Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 270523
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1223 AM CDT Thu Apr 27 2017

.UPDATE...
Issued at 825 PM CDT Wed Apr 26 2017

Strongest convection continues to push across far southern Illinois
this evening closer to the better instability and shear with
showers and scattered thunderstorms continuing in our area just
ahead of the slow moving cold front. The front as of 8 pm was
located right along the I-55 corridor with the latest surface
analysis indicating a weak surface wave on the front just west of
Springfield. As the shortwave over the Southern Plains finally
lifts northeast, we look for the wave to push to our north later
tonight which should give the cold front a nudge to the east.
Impressive upper level diffluence across the region ahead of the
strong upper wave which should enhance the rainfall rates with
some of the stronger convection which may linger along and just to
the east of the front this evening. We should see a northward
expansion to the shower area tonight as the shortwave approaches
from the southwest. Current forecast has this handled well, so
other than some minor adjustments to the grids, no significant
changes were made that would require an additional update this
evening.

&&

.SHORT TERM...(This evening through Thursday)
ISSUED AT 316 PM CDT Wed Apr 26 2017

A wet night is on tap across central and southeast Illinois as
periods of showers and thunderstorms accompany a slow moving cold
front and upper-level energy tracking along the boundary. The bulk
of the heavier rainfall and thunderstorms should be east of the area
by Midnight with the passage of the front and/or loss of diurnal
instability.

Aside from a low risk of showers in the morning, Thursday should end
up a mostly dry day as weak high pressure builds across the area.
Temperatures will be noticeably cooler in many areas than today, with
peak  readings mainly around 60 degrees.

&&

.LONG TERM...(Thursday night through Wednesday)
ISSUED AT 316 PM CDT Wed Apr 26 2017

The next stronger piece of upper-level energy will amplify the
broad/shallow troffing across the lower 48 states to start the
period. After a brief dry break, this will being a extended wet
weather period across the region through the weekend. Initially,
Thursday night into Friday night, the bulk of the heavier rainfall
will occur over the southeast 1/2 of the forecast area, closer to a
nearly stationary frontal boundary and associated richer moisture.

A vigorous wave within the mean troffing will lift northeast from the
southern/central Plains into the Great Lakes from Saturday into
Sunday night. The passage of this system will likely be accompanied
by significant rainfall across much of the forecast area, with the
heaviest rainfall likely to fall Saturday night. Much of the
forecast area is likely to see several inches of rainfall by the end
of the weekend. This much rain will result in significant rises on
area rivers, as well as non-river related flooding/flash flooding.
However, it is still too soon to pin-point exact locations/amounts.
So, do not plan to issue any flooding related watches at this time.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1223 AM CDT Thu Apr 27 2017

Cold front is pushing slowly eastward across central Illinois,
recently passing KPIA and about to come into KSPI. Ceilings
behind the front have fallen to below 1,000 feet. MVFR conditions
further east are more due to lower visibility in heavier rain
showers, but ceilings as far east as KCMI should drop to IFR
levels by about 10Z. As the rain pulls out the northeast, ceilings
will slowly improve from southwest to northeast Friday morning.
MVFR conditions will linger past midday, and should lift above
3,000 feet by about mid-afternoon. VFR conditions will prevail
late in the period, with clouds mainly in the 10kft range.

&&

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

$$

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


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