Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 242340

Area Forecast Discussion
National Weather Service Lincoln IL
640 PM CDT FRI JUN 24 2016

.SHORT TERM...(Tonight)
ISSUED AT 230 PM CDT Fri Jun 24 2016

High pressure centered over the Great Lakes will continue to control
the weather across central Illinois tonight.  Robust diurnal Cu
field that has developed this afternoon will rapidly dissipate
toward sunset, leaving behind mostly clear conditions by this
evening. Nearly calm winds initially will become light from the E/SE
overnight as the high slowly shifts away and the pressure gradient
begins to tighten. Overnight low temperatures will drop into the
middle to upper 60s.

.LONG TERM...(Saturday through Friday)
ISSUED AT 230 PM CDT Fri Jun 24 2016

The main forecast challenge this period will be with thunderstorm
chances and coverage late Saturday through Sunday evening as a
cold front slowly pushes through the forecast area.

The area of high pressure that brought the pleasant weather today
will shift well off to our east allowing southerly winds to draw
low level moisture back north into our area for the weekend. A
stalled frontal boundary well to our south will shift north as a
warm front and be just west of our area by late in the day Saturday.
With a sun-cloud mix on Saturday and southerly winds, look for
afternoon temperatures to soar back to or just above 90 degrees
accompanied by rather uncomfortable humidity levels again. Forecast
soundings continue to indicate plenty of instability across our
area by afternoon, and that combined with the approach of weak
shortwave energy, widely scattered to scattered convection should
develop across the western half of the forecast area by late in
the day. Most model suggest Mixed Layer Capes around 2500-3000
j/kg by afternoon with the stronger wind fields well to our north.
Our 0-6km shear ranges from 15 to 20 kts so a few storms may
produce gusty winds associated with the more persistent updrafts,
but organized strong to severe storms are not expected

Coverage should decrease just after sunset Saturday but start to
pick up again after midnight across our northwest as a cold front
approaches from the northwest. The GFS is a bit more aggressive
in bringing the precip further southeast into at least half of our
forecast area Sunday morning, while the NAM-WRF suggests whats left
of the overnight convection should dissipate just to our northwest
Sunday morning, before refiring over central Illinois Sunday
afternoon just ahead of the cold front. This may have an impact on
afternoon temperatures but will still take the warmer guidance
values Sunday afternoon. Shear profiles Sunday afternoon still quite
weak, but with these high instability/low shear cases, the potential
for some downburst winds exists during the mid to late afternoon
hours. What`s left of the storms Sunday evening should gradually
sink southeast along with the cold front overnight and most of
the activity should push out of our area by Monday.

For the medium and longer range period, we are still looking at a
rather deep trof over the eastern U.S. while ridging dominates the
western U.S. translating to somewhat cooler air for next week. With
a northwest flow pattern developing, MCS activity will start to pick
up as well but most of the longer range models indicate the main
low level baroclinic zone will shift south and west of our area
which should keep the track of the MCS activity mainly to our
southwest. One such MCS is advertised to approach and skirt mainly
to our southwest later Wednesday into Thursday, but close enough to
the forecast area to warrant at least a mention of showers and
thunderstorms, especially Wednesday night into Thursday.


.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 626 PM CDT Fri Jun 24 2016

High pressure will slowly drift away from the central Illinois
terminals during the 00Z TAF valid time. The majority of the
period should be quiet/VFR. However, there may be a stray shower
or two over west-central Illinois by Saturday afternoon as a
frontal system approaches the area. Chances for rain at a specific
terminal are too low to carry at this time.


.ILX Watches/Warnings/Advisories...


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