Watertown, South Dakota 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

401
FXUS63 KABR 031611 AAB
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1011 AM CST Tue Dec 3 2024

.KEY MESSAGES...

- A brief warmup today with highs in the 30s and 40s for many areas,
  more so along and west of the James River.

- Potent cold front moves through Wednesday morning, bringing strong
  northwest winds, potential snow showers, and falling temperatures
  through the day.

- Milder temperatures for late in the week and into the weekend with
  highs/lows forecast to be some 10 to 20 degrees above normal.

&&

.UPDATE...
Issued at 1010 AM CST Tue Dec 3 2024

The forecast is on track this morning. No major changes are
planned.

&&

.SHORT TERM /TODAY THROUGH WEDNESDAY AFTERNOON/...
Issued at 441 AM CST Tue Dec 3 2024

Much of the CWA is mostly clear early this morning as the deck of
mid clouds continues pushing eastward into MN. Southerly winds are
occurring across the region and am also anticipating some downslope
winds to develop over the next few hours across the Sisseton hills
region. This feature shows up nicely in hi-res wind guidance and
could lead to a bit of drifting/minor blowing snow this morning.
925mb winds are only about 30 knots, so not an overly strong event,
but will be watching obs over there in the Peever, etc. region over
the next few hours. Gusts may be around 35 to 40 mph or so, with a
lull in the afternoon before a brief return of these winds around
00Z this evening. Constructed wind grids to reflect more hi-res
guidance in the Sisseton hills region as they pick up on the
downslope winds better. Otherwise, the main highlight for today will
be the warmer temperatures moving in with rather strong warm air
advection at 925/850mb. Will be hard to warm much above the upper
20s/low 30s across the eastern CWA where there is more snow cover,
and also where the air mass aloft is not quite as warm. But across
central SD, it appears 40s could easily be achieved along and west
of the Missouri, with readings possibly flirting with 50 degrees
over the far southwest CWA.

Focus then shifts to the potent cold front dropping south over the
area Wednesday morning. Timing looks to be close to 12Z along the
ND/SD border, then pushes south through the rest of the morning.
Pretty strong cold air advection behind the front as 925mb temps
fall from around 0C at 12Z Wed to as much as -15C or so across
northeast SD by 00Z Thurs. With the strong low-level cold air
advection, falling temps during the day seems a pretty good bet.
Hourly temp grids reflect this. Will also be watching potential for
snow showers along the front and have expanded slight chance PoPs
further west across the CWA after looking at hi-res guidance. Also,
it does appear guidance is showing more convective-type nature
precip, so opted to go with snow shower wording and coverage terms
(isolated) during the morning hours. Sounding profiles would also
support more of a shower-type snow potential.

Winds will also be an issue on Wednesday in the post-frontal
environment. 850mb winds on the order of 45 or 50 knots spread
across eastern SD during the morning hours. HREF Grand Ensemble mean
gusts are around 40 mph during the morning hours, mainly in the
higher elevations. Although, 75th/90th percentiles are closer to 45
or even 50 mph for gusts in those same higher elevations. So,
potential is there for some advisory-level gusts in spots. NBM probs
for greater than 45 mph gusts highlight the Leola hills region the
most, with values greater than 60-70 percent. Drifting/blowing snow
also possible mainly in the eastern CWA where there is more
fluffy/blowable snow and cooler temperatures. Potential gets a bit
more uncertain wherever temperatures rise greater than 32 degrees
today as melting/re-freezing of snow will make things a bit harder
to blow around.

&&

.LONG TERM /WEDNESDAY EVENING THROUGH MONDAY/...
Issued at 441 AM CST Tue Dec 3 2024

Upper wave is departing at the start of the extended, embedded
within northwest flow. This regime persists through the end of the
work week, with some minor subtle embedded waves but none of these
looks to leave much of a mark on the forecast precipitation-wise. For
about half way through the weekend the upper pattern becomes more
zonal with a deepening western CONUS trough. This western CONUS
trough eventually shifts east, allowing for a central CONUS longwave
to settle overhead early next week. The split flow pattern that
develops by this point also means that any systems moving through
will be generally weak, and as such overall the predictability and
QPF of any of these nuisance systems is low.

Temperatures across the extended will see quite a bit of fluctuation
as the pattern changes. We begin in the post cold frontal airmass
Thursday with a 1040`ish mb high overhead. Limited mixing and snow
on the ground, with 850mb temperatures a standard deviation below
climo to start the day means another cold day with highs east river
in the teens. Only silver lining here is that winds the night
before will keep temperatures from bottoming out too much.

As the high moves east we get into light return flow Thursday
evening/overnight. These light winds shift to westerly for
Friday/Friday night with 850mb temperatures around a standard
deviation above climo. This airmass will persist through the weekend
as we see the upper pattern transition. Already NBM is advertising
temperatures that are 10 to 20 degrees above climo. The only issue I
can foresee with this mild airmass is that snow on the ground, once
melted, may combine with light winds to result in fog formation,
which... again thanks to light winds, would persist until cleared by
a frontal passage next week.  Too far out to throw into the forecast
just yet, but seems like a good bet this time of year.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 532 AM CST Tue Dec 3 2024

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are forecast for the majority of the TAF period,
although MVFR CIGs are possible late in the period with the
arrival of a cold front early Wednesday morning. Low-level wind
shear (LLWS) will also be a concern across the region tonight and
have inserted mention of this.


&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&

$$

UPDATE...Wise
SHORT TERM...TMT
LONG TERM...Connelly
AVIATION...TMT