Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 220259
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
859 PM CST Fri Nov 21 2014

.UPDATE...
ISSUED AT 859 PM CST FRI NOV 21 2014

The warm air surge aloft and increasing warm advection with
southeast surface winds are proving to be too strong to allow the
surface temps to cool below freezing prior to the rainfall
arriving. Even our NE areas near CMI and Rantoul are seeing
surface temps rising farther above freezing with the arrival of
clouds and increasing SE winds. Calls around the area where precip
has developed has shown no icing occurring, and thermal profiles
show a continued warming trend the rest of the night. Analyzing
surface obs and road surface temps across the area show no
freezing temps in the advisory area, despite wet bulb temps around
26 to 28F in most areas. All indications show rising temps since
sunset, with no change in that trend expected. Therefore, the
freezing rain advisory will be cancelled with the evening
update.

Will remove mention of freezing rain from tonight`s grids, but will
not alter the coverage of the likely and chance PoPs through 12z.
May add a mention of fog for areas NW of the IL river later
tonight, or add some drizzle to the forecast in addition to the
showers. Will not make any changes beyond tonight`s grids with this
update.

&&

.SHORT TERM...(Tonight)
ISSUED AT 306 PM CST FRI NOV 21 2014

Will remove southwest counties from freezing rain advisory this
evening from Springfield sw as temperatures currently in the upper
30s do not appear to drop to freezing this evening per latest
forecast models. Frost depth is around 2 inches in our sw counties but
some thawing of ground surface this afternoon with temps in the mid
to upper 30s with ample sunshine so far today. 1035 mb Canadian high
pressure near the OH/WV border will drift off to the mid Atlantic
states by midnight tonight while a weak short wave ejects ne from
the central Plains into IA and central/northern IL. Clouds over MO
and spreading ne into sw parts of IA/IL early this afternoon to
spread ne across central/se IL rest of the afternoon. Patches of
light precipitation developing during the evening over central IL,
reaching areas from I-74 ne after 9 pm. Areas from Springfield sw
and in southeast IL to stay above freezing tonight to support just
rain. Areas ne of Springfield to drop to near or just below freezing
for a time this evening before temps rise overnight and reach back
into the mid to upper 30s by dawn Sat. Deeper frost depth of 4-6
inches from Lincoln ne so freezing rain more likely but ice
accumulations still less than a tenth inch, but could cause some
travel difficulties. Thus will continue the freezing rain advisory
northern half of CWA this evening and continue from I-74 ne until 4
am.

&&

.LONG TERM...(Saturday through Friday)
ISSUED AT 306 PM CST FRI NOV 21 2014

Rain chances will continue into Saturday as southwesterly flow
continues over the area through the weekend. Models look similar on
timing of the pcpn, but differ on location of some of the heaviest
pcpn amounts. However, Sunday will be the period with the highest
pops and qpf values, given this will be just ahead of the cold front
that will move through the area Sunday night. The mid level trough
will not move through the area until Monday through Monday night, so
pcpn chances will decrease from likely on Sun night to small chances
by Monday afternoon. The colder air will lag behind the cold front
and move through the area Monday during the day. Therefore, will
have falling temps Sunday night, then steady temps Monday morning,
and then falling temps Monday afternoon through Mon night.

Temps over the weekend will be above normal with warmest temps being
in the 50s and Sat night temps in the 40s.

Northwest flow will dominate the pattern early next week after the
weekend system. This will bring the cold temps back into the region
for the week. There will be a clipper-type system drop through the
area mid week with the chance of snow and then the return to colder
temps for the last part of the week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
ISSUED AT 600 PM CST FRI NOV 21 2014

VFR conditions early this evening will deteriorate to MVFR between
01z-03z as a period of light freezing rain spreads NE across
central IL. SPI may remain above freezing even at the onset of
precip this evening, preventing much in the way of icing there.
The other terminal sites have a better chance of seeing anywhere
from 1 to 4 hours of freezing rain/drizzle before air temperatures
climb back above freezing. Very slippery conditions could quickly
develop as the precipitation falls on dry cold pavement. The very
strong push of warm air aloft will eventually translate to the
surface and push ground level temps above freezing after a few
hours.

The MVFR ceilings will generally dip to around 1500FT in most
areas, with vsbys as low as 4-6 miles from late evening into Sat
morning. LLWS chances increase later tonight and Sat morning as
winds at 2k ft from the SW increase to 45-55 kts. Surface winds SE
at 10-14 kts this evening to veer south overnight and increase to
near 15 kts by 15Z/Sat.

The precip will be triggered by a shortwave aloft and a strong low
level jet pulling warm and moist air over the top of the cold dome
of high pressure in place across IL this evening. Rain chances
will linger through much of the day on Saturday, but no additional
freezing rain conditions are expected after the first few hours of
precip this evening and overnight.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

UPDATE...Shimon
SHORT TERM...07
LONG TERM...Auten
AVIATION...Shimon





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