Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 302128
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
328 PM CST Fri Jan 30 2015

.SHORT TERM...(Tonight)
ISSUED AT 327 PM CST FRI JAN 30 2015

Little happening in the short term, as axis of high pressure extends
northeast-southwest across the forecast area this afternoon. Cirrus
clouds beginning to spread eastward across the Missouri/Illinois
border ahead of the organizing storm system to our southwest, and
skies will become partly cloudy overnight. Coolest conditions
expected over the northeast CWA where less cloud cover is
anticipated, with lows near 20. Temperatures not expected to move
much after midnight as southerly winds start to increase.

&&

.LONG TERM...(Saturday through Friday)
ISSUED AT 327 PM CST FRI JAN 30 2015

Models have shifted a tad north again with the track/location of the
heaviest snowfall with the approaching weekend system. As with
previous systems that have moved across the area the past couple of
months, our CWA will be right in the middle of where two mid level
troughs will be phasing together. On the surface, the low pressure
area is still developing in the southwestern US and will not move
out into the southern plains until Saturday evening. However, a cold
front will be dropping down into Illinois at the same time, and how
far this gets into central Illinois will determine where the cutoff
of the warm air and cold air is, which will also determine where the
heavy snowfall will occur. Models are in fairly good agreement, but
have trended north, so there remains some uncertainty as to amounts
and locations of the heaviest snowfall this weekend. What is known,
is that precip will begin Sat afternoon in the west and then
progress eastward through the night and continue through Sunday,
then taper off and end Sun night. The question still remains pcpn
type. Based on current forecast guidance, the precip should be
either rain or snow, or a mix. Conditions do not look favorable for
the other types of winter weather at this time; i.e. freezing rain
and sleet.

So after considerable analysis and discussions with surrounding
offices, we have come to a consensus with the forecast for this
weekend. With the resulting low pressure area tracking eastward
across southern Illinois, it looks like the heaviest snowfall will
be along and north of a Rushville to Danville line Saturday night
through Sunday. With decent isentropic lift and sufficient moisture
to work with, believe highest amounts will be in the 7 to 9 inch
range. Just south of that line, snowfall amounts look to be in the 5
to 7 inch range. Lesser amounts will be likely south of this area,
in southeast Illinois, due to the warmer temps hanging around Sat
night into Sunday morning...and the possibility of the precip being
a mix of rain and snow. This area, the amounts should be roughly in
the 3 to 5 inch range, and will include the I-70 area.

So based on this, we have already issued a Winter Storm Watch for
most of central and eastern Illinois, beginning tomorrow at 6 pm and
continuing through midnight Sunday night. The bulk of the snow,
especially in the north, should fall between 6 pm Sat through 6 pm
Sun. If the warm air get further north and/or hangs around longer,
or the low tracks a little further north then snowfall totals will
be much less across the whole area. Due to these continued
uncertainties and possible changes, it was decided not to go with a
warning and just keep the watch going at this time.

Beyond the weekend system, conditions will be relatively dry. After
a cold day on Mon, temps will rise to around freezing for Tue. Then
temps will fall again to below freezing for the rest of the week.
There is a couple of weak waves coming through but moisture appears
limited, so there will not be any mentionable pcpn in the forecast at
this time.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
ISSUED AT 1135 AM CST FRI JAN 30 2015

VFR conditions to remain on tap through the forecast period. We
are seeing some stratocumulus developing over the eastern half of
Illinois around 2000 feet, but this should remain scattered for
the most part. General trend will be for high clouds to spread in
from the west later tonight and especially on Saturday. Northeast
winds have started to become light and variable as an axis of high
pressure moves overhead, but will trend more south/southwest this
evening as the axis moves to the east.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH from Saturday evening through Sunday evening
FOR ILZ027>031-036>038-040>057.

&&

$$

SHORT TERM...Geelhart
LONG TERM...Auten
AVIATION...Geelhart






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