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Area forecast discussion 
National Weather Service Lincoln Illinois
issued by National Weather Service Chicago Illinois
1150 am CST Tue Jan 27 2015

Short term...(today)
issued at 326 am CST Tuesday Jan 27 2015

What we feared yesterday morning at this time panned out with the
freezing drizzle breaking out late yesterday afternoon and evening
along the tail end of the band of light snow that brought a few
areas a half inch to one inch of snow. The 4km WRF forecast soundings
were showing the ice crystals departing around 400 PM yesterday
afternoon with some weak Omega/lift remaining in the low levels of
the atmosphere where moisture was still present, along with just
enough shear in the 950-850mb layer. Radar mosaic showing the last
batch of light snow and freezing drizzle tracking south through east
central Illinois early this morning and based on the present
movement, most of it should push out of our forecast area by 14z.
Based on that, we will continue the Freezing Rain Advisory until
the expiration time of 600 am.

Current surface analysis indicating weak low pressure shifting to
our south with an inverted trof extending north from the low through
central and northern Illinois. The main forecast concern today will
be with temperatures as the extensive cloud cover is expected to hold
over our area as forecast soundings depict most of the low level
moisture trapped beneath a strengthening subsidence inversion thru
the day. We are seeing some breaks in the cloud cover from time to
time early this morning but as our boundary layer winds become more
north to northeast, the large area of low clouds to our north will
filter south across our area today. Coolest readings, generally in
the lower 30s, will be found over our east and northeast counties,
while over far southwest Illinois, look for afternoon temperatures
around 40 degrees.

&&

Long term...(tonight through tuesday)
issued at 326 am CST Tuesday Jan 27 2015

Low clouds to decrease during the evening as 1027 mb high pressure
drifts over Illinois/in by overnight. Lows tonight range from upper teens
to near 20f NE counties (where clearing may occur soonest) to mid
20s SW counties. High pressure drifts east into eastern Ohio River
valley by 18z/noon Wed and get a breezy south-southeast flow developing over Illinois
and bringing in milder air with partly to mostly sunny skies. Highs
Wed range from lower 40s eastern Illinois to the upper 40s to around 50f
from Jacksonville west to the MS river.

Low pressure ejects east from northern rockies into western Great
Lakes by dawn Thu and pulls cold front east across Illinois late Wed night
into Thu morning. This to bring chances of light rain overnight Wed
night into Thu morning and possibly lingering over eastern Illinois Thu
afternoon where light snow could mix in over northern counties
before ending. Lows Wed night of 33-38f with coolest readings in
east central Illinois. Highs Thu in upper 30s and lower 40s central Illinois and
mid 40s in southeast Illinois southeast of I-70.

1040 mb Canadian high pressure moves down into the Midwest Friday
and returns mostly clear to partly cloudy skies and cooler
temperatures Thu night through Fri night. Cooler highs Friday of
30-35f. Most of Saturday now appears dry over central and eastern Illinois
with chance of light snow/rain moving into west central Illinois later
Saturday ahead of next storm system. Seasonable highs Saturday in mid
to upper 30s.

00z extended models show more phasing of southern and northern
stream system this weekend and bring better chances of light snow to
central and southeast Illinois Sat night into Sunday evening as surface
low deepens NE from southeast Texas into the eastern Ohio/Tennessee River
valleys. This could bring a few inches of snow accumulations
especially in southeast Illinois where even a mix of precipitation appears
possible south of Highway 50. Another Canadian high to drift
southeast into Illinois early next work week bringing colder/below normal
temperatures.

&&

Aviation...(for the 18z tafs through 18z Wednesday afternoon)
issued at 1141 am CST Tuesday Jan 27 2015

Main aviation concern revolves around existing MVFR and IFR ceilings.
IFR ceilings are becoming less common across the terminals as drier
air slowly filters in from the northeast. Expect kbmi will hang
onto IFR a bit longer before transition MVFR ceilings in the 1000-1500
feet range. Challenge then turns to how quickly the lower cloud base
erodes. Hrrr and rap guidance are a bit mixed to how quickly this
occurs. The general feeling is that sometime this evening the MVFR
deck will lift above 2000 feet and scatter out as the hrrr
suggests...but confidence on this timing is medium. Highest confidence
on timing this occurrence is at kcmi and eastern locations where
drier air will more readily advect in. Meanwhile the rap and NAM
hold onto the clouds through 6z or slightly later as a low level
inversion remains in place. Winds overnight will veer to the
southeast and weaken before strengthening tomorrow morning. Some
patchy fog may develop after clouds clear but held off any mention
at this point.

&&

Ilx watches/warnings/advisories...
none.
&&

$$

Short term...Smith
long term...07
aviation...kmd

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