Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 261201

Area Forecast Discussion
601 AM CST Wed Nov 26 2014

.SHORT TERM...(Today)

08z/2am surface chart shows 1010mb low centered just north of Omaha,
with light snow observed as far east as the Des Moines area.  00z
Nov 26 models are consistent with prior runs, showing the low
tracking southeastward into northeast Missouri this afternoon, then
into the lower Ohio River Valley by evening.  Model QPF fields have
come into better agreement, now showing a much more compact area of
precip associated with the wave skirting across mainly the W/SW KILX
CWA today.  With so much dry air initially in place, think this
makes sense as precip should be confined to locations immediately
along and to the north of the low track where lift is strongest.  As
a result, have continued to hit PoPs hardest along and southwest of
a Robinson line.  Forecast soundings
support snow as the precip begins by mid to late morning: however,
as surface temperatures rise into the middle to upper 30s this
afternoon, the snow will mix with rain.  This will serve to mitigate
potential accumulations, which are still expected to be minimal.
Snowfall amounts of one half to one inch can be expected
along/southwest of a Galesburg to Taylorville line.  Further
northeast, have opted to go with a dry forecast along/northeast of a
Bloomington to Paris line.


.LONG TERM...(Tonight through Tuesday)

Light snow will linger across much of central and southeast Illinois
this evening, as a trough axis extends northwestward from departing
low pressure in the Ohio River Valley.  A couple tenths of an inch
will be possible south of I-70 in closer proximity to the actual
low, with only trace amounts further northwest.  Any light
snow/flurries will come to an end overnight with cloudy skies
persisting through the night.  Still some question as to how quickly
skies will clear on Thursday, with the NAM suggesting clouds hanging
around for much of the day.  Given what happened with the clearing
trend yesterday and the presence of plenty of lingering low-level
moisture on forecast soundings, have opted to start the day cloudy,
followed by a gradual west-to-east clearing by afternoon.  Will be a
much colder day as well, as the departing clipper system taps
into a very chilly airmass over southern Canada.  A glancing blow
of this cold air will result in highs ranging from the middle 20s
north to the middle 30s far south.

The cold air will be short-lived however, as high pressure will
quickly shift east of the region and a strong southerly flow will
develop on Friday.  Tight pressure gradient will lead to winds
gusting to between 25 and 30 mph at times, which will help boost
afternoon highs into the 40s.  Even warmer weather is expected over
the weekend, as digging upper trough over the Northern Rockies
induces downstream ridging across the central CONUS.  With continued
southerly flow and partial sunshine, temps will soar into the lower
to middle 50s on Saturday and may even reach the lower 60s across
the far SE CWA on Sunday.  As the Northern Rockies wave tracks
eastward along the northern tier of states, it will gradually push a
cold front into the region early next week.  There are still some
model discrepancies concerning timing of FROPA and any potential
PoPs, with the latest model solutions delaying the front until late
Sunday.  Sprawling high pressure along the Gulf Coast will limit
northward moisture return, so think precip chances along/ahead of
the front will be minimal.  Will carry low chance PoPs across the
central/southern zones Sunday, then across the far south Sunday
night.  Front settles southward into the Ohio River Valley and
another shot of colder air temporarily arrives on Monday with highs
falling back into the 30s and lower 40s.  After that, model
solutions diverge as GFS builds another upper ridge across the
central/eastern CONUS on Tuesday/Wednesday while the ECMWF shows a
more progressive zonal flow continuing.  The latest ECMWF is much
different than its previous run, so am skeptical to jump on this
solution just yet.  As a result, will follow the GFS more closely,
resulting in warmer weather for the middle of next week with
increasing rain chances coming into the picture by Wednesday.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)

A clipper system will impact the central Illinois terminals
through the 12Z TAF valid time. Clouds will thicken and lower this
morning into this afternoon, with light snow expected to develop
during the afternoon. The snow chances, once they develop, will
linger into this evening. VFR conditions should prevail until the
snow breaks out, with KSPI & KDEC most likely to see an extended
period of MVFR cigs and vsbys. KPIA, KBMI, and KCMI stand a better
chance of staying VFR once the snow develops, but they should see
at least a period of MVFR vsbys. Southeast winds will start the
period, with winds trending variable later today as the low
pressure center tracks nearby. Northwest winds are expected on the
back side of the system later tonight.




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