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Area forecast discussion 
National Weather Service Lincoln Illinois
329 am CDT Friday Jul 29 2016

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 Illinois. 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. Storm Prediction Center highlights
this area for a marginal risk of severe storms.

By around midnight the trough axis should be near the in/Illinois boundary
with thunderstorms diminishing from west to east behind the trough

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


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 Illinois 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 Continental U.S. Begins
to shift, putting another warming trend in place for central
Illinois for next week.


Aviation...(for the 06z tafs through 06z Friday night)
issued at 1146 PM CDT Thu Jul 28 2016

Very tricky aviation weather forecast for the next several hours.
Skies across central Illinois are mostly clear at the moment, but
there area some patches of low end VFR and MVFR clouds floating
around. More widespread cloudiness exists upstream, as close as
the WI/Illinois border area, with VFR, MVFR, and IFR conditions all
represented. These clouds are ahead of an upper-level disturbance
that will help produce scattered thunderstorm across the area
tomorrow. Main concern until the more widespread cloudiness moves
in is if additional cloud cover will develop overhead and/or fog
becomes more widespread.

The short-range model guidance has overdone the low clouds/fog in
this airmass of late, and this may be the case again tonight.
Run-to-run consistency has not been good either tonight, with
guidance becoming cloudier/foggier one run, only to back off the
next hour. For now, have gone more optimistic than the current
guidance based on trends from recent nights. However, have still
carried periods of MVFR ceilings & local IFR visibilities. Have conditions
improving diurnally tomorrow, with a chance of thunderstorms
developing by afternoon.


Ilx watches/warnings/advisories...


Short term...Onton
long term...hjs

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