Area Forecast Discussion
Issued by NWS Central Illinois

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068
FXUS63 KILX 142312
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
512 PM CST Fri Dec 14 2018

.SHORT TERM...(This evening through Saturday)
ISSUED AT 233 PM CST Fri Dec 14 2018

Fog has been a real headache today. Short-term models have not
handled the stubborn visibilities well at all. Increased gradient
was expected to increase winds and mixing leading to improvement
as afternoon proceeded. That has obviously not occurred at many
locations despite winds gusting 10-15 kts. With KGBG currently at
m1/4sm and KBMI remain at 1/16sm through much of the day, the low
sun angle, and sunset approaching, see no reason that for rapid
improvements. Will keep current dense fog advisory in place
through 03z and have the evening shift re-evaluate as 00z models
arrive - though models today haven`t been a whole lot of help. At
this time some partial clearing is still possible late tonight in
KGBG area as clearing line currently in ern IA approaches. If we
do get some drier air into that area, temps may fall below
freezing. Otherwise, areas with fog and clouds should remain above
freezing and freezing fog is not expected.

Gradual clearing is expected Saturday as the upper low pulls away
from IL and drier air advects into northwest IL and then spreads
southeast. Weak cold advection will offset clearing in northwest
counties and highs should be rather uniform across central and
southeast IL, generally in the middle to upper 40s.

.LONG TERM...(Saturday night through Friday)
ISSUED AT 233 PM CST Fri Dec 14 2018

Upper low moving into mid-Atlantic should continue off to the east
as kicker short-wave progresses in nrn stream. Cold air remains
bottled up near the Canadian border and above normal temperatures
are expected to persist through early next week. 500mb heights and
850 temps increase through Wednesday as flow becomes more
meridonal in response to a digging trough over the western U.S.

As mid-week arrives, models are relatively consistent in
progressing energy over the west into the midwest as it phases
with a deepening nrn stream system. Amount of pcpn and cold
advection in the wake of the system is dependent on the amount of
phasing that occurs. As usual the GFS is phasing the energy more
than ECMWF and reflects a stronger system and colder temps in the
wake of the low. The GEFS envelope mean is even colder with
boundary layer temps for the end of the week. With so much range
in solutions, will go with a blend.

Some mixed pcpn is possible in the northern forecast area
Wednesday Night but with sfc temps expected to remain above
freezing no accumulations are expected.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 505 PM CST Fri Dec 14 2018

IFR to VLIFR conditions to prevail through at least this evening
with the potential the low cigs and vsbys will hold into Saturday
morning. Low pressure will track well south of our area later
tonight into Saturday with another band of rain expected to pass
just south of our southern TAF sites. The low level flow will
remain from a northeasterly direction tonight into early Saturday
which is not a particularly good direction for clearing around
here so confidence on any significant improvement tonight is low.

The backedge of the low clouds is out by the Mississippi River
early this evening and was edging slowly southeast at the same
time widespread mid and high level clouds were streaming back over
our area ahead of the next wave passing to the south. PIA looks
to have the best chance for seeing a slow improvement in cigs
and vsbys after Midnight, with the remainder of the TAF sites
holding in the lower cigs and vsbsy into Saturday morning.

Northeast winds of 10 to 15 kts can be expected tonight with
a few gusts up to 23 kts at times at CMI, DEC and BMI. Northeast
to north winds expected on Saturday at 12 to 17 kts.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 9 PM CST this evening for ILZ027>031-
036>038-040>043-047>051.

&&

$$

SHORT TERM...Barker
LONG TERM...Barker
AVIATION...Smith



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