000
FXUS63 KILX 300827
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
227 AM CST Sat Nov 30 2013

.DISCUSSION...
ISSUED 227 AM CST Sat Nov 30 2013

Main forecast challenge focuses on departing storm system for the
middle and end of next week...and whether or not it will produce
any wintry precipitation across central Illinois.

SHORT TERM...Today through Monday

Mild and quiet weather will prevail through the short-term.
Increasing southerly winds on the back-side of high pressure
anchored along the East Coast will bring above normal temperatures
back into the area today. Despite a chilly start to the day, the
southerly flow coupled with ample afternoon sunshine will boost
highs into the middle to upper 40s, with a few locations across
the S/SW KILX CWA potentially reaching the 50 degree mark. A weak
cold front will sag southward into the area on Sunday, bringing a
few clouds and a shift in the winds. Thanks to northerly winds
behind the boundary across the northern half of the CWA,
temperatures will be a couple of degrees cooler than today.

Front will become parallel to the zonal upper-level flow and will
stall across the Ohio River Valley Sunday night into Monday. As
Gulf moisture continues to flow northward over the boundary and a
short-wave trough ripples eastward out of the Plains, a few light
rain showers may develop on Monday. Several of the operational
models are hinting at this, so have included a 20 POP accordingly.

LONG TERM...Tuesday through Friday

Main show will hold off until the extended, as an upper-level low
currently over Alaska sinks southward and carves out a long-wave
trough across the western CONUS by the middle of the week.
Downstream ridging will produce deep southwesterly flow over the
Midwest, resulting in cloudy skies and increasing precip chances
Wednesday into Thursday. Model spread is still significant, so
exact evolution of the developing storm system is uncertain at
this time. General consensus develops surface low pressure in the
lee of the Rockies, then tracks it northeastward into Canada by
Thursday. Trailing cold front will likely push through Illinois
Wednesday night into Thursday, triggering scattered showers and
perhaps a thunderstorm. Things get tricky once the front passes
and the colder air begins to arrive Thursday into Friday. 00z Nov
30 GFS/GEM both show front quickly advancing eastward, with precip
largely ending before the cold airmass spreads into the area. This
would tend to support a brief change-over to light snow Thursday
night as the front slides eastward into Indiana before the precip
comes to an end on Friday. Meanwhile, the 00z ECMWF suggests much
more precip will hang back in the cold air Thursday night,
followed by another wave of low pressure riding along the boundary
and a renewed round of precip in the cold airmass on Friday. This
could lead to a much more wintry scenario, with rain changing to
snow Thursday night and another chance for snow on Friday. At this
point, will trend toward the GFS/GEM consensus. As a result, will
mention a rain/snow mix west of the Illinois River as early as
Thursday, with rain changing to light snow further east to the
Indiana border Thursday night. Will go with a mainly dry forecast
for Friday, but will hold on to a chance for rain/snow across the
far E/SE CWA in case secondary wave does indeed develop along
departing front. Once this system exits the region, much colder
weather will be on tap for the end of the week.

Barnes
&&

.AVIATION...
ISSUED 1126 PM CST Fri Nov 29 2013

VFR conditions will continue at all TAF sites next 24hrs. Broken
high cirrus is over the area currently and will continue
overnight, but then will become clear during the morning hours.
Then expecting an increase in low level moisture around 4kft from
the west and southwest ahead of the next dry front, that should
move through the area after TAF period. Winds will be southeasterly
and then become southerly in the morning, then southwest ahead of
the front during the evening hours.

Auten
&&

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

$$