991
FXUS63 KABR 052309 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
609 PM CDT Wed Aug 5 2026

.KEY MESSAGES...

- High temperatures will be around to slightly above average
Thursday, cooling to slightly below average on Friday. Temperatures
will steadily warm back up through the weekend before cooling back
down early next week.

- There are a few windows of opportunity for night-time showers and
thunderstorms later this week, primarily Thursday evening through
Friday morning and again late Friday night into Saturday morning
over portions of south central and northeastern SD through western
MN. Right now, the best chance for widespread rainfall (35-55%
chance) is lining up for Sunday evening through Monday morning.

- There is a Marginal Risk (level 1 of 5) for isolated severe storms
Thursday evening over the southern half of Jones and Lyman Counties.
The main threats will be 1" in diameter hail and wind gusts of 60
mph.

&&

.UPDATE...
Issued at 607 PM CDT Wed Aug 5 2026

The forecast remains on track this evening. No major changes are
planned.

&&

.DISCUSSION...
Issued at 116 PM CDT Wed Aug 5 2026

The Northern Plains lies under a broad upper trough, in zonal to
slight northwest flow, extending from a large closed low hovering
over the Hudson Bay as a ridge (and its mid level high
underneath) continues over the western CONUS. Through the end
of the week and into the start of the weekend, this low will
pretty much wobble over the Hudson Bay area (and retrograding a
bit) before finally weakening and tracking southeast by the end
of the weekend into early next week. With this, several embedded
shortwaves/vort maxes will spin cyclonically around the low
across the Northern Plains into Canada within this ongoing west
to northwest flow aloft. Behind the upper low, the ridge out
west weakens and becomes more broad, with the axis still through
the western CONUS with the Northern Plains on the downstream
side of it through the middle part of next week as there is not
much movement in the pattern. At the surface, the high pressure
system that has been over the region will drift off towards the
southeast through this evening with winds at the surface that
becoming more southerly tonight/overnight. A surface trough
sets up over west central SD Thursday into Thursday evening with
overall southerly flow continuing before a weak cold front
moves through early Friday, switching winds out of the north to
northeast. By the weekend, the front lifts back northward as a
stationary front as low pressure develops over western SD
through MT.

Embedded shortwave energy over NE through northeastern SD aloft
Thursday evening/Friday morning will interact with the surface
trough and cold front to provide weak energy/lift. To the east
of the trough, WAA flow at 850mb/surface will aid in dewpoints
rising into the 60s by the afternoon, along with warm temps,
helping the atmosphere to destabilize creating the potential for
showers and thunderstorms as a weak LLJ develops through the
night. NBM highlights pops of 15-25% starting over NE/south
central SD Thursday evening and tracking east combining with
another potential area of convection (pops of 30-45%) tracking
southeast out of ND/MN with much of the convection mainly east
of the James River (associated with the cold front and help from
LLJ) through early Friday morning. However, CAMs tell a
different story and really do not show much in the way of any
convection firing up with Fv3 being the only model to show
something as CAMs handle weak forcing poorly. Also, drier air
will be in place over much of the region. Therefore, as of now
confidence remains low at this time. So if cells can initiate,
there will be marginal instability to work as HREF indicates up
to 1500 j/kg of mean SB/MUCAPE, highest over south central
through northeastern SD with max potential to around 2500j/kg
here, and bulk shear around 30kts (enough to produce a couple
supercells). Instability does decrease after sunset, however
bulk shear/LLJ, will be ongoing. The SPC has highlighted a Day 2
marginal risk (level 1/5) for isolated severe storms that
covers the southern half of Jones and Lyman Counties and
southward where this better instability+shear lies. Main threat
will be 1" diameter hail and wind gusts of 60 mph. Other then
slight pops (15-20%) over south central SD Saturday morning, the
forecast remains dry through the day Sunday. Our next potential
for widespread chances of rain (pops 35-65%) will not be until
Sunday evening into Monday morning per stronger northwest flow
aloft, per another shortwave, coinciding with an area of low
pressure/frontal boundary and warm and moist air at the surface.
Still a bit early on severe potential with ML guidance
indicating a 5% chance of severe weather over the Northern
Plains.

With southerly flow returning, overnight temps will be warmer than
the previous 2 nights, ranging in the upper 50s to the lower 60s and
highs back into the upper 80s to upper 90s west of the James River
for Thursday. Behind the cold front Friday, highs will range in the
upper 70s to the upper 80s, warmest across central SD. Temps will
warm back up for the weekend, ranging in the lower 80s to the lower
90s, again warmest across central SD. As for the smoke, light
concentrations of surface smoke are possible over central SD this
evening and tonight before lifting northward. This should not reduce
visibility at the surface. Smoke aloft continues with widespread,
thicker smoke moving in over the entire region Thursday night and
Friday behind the cold front. Lastly, with southwest flow gusty
downslope winds off the Coteau are possible both early Thursday and
Friday morning with gusts of 35 to potentially to 40 mph.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 607 PM CDT Wed Aug 5 2026

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are expected to prevail through Thursday
afternoon.

&&

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

&&

$$

UPDATE...20
DISCUSSION...MMM
AVIATION...20