312
FXUS63 KDVN 101801
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1201 PM CST Wed Dec 10 2025

.KEY MESSAGES...

- Additional clipper systems will likely result in periods of
  accumulating snow Thursday through Sunday.

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

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 301 AM CST Wed Dec 10 2025

Early this morning an impressive 15 hPa MSLP gradient existed
across the state of Iowa. MSLP 3hr pressure falls are 6 to 7
hPa ahead of the 990 hPa surface low quickly moving northeast of
the area today. This intense gradient is leading to westerly
winds gusting 40 to 50 mph across the area. As far as 50 kt
gusts have gone, they have currently been limited to far NW IA
and just ahead or behind the cold front. This means that some of
our better wind gusts will likely occur between 11z and 14z,
before starting to slacken.

Also, upstream no blowing snow has been reported. This is
likely due to the temperatures being above freezing, leading to
snow melting on top and acting as a better cap on any blowable
snow underneath. Will continue to monitor upstream and will
message with graphicasts if we start to see blowing snow.

Showers on the back side of the low are wrapping down into the
area this morning. As noted by other shifts, we have ingredients
in place for strong snow showers/snow squalls. Instability
exists in most soundings, coincident with the arrival of the
cold air. CAMs don`t really have a signal for potential showers.
Also, looking at the soundings when we do have instability it
appears that we may not have ice nucleation, so if squalls were
to develop, I wonder if they would mostly be graupel instead of
snow. Nonetheless, ingredients remain in place this morning for
snow squalls with strong winds and if they were to occur we
could see significant reduction in visibilities and rapid
accumulation. While temps do drop, I`m not sure we drop fast
enough to see a flash freeze coincident with potential squalls.
I am more concerned about the melt washing road treatment off
area roads so that when the cold air arrives, we actually end
up with icy roads. So be cognizant of that potential, especially
later in the morning.

Snow showers are still possible today on the backside of the low
in the cyclonic flow. CAMs have some signals but aren`t that
robust. With winds weakening, any of these showers that form may
drop some light snow accumulations at best.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Issued at 301 AM CST Wed Dec 10 2025

Overall changes in the long term forecast were minimal. Do think
we will need an advisory for accumulating snow Thursday night
into Friday morning where 3 to 5 inches are possible across the
CWA. Some guidance has a better signal for a wintry mix across
our southern CWA, so that could be an issue as well and will
likely warrant an advisory as well. With current products out,
decided not to issue anything new on this shift but will use
packets and social media to message the next two clippers.

For a more robust technical discussion of the two clipper
setups, please refer to the discussion below from the earlier
shift!

First, let`s discuss the clippers. The first is progged to come
through Thursday night, driven by 850-700 mb layer warm air
advection/frontogenetic forcing. Precipitation types appear to be
largely snow in our CWA, although there is a noticeable warm nose
aloft around the 700-800 mb layer in the NAM/GFS soundings over our
southern counties, which could support a wintry mix. Where snow is
expected, this clipper could bring a few inches of new snow
accumulation, given NBM probabilities of two inches of snow or
greater is around 40-60%, particularly over northwestern Illinois
into northeastern Iowa. The character of the snow appears to be more
of a slightly drier snow to the northeast (snow ratios of 13-15:1)
compared to farther southwest, where a wetter snow is more likely
(snow ratios 7-10:1). Precipitation should be mostly over by sunrise
Friday morning, with high pressure gradually nosing into the region
through the day. A much colder air mass is expected to move into the
region Friday night, right before the second clipper moves across
the area Saturday. Friday night low temperatures look to fall to the
single digits above zero for most locations. Due to the colder air
mass in place, p-types are expected to be entirely snow, and pretty
dry and fluffy snow at that. LREF ensemble mean soundings shows a
deep thermal profile (from the surface up to around 700 to 600 mb)
firmly within the DGZ, which supports a dry, fluffy snow character.
Snow ratios of 15-19:1 are very much on the table, but with a weak
signal for snow, it appears that blowing snow isn`t going to be much
of an issue. The second clipper appears to have a weaker signal for
snow accumulations compared to the first, with NBM probs of two
inches only around 30-50%.

In the wake of the second clipper system, an arctic air mass builds
in for Saturday night into Sunday morning. 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. LREF
exceedance probabilities of wind chills 20 degrees below zero or
colder is around 50-80% for locations along and north of Interstate
80, so a pretty strong signal for a bitterly cold morning. Cold
weather headlines are likely needed, if these trends continue. 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 THURSDAY/...
Issued at 1155 AM CST Wed Dec 10 2025

Low clouds across the area will continue into tonight with
prevailing MVFR expected, and then potential for some
improvement late into Thursday AM. A weak wave may bring some
light snow and reduced visibilities to portions of eastern Iowa
and northwest Illinois this evening, most likely at DBQ and
MLI, which has been mentioned in TEMPOs with this update. Gusty
N to NW winds will gradually decrease through the afternoon and
evening.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...None.
MO...None.

&&

$$

SHORT TERM...Gibbs
LONG TERM...Gibbs/Schultz
AVIATION...Uttech