Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 082319

Area Forecast Discussion
National Weather Service Lincoln IL
519 PM CST Thu Dec 8 2016

.SHORT TERM...(This evening through Friday)
ISSUED AT 240 PM CST Thu Dec 8 2016

1045mb high extending from Alberta/Saskatchewan southeastward to
Oklahoma will shift slowly eastward over the next 24 hours...with
the ridge axis eventually reaching the Mississippi River by Friday
evening.  In the meantime...central Illinois will continue to be
influenced by cyclonic flow around a deep upper low over Quebec.
Widespread cloud cover currently blankets central/northern
Illinois...with the southern edge of the cloud shield roughly along
a Des Moines, Flora line.  Main short-
term challenge will be predicting how quickly the clouds shift
eastward.  With deep-layer northwesterly flow in place, any
appreciable clearing will be slow to take place.  While model
solutions vary, think slow is the way to go in this particular
pattern.  As a result, will continue with a mostly cloudy forecast
across much of the CWA tonight and Friday.  Skies will at least
partially clear along the S/SW periphery of the CWA...especially
along/southwest of a Robinson line.
A few snow flurries have been reported from time to time beneath the
overcast, so have included mention of flurries across the northern
CWA through tonight.  Due to persistent cloud cover and northwest
winds, much below normal temperatures will continue...with lows
tonight in the teens and highs on Friday remaining in the 20s.

.LONG TERM...(Friday night through Thursday)
ISSUED AT 240 PM CST Thu Dec 8 2016

Temperatures will begin to moderate to start the period. These
milder, but still below normal, temperatures will last through the
beginning of next week before the next shot of Arctic air arrives.

The precipitation scenario for the weekend has changed a bit since
yesterday, and model agreement is better. A clipper type wave will
streak across the area Saturday afternoon and night bringing a quick
shot of snow to northern portions of the forecast area. This wave
has trended further north the last few model runs, and would expect
most of the snowfall to occur along/north of the I-74 corridor.

A more substantial wave will dig into the Plains on Sunday,
developing a surface low that will track northeast across the
forecast area Sunday night. This system looks increasingly like it
will tap into enough warm air that the precipitation on the warm
side of the low will mostly fall as rain, while mostly snow is
expected on the cold side. This is resulting in a complicated
weather type forecast across the forecast area from Sunday afternoon
through Sunday night, as there are still important differences in
the forecast storm track. A blended solution remains the way to go
given the uncertainty, and expect several forecast adjustments to be
needed to the details between now and Sunday. At this point, the
window for all snow, with sufficient intensity, looks too small for
significant snow accumulation.

Quiet weather returns for Monday. The passage of an Arctic cold
front Tuesday/Tuesday night will be accompanied by snow showers, but
they should not be significant. However, the cold air behind the
front will be (significant).


.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 512 PM CST Thu Dec 8 2016

Backedge of low VFR/MVFR clouds extend from KFSW to just south of
K3LF with some erosion noted over extreme western IL over the past
few hours. Overall, this band of clouds was tracking southeast
with a slight eastward shift seen in the latest satellite data.
However, with northwesterly flow locked in place across the region
any eastward shift in the cloud cover will be on the slow side.
KSPI the closest to the clearing this evening and will keep an eye
on the clearing just to its west and make a last minute call on
that site. Further north and east, MVFR clouds should hold thru
the night before we see cloud heights come up to low VFR excpt for
KBMI where MVFR cigs are expected to hold. Surface winds will
diminish out of the northwest to 7 to 12 kts and then turn more
into a west to northwest direction on Friday with speeds ranging
from 8 to 13 kts.




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