Waverly, Iowa 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

177
FXUS63 KDMX 161119
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
519 AM CST Tue Dec 16 2025

 ...Updated for the 12z Aviation Discussion...

.KEY MESSAGES...

- Patchy fog this morning. Warm temperatures and melting
  snowpack today. Potential for re-freeze and patchy fog again
  tonight.

- Gusty winds and precipitation arrive late Wednesday night
  through Thursday. Mostly rain expected Wednesday night and
  Thursday morning, with potential for a few snow showers
  Thursday.

- Cold temperatures Thursday night into Friday morning, then
  warming back around normal on Friday.

&&

.DISCUSSION...
Issued at 341 AM CST Tue Dec 16 2025

Fog has generally remained at bay early this morning, as
visibilities generally remain around 4 to 6 SM, with brief, isolated
pockets of lower visibilities. This is likely in part thanks to the
thin stream of high cirrus that is steadily drifting over the
state. However, cooling to the dewpoint doesn`t seem to be the
entire issue this morning. The dewpoints are also cooling as
fast or faster than the temperatures are. In fact, many
locations over the snowpack are multiple degrees colder than
their dewpoints earlier last evening, despite little to no
wind/advection to change air masses. This forecasters assumption
is that the snowpack is siphoning moisture from the air through
deposition, therefore lowering the dewpoint as the temperatures
fall towards it. This, in conjunction with the slightly slowed
cooling provided by the cloud cover and occasional increases in
wind, is ultimately keeping the condensation production/fog
under control. As of 3 AM, the cooling dewpoints do seem to have
leveled out in the last hour or so, and coverage of the high
clouds is diminishing, so certainly still possible that we see
more fog development in the next few hours leading up to
sunrise. Will continue to monitor short term trends and any need
for additional messaging to accompany additional fog
development this morning.

Warmer temperatures and higher dewpoint air will move over the
snowpack through the day today, boosting wetbulb temperatures
into the mid to upper 30s. This warm, moist air will quickly eat
away at the snowpack today. However, temperatures are expected
to drop back below freezing again tonight and may lead to a re-
freeze of any liquid that`s collected from the melting snow. Be
cautious of slick spots on roadways and sidewalks as
temperatures drop off tonight. In addition to refreeze, added
moisture to the air from the melting snow will linger as
temperatures drop tonight again suggesting some fog potential.
However, despite the increased moisture, winds remain fairly
breezy through the first part of the evening, which will inhibit
radiational cooling and fog development. Winds then eventually
diminish early tomorrow morning, but will have flipped to more
northwesterly, advecting in drier air. Therefore, while at least
some patchy fog is possible again tonight into Thursday
morning, there are too many factors working against it to be
overly confident in dense or freezing fog development at this
time.

Wednesday will again be warm with temperatures climbing into
the 40s and wetbulbs in the upper 30s which should melt off most
of the remaining snowpack, aside from potentially the deeper
areas. These warmer temperatures will precede an approaching
500 mb trough, which will bring windy conditions and the return
of precipitation chances late Wednesday night into Thursday.
Winds will initially pick up later in the day Wednesday as the
system approaches, then remain breezy through Wednesday night.
Two cold fronts will then pass through late Wednesday night and
into Thursday. The first will be a subtle cold front passing
through overnight Wednesday into early Thursday morning and
producing mostly rain as it moves from west to east through the
area. The second, more prominent cold front will be hot (cold?)
on the heels of the first, dropping into northwest Iowa around
sunrise on Thursday and through central Iowa around mid-day.
This secondary front will be drier, but much colder, producing a
shallow layer of instability through the dendritic growth zone,
implying snow shower potential in northern and north central
Iowa. Accumulations appear minimal, but enhanced winds will
accompany the strong cold air advection behind this front,
resulting in sustained winds of 25 to 30 mph and gusts over 40
mph at times. Strong winds, in conjunction with falling snow
could lead to drops in visibility at times through Thursday.
Couple this with a dusting of snow on roads, and/or re-freezing
rain from the first front and there could be some travel
concerns with this system. We are just now getting into the
window for high resolution models, so will be watching mesoscale
trends with this system in the coming days.

Finally, with the strong cold air advection comes temperatures
plummeting overnight Thursday into Friday, as lows fall into the
single digits below zero for all but southern Iowa by Friday
morning. Fortunately, this cold air is short-lived, with return flow
quickly increasing on Friday and keeping highs generally seasonal to
slightly below seasonal (upper 20s northeast to near 40 southwest).
These seasonal temperatures continue into the weekend.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 512 AM CST Tue Dec 16 2025

Primarily VFR conditions prevail today and will generally
continue through the day. Fog has generally underperformed this
morning, and with winds now beginning to increase, it`s unlikely
fog will worsen. Winds will be light to occasionally breezy in
the north today. Did add in some low level wind shear for
northern Iowa tonight when winds pick up aloft.

Fog development is possible again tonight, but with too many
competing factors, have left out of TAFs at this time.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Dodson
AVIATION...Dodson