Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 202353
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
553 PM CST Thu Nov 20 2014

.SHORT TERM...(Tonight)
ISSUED AT 248 PM CST THU NOV 20 2014

Surface ridge over lower Missouri Valley will push east into
Illinois overnight. Resultant drop in wind speeds will combine with
mostly clear sky to produce near ideal radiational cooling
conditions across central and southeast Illinois. Coolest readings
should be in GBG area and in the area from Paris to Effingham where
some snow cover is still observable in visible satellite. Have
generally used MAV guidance as NAM/WRF and resultant MET have been
on cold side last night and today.

&&

.LONG TERM...(Friday through Thursday)
ISSUED AT 248 PM CST THU NOV 20 2014

Upper air and moisture channel imagery this morning shows main
northerly jet from Canada into northern IL and then curving off to
the east. upper trof over eastern US is now moving east, as strong
closed low system seen moving coast to west coast. That system will
be the system that will trigger precipitation (pcpn) over midwest
into the weekend. Models similar in movement of that system, as
surface high pressure area over MO drifts off to the east.

As west coast system digs into the southwest US, surface high moving
into central east coast will aid in southern moisture advection from
the gulf into midwest n Friday. Cold air at surface will be overrun
by moisture from AR and MO, increasing on Friday and reaching region
Friday evening. Warm air overriding lingering cold dome will result
in some freezing rain on Friday evening, as the warm air advects
north into area. NAM and GFS soundings, and temperature Meteograms
show timing of the pcpn and the retreat/warming of the boundary
layer will be critical in freezing rain development. NAM seems to be
too cold, but each new run seems to warm NAM. Temperature timing in
Friday afternoon through evening and overnight was a blend of GFS
and a warming of the NAM. Freezing line is expected to retreat
northward over CWA in the evening and overnight, with brief freezing
in the south sections and longer periods in the north. Pcpn amounts
however, will be light, less than tenth of an inch. However some
slick areas will be possible on secondary roads.

For Saturday into Sunday, upper system will dig into TX and then
move north through midwest into Great Lakes by Sunday night. This
will bring periods of rain over region through the weekend, with the
heaviest rainfall on Sunday as the low center moves through. Colder
air moves in by Tuesday will some lingering pcpn.

Models then start to diverge for Wednesday and Thursday. Coordinated
will surrounding offices and consensus to drop pcpn chances for Wed
night into Thursday night until future model runs.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
ISSUED AT 552 PM CST THU NOV 20 2014

The surface ridge extending from SE North Dakota across SW Illinois will
push east across IL over the next 24 hours. Winds tonight will
start out WNW at 7 to 10 kt but become light and variable by late
evening. As the ridge axis advances east of the terminal sites on
Friday, winds will increase from the southeast. Winds speeds
should climb into the 10-12kt range by 21z Friday. Mid clouds at
15k ft will advance into the region from the SW as moisture begins
to overrun the cold high pressure. Any precipitation is expected
to hold off until after the end of this TAF period.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Barker
LONG TERM...Goetsch
AVIATION...Shimon






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