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fxus63 kilx 191510 
afdilx

Area forecast discussion
National Weather Service Lincoln Illinois
1010 am CDT Tue Sep 19 2017

Update...
issued at 1010 am CDT Tue Sep 19 2017

The shortwave trough responsible for last night's thunderstorm
activity has reached the Illinois/in state line this morning, continuing
slowly eastward. Associated precipitation on radar is now east of
the central/southeast Illinois forecast area, although perhaps a few showers
or an isolated thunderstorm redeveloping with afternoon heating
can't be ruled out near the Indiana border. Have trimmed pops down
with morning update. In addition...dense fog from overnight has
thinned and lifted so have expired the dense fog advisory for
west- central Illinois. Added patchy fog for late morning, however as a
few observations of light fog continue.

&&

Short term...(today and tonight)
issued at 300 am CDT Tue Sep 19 2017

A welcome area of showers and thunderstorms continues to push
across locations east of I-57 early this morning, as a weak
disturbance slowly moves across eastern Illinois. The western
portion of the County Warning Area has seen some clearing behind the boundary,
which has resulted in the prompt development of low clouds and
areas of dense fog. A dense fog advisory was issued for locations
from about Galesburg-Springfield westward earlier, and surface
reports indicate some dense fog patches as far east as
Taylorville. So far, the dense fog in our County Warning Area has been fairly
variable, except in the extreme southwest corner of the County Warning Area where
a more solid dense fog has persisted. However, the rap/hrrr
models, as well as the GFS, show some potential for it edging a
bit further eastward. Will hang onto the current configuration for
now, but will need to watch this closely over the next couple
hours.

The lingering showers and storms over eastern Illinois will
through about midday, but will diminish once the upper wave
passes. The low cloud deck is expected to erode mid to late
morning, giving the afternoon some decent sunshine over the
western County Warning Area. Temperatures will remain well above seasonal normals,
mainly reaching the lower to mid 80s.

Long term...(wednesday through monday)
issued at 300 am CDT Tue Sep 19 2017

Not much has changed with the forecast philosophy through the
weekend. An upper ridge will amplify across the Mississippi
Valley, as the slow movement of Hurricane Jose up the East Coast
blocks the overall progression of systems from west to east. A
deepening trough over the western U.S. Will keep a southwest flow
in place for US, sending 850 mb temperatures of 17-20c through the
weekend. Surface highs 10-15 degrees above normal are likely, with
lower 90s at least into Friday. May need to warm weekend highs a
bit as well, but will mainly go upper 80s at this time. Record
highs Wednesday and Thursday are mostly in the mid 90s.

With the strengthening ridge, the only precipitation question will
be Wednesday afternoon and night. A cold front moving toward the
ridge will struggle to make any decent headway into our County Warning Area
Wednesday evening. The GFS remains the only model that punches
showers and storms all the way through the forecast area, with the
other synoptic models dissipating the rain as the front stalls
over eastern Iowa/northwest Illinois. Will maintain only the area
northwest of the Illinois River seeing pop's above slight chances.

&&

Aviation...(for the 12z tafs through 12z Wednesday morning)
issued at 646 am CDT Tue Sep 19 2017

Dense fog and vlifr conditions will affect the terminal sites
through 15z. There are areas of LIFR and even IFR, but prevailing
conditions through the first 3 hours of the 12z tafs should be
vlifr/LIFR due to vis and/or ceilings. Forecast soundings are
pointing toward a few hours of stratus after the fog lifts, then
skies becoming scattered by mid-day.

Any showers and storms associated with a departing weather
disturbance should remain east of the terminals, with cmi and Dec
having a small chance of light rain this morning.

Winds will be light and variable this morning, with directions
this afternoon shifting around from the west to the southeast.
Light southeast winds are expected tonight, with MVFR fog possible late
tonight.



&&

Ilx watches/warnings/advisories...
none.
&&

$$

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