Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 211752
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1152 AM CST Fri Nov 21 2014

.UPDATE...
ISSUED AT 1045 AM CST FRI NOV 21 2014

Just a few minor updates to the forecast today with addressing
increasing cloud cover this afternoon from the southwest after
ample sunshine this morning. Highs in the low to mid 30s this
afternoon with mildest readings sw areas and in southeast IL.
Southeast winds 8 to 16 mph with gusts to 20 mph this afternoon.

1036 mb Canadian high pressure over southern Ohio and ridging west
into eastern IL was provided sunshine this morning over central/se
IL with se winds 8-15 mph and a few gusts of 15 to 20 mph over
western IL. This Canadian high brought cold temps to IL early this
morning with lows of 4F in Altona (northern Knox county), 6F on ne
side of Normal, 7F at NWS office in Lincoln and 8F at airports in
Bloomington and Champaign.

High pressure to continue drifting east across the ohio river
valley this afternoon with increase se breezes over central IL.
MVFR clouds over central and sw MO into sw KY to spread ne into
central IL during the afternoon with skies becoming mostly cloudy
sw areas by late afternoon while areas from I-74 generally have
mostly sunny skies today. Will look at latest models before making
any changes to headlines tonight, so freezing rain advisory
continue tonight northern half of CWA for ice accumulations
mostly less than a tenth inch.

&&

.SHORT TERM...(Today)
ISSUED AT 349 AM CST FRI NOV 21 2014

High pressure ridge over the region this morning with light and
variable winds across Central Illinois.  Another cold day expected
with highs in the low to upper 30s, but some moderation in the
airmass is expected going into the evening  hours. Southeasterly
winds increasing through the afternoon as the ridge axis slips
eastward.  Main issue for the forecast remains the onset of rain
this evening as the temps drop below freezing.  Models are still
changing a bit with the timing of the cold air and the approach of
the precip. Moisture advecting into the region on the back  side of
the ridge building some weak showers north as temperatures drop
after sunset. The window for freezing rain may be short-lived,
particularly along a line from Springfield to Jacksonville. Rain
spreading north into the region before the bulk of the warm air
moves into place and sfc temps will still be at or below freezing at
onset. Also, the ground is still frozen and am concerned that the
warm air will be a little slower to erode the cold dense air at the
surface. Best chances for the freezing rain will be narrow and variable
windows from 6 pm to midnight, shifting northward as the evening
progresses. The threat will come to an end as the warm air works
its way into Central Illinois. Some adjustment likely to the
advisory after the morning run of models comes in. Variation with
every run has resulted in low confidence about the duration of the
freezing rain threat, so there is a bit of a cushion in the timing
of the ice accumulation. Accumulations are expected to be low, and
in some areas, may see little more than freezing drizzle,
particularly east of the Interstate 55 corridor north of Lincoln,
closer to the drier air under the sfc ridge. Either way, the first
icing event of the year, regardless of duration, will be issuing
an advisory. Freezing rain advisory out for the evening hours,
ending before the morning traffic picks up.

&&

.LONG TERM...(Tonight through Thursday)
ISSUED AT 349 AM CST FRI NOV 21 2014

More southerly winds will begin to set up late Friday in advance of
a developing system to the SW. Same developing system will continue
to produce rain through the weekend.  A gap continues to show up in
the models between the developing warm frontal feature and the core
of the sfc low. But the timing is just different enough in the
GFS/NAM/ECMWF to maintain a rather high chance/likely pop through
the overnight Sat night. Best chances for the weekend is in the high
chance/likely category for precip, and has moved to categorical on
Sunday with the highest QPF.  Temps not high enough to significantly
warm the ground, so some frozen ground will increase some threat for
rising creeks and rivers with increased runoff. Beyond tonight,
Saturday through Sun night will be dominated by rain before possibly
seeing some snow on the back side of the system as cold air moves
back in late Sun night/early Monday as the precip comes to an end.
A soggy weekend overall, with temps struggling into the 50s for
Sunday.

Next week will see a return of some cold temps as another trof digs
into the center of the country.  A chance at a clipper system
starting to show up in the model runs for Wednesday, potentially
impacting a busy travel day, and have upped to a chance pop to start
the trend for that system a little earlier than the SuperBlend.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
ISSUED AT 1150 AM CST FRI NOV 21 2014

VFR conditions this afternoon and early evening across the central
IL airports expected to deteriorate during mid/late evening as
a period of light freezing rain spreads ne across central IL.
MVFR ceilings 1-3k ft and possibly vsbys as low as 4-6 miles to
develop toward late evening and continue into Sat morning. Just
about a 4 hour period of light freezing rain/drizzle before temps
warm above freezing to change to light rain/drizzle overnight.
Added LLWS overnight into Sat morning with 2k ft sw winds of 45-55
kts. SE surface winds 10-14 kts this afternoon to veer south by
overnight and increase to near 15 kts by 15Z/Sat.

1035 mb Canadian high pressure over southern Ohio will drift east
into the mid Atlantic states by midnight, will increase WAA and
isentropic lift pattern developing over IL tonight. Weak short
wave to eject northeast from the central Plains into IA and
central/northern IL by mid evening spreading in patches of light
freezing rain/drizzle and changing to light rain/drizzle toward
overnight. Broken to overcast MVRF clouds over MO sw of St Louis
will spread ne across central IL by early evening and could get to
SPI by 00Z. Mixed light precipitation to follow a few hours later
with MVFR clouds and chances of light rain rain/drizzle lingering
overnight and Sat morning.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
FREEZING RAIN ADVISORY from 9 PM this evening to 4 AM CST
Saturday FOR ILZ027>031-037-038-045.

FREEZING RAIN ADVISORY from 6 PM this evening to 1 AM CST
Saturday FOR ILZ036-040>044-047>051-053.

&&

$$

UPDATE...07
SHORT TERM...HJS
LONG TERM...HJS
AVIATION...07





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