Watertown, South Dakota 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

867
FXUS63 KABR 302308 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
608 PM CDT Sun Mar 30 2025

.KEY MESSAGES...

- There is a 20% chance of snow over portions of south central SD
  tonight.

- Precipitation in the form of rain and snow will impact the
  region Tuesday through Wednesday. The coldest air and highest
  precipitation amounts are expected to cause plowable snow for
  northeastern South Dakota and western Minnesota. There is lower
  confidence on specific amounts at this time. However, travel
  may be impacted, particularly for the Wednesday morning commute.

- Winds will gust out of the east to southeast 25 to near 40 mph
  on Tuesday.

&&

.UPDATE...
Issued at 605 PM CDT Sun Mar 30 2025

See below for an aviation forecast discussion for the 00Z TAFs.

&&

.SHORT TERM /THIS EVENING THROUGH MONDAY NIGHT/...
Issued at 252 PM CDT Sun Mar 30 2025

The mid afternoon surface weather map shows the exiting low over
Lake Michigan with high pressure over central Canada extending a
ridge across the Dakotas.

A weak wave at 500mb will help support low precipitation chances
over southwestern SD, including a 30% chance of snow for portions of
Jones and Lyman Counties. Otherwise, dry weather will continue
across the forecast area.

The surface ridge will shift across eastern SD and western MN by 15Z
Monday before exiting across MN Monday afternoon. The pressure
gradient will start to strengthen over central SD in the afternoon,
between the exiting ridge and nearing elongated trough across the
Rockies. Surface winds will remain elevated Monday night, gusting 20-
30kts over central SD by 06Z and then to the Prairie Coteau area by
daybreak. Look for increasing clouds Monday night with a 40% chance
of mainly snow (rain and snow over central to south central SD) to
increase in coverage and expand to the rest of the area by daybreak.
The warmest air will alight with the highest precipitation amounts,
with snow to liquid ratios averaging 5:1 and most locations picking
up less than an inch of new snow.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 252 PM CDT Sun Mar 30 2025

We continue to monitor the next system moving in mid week this week
as it comes further into focus. Ensembles are converging on the low
track moving across Nebraska and Iowa Wednesday morning, and will
support precipitation Tuesday through Wednesday over central and
northeastern South Dakota and western Minnesota. GEFS does still
favor a track that is slightly further north, but that appears to
only produce a slightly higher QPF that could very well be due to
other factors due to a similar spatial signal with the other
ensembles.

Precipitation type is going to be a key factor with this system, as
both near-surface and lower-level temperatures will be hovering
around freezing through both Tuesday and Wednesday. With that said,
models have trended in the direction of a profile more supportive of
snow, but nothing is certain at this point. Ensemble mean QPF has
increased with the latest forecast cycle, and much of the area will
likely receive upwards of an inch of precipitation in total. The
heaviest precipitation is still expected Wednesday morning over
northeastern South Dakota, where both surface and mid-level
temperatures are expected to be below freezing. Assuming then that
all precipitation is falling as snow, we could see heavy, wet
snowfall rates up to 1" per hour. Due to all the uncertainty with
temperatures, the storm total snowfall has a very large level of
uncertainty. Ensembles are in agreement that northeastern South
Dakota and western Minnesota could easily see upwards of 10 inches
(50-70% probability), and 75th percentile values put totals upwards
of 15 inches. One important caveat to those ensemble totals is that
the models use a set 10:1 ratio for snow, which given the setup may
be a bit too high of a ratio. Instead values closer to 5-7:1 may be
more realistic, which is why the NBM probabilities of higher
snowfall totals are a bit lower than other ensembles. Euro/GEFS
probability of 10 inches is 50-80%, while NBM is "only" 40-60%. The
same is observed with 15 inches at 20-40% vs 0-20% respectively.
Regardless of the observed decrease in probabilities within the NBM,
there are still high chances for significant snowfall, and the
probability of reaching Winter Storm Warning criteria (6 inches) is
greater than 50% over nearly all of northeastern South Dakota and
western Minnesota. At this time, a Winter Storm Watch has been
issued for Brown, Marshall, Day, Roberts, and Grant counties in
South Dakota, as well as Traverse and Big Stone in western
Minnesota. Additions, subtractions, and other adjustments are likely
over the next few forecast cycles due to the high variability and
low confidence in snowfall amounts in the event.

On top of all that, wind could also be a factor with this event,
particularly Wednesday morning when winds coincide with the highest
snowfall rates. Winds will initially be out of the southeast on
Tuesday before backing to become northerly Wednesday with the
approaching low. With this shift north, wind gusts will approach 30
knots, and may cause significant reductions in visibility when
combined with falling snow. There will also likely be some
accumulation by that point, meaning that even for areas not
experiencing the snowfall rates near 1"/hour, visibility reductions
may still be a concern and travel could be impacted for the
Wednesday morning commute.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 605 PM CDT Sun Mar 30 2025

Terminals KABR,KATY,KPIR,KMBG

VFR conditions have returned, and are forecast at all four
terminals through Monday afternoon.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Winter Storm Watch from Tuesday evening through Wednesday
     evening for SDZ006>008-011-021.

MN...Winter Storm Watch from Tuesday evening through Wednesday
     evening for MNZ039-046.

&&

$$

UPDATE...10
SHORT TERM...06
LONG TERM...BC
AVIATION...10