Watertown, South Dakota 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

544
FXUS63 KABR 200147 AAB
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
847 PM CDT Sat Jul 19 2025

.KEY MESSAGES...

- There is a Slight Risk,level 2 out of 5, for severe storms over
  western SD and Marginal Risk, level 1 out of 5, over central
  South Dakota late this evening into the overnight hours. Winds
  of 60 miles per hour and hail of 1 inch in diameter are the main
  threats.

- There is a Slight Risk, level 2 out of 5, for severe weather
  late Sunday afternoon into Sunday night over much of central
  SD. There is a Marginal Risk, level 1 out of 5, for severe
  thunderstorms Monday afternoon into Monday night. Hail of 1 inch
  in diameter and winds of 60 miles per hour are the main
  threats.

- Heat index values will be in the upper 90s to near 100 degrees
  Monday afternoon and again potentially on Tuesday, across
  central SD primarily south of Pierre.

&&

.UPDATE...
Issued at 845 PM CDT Sat Jul 19 2025

No changes planned to the tonight period forecast. Monitoring
convective trends over far western South Dakota up into southeast
Montana.

UPDATE Issued at 619 PM CDT Sat Jul 19 2025

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

&&

.DISCUSSION...
Issued at 348 PM CDT Sat Jul 19 2025

The afternoon surface weather map shows high pressure over south
central Canada and eastern ND/western MN extending a ridge through
our entire forecast area. Stratus clouds and daytime flat fair
weather cumulus clouds have dominated the sky. An area of persistent
light rain with just a few pockets of lightning (mainly in cloud)
has resided north of I-90 and south of Mobridge and east to Redfield
this afternoon. Forecast models continue to show this area
diminishing in coverage as it shifts more to eastern SD through the
rest of the afternoon hours as the weak wave at 500mb in the
otherwise zonal flow exits. Our focus for additional precipitation
will shift to the west where there is currently a trough of low
pressure extending over eastern MT/WY and CO through western KS.
Another 500mb wave moving suppressing the weak 500mb ridge will
continue mainly zonal flow overhead through Sunday. The surface
trough/in the form of a warm front will shift into western SD by 12Z
Sunday. The surface trough over western SD will be a near
persistent feature through at least Monday morning.

As for specifics, storms are still expected to develop 20-23Z near
the WY/MT/SD border. The quickest solution brings the remnants of
these storms along our western border by 03-05Z. There are some
significant differences on where these storms may stay (farther
north central SD like the 18Z HRRR or over any of our western
counties like the 12Z FV3, or with little to no storms like the 12Z
NAMNest). Given the significant uncertainly, slightly lower chances
of precipitation seemed reasonable, with chance coverage west of the
MO River by 06Z and all of central SD by 09Z. A favorable 25-35kt
low level jet could help sustain any storms that develop with
dewpoints mainly in the low 60s. CAPE is limited over or forecast
area. Expect the storms to weaken for the most part as they move out
of the area of better instability. The SPC Slight Risk of severe
weather west of the MO River looks reasonable at this time.
Confidence is lower for locations east of the MO River to Eureka-
Redfield.

Instability will increase Sunday. The main question Sunday will be
in low clouds. The NAM is more robust with the low level moisture,
which plays into the potential for more lower clouds in the morning.
It also indicates a little more curvature in the hodographs for the
afternoon. We`ll have to see how the late afternoon and evening
evolve as the cap erodes. ML CAPE continues to focus over mainly
central SD through 00Z Monday with a surface trough extending up
over our western counties. A marginal to slight risk has been added
for Sunday, mainly from late afternoon/evening on, again focusing
over central SD.

Monday will bring another round of potential severe weather as main
area of low pressure still resides near the cwa. The surface low
will finally exit to southeastern SD midday Wednesday, putting an
end to the 18-24 hour threat of severe storms.

Temperatures Monday afternoon will warm another 5F compared to
Sunday, topping out in the 80s and 90s. Dewpoints will be in the
upper 60s and 70s, resulting heat index values of 100 to near 105F.
Heat headlines may be needed. Tuesday will still be warm and humid,
especially over our southwestern counties where heat index values
will again near 100F.

Clusters are in decent agreement of zonal flow aloft starting out
Friday evening as a low amplitude ridge, positioned over the
northern Rockies, will shift eastward and over the Northern Plains
through the weekend. Behind this ridge, a -PNA pattern sets up over
the northwestern to western CONUS Saturday with a mid level low
forming over the western Canadian provinces. This low, becoming an
open wave, will track eastward over Canada through early next week.
Otherwise, an overall -PNA pattern continues through the end of next
week with the Northern Plains in zonal flow, within the crest of a
ridge (Clusters diverge on exact amplitude at this time) that
resides over a large subtropical high that will just sit over the
southern/southeastern US. This unsettled weather pattern continues
as several weak waves/pulses will push west to east within this flow
over the Northern Plains.

At the surface, the area of low pressure will continue to track
south of the CWA Friday evening/early Saturday as a high pressure
system moves in behind it from the north. As of now, lingering
showers and thunderstorms (NBM pops of 15-30%) are possible just
north of this low/front mainly over south central to east central SD
during this time. This high will keep the area dry for most of
Saturday with the exception of along and west of the Mo River where
pops of 15-25% are possible, closer to the next incoming low
(marginal risk of severe weather here). The high will track eastward
Saturday evening/Sunday with this low (and fronts) forecasted to
move across the Northern Plains through early next week (associated
with the shortwave across Canada) with a secondary lee low/front
forming and stalling out over the area through the midweek. This
will bring the return of shower and thunderstorm chances (30-45%)
during this time. With this being several days out timing of the low
and track may change. CSU Machine learning does highlight a broad 5-
15% chance of severe weather, with NSSL up to 30% chance, over the
Northern Plains with this system, however, confidence remains low on
exact setup. Ongoing low chances of precip (20-35%) continue through
the end of the week in this unsettled weather pattern setup.

Highs will still run about 5-10 degrees below average on Saturday
with highs ranging in the mid 70s to the lower 80s. Temps will
gradually warm back up into the 80s, with highs in the upper 80s to
around 90 along and west of the MO for Sunday. This warmer air will
spread eastward over the CWA early next week, as southern winds will
bring in heat and moisture ahead of the low, with highs overall in
the 80s/90s through the middle of next week.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 619 PM CDT Sat Jul 19 2025

Terminals KABR,KATY,KPIR,KMBG

VFR conditions should prevail for most of the TAF valid period.
Can`t rule out some night-time/early Sunday morning stratus
developing. Later tonight, there could be some thunderstorms
nearing/moving over the KPIR/KMBG terminals. Prob30`s are in the
forecast for that potential. Sunday afternoon, thunderstorms may
happen at KMBG. A Prob30 is in the forecast for that, too.

&&

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

$$

UPDATE...10
DISCUSSION...06
AVIATION...10