Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 272332
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
532 PM CST Thu Nov 27 2014

.SHORT TERM...(Tonight)
ISSUED AT 259 PM CST THU NOV 27 2014

Small area of light snow and flurries, which moved in from the Quad
Cities area around mid morning, has held together relatively well
and was now over by Champaign. Have had a tenth or two of
accumulation accompany this feature in the heavier snow bands, which
have reduced visibility down to a mile at times. While remaining
mostly cloudy during the day, the clouds are now breaking up
northwest of the Illinois River, although temperatures there were
only in the lower 20s as stronger cold-air advection spreads in from
the northwest.

Latest surface map shows high pressure axis extending north-south
along the Mississippi Valley. This will slowly settle southeast
across the Midwest tonight, as the next clipper system quickly moves
into the upper Mississippi Valley. The snow from this feature will
remain well to our north, but a band of mid-level clouds will
quickly be moving in later this evening. Low temperatures will
likely be set this evening before the arrival of the clouds, with
temperatures steady or drifting upward overnight as winds start to
turn to the southeast. Teens will be widespread this evening,
possibly as low as 10 degrees near Galesburg.

&&

.LONG TERM...(Friday through Thursday)
ISSUED AT 259 PM CST THU NOV 27 2014

The upper trough will translate east of Illinois for Friday, leaving
zonal flow across the Plains and into Illinois through the weekend.
That pattern change will allow a return flow of warm air and
increasing dewpoints from Friday through Sunday. Highs on Friday may
be tempered a few degrees down due to some lingering snow cover in a
corridor from Rushville to Effingham, and have trimmed a couple
degrees from highs in that area. Periodic mid and high clouds across
the north on Friday may also help to keep highs down slightly,
especially with such a cold start to the day.

Saturday will see low clouds developing in the east and south due to
lift from increasing warm frontogenesis in the 850 mb layer. Despite
the cloud cover, surface temps should be noticeably warmer as highs
reach the low to mid 50s. The GFS even triggers a few showers during
the afternoon, but confidence is low that any measurable rain will
occur. Sunday will see a continued increase in low clouds with the
arrival of a cold front from the NW. Some added energy from an
intensifying 300mb jet max will increase lift ahead of the front and
a few showers will possible in our southeastern counties. Rain
chances will be mainly confined to areas SE of a line from Effingham
to Danville, but sprinkles could extend as far west as Peoria to
Jacksonville.

The front is forecast to progress into the Ohio River Valley by
Sunday night, with a colder airmass settling southward early next
week. Any lingering rain showers Sunday night into Monday morning
across our SE counties could transition to light snow due to
deepening of the cold pool. No snow accumulation is expected
however.

Dry and cooler conditions are forecast for Tuesday and Wednesday
under a high pressure ridge. Major model differences are still
present beyond that with respect to the evolution of a closed low
off the West Coast of California. The GFS continues to progress
that wave across the Rockies, triggering surface cyclogenesis
across the Plains on Wednesday. It then progresses that deepening
low into the Great Lakes Thursday-Friday, dragging a cold front
across IL Thursday night. Pre-frontal showers are forecast as
early as Wed night and lingering through Thurs night. The ECMWF
takes the low and gradually absorbs it into a stronger low over
the Gulf of Alaska, with a downstream trough providing cool/dry
weather to Illinois on Wednesday-Thursday. The Canadian GEM shows
indications of primarily keeping the low off the coast, or at
least keeping a long wave trough along the west coast through the
end of the week, providing a dry scenario for IL during that time.
The SuperBlend was biased by the strong GFS precip signal, but
through collaboration with surrounding offices, we lowered precip
chances to the slight category Wed night and Thurs due to so much
uncertainty.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
ISSUED AT 515 PM CST THU NOV 27 2014

An area of predominantly MVFR cigs with sct -shsn occasionally
bringing IFR-MVFR vsby will continue to affect areas east of
K1H2-KBMI until around 03Z. Otherwise, VFR conditions expected for
the next 24 hours. Winds NW up to 10 kts until 04Z, becoming
light and variable overnight as surface high pressure crosses the
region. Winds increasing after 12Z becoming S10-16kts with gusts
up to 25 kts through afternoon as a clipper system moves by to the
north.

&&

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

$$

SHORT TERM...Geelhart
LONG TERM...Shimon
AVIATION...Onton






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