Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 230445

Area Forecast Discussion
National Weather Service Lincoln IL
1145 PM CDT THU SEP 22 2016

Issued at 851 PM CDT Thu Sep 22 2016

No significant updates to forecast this evening although some very
light shower activity associated with a decaying thunderstorm
cluster from eastern Iowa will slowly drift toward Knox, Stark,
and Marshall counties late this evening. Current trends are that
even a sprinkle will be unlikely in those counties. Overnight,
additional precipitation looks to re-develop just northwest of
the central IL forecast area as 850 mb warm advection strengthens
there. Most models keep conditions dry for this area and will
continue the dry forecast for now. Otherwise, lows ranging from
around 63 from I-72 southward and mid-upper 60s to the north look
good, with light south winds.


.SHORT TERM...(This evening through Friday)
ISSUED AT 259 PM CDT Thu Sep 22 2016

Unseasonably warm conditions will continue in the short term as
upper level ridging holds over much of the Midwest and a nearly
stationary front remains from eastern Nebraska across central Iowa
into southern WI.

Spotty showers across southeast Iowa this afternoon are trying to
work their way into northwest IL, but plenty of mid-level dry air
should result in rapid dissipation. Wouldn`t be surprised to see a
few sprinkles make it through toward Galesburg early this evening,
but not enough for measurable rainfall. Only the GFS and SREF are
allowing for light rainfall overnight, with the other models
continuing dry weather for us and keeping the focus on waterlogged
areas of NE Iowa and SW Wisconsin overnight.

The upper level ridge is expected to strengthen a bit over us on
Friday which will keep the synoptic front to our north. This will
result in another very warm day with highs around 90 in much of
central IL. The exception will be in areas roughly north of I-74
where a few more clouds will keep temps in the mid 80s. With the
front to our north and only a light south wind/very weak convergence
will keep the rain chances out of the forecast through Friday.

.LONG TERM...(Friday night through Thursday)
ISSUED AT 259 PM CDT Thu Sep 22 2016

The 12z models have kept a similar solution for Friday night
through Sunday, with warm and humid conditions in Illinois under
upper level ridging. A long wave trough over the central Rockies on
Friday with lift NE toward Canada this weekend. This will cause a
sharpening of the ridge across Illinois. Southwest flow aloft will
increase as a result, bringing a continued flow of low level warmth
and humidity. Highs will likely maintain in the mid 80s to around 90
Saturday and Sunday, with overnight lows in the mid to upper 60s.
Dewpoints will linger in the mid to upper 60s, creating a muggy

Precip chances for the first half of the weekend look to remain
primarily north of Illinois, closer to a warm frontal boundary.
However, there is continued support in the ECMWF, GFS and NAM that a
cold front will push across IL on Sunday or Sunday evening. The NAM
is the fastest, pushing it to the Indiana border by 7 pm
Sunday/00z Mon. The GFS and ECMWF are next in timing, indicating the
front should reach the Indiana border shortly after 06z/1am Monday.
The Canadian Global halts the front near the Mississippi river in
response to cutting off the Plains upper low and drifting it south
toward Oklahoma on Monday. We held with the consensus of a frontal
passage later on Sunday into Sunday evening, with increasing chances
of storms Sunday afternoon west of I-57. Storm chances look to
continue in the post frontal airmass through Monday, as the upper
level trough axis finally progresses across the area.

A cooler and less humid air mass will arrive for Monday, and linger
through Thursday. While we see slight chances of diurnal showers
each day due to steep mid level lapse rates, most areas should
remain dry. High temps from Monday to Thursday should be in the mid
70s, with lows in the mid 50s.


.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1145 PM CDT Thu Sep 22 2016

Light S-SE winds under 7 kts and periods of mid and high cloud
cover expected the next 24 hours as showers and thunderstorms
associated with a frontal boundary continue to the northwest of
the central IL terminals. Slightly higher crossover temperatures
Thursday afternoon indicate some potential for light fog late in
the night at KPIA so 06Z TAF indludes TEMPO for MVFR vsby from


.ILX Watches/Warnings/Advisories...


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