Area Forecast Discussion
Issued by NWS Central Illinois

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS63 KILX 080949

Area Forecast Discussion
National Weather Service Lincoln IL
349 AM CST Thu Dec 8 2016

.SHORT TERM...(Today and tonight)
ISSUED AT 349 AM CST Thu Dec 8 2016

High pressure ridge is still well west and southwest of the area
which allows the colder air and brief mid level troughs to move
through the CWA. Another weak trough in the northwest flow will be
bringing mostly cloudy skies to a portion of the CWA today.
Observations upstream of central IL have reported some flurries with
these clouds, so will be adding flurries in the forecast for this
morning and early afternoon. The area will be roughly along and
north/northwest of I-74. As the trough moves through, dry conditions
will return for late this afternoon and continue through tonight.
West to northwest winds will continue through today and breezy
conditions will continue as well. Gusts of around 25 mph will be
common across most of the CWA. Temps will be below freezing today
with the coldest temps being in the north where most of the cloud
cover will be. Overnight lows will fall into a range of 14-20
degrees by morning. Wind chill readings will be in the single digits
again overnight.


.LONG TERM...(Friday through Wednesday)
ISSUED AT 349 AM CST Thu Dec 8 2016

Once again the precipitation forecast for the weekend is troubled,
but the cold air snaps are more concrete.  The cold Arctic air
moving into the Midwest for the end of the week will be countered by
some relatively warmer air for the end of the weekend...only to lose
ground to bitterly cold temperatures for next Tuesday and beyond.

Cold Arctic air in place over the area will keep the max temps in
the 20s for Friday. Winds Friday morning will be up a bit, dropping
wind chills to single digits. The bitter cold will be a bit of a
shock from the mild weather in place for much of the season up to
this point.  Temps begin to moderate slightly on Saturday later as
the winds take on a more southerly component and weak WAA starts up.

Models have been consistently inconsistent for the weekend. Both the
ECMWF and the GFS...and to some extent the Canadian shift from
northwesterly flow to more northerly, sheering out a wave across the
Great Lakes for Sat afternoon and overnight.  The second wave is now
starting to differentiate from the prev wave with the last few runs
for Sun afternoon and overnight as a surface system develops to the
WSW and moves into the Mid Mississippi River Valley.  The questions
remain as to how much of the models are lingering precip too long
and muddying the division of the systems or if the dynamics will be
able to interact and enhance one another.  For now...chance pops
dominate...but with some higher pops in for Sunday night and the
better sfc development/deeper wave aloft.  Mostly snow anticipated
early... but as the warm air advects into the region...the southern
half of the state could see more rain/wintry mix for Sunday,
particularly in the afternoon.

Beyond the precip issues with the weekend...cold air is coming for
next week.  Highs by midweek already showing as teens and low 20s
for Wednesday as a frigid Arctic airmass moves into the CONUS.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1125 PM CST Wed Dec 7 2016

A small band of MVFR cigs has pushed southeast into our northern
TAF sites this evening but we are already seeing the backedge of
this particular cloud band just west of PIA, which should shift
east of PIA and BMI by 07z. Further to the northwest, a larger
band of MVFR cigs was located over northeast Iowa with cloud
bases mostly in the 2000-3000 foot level with most short term
models suggesting this area should slip into the north again
by 12 to 15z with most of our TAF sites seeing some MVFR or
low VFR cigs during the afternoon. Forecast soundings indicate
once the clouds move in tomorrow, they will be around through
the night before any improvement is seen either late Thu night
or during the day Friday. There may be a scattering of flurries
during the day on Thursday but coverage too limited to include
any mention in this set of TAFs.

Gusty west to northwest winds are expected through Thursday with
speeds of 12 to 17 kts, with a few gusts around 24 kts at times
before diminishing around 00z.




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