Area Forecast Discussion
Issued by NWS Central Illinois
FXUS63 KILX 130439
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1139 PM CDT MON OCT 12 2015
ISSUED AT 838 PM CDT MON OCT 12 2015
Clouds associated with a large upper low over the Great Lakes will
spread into areas from I-74 northward overnight...but otherwise
mostly clear conditions and steady WNW winds around 10 mph will
affect most of central IL. Low temperatures should steadily drop
into the upper 40s in the cooler air mass following today`s cold
front...although the steady breeze will keep the temperatures
several degrees higher than what might otherwise be expected. Have
updated cloud cover to account for the clouds spreading a bit
further south than initially anticipated...but otherwise forecast
is on track.
ISSUED AT 311 PM CDT MON OCT 12 2015
Some clouds will linger to the north this evening associated with a
big upper low over the western Great Lakes. However, most of
Central Illinois will clear out behind the exiting cold front and
high pressure will build back into the region. Temperatures tonight
with northwesterly winds and clearing skies should drop about 10
degrees below last nights lows...falling into the upper 40s. Winds
are expected to stay up i the 10-15 mph range as the pressure
gradient reestablishes behind the sfc trof.
.LONG TERM...(Tuesday through Monday)
ISSUED AT 311 PM CDT MON OCT 12 2015
The upper trough and surface low will pull away to the east on
Tuesday. However, a relatively tight surface pressure gradient will
remain across Illinois, setting up another round of breezy NW winds.
Momentum transfer projections indicate gusts could reach 20-25 mph
A northwest upper level flow pattern still looks to dominate the
extended forecast. That will set up a couple of fast moving waves
later in the week. One very weak wave is expected to clip far
western IL on Wednesday, with little to no impact on our weather.
Then later on Thursday, a more prominent system is forecast to
arrive in northern IL, and progress across our forecast area
Thursday night. There is better agreement between the 12z GFS,
ECMWF, and Canadian on the location of the central surface low near
eastern Lake Superior at 00z/7pm Thurs, as well as the cold front
placement, extending across IL just south of I-72.
There still is a relatively low amount of moisture for the system to
work with, but more than the system today(Monday) which produced a
line of light showers/sprinkles and even a few lightning strikes. We
have gone with the model blend of chance PoPs (30%) for our northern
counties Thursday night east of Peoria to Lincoln to Decatur, with
slight chances elsewhere. We introduced a narrow area of slight
chance (20%) of showers late Thursday afternoon north of Peoria to
Bloomington as the front arrives.
High pressure settling in behind that front will bring much cooler
air for Friday and Saturday. Lows Friday night and Saturday night
lows may drop to around 33-35F, especially north of a line from
Lincoln to Paris, which could produce frost in low lying areas.
Saturday night looks to be the colder of the two nights. Highs
Saturday will likely be in the mid to upper 50s, with north winds
adding a Fall chill to the air.
A warming trend is indicated for Sunday and Monday, as highs climb
back into the upper 60s Monday afternoon.
.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
ISSUED AT 1140 PM CDT MON OCT 12 2015
Brisk WNW flow around low pressure centered over the Great Lakes
will affect central IL for much of the next 24 hours. In
addition...cloud cover associated with this low will affect KPIA-
KBMI-KCMI northward overnight with only a slight chance for
brief/local MVFR ceilings extending into central IL. Winds WNW
10-12 kts overnight...becoming WNW 12-15 with gusts 20-22 kts
after 15Z. Winds decreasing to less than 8 kts after 00Z