566
FXUS63 KDVN 111801
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1201 PM CST Thu Dec 11 2025

...18z Aviation Update...

.KEY MESSAGES...

- Winter weather advisory in effect this afternoon through late
  tonight for 2 to 4 inches of snow during the evening commute.

- Another clipper system Saturday will bring snow to the region.

- Temperatures will drop for the weekend with wind chills well
  below zero Friday and Saturday night.  Temperatures will warm

&&

.UPDATE...
Issued at 1045 AM CST Thu Dec 11 2025

Watching upstream trends, upward omegas combined with lowering
Cond P-Defs, and incoming forcing bands up through H7 MB, have
collaborated with a few neighboring offices to adjust the
heavier NW- to- SE oriented snow swath further south with the
morning update. Many of the latest CAMs and even deterministics
have trended the same way. LSR`s ranging from 11:1 to 14:1 from
south to north during most of the event, and still getting a
nice swath of 2-4 inches(3" is a common number) by midnight
tonight. For now have left the northern periphery of the ongoing
advisory alone since the event hasn`t even begun yet, but have
added another tier of counties to the south and west. There
still may be some spotty sleet or even a few rain drops in the
far south, but this event is looking more and more like a mainly
snow show and have removed the freezing rain mention.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 150 AM CST Thu Dec 11 2025

The first of two clippers will approach the area late this
morning. The track of this clipper has been wobbling and
unfortunately, the overall width of the heavy snow axis is small
(two counties wide or so), such that any change will affect
where it falls. Currently this morning, guidance has the
heaviest snowfall from a on a line from Marengo, to Muscatine
to Galesburg. This could shift, as guidance had been further
northeast earlier, so we will need to keep an eye on this
through the morning.

Looking towards totals of snow, WPC QPF has decreased from
yesterday. It still is slightly higher than the NBM, which would
suggest 2 to 3 inches of snow. The GFS appears to be the odd
one out with a ton of QPF and thus a very narrow stripe of 6
inches of snow! I don`t buy it because it is way way too far
removed from the rest of the snowfall forecasts. In reality, I
think if the forecast were to bust, it would be towards lower
amounts. That said, 2 to 5 with isolated amounts of 5 looks to
be most reasonable forecast within the advisory. There still is
a small signal for fzra on the southern extent of the snowfall.
CAMs have backed off of this since last night, but still
maintains a schc for this occurring. If it does, I don`t think
it will be impactful at all.

Now to the advisory, while snowfall totals are still not
entirely certain, what does seem to be certain is this snow
affecting the evening commute. HREF mean has about half inch an
hour snowfall rates. Omegas in the DGZ ramp up as the system
approaches the area, supporting higher snowfall rates as well. With
the snowmelt yesterday, there is a chance that any road
treatments have been washed away. So do think we see a slick
commute today. This is what pushed me into an advisory, even
with some more uncertainty on amounts and placement.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Issued at 150 AM CST Thu Dec 11 2025

Attention now turns to the weekend with the second clipper is
forecast to move through the area. Latest guidance has slide
this system slight further south, with areas south of I-80
seeing most of the snow. With clippers, we usually see some
bouncing around of tracks, as is evident with the current one,
that could mean a large difference in overall impacts for an
area. Another factor with this clipper is the cold airmass in
place. Snow ratios will be much larger than this current event
and thus very sensitive to QPF forecasts. So a lot of
uncertainty with this clipper still. What is more confident is
the much colder airmass.

Both the GEFS and ECMWF ensembles for 850 mb temperatures
suggest magnitudes around 12 to 16 degrees C below zero, which
would be some of the coldest air yet this season. These 850
temperatures would be near the daily minimum for December 14th
at 12z (6 AM) per SPC sounding climatology, so a very cold air
mass for this time of the year. Northwest winds look to stay
elevated enough to combine with negative single digit and lower
teens low temperatures to support widespread wind chill values
of -15 to -30 degrees for most of the CWA Sunday morning. Cold
weather headlines will likely be needed. After Sunday,
temperatures look to gradually warm as southerly return flow
around the departing high should moderate temperatures into the
early portions of next week.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1152 AM CST Thu Dec 11 2025

Clipper system and it`s associated snow is on it`s way in acrs
the area from the northwest, along with lowering CIGs and precip
reduced VSBY`s to MVFR levels, and eventually low CIGs to IFR or
even bouts of LIFR into Friday morning. The heavier or more
organized snow band potential has now looked to shift to the
south and southwest, thus the BRL site may have the longest
snow duration and intensity VSBY reduction, before the snow
tapers off to flurries just after 11 PM or midnight tonight.
Latest trends also suggest any wintry mix of sleet or freezing
rain will stay south of the TAF sites. With a weak sfc trof
moving acrs the local area, sfc winds will be light and variable
into the evening, then there should be a trend to become east
to northeast overnight into Friday morning but speed should
remain on the light side of 4-8 KTs or so.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Winter Weather Advisory until 3 AM CST Friday for IAZ040-
     051>053-063>068-076>078-087>089-098-099.
IL...Winter Weather Advisory until 3 AM CST Friday for ILZ015-016-
     024>026-034-035.
MO...None.

&&

$$

UPDATE...12
SHORT TERM...Gibbs
LONG TERM...Gibbs
AVIATION...12