591 
FXUS63 KILX 052337
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
537 PM CST Fri Dec 5 2014

.SHORT TERM...(Tonight)
ISSUED AT 258 PM CST FRI DEC 5 2014

20z/2pm surface analysis shows 1015mb low over northwest Oklahoma, 
with stationary frontal boundary extending northeastward into the 
Ohio River Valley.  Widespread rain has been occurring along/north 
of this system throughout the day and is expected to continue 
through the evening.  Latest radar mosaic is showing a large area of 
moderate/heavy rain with a few embedded thunderstorms across 
southeast Missouri into southern Illinois.  Based on its E/NE 
trajectory, this area of precip will impact the SE KILX CWA over the 
next few hours.  Have therefore decided to include isolated thunder 
mention south of I-70 this evening.  Further north, a much lighter
band of rain associated with the deformation zone of the system 
extends across central Illinois back across northern/central 
Missouri into eastern Kansas.  This precip area will shift eastward 
and will ensure continued rain chances across the remainder of the 
CWA through the evening.  As low pressure tracks into northern 
Kentucky by 06z, the rain will begin to come to an end from 
northwest to southeast after midnight.  Have dropped PoPs entirely 
for locations west of the I-55 corridor after midnight, but have 
continued with categorical PoPs through the entire night along/south 
of I-70.  Despite winds shifting to the north behind the departing 
system, persistent cloud cover will keep overnight low temperatures 
a few degrees above guidance numbers, ranging from around 30 
northwest of the Illinois River to the lower 40s far southeast 
around Lawrenceville.

&&

.LONG TERM...(Saturday through Friday)
ISSUED AT 258 PM CST FRI DEC 5 2014

High pressure will build into the Midwest on Saturday, bringing cool 
and dry weather.  Skies will initially be cloudy, but will clear 
from northwest to southeast as the day progresses.  Even the usually 
more pessimistic NAM clears things out across most of the area by 
afternoon as strong synoptic subsidence/drying arrives behind 
exiting wave.  The exception will be the far SE CWA, where clouds 
will likely hang on throughout the day.  Given the morning 
cloudiness and a stiff northerly breeze, have gone slightly below 
guidance, with afternoon highs in the upper 30s to around 40 degrees.

Skies briefly clear across the entire region Saturday night before 
clouds once again increase ahead of the next fast-moving system 
embedded within the prevailing zonal flow pattern.  The system in 
question is currently evident on water vapor imagery off the coast 
of Oregon and is handled differently by the models as it moves 
across the country late in the weekend.  The 12z NAM tracks the 
upper vort max eastward across the Northern Rockies Sunday morning, 
then dives it southeastward into the lower Ohio River Valley by 
Monday evening.  Meanwhile, the GFS/ECMWF/GEM all keep the wave much 
further north across the Upper Midwest/Great Lakes.  With the NAM 
being the odd model out, its solution has been rejected in favor of 
the model consensus.  As a result, am expecting strongest lift to 
remain north of central Illinois as the feature skirts by to the 
north Sunday night into Monday.  Forecast soundings are initially 
quite dry at all levels on Sunday, with only modest moistening from 
the top-down noted Sunday night.  Ample dry air remains in place 
below 700mb through the entire period, so am skeptical about precip 
chances.  Have cut back on the PoPs accordingly, with only slight 
chances across the northern CWA late Sunday night into Monday 
morning.  If precip can overcome the low-level dry airmass and reach 
the ground, a light rain/snow mix can be expected.

Once this system passes, another shot of cooler air arrives for 
Tuesday and Wednesday, resulting in highs only in the 30s.  After 
that, all signs are pointing to a deep trough digging across the 
western CONUS by the end of next week.  Corresponding downstream 
ridging across the Plains/Midwest will lead to a warming trend with 
highs climbing well into the 40s by Friday and perhaps even higher 
next weekend.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
ISSUED AT 525 PM CST FRI DEC 5 2014

IFR/LIFR conditions with some local VLIFR cigs/vsbys are expected
to continue thru the overnight hours before we see a very slow
improvement in cigs on Saturday as the storm system shifts off to
our east. A large band of rain continues to track east northeast
into our area this evening and we really don't see much change in
that overnight as the storm approaches from the south. Further
north towards Peoria, there may be some tempo breaks in the IFR
cigs to MVFR but at this time am not expecting it to last.
Forecast soundings off the short term models not very optimistic
with respect to clearing on Saturday in the wake of the storm
system and with boundary layer winds still forecast to be out of
the north to northeast during the day, that may be the way to go
so will continue to keep at least MVFR cigs going into the
afternoon hours. Surface winds will be out of the east and then
trending more northeast later tonight and during the day on Saturday
with speeds increasing a bit to 10 to 15 kts with a few gusts near
20 kts, especially near BMI and CMI. 

&&

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

$$

SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...Smith