forecast soundings thru tomorrow morning characterized by a dry
and stable atmosphere over the entire region and that will steadily
change as a warm front shifts northeast into our area by late in
the day or at night. Still appears the better chances for showers
and storms will be across the north Friday, but based on the
movement of the storms over northwest Iowa, we may have to watch
our west and southern counties if the trajectories hold. Warmest
temperatures Friday will be across the south and west where cloud
cover and rain threat will be minimal. We should see temperatures
climb into the lower 80s there with upper 70s across the north and
east where cloud cover will be a little thicker.

Warm front should begin to lift north of the area tomorrow evening
with the better convection chances along and to its north. Will
maintain the higher pops across the north closer to the boundary
with progressively lower pops south Friday night. A rather stout
elevated mixed layer or cap will invade the region on Saturday
bringing hot and humid weather back into the region. Big question
becomes convection chances and coverage during the day Saturday
as the area will see a significant cap hold until late in the day.
Several of the forecast soundings indicating the cap weakening
after 20z on Saturday as a frontal boundary edges into the forecast
area so pops will be higher in the afternoon with likely pops
looking reasonable Saturday night with precipitable water values
above 2 inches and warm cloud depths of over 13000 feet indicating
the likelihood for heavy rainfall in parts of our area.

The upper wave should begin shifting across our area Sunday
morning with showers and thunderstorm chances gradually lowering
from west to east during the afternoon. Possible redevelopment
of storms across our far east but not very confident on that,
especially if a large MCS affects the area later Saturday night
into Sunday. Rain chances, other than our far eastern counties,
will diminish Sunday evening with much cooler and less humid air
filtering southeast into the forecast area on Monday.

LONG TERM...Monday through Thursday

Ensembles showing good agreement with the deep trof expected to
form over the eastern U.S. bringing another bout of unseasonably
cool weather for most of this forecast period. Only challenge,
other than how cool the night-time lows will get, will be if
the very cool temperatures aloft will be able to produce some
diurnally driven showers each afternoon. At this point, it appears
that is a low probability event, so will continue to hold on to
our dry and cool forecast thru Thursday.


ISSUED 1242 PM CDT Thu Jul 24 2014

VFR conditions are expected during this forecast period. High
pressure to our north this afternoon will drift off to our east
this evening allowing winds to turn more into the southeast
overnight. A weather disturbance out across the Northern Plains
will drop southeast into the region increasing our cloud cover
after midnight and bringing rain chances to parts of the area.
As of now, will include VCSH in PIA as a complex of storms will
track southeast into parts of eastern Iowa before running into
our very dry air mass and weakening. Initially, we will see some
mid level cloud cover move in after 10z across the north with
some sct-bkn mid and high level cloud cover durnig the day further
south. Surface winds will become light southeast to south late
tonight and out of the south on Friday with speeds of 5 to 10 kts.



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