Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 250806

Area Forecast Discussion
National Weather Service Lincoln IL
306 AM CDT Tue Apr 25 2017

.SHORT TERM...(Today and tonight)
ISSUED AT 219 AM CDT Tue Apr 25 2017

Still quite a bit of dry air over the forecast area early this
morning, with 2 am dew points in the 30s along and west of I-55.
However, dew points in the 50s have pushed as far north as central
Indiana, and will spread westward with time through the day. With
temperatures a couple degrees warmer than yesterday -- generally
around 80 degrees -- the added moisture will become a bit more

Latest surface map showing low pressure over north central Iowa,
with a frontal boundary extending southwest to another low over
the Oklahoma panhandle. As this southern low rides northeast
today, the warm front will surge northward, and much of the rain
will be on the northern flank. However, showers and thunderstorms
will be developing along the trailing cold front this evening. ARW
model has a line of storms moving into the northwest CWA as early
as late evening, but other higher resolution models are more
focusing on Missouri with a brush-by over western Illinois after
midnight. Have included chance PoP`s as far east as Springfield
and Lincoln overnight.


.LONG TERM...(Wednesday through Monday)
ISSUED AT 219 AM CDT Tue Apr 25 2017

Lots to focus on during this part of the forecast, in terms of
severe weather potential and heavier rainfall.

Latest SPC Day1 outlook introduced a slight risk of severe weather
over most areas west of I-57 on Wednesday. Most models have the
cold front moving into the western CWA during the afternoon hours,
when 0-6km bulk shear is over 50 knots and MUCAPE`s reach the
1500-2000 J/kg range. High-res models are a bit variable with the
timing, with the ARW fastest (along I-57 by sunset) and the
NAM slowest (still west of the Mississippi River at the same
time). Highest PoP`s during the afternoon will be west of I-55 and
80-90% PoP`s arrive early evening. In terms of timing of the rain
end, the GFS has a fairly clean back edge, but most models linger
some showers through the night as the upper trough arrives, so
have only scaled back to around 50% over the far western CWA after
midnight and lingered some rain over the east into Thursday
morning. With precipitable water (PWAT) values around 1.5 to 1.7
inches Wednesday into Wednesday evening, some heavier rains are
likely mainly focused along the I-55 corridor.

Late week storm system remains a challenge. Evening model guidance
continues to dig a broad upper trough over the Rockies, closing
off a low near the 4-corners region by late Friday evening. Some
better agreement is being seen with this low lifting into the
central Plains, with the surface cyclone tracking across northwest
Illinois early Sunday. While a warm front sets up shop over
central Illinois, the speed of it lifting north is more uncertain,
with the GFS over the northern CWA by late Saturday afternoon and
the ECMWF about 12 hours slower with that position. However, the
heavy rain aspect is in better agreement, with an extended period
of 1.50+ inch PWAT`s from late Friday night into midday Sunday.
Widespread soaking rains are likely this weekend, which may start
to cause some impacts with time.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1210 AM CDT Tue Apr 25 2017

VFR conditions to continue the next 24 hours, with mainly periodic
high clouds, although some lowering will begin around KPIA/KBMI
toward the end of the period. Main issue will be the winds during
the day, as surface gusts of 20-25 knots are likely from late
morning through the afternoon hours. Southerly winds will ease up
by early evening, but will still average at least 10 knots.




SHORT TERM...Geelhart
LONG TERM...Geelhart
AVIATION...Geelhart is the U.S. government's official web portal to all federal, state and local government web resources and services.