Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 202048
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
248 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 18Z TAFS through 18Z Friday afternoon)
ISSUED AT 1120 AM CST THU NOV 20 2014

Subsidence behind weak trough has lead to SKC to SCT conditions
across the Central Illinois TAF sites has allowed momentum transfer
to produce wind gusts around 20 kts at times from west. The surface
ridge over Central U.S. will push east into the terminal sites
late this afternoon and overnight which should reduce winds and
gusts below 10 kts.

Southeast flow on backside of ridge is expected to develop Friday.


&&

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

$$

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






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