Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 230915

Area Forecast Discussion
315 AM CST Sun Nov 23 2014

.SHORT TERM...(Today)

Weak short-wave that brought showers to east-central Illinois
earlier this evening has now lifted into the southern Great Lakes,
leaving behind cloudy, but dry conditions across central Illinois.
Upper air analysis indicates a plume of rich 850mb moisture streaming
northward from the western Gulf of Mexico.  As the low-level jet
gradually strengthens to around 40kt, models are showing showers
re-developing in this moistening airmass across north-central
Missouri between 09z and 12z.  The showers will increase in areal
coverage and lift northward into the Illinois River Valley this
morning, while locations further east toward the Indiana border may
see a lull in the precip chances through midday.  As northern stream
upper wave currently over the Rockies pushes eastward and helps
eject vigorous wave over southern Texas northward, synoptic lift
will increase markedly across the region later today.  Given strong
lift interacting with deep-layer moisture, showers will become
widespread across the entire area by mid to late afternoon.  In
addition to the precip, it will be a breezy and warm day.  Forecast
soundings suggest southeasterly wind gusts of 20 to 25mph, which
will help push high temps a few degrees above guidance into the
middle to upper 50s.


.LONG TERM...(Tonight through Saturday)

00z Nov 23 GFS/ECMWF have both shifted the track of the approaching
surface low westward, and now look very similar to previous runs of
the NAM.  The new projected track will take the low from Kansas this
morning to northwest Illinois tonight, meaning central Illinois will
punch into the warm sector of the system this evening.  Given
presence of strong upper dynamics and marginal elevated instability,
have decided to expand the thunder mention further west and north
across nearly the entire area this afternoon/evening.  Rain chances
will be greatest during the afternoon and early evening, then will
decrease by mid to late evening as mid-level dry slot tries to push
into the area from the southwest.  As the low lifts further
northeastward into the Upper Peninsula of Michigan overnight, a
strong cold front will get pulled eastward.  NAM is slightly
faster with the arrival of the cold air, while the GFS generally
delays it until Monday morning.  Will take a blend of the models
here, resulting in deformation zone rain showers mixing with snow
across the Illinois River Valley toward dawn.  As the colder air
arrives in earnest, snow-showers will spread further eastward
toward the I-55 corridor Monday morning.  Heaviest precip will
generally be lifting northeastward with the low, so best chances
for accumulating snow will be along/northwest of a Rushville to
Bloomington line where around 1 inch will be possible.  Further
south and east, precip will be lighter and will remain in the form
of rain east of the I-57 corridor.  Aside from the precip chances,
blustery and much colder conditions will develop courtesy of
westerly winds gusting to between 30 and 35mph.  High temperatures
will be achieved early in the day, followed by readings falling
through the 30s during the afternoon.

Once this system exits the region, cold and dry weather will be the
rule for much of the week.  The only other chance for precip will
arrive on Wednesday as a clipper system skirts through the region.
WAA ahead of the wave will help boost temperatures well into the 30s
and even into the 40s across the far southern CWA, so precip type
will likely be a rain/snow mix.  Since QPF is expected to remain
rather light and temps will be well above freezing, am expecting
little or no snow accumulation Wednesday/Wednesday night.  After
that, a return to cold/dry weather is anticipated for
Thursday/Friday followed by moderating conditions by next


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)

A short period of IFR ceilings will affect PIA and BMI at the
start of this TAF period, but a return to MVFR ceilings is
expected for a couple hours after that. Some area could climb to
VFR based on upstream cloud reports. Spotty showers or sprinkles
will be the main precip the rest of tonight and into Sunday
morning. A strong SW LLJ will continue tonight, providing LLWS
conditions for much of the night and into Sunday morning.

AS the main wave of rain overspreads the area later Sunday
morning with moderate rains Sunday afternoon, visibility will dip
to MVFR at all TAF sites, and possibly as low as IFR for DEC and
CMI Sunday afternoon during any moderate rains. Kept the more
pessimistic IFR ceilings at all terminals Sunday afternoon, when
categorical rain chances are forecast for all TAF sites. Winds
will remain somewhat gusty the rest of tonight. SSW winds 12-16
kts with gusts 18-24 kts may continue for a few hours for SPI and
BMI. The other terminals seem to have diminished enough to keep
gusts at bay. Gusts will return to all TAF sites on Sunday as the
low pressure approaches, then moves across NW IL. Wind directions
will become complicated near the low Sunday evening. For now we
show a backing from S to SE, but directions could become NE for a
time ahead of the low Sunday late afternoon/early eve.




LONG TERM...Barnes
AVIATION...Shimon is the U.S. government's official web portal to all federal, state and local government web resources and services.