Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 260838
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
238 AM CST Sun Feb 26 2017

.SHORT TERM...(Today and tonight)
ISSUED AT 236 AM CST Sun Feb 26 2017

Above normal temperatures return to central and southeast Illinois
starting today. A ridge of high pressure will shift east of the
forecast area early today, with southerly low-level winds pushing
today`s highs to around 50 degrees. Tonight`s lows will generally be
in the 30s.

Aside from the moderating temperatures, the main weather concern
today revolves around the threat for rain as a weak short wave
tracks through the region late today into tonight. The model trend
continues to be drier for the forecast area with this feature, with
the bulk of the rainfall likely to stay south of the forecast area.
That being said, forecast soundings suggest enough moistening of the
local airmass will have taken place south of I-70 by tonight for
some rain showers to occur. In any event, the rainfall tonight does
not look significant.

&&

.LONG TERM...(Monday through Saturday)
ISSUED AT 236 AM CST Sun Feb 26 2017

Not a lot of change in the overall upper air pattern this week.
Transition of the southern stream into more of a southwest-northeast
configuration is starting this morning, as one upper low drops
southeast from San Francisco and a second settles southward toward
northwest Washington state. This will bring a couple days of very
mild air once again, but no chance of it lingering as long as last
week, as a broadening trough tracks east across the Plains during
midweek. As this moves into the Midwest later in the week, the
longer range models bring a slug of cold air into the Great Lakes,
with our area generally on the periphery of the air mass. Rapid
moderation takes place for the weekend as the flow becomes more
zonal.

Main weather maker remains the Tuesday-Wednesday storm system. Some
variations on the low track among the main models, with one wave
moving across Iowa Tuesday afternoon followed by the main low
further south Tuesday night. The ECMWF is the fastest and has the
low all the way to Lake Huron by early Wednesday, while the NAM and
GFS have it somewhere in central Illinois. Favoring more of the
slower solution at the moment and thus keeping very high PoP`s
across most of the forecast area into Wednesday morning. Some decent
precipitable water values of over an inch are progged by the NAM and
GFS with this system Tuesday afternoon and night, favoring
especially the southeast CWA where rainfall amounts of 3/4 to 1 inch
currently appear feasible. Thunder-wise, the NAM appears too
aggressive with bringing CAPE`s as high as 2000+ J/kg late Tuesday
night, with the GFS lower but still near 1000 by late afternoon
over the southeast CWA. However, 0-6km bulk shear quite impressive
at 60-80 knots, so some strong/severe storms are possible, and
latest SPC Day3 outlook does include a slight risk from about
Jacksonville-Bloomington southeast.

As the pattern shifts, a clipper-type system will drop southeast
across the north half of the state Thursday afternoon/evening. While
starting as rain, a transition to snow is possible in the evening
before the system quickly exits.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1129 PM CST Sat Feb 25 2017

VFR conditions will prevail across the central Illinois terminals
through the 06Z TAF valid time. Mid-level CIGs will be common as
an upper-level disturbance moves through the area, but heights
will be well into the VFR category. Light westerly winds will
trend southerly by daybreak, becoming gusty at times for much of
the daytime hours.


&&

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

$$

SHORT TERM...Bak
LONG TERM...Geelhart
AVIATION...Bak



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