Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 310428
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1128 PM CDT Mon Mar 30 2015

.UPDATE...
ISSUED AT 903 PM CDT MON MAR 30 2015

Quiet and milder than normal conditions are expected tonight across
central and southeast Illinois. A clipper system will pass to our
north tonight, dragging the trailing cold front through the area
by Tuesday morning. The front will come through the area dry, with
fairly minimal cloud cover. The southerly winds ahead of the cold
front for much of the night will keep temperatures warmer than
they have been lately.

Going forecast is in good shape overall. Only a few tweaks are
needed for the latest hourly trends.

&&

.SHORT TERM...(Tonight)
ISSUED AT 246 PM CDT MON MAR 30 2015

Surface high center in AR with southwest winds ahead of low pressure
center in northern plains. Only scattered high clouds over region as
the low center and associated short wave tracks north of central IL,
dragging weak cold front into state overstate.

&&

.LONG TERM...(Tuesday through Monday)
ISSUED AT 246 PM CDT MON MAR 30 2015

Above normal temperatures can be expected to continue into mid-week
as shortwave ridging approaches Illinois. Steady 500mb height rises
reaching almost 5700m by the time the axis pushes across the state
Wednesday. Model suite at 12z consistent in developing 850 mb temps
above 10C by Wednesday Night. An increase in cloud cover once the
ridge axis passes may temper highs somewhat on Wednesday, but even
with clouds temps should be in the upper 60s to lower 70s.

Models have been trending slower with shortwave on backside of ridge
bringing precip in late Wednesday Night.  Big challenge involves the
timing of the associated cold front.  Slower solutions suggest a
frontal passage Thursday afternoon allowing good boundary layer
moisture return and enabling 500+ J/kg CAPE to develop along and
just ahead of the boundary.  Latest GEFS suggests there is still
significant spread in amount of instability with higher values
southwest of the forecast area. If slowing trend in models continue
though the strong southwest winds ahead of the front may be able to
advect higher boundary layer moisture into area. Will have to
monitor evolution closely.

As second wave is progged to move across the Mississippi Valley on
Friday. The forecast area should be mostly into the cold air by
then. ECMWF is strongest with the strength of this wave enabling
some overrunning rainfall across the entire forecast area Friday.
GFS confines significant precip near and southeast of
I-72/Danville.  will go with a blend for now which suggest at least
some chance PoPs all the way back into KGBG and KPIA. Either way, a
dreary day may keep temps below normal as strong cold advection
evident.

This second wave should push the front out of the Ohio Valley and
into the southeast U.S. bringing a dry but cool Saturday. GFS is
stronger than ECMWF with moisture return Sunday suggesting some low
PoPs may be needed by Sunday afternoon.  This seems a bit fast and
will generally follow drier ECMWF which holds off on introducing
PoPs until Monday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
ISSUED AT 1126 PM CDT MON MAR 30 2015

VFR aviation weather conditions expected across the central
Illinois terminals through the 06Z TAF valid time. A clipper
system will track across the Midwest/Great Lakes tonight, but it
will come through dry locally with minimal cloud cover. The most
notable change will be a wind shift from southwest to northwest
later tonight as the trailing cold front comes through the area.
Winds will eventually trend light/variable Tuesday night as high
pressure builds across the Midwest.

&&

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

$$

UPDATE...Bak
SHORT TERM...Goetsch
LONG TERM...Barker
AVIATION...Bak





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