Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 191734
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1234 PM CDT Mon Jun 19 2017

.UPDATE...
Issued at 1042 AM CDT Mon Jun 19 2017

Breezy west to northwest winds are developing across central and
southeast Illinois this morning in the deep cyclonic flow across
the region. Wind speeds/gusts should continue to increase into the
afternoon as forecast soundings suggest deep mixing to as high as
8K feet. While the local air mass is fairly dry, there remains
enough moisture to support several hundred J/KG of CAPE during
peak afternoon heating. This instability, and the expected
passage of a couple upper-level impulses, should be sufficient
for an isolated shower or thunderstorm over much of the area this
afternoon. Going forecast was in pretty good shape and only had do
make minor tweaks to the hourly trends.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 243 AM CDT Mon Jun 19 2017

A couple small areas of showers have been moving southeast across
the region early this morning. The first one has reached
Bloomington as of 2 am and earlier produced some wind gusts to
near 25 mph at Peoria, while the second one was in southeast
Iowa approaching the Mississippi River. These were being triggered
by some weak impulses zipping along in the northwest flow aloft.
Additional impulses were visible in water vapor imagery from North
Dakota into western Minnesota early this morning, and will help
trigger some additional convection toward midday into the
afternoon hours. Best chances will be a bit further north, but
will include isolated storms over most areas from about
Jacksonville-Paris northward. These should fade off early evening
with loss of daytime heating. Not expecting much in the way of
rain with these storms, as forecast soundings are quite dry below
about 5,000 feet and surface dew points will generally only be in
the mid 50s at the time.

.LONG TERM...(Tuesday through Sunday)
ISSUED AT 243 AM CDT Mon Jun 19 2017

As the northwest flow persists into Tuesday, a sharper wave will
be swinging across the Great Lakes. This should push a frontal
boundary southward into northern Illinois by early Tuesday
afternoon, although the evening models try to wash it out to some
extent by evening. Additional isolated storms are possible with
this boundary Tuesday afternoon into evening, with Wednesday
largely dry as weak high pressure drifts across the Great Lakes.

The upper level ridge over the western U.S. will begin to break
down on Tuesday, allowing for some more significant troughing
over Canada to push southward into the northern states Wednesday
night and much further south late week. Both the GFS and ECMWF
show a southward surge into the mid Mississippi Valley by early
Sunday, helping to cool things off. In the meantime, the warm air
mass over the West will will be spreading eastward during the
middle week, with 850 mb temperatures approaching 20C over our
area by early Thursday. Surface temperatures expected to peak near
90 on Thursday, before slowly easing off. A cold front will
approach from the northwest on Thursday, before hanging up from
about Nebraska to northern Indiana as it becomes parallel to the
upper level flow. Rain chances will increase from the north
Thursday night, and linger over the southern CWA through Friday
night. Weekend rain chances are more uncertain, with the ECMWF
taking a more northern track to this system and the GFS closer to
the Ohio Valley. However, 30-40% PoP`s appear reasonable at this
time.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1219 PM CDT Mon Jun 19 2017

Deep mixing will result in gusty west-northwest winds into early
evening across the central Illinois terminals. Winds should
decouple early this evening, with speeds falling below 10kts for
the remainder of the 18Z TAF valid time. Peak daytime heating,
coupled with a couple upper-level disturbances, will result in
spotty showers or thunderstorms into early evening. Coverage
should remain too low to go above a VCSH/VCTS mention at this
time. VFR conditions should prevail through the entire forecast
period.

&&

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

$$

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



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