Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 230558
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1158 PM CST Thu Jan 22 2015

.UPDATE...
ISSUED AT 858 PM CST THU JAN 22 2015
High pressure ridge axis just off to the west and light and
variable winds expected as a result through the overnight hours.
Erosion of the cloud deck to the west has slowed considerably
after sunset. Low level moisture trapped underneath this evenings
inversion not mixing out and keeping the clouds around overnight.
Adjusted the forecast to accommodate the cloudy skies and to
adjust the overnight lows to slightly warmer. Updates out
momentarily.

&&

.SHORT TERM...(Tonight)
ISSUED AT 258 PM CST THU JAN 22 2015

Area of high pressure extends from northeast Kansas into west
central Illinois early this afternoon. Large stratocumulus shield
remains in place over a large part of the Midwest, but is showing
erosion southward from Wisconsin and eastward from the central
Plains. The main forecast concern for this period is the speed of
this erosion. The high will be settling southward across the CWA
this evening, but forecast soundings show a tight inversion around
2000 feet hanging in place. Low level layer humidity plots off the
RAP and NAM suggest the clouds will gradually contract from all
sides. Looking at the forecast soundings off the RAP, the cloud
layer remains about 600-700 feet thick after midnight over most of
the area, but continues to erode from the west and north late in the
night. Have used this contraction philosophy in the sky grids for
tonight, going mostly cloudy everywhere this evening, then becoming
partly cloudy everywhere except east central Illinois after
midnight. With that area keeping the clouds longer, the temperatures
will remain more elevated in eastern Illinois, but went with lows in
the lower 20s across the northwest CWA where the clouds should break
up sooner.

&&

.LONG TERM...(Friday through Thursday)
ISSUED AT 258 PM CST THU JAN 22 2015

Mostly quiet weather is expected across central and southeast
Illinois through the next week. However, it can not be said that
completely dry weather is anticipated due to a persistent northwest
upper-level flow that will have mainly weak impulses embedded within
it. Any of these waves have at least the potential for a little
light snow or light rain, depending on the low-level thermal
profiles, but dry conditions are expected more often than not. Also,
most of the weak impulses, not surprisingly, exhibit a spread of
timing and/or track solutions that makes singling out a specific
threat of precipitation difficult at best.

However, there is one clipper system that has been more consistently
agreed upon during the period. This system is still on track to dive
across the Midwest late Saturday night into Sunday night. Not much
of a shift has been seen in the storm track in the latest model
runs, but this system had been trending north lately. At this point,
the ECMWF is the furthest south, crossing northern Illinois on
Sunday. Most other solutions take the clipper across southern
Wisconsin. This track is not terribly favorable for the forecast
area to see much precipitation at all, and what does fall is more
likely to be rain given the more northerly track of the system.
However, thermal profiles on the ECMWF support at least a little
snow across the north before the precipitation threat completely
ends. In any event, barring any southward shift in the storm track,
our local precipitation threat will be pretty minimal.

Temperatures through the next several days will average at or above
normal, with the coolest conditions expected for Monday behind the
late weekend clipper. A better cold shot looks likely beyond this
forecast period, heading into the next weekend.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
ISSUED AT 1152 PM CST THU JAN 22 2015
MVFR expected through the overnight. HRRR and even timed
progression on sat imagery keeping the MVFR through midday. Think
that may be a little on the pessimistic side, but have slowed the
break up of the MVFR deck to at least mid morning. Some tempo vis
drops possible but not putting in predominant groups with the
increased cloud cover keeping the temps up a few degrees. Winds
light and variable tonight...light and increasingly southwesterly
through the day tomorrow.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...HJS
SHORT TERM...Geelhart
LONG TERM...Bak
AVIATION...HJS






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