Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 241748
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1148 AM CST Mon Nov 24 2014

.UPDATE...
ISSUED AT 1045 AM CST MON NOV 24 2014

Updated the forecast to adjust winds and precipitation chances
today. Kept the wind advisory going into the afternoon for eastern
IL but will likely be able to cancel early as very strong and
still deepening 977 mb low pressure over eastern Ontario pulls
ne away from the Great Lakes region. Still getting some sustained
winds 25 to 30 mph with gusts of 35 to 45 mph in our ne counties
late this morning. Light snow north of I-72 is starting to
diminish and expect this trend to continue into this afternoon as
light snow chances diminish to slight chance and flurries. Highs
have already been reached early this morning with current temps
ranging from 30F at Galesburg to 45F at Mount Carmel airport.
Temps to mostly be in the low to mid 30s today and settle into the
upper 30s to near 40F in southeast IL this afternoon.

&&

.SHORT TERM...(Today)
ISSUED AT 329 AM CST MON NOV 24 2014

Several short-term forecast challenges today, as a potent storm
system tracks through the area.  Of particular concern are
strong/gusty winds behind a departing frontal boundary and the
potential for a light accumulation of snow across the W/NW KILX
CWA.

08z/2am surface analysis shows cold front extending from southern
Lake Michigan to the Ozarks.  An area of low pressure along the
boundary over southeast Missouri is currently enhancing lift and
triggering a few thunderstorms along/south of the I-70 corridor.
This activity will push E/NE into Indiana by dawn.  Further west, an
area of precipitation along/behind the front will continue to lift
northward, mainly impacting locations along/west of I-57.  As colder
air streams into the region, the rain will gradually mix with and
change to snow by mid-morning.  Based on upstream temp falls across
Iowa/Missouri, readings will drop into the middle 30s across the
Illinois River Valley by 12z/6am, then further east to the I-55
corridor by 15z/9am.  At the same time, the precip will be pulling
northeastward out of the area, so there appears to be only a narrow
window of opportunity for snow across the W/NW.  Will carry likely
to categorical PoPs across the western half of the CWA for rain
changing to snow this morning, with lower rain chances further east
and south across the remainder of the region.  Main area of snow
will lift into northern Illinois by midday, with only a few
flurries/snow-showers persisting along/north of I-72 this
afternoon.  Total snow accumulation will be limited due to light QPF
and marginally favorable temps.  Around 1 inch is expected
along/north of a Canton to Bloomington-Normal line, with trace
amounts as far southeast as a Litchfield to Champaign-Urbana
line.

Other big story today will be the strong winds behind the cold
front.  Upstream obs have already shown gusts as high as 30-40mph
and think these will translate eastward across central Illinois this
morning.  Main question will be whether there may be a corridor of
enhanced winds approaching Wind Advisory criteria across the E/SE
CWA.  Current MSAS analysis shows max 3-hour pressure rises of 6mb
over southern Missouri/northern Arkansas.  Both the 00z and 06z runs
of the NAM have shown these rises tracking northeastward and
increasing to around 9mb over southeast Illinois later this
morning.  HRRR 10m wind gust graphic also indicates increasing winds
ahead of the pressure change couplet as it moves across the
southeast CWA between 12z and 18z.  Given this consistent signal,
think it is prudent to issue a Wind Advisory for locations
along/southeast of a Champaign to Taylorville line.  While all of
central Illinois will experience wind gusts of 30 to 35 mph, this
particular area may see higher gusts exceeding 40 mph.

&&

.LONG TERM...(Tonight through Sunday)
ISSUED AT 329 AM CST MON NOV 24 2014

Low pressure will lift into the Great Lakes tonight, taking the bulk
of the precip with it.  Wrap around moisture may brush across the
northern CWA, so have included scattered flurries in the forecast
this evening along/north of I-72.  Forecast soundings indicate low
clouds will persist tonight and may even be slow to clear on
Tuesday, despite approaching surface ridge axis.  Have therefore
slowed the clearing trend, with cloudy skies tonight followed by
decreasing clouds on Tuesday.

Fast-moving clipper system is still on target for mid-week, with
model consensus bringing the system across central Illinois on
Wednesday.  This particular track is slightly further south than
previously advertised, so WAA ahead of the wave may not be quite as
pronounced as once thought.  Even still, high temperatures will
climb well into the 30s and into the lower 40s across the southeast
CWA.  End result will be light snow across the far north from the
Peoria area northward, a mix of light rain/snow across much of the
area, and mainly rain south of I-70.  Due to the limited period of
light precip and warm temps, snow accumulations will be minimal.
Once this system passes to the east, another shot of cold air will
arrive for Thursday.  After that, signs are still pointing to warmer
conditions by the end of the week, with temps climbing well into the
40s by Saturday.  Both the GFS and ECMWF indicate a cold front will
drop through the region Saturday night, so temps will likely drop
back into the upper 30s/lower 40s by Sunday/Monday.  Moisture will
be limited, so will maintain a dry FROPA at this time.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
ISSUED AT 1150 AM CST MON NOV 24 2014

Light snow showers and flurries will occur into mid afternoon over
mainly northern TAF sites of PIA and BMI where MVFR vsbys 3-5 miles
to occur at times. Have just flurries further south along I-72 TAF
sites this afternoon with vsbys generally above 5 miles. MVFR overcast
ceilings to continue through tonight with BMI as low as 900 ft at
midday. Strong and deeping 976 mb low pressure near the
Ontario/Quebec province line continue to pull northeast away from
the Great Lakes region as it lifts across Quebec but still have
cyclonic flow over IL through tonight. This will likely keep
broken to overcast low clouds over central IL through tonight and
have ceilings lifting up to VFR during mid/late Tue morning.
Strong WSW winds 17-25 kts and gusts of 28-35 kts early this
afternoon to gradually diminish later this afternoon and evening
reaching speeds of 10-15 kts after 02Z with west winds around 10
kts overnight into Tue morning.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY until 6 PM CST this evening FOR ILZ044>046-052>057-
061>063-066>068-071>073.

&&

$$

UPDATE...07
SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...07





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