Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 121800

Area Forecast Discussion
National Weather Service Lincoln IL
100 PM CDT Thu Oct 12 2017

Issued at 1045 AM CDT Thu Oct 12 2017

Forecast looks on track today as low stratus clouds continue with
just a few breaks in overcast. Patchy drizzle this morning should
be more east into IN this afternoon. Temps currently in the upper
50s to near 60F and will only climb a few more degrees to reach highs
of 60-65F with light winds.


.SHORT TERM...(Today and tonight)
ISSUED AT 321 AM CDT Thu Oct 12 2017

07z/2am surface map shows low pressure over western Pennsylvania,
with a trough axis extending westward into central Illinois.
Patchy drizzle persists within the weak convergence zone along
the trough, and this trend is expected to continue through at
least mid-morning. Forecast soundings remain saturated below 850mb
through the entire day, before a developing southerly flow
gradually brings drier air into the region from the S/SW starting
this evening. Have therefore gone with overcast conditions today,
with high temperatures only reaching the lower to middle 60s.
Skies will initially be mostly cloudy early this evening, but will
gradually become mostly clear overnight. Low temperatures will
drop into the lower 50s.

.LONG TERM...(Friday through Wednesday)
ISSUED AT 321 AM CDT Thu Oct 12 2017

With abundant sunshine and southerly flow returning to the region,
much warmer weather is expected for Friday as afternoon high
temperatures rise into the upper 70s to around 80 degrees.
Meanwhile, a cold front draped across the Plains will slowly begin
to approach from the northwest Friday night. 00z Oct 12 models
have slowed its southeastward progress and generally keep it well
to the N/NW of the KILX CWA through Saturday. Will see clouds and
scattered showers/thunder mainly along and north of a Rushville to
Bloomington line Friday night and Saturday...with dry weather
further south. High temperatures on Saturday will range from the
upper 70s far north around Galesburg and the middle 80s
along/south of I-72.

The airmass will become moderately unstable across west-central
Illinois Saturday afternoon/evening, with NAM SBCAPEs of
800-1000J/kg. At the same time, 0-6km bulk shear values will
increase to 40-50kt. Strong to potentially severe thunderstorms
will develop further west along the frontal boundary from Kansas
City northeastward to Des Moines during the afternoon, with these
storms gradually working their way eastward into portions of
west-central Illinois late Saturday evening. Latest SPC Day 3
outlook highlights areas along/west of I-55 for a Marginal Risk
for severe weather...with the main threat from the storms likely
being potentially strong/gusty winds. Have carried likely to
categorical PoPs across the western half of the CWA accordingly.
The front will quickly push eastward into Indiana by midday
Sunday, with showers coming to an end from west to east during the

Once the front passes, cooler/drier weather will be on tap for
Monday and Tuesday. High temperatures both days will be in the
60s, and low temperatures will be in the lower 40s. In fact, some
numeric guidance suggests temperatures could potentially bottom
out as low as the upper 30s Monday morning. After that, upper
heights will once again begin to rise and a warming trend will get
underway for the middle and end of next week.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1259 PM CDT Thu Oct 12 2017

MVFR ceilings expected to continue into this evening across
central IL. Cloud deck with bases of 1.5-2.5k ft and cloud tops of
4-4.5k ft is about 2k ft thick and KILX 12Z sounding continues to
show a strong low level inversion up to 680 mb trapping low level
moisture. Visible satellite loop shows low stratus desk upstream
into central MO and only slowing clearing toward ne MO. Latest
HRRR model keeps low clouds over central IL through 10Z/5 am Fri.
The more optimistic CAM models show low clouds scattering out
between 03-07Z starting at SPI 1st and then getting to CMI last.
Decided to push back the clearing about 3 hours later than this
with SPI at 06Z and along I-74 from 08-10Z. Would not be surprised
to see low level stratus clouds linger linger into early Fri
morning as some models like the NAM continue to show a pinch of
moisture around 5k ft into Fri morning. South to SSW winds 4-8
kts this afternoon and south tonight to increase to 8-14 kts
after 14Z/9 am Fri.




LONG TERM...Barnes
AVIATION...07 is the U.S. government's official web portal to all federal, state and local government web resources and services.