Area Forecast Discussion
Issued by NWS Central Illinois

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260
FXUS63 KILX 291549
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1049 AM CDT FRI JUL 29 2016

.UPDATE...
Issued at 1045 AM CDT Fri Jul 29 2016

Fog which was locally dense earlier this morning, has lifted
during mid morning across central IL. Low clouds still linger
north of a Shelbyville to Charleston/Mattoon to Paris line late
this morning. Have increased clouds over northern half of CWA into
midday, with skies becoming partly sunny in the afternoon. Dry
conditions have prevailed this morning over CWA, but still
expected isolated showers and thunderstorms to develop during the
afternoon in humid airmass with moist dewpoints in the lower 70s
(upper 60s nw of IL river). A 578 dm 500 mb low near the IA/WI
border will track east across northern IL this afternoon with a
short wave trof moving into central IL by late afternoon.
Meanwhile a weak surface boundary was over southeast parts of
IN/IL/MO. The combination of nearby boundary and approaching short
wave trof should help to support development of isolated
convection this afternoon through sunset. SPC day1 outlook has
marginal risk (5%) of severe storms in southeast CWA from Paris to
Effingham southeast this afternoon and early evening where bulk
shear and instability is a bit stronger. Highs this afternoon
range from around 80F northern CWA to the mid 80s in southeast IL
where more humid conditions will be closer to the front.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 329 AM CDT Fri Jul 29 2016

Main features today will be a nearly stationary frontal boundary
along the Ohio River and an upper level shortwave trough moving from
the central Plains into the southern half of Illinois. A weak upper
wave with this disturbance will cross Illinois perhaps bringing some
lift to the entire area.

Initially relatively clear skies and light winds are in place this
morning with patchy fog forming over especially east central and
southeast IL. This will transition to increasing clouds as the
disturbance approaches from the west...while fog will diminish by
mid morning with daytime heating. By around noon scattered
thunderstorms will be possible across most of the area as the
approaching wave provides some lift. The best chances for strong
thunderstorms containing strong wind gusts will be from near
Shelbyville to Danville southward in closer proximity to the frontal
boundary and where stronger upper level flow will result in up to 30
kts sfc-6km bulk shear by late afternoon-evening. SPC highlights
this area for a marginal risk of severe storms.

By around midnight the trough axis should be near the IN/IL boundary
with thunderstorms diminishing from west to east behind the trough
axis.

Expect highs today ranging from 78 in Galesburg to 85 in
Lawrenceville and lows tonight from 64 in Galesburg to 68 in
Lawrenceville.

.LONG TERM...(Saturday through Thursday)
ISSUED AT 329 AM CDT Fri Jul 29 2016

Rich boundary layer moisture will result in an extension of the
patchy fog potential into Saturday morning. Another possibility for
showers and thunderstorms continuing on Saturday as a weak open wave
aloft provides some lift to an already unstable airmass. Remainder
of the forecast remains very much the same. Sunday has the best
chances in the forecast to be briefly dry once the wave shifts
eastward...but southern IL will maintain some precip invof a
decaying boundary. Weak high pressure ridge builds into the eastern
half of the CONUS, although its influence is lacking this far west
of the ridge axis. Sun night/Monday maintaining some consistency
with small disturbance moving into the region with another round of
precip, particularly to the south. Though forecast for Tuesday had a
drying trend previously, still have to concede the potential
mesoscale influences over a warm and moist airmass will keep the
shower and thunderstorm threat in place over a large part of the
Midwest through the forecast period. Still think the qpf fields are
overdone in the models, and expect activity to be far more scattered
and periodic.

Temps staying in the lower 80s through the first half of the weekend
with the more northwesterly flow. After the first half of the
weekend, the building heat in the western half of the CONUS begins
to shift, putting another warming trend in place for Central
Illinois for next week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 650 AM CDT Fri Jul 29 2016

Main weather feature today will be development of isolated to
scattered TSRA this afternoon as an upper level wave moves across
the area. Some brief morning fog is possible for the first hour or
two of the forecast period, with occasional dense fog already
affecting KCMI. Afterward, primarily VFR conditions expected
until after 17Z as fog dissipates with daytime heating. Chances
for thunderstorms should start around 17-18Z with the best chances
from 21Z-03Z. Storms may produce MVFR cigs and vsby. With skies
generally clearing overnight there will be a good chance of fog
re-developing after around 09Z.


&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

UPDATE...07
SHORT TERM...Onton
LONG TERM...HJS
AVIATION...Onton



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