Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 240810

Area Forecast Discussion
National Weather Service Lincoln IL
310 AM CDT Tue Oct 24 2017

.SHORT TERM...(Today and tonight)
ISSUED AT 310 AM CDT Tue Oct 24 2017

07z/2am water vapor imagery shows a deep upper trough in place
over the Great Lakes/Upper Midwest...with numerous short-waves
embedded within the prevailing flow. As a wave over north-central
Illinois pivots toward Lake Michigan, an area of showers
currently along/north of the I-80 corridor will sink S/SW this
morning. Based on radar trends and latest HRRR forecast, it
appears these showers will spill into the northern KILX CWA from
Peoria to Bloomington by 12z...then will spread further south
toward the I-72 corridor as the morning progresses. Further
southeast, conditions will remain mostly dry through the morning
south of I-70 before showers arrive by early afternoon. Due to
extensive cloud cover, rain, and brisk W/NW winds gusting to 30mph
at times...temperatures will struggle to rise much from early
morning lows. Afternoon highs will generally be in the middle to
upper 40s...with a few lower 50s south of I-70.

The prevailing upper trough will begin to shift eastward out of
the region tonight, with lingering showers coming to an end across
east-central Illinois during the early evening. Forecast soundings
suggest a clearing trend from west to east...with mostly clear
conditions expected across the board by late tonight. Despite the
clearing and overnight lows dropping into the lower to middle 30s,
west winds of 8-10mph will prevent frost formation.


.LONG TERM...(Wednesday through Monday)
ISSUED AT 310 AM CDT Tue Oct 24 2017

Another short-wave trough will drop southeastward out of Manitoba
on Wednesday, brushing central Illinois to the northeast. Based on
this particular track, it appears most of the light precipitation
associated with this wave will stay N/NE of the area across
northeast Illinois into the Great Lakes. Have included a slight
chance PoP northeast of a Rantoul to Paris line in case a few
light rain showers develop further south. Will be another cool
day...with highs in the lower to middle 50s. As a more significant
wave approaches from the northwest, short-wave ridging will
develop across the Midwest on Thursday. With upper heights rising
significantly and surface winds becoming southerly, a temporary
warming trend will get underway. Based on 850mb temps progged to
reach 10-14C by Thursday afternoon, high temperatures will climb
well into the 60s.

Cold front will sweep through central Illinois Thursday night, but
will be devoid of precip due to the dry airmass in place. As a
strong upper trough approaches from the northwest, several weak
waves of low pressure are expected to develop along the departing
boundary Friday/Friday night. Models have been flip-flopping on
exactly how much post-frontal precip will occur and how far west
it will develop. 00z Oct 24 GFS and GEM are in relatively good
agreement, keeping most of the precip along/east of I-57. Have
therefore carried likely PoPs for rain showers across the eastern
CWA Friday afternoon, with chance PoPs for showers lingering into
the evening. The front will edge further eastward Friday night,
resulting in an end to the precip by around midnight.

Once the front departs, a very cool airmass will take hold across
the region this weekend into early next week. High temperatures
will only be in the 40s Saturday and Sunday, while overnight lows
dip into the upper 20s and lower 30s. It is still too early to
pinpoint the exact cloud cover/wind speed forecast that far out,
but it appears likely a frost/freeze will occur across central
and southeast Illinois this weekend.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1052 PM CDT Mon Oct 23 2017

VFR conditions are expected through about 06z, then we will see
deteriorating cigs develop from north to south with mostly MVFR
conditions expected across the entire area by 10z with the lower
cigs holding through the day. Scattered showers and isolated
thunderstorms were occurring over parts of central and eastern
Illinois ahead of a rather vigorous upper wave seen on the water
vapor loop this evening. At the surface, a cold front was analyzed
to our west and as that boundary pushes across the area
overnight, the cigs will gradually lower and winds will veer more
into the northwest. Speeds should average from 10 to 15 kts with a
few gusts up to 20 kts later tonight.

Additional shower activity should spread southeast into the area
during the early morning hours but coverage appears to be rather
limited at this time so will try to cover that with VCSH for now.
As a secondary trof rotates southeast over the area tomorrow,
better coverage of showers is expected along with northwest winds
of 15 to 20 kts with gusts of around 25 kts at times through the
afternoon before the gusts start to subside just after sunset.




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