Area Forecast Discussion
Issued by NWS Central Illinois

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KILX 280915
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
415 AM CDT Fri Apr 28 2017

.SHORT TERM...(Today and tonight)
ISSUED AT 415 AM CDT Fri Apr 28 2017

Initial batch of rain showers is pushing eastward across Missouri
early this morning, as a frontal boundary starts to set up over
the mid- Mississippi Valley. Most impact of this batch will be
across the northwest half of the forecast area this morning, with
a secondary area of showers tracking northeast toward the I-70
corridor early in the afternoon. This southeastern area will see
the beginnings of the frontal boundary which will plague the area
this weekend. May see a few strong to severe thunderstorms this
afternoon and evening in that area, although latest runs of the
high-resolution models suggest the line of storms may form a
little closer to the Ohio River early this evening. However, this
line should start to lift northward after midnight, and have
included categorical PoP`s around 80% from about the I-70 corridor
southward. Northern part of the CWA may actually remain dry for a
good part of the night until the front lifts northward.

&&

.LONG TERM...(Saturday through Thursday)
ISSUED AT 415 AM CDT Fri Apr 28 2017

The seeds of a strong upper low are starting to take shape over
Colorado early this morning, and will strengthen over the
4-corners region tonight. Copious moisture advection will take
place off the Gulf into this frontal zone, with an extended period
of precipitable water values of 1.5-2 inches through the weekend.
The front will slowly lift northward Saturday as the low moves to
the Texas panhandle, with a formidable surface cyclone forming
Saturday night and Sunday as the low ejects northeast into the
Plains. The front will make more northward progress on Sunday as
the low lifts northeast, with a cold front sweeping eastward
Sunday evening.

Have made no changes to the flood watch at the present time,
although recent model trends suggest an expansion at least to the
Illinois River may need to be considered soon. Rainfall totals of
4 to 6 inches are possible between I-55 and I-57, with 4 inches as
far northwest as the Illinois River. The heaviest rain is likely
Saturday afternoon and night, as a 50-60 knot low level jet sets
up around 850 mb to pump in the moisture. Once the cold front
sweeps through, only scattered showers are expected through Monday
evening, due to the wraparound from the exiting low.

The front is also going to cause a significant headache with
temperatures. A very large temperature range is expected over the
CWA on Saturday, ranging from near 50 degrees around Galesburg to
the lower 80s near Lawrenceville. Potential exists for major
temperature busts if the front does not set up near the I-70
corridor as expected. More of the CWA will be in the warm sector
on Sunday, with 70s more likely as far northwest as the Illinois
River. The deep cold air advection behind the low will result in
highs only in the 50s on Monday, but temperatures should moderate
back into the 60s for the remainder of the week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1217 AM CDT Fri Apr 28 2017

Arrival of rain from the southwest after 12Z will lead to a
steady lowering of ceilings through the day, with MVFR ceilings
near KSPI/KPIA by around 18Z and east to KCMI toward 21-22Z.
Initial batch of showers will exit by 00Z, but low MVFR clouds
will hang around through the end of the period.


&&

.HYDROLOGY...
Issued at 415 AM CDT Fri Apr 28 2017

A large area of 3 to 5 inches of rain is expected this weekend
over central and southeast Illinois, with the heaviest totals
between the I-55 and I-57 corridors. Contingency river forecasts
using 3 to 4 days of QPF suggest flooding would likely develop
Sunday or Monday on the Embarras, Sangamon, and Illinois Rivers,
and a bit earlier on the Little Wabash River where Wednesday`s
rainfall totals were heavier and still causing rises. Some of the
model trends have been shifting the heaviest rain axis a bit
further northwest, which could cause a bigger impact on the
Illinois River. People with interests on area rivers need to
monitor the forecasts closely over the next couple days.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch from this evening through Monday morning for
ILZ038-042>046-048-051>057-061>063-066>068-071>073.

&&

$$

SHORT TERM...Geelhart
LONG TERM...Geelhart
AVIATION...Geelhart
HYDROLOGY...Geelhart


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.