305
FXUS63 KDMX 052101
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
301 PM CST Fri Dec 5 2025

.KEY MESSAGES...

- Any light snow in north central Iowa exiting late this
  afternoon with potential for fog in parts of southern and
  western Iowa tonight.

- Accumulating snowfall arriving over all of central Iowa
  Saturday afternoon and exiting by sunrise Sunday. A band of 5
  to 7 inches is likely over north central Iowa.&&

.DISCUSSION...
Issued at 301 PM CST Fri Dec 5 2025

GOES-East upper level water vapor imagery shows our current
shortwave trough (aka clipper) moving just north of Iowa this
afternoon. 300mb analysis shows a 100 knot jet streak over the state
contributing lift via the left exit region and resulting in light
snow, mainly over northern Iowa. There have been a few brief reports
of light snow as far south as Fort Dodge and there may even be a
brief bout of freezing drizzle per mPING reports earlier in the day.
Accumulations have been minor around a dusting per Mason City
webcams impacting more the city streets than the interstates.

As the first clipper departs into this evening, winds will drop off
over the state. MOS, LAMP, and NBM text guidance and BUFKIT
soundings from the RAP and GFS point to fog potential tonight over
parts of southern and western Iowa and this has been added to the
forecast. Attention on Saturday will be on the next and more robust
clipper, which as of Friday afternoon is upstream and moving into
the Pacific Northwest. While Saturday will start out dry over
central Iowa for any weekend errand or holiday shopping runs, strong
QG convergence will quickly spread over the state Saturday while the
columns saturates. Snow will spread in from west-northwest to east-
southeast in the afternoon hours. QPF will not be as high as last
weekend`s event as isentropic analysis shows the fetch not as long
on the 285 or 290K surfaces. Thus, liquid from the snow will top out
around or a bit above 0.50" in the max band. Snow ratios of 12-15:1
will start the event and trend up as colder air filters in Saturday
night and may near 20:1 over northern Iowa per Cobb table. In
addition, there will be stronger low level frontogenesis as this
moves in and cross sections show a dendritic growth zone (DGZ) with
moderate lift passing through in the 3 to 4km depth DGZ. This will
result in higher snow rates with the 12z HREF and 9z SREF showing
1"/hr rate probabilities of 40-60% and 20-30%, respectively. Mean
rates from the HREF over three-quarters of an inch per hour will be
passing through in a several hour period window (2-4 hours) toward
sunset through the evening hours. The snow will continue and end
from west to east by sunrise Sunday in central Iowa. Total snowfall
has been trending upward - which may continue to occur as we fine
tune the QPF - with storm total snowfall by Sunday morning around 5
to 7 inches with a few points nearing 8 inches from Emmet to
Pocahontas counties angling east-southeastward towards Black Hawk
County/Waterloo/Cedar Falls area. This is the area that is being
highlighted by the recently issued Winter Storm Warning. Around this
and in areas where generally 3 or more inches of snowfall is
forecast is where a Winter Weather Advisory is in effect. An
interesting aspect of this event is the placement of the highest
snow band in the models with the FV3 cores favoring a southern
solution closer to I-80, the HRRR/RAP/NAM shifting north towards far
northern Iowa, and the less shifty ECMWF in the middle. Our official
forecast of the max band based on our analysis of the QPF and snow
ratios ends up between the two camps as highlighted with the warning
area, but will be monitoring incoming data for any shifts north or
south, which could result in adding a few counties.

With the higher snow ratios resulting in a drier snow and fluffier,
have to consider what kind of blowing snow potential there may be.
As the system departs and the snow ends, winds are forecast to
average 10 to 20 mph with gusts up to around 25 mph with these winds
decreasing through the day. Thus, expect streamers or crawlers on
some east west roads with the northerly winds, but winds speeds at
this time point to any blowing snow reducing visibility being
minimal. Sunday will be colder with highs around 10 degrees in far
northern Iowa to the low 20s in far southern Iowa. Moving into next
week, the pattern will remain in active northwesterly flow with
systems arriving over the region every 24 hours or so. Whether these
systems will have any sensible weather impacts on Iowa remains to be
seen as the deterministic models (0/6z runs) are more focused north
of the area with shots of PoPs highest over northeastern or northern
Iowa. Temperatures will continue to waver up and down, but generally
be below normal to at best near normal.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1131 AM CST Fri Dec 5 2025

Light snow is falling over a few places in northern Iowa at
midday and have continued with PROB30 at MCW. At FOD and ALO,
no mention of any wintry precipitation, but have seen a few
reports of freezing drizzle. However, confidence is too low to
include even a PROB30 line with it fleeting at best. MVFR
ceilings will sink southward this afternoon over MCW, FOD, and
ALO and into tonight at the other terminals. Outside of MCW
that has IFR ceilings for a period tonight, brief periods of IFR
cannot be ruled out at the other terminals and may need to be
added later. Towards Saturday morning, guidance is showing fog
developing over portions of southern into western Iowa and at
this time it is not close enough to DSM or FOD to include.
Conditions may improve at MCW or ALO toward the end of the
period, but maintained restrictions given uncertainty with
ceilings as the accumulating snow system spreads into the area
after 18z.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning from noon Saturday to midnight CST
Saturday night for IAZ004-005-015-016-023>025-035-036.
Winter Weather Advisory from noon Saturday to midnight CST
Saturday night for IAZ006-033-034-044>047-057>059-071-072.
Winter Weather Advisory from 3 PM Saturday to 6 AM CST Sunday
for IAZ007-017-028-048>050-060>062-073>075.
Winter Storm Warning from 3 PM Saturday to 6 AM CST Sunday for
IAZ026-027-037>039.

&&

$$

DISCUSSION...Ansorge
AVIATION...Ansorge