583
FXUS63 KABR 032005
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
305 PM CDT Thu Jul 3 2025

.KEY MESSAGES...

- Heat and humidity will continue on Friday, however, heat indices
are forecasted to stay below 100 degrees with cooler temperatures and
dewpoints on Saturday.

- A system will bring showers and thunderstorms over central South
Dakota Friday afternoon with this activity moving across the eastern
half of the state Friday evening through Saturday morning. The
highest chances of rainfall (60 to 80%) run along and east of the
Missouri River.

- Rainfall amounts of 1 to 2 inches is possible Friday afternoon
through Saturday morning along and east of the Missouri River.
Localized areas could exceed 2 inches, especially over portions of
north central through northeastern SD into west central MN.

- Weather pattern stays active into early next week with
disturbances Saturday night/Sunday and again Monday night bringing
opportunities for rainfall.

&&

.DISCUSSION...
Issued at 304 PM CDT Thu Jul 3 2025

Main concern in the forecast period will be one more day of the heat
and humidity along with showers and thunderstorms expected Friday
afternoon through Saturday afternoon and heavy rain potential. As of
230pm, the lingering MCV, bringing scattered clouds, continues to
push eastward over northeastern SD into ND/MN. Light returns on
radar have been noted here and there skirting across the ND/SD
border through this morning indicating light showers at most. Temps
range in the mid to upper 80s to the upper 90s, highest over south
central SD with dewpoints as high as the mid 70s! Overall dry
conditions expected tonight with the exception of far western Corson
County where 15-20% pops are possible late on the leading edge of
the surface trough. Most of the activity will stay to our north over
ND through northwestern SD, however, cannot rule out an isolated
chance of a severe storms in this area with quarter size hail and
60mph gusts.

The axis of the ridge will continue to push eastward this evening
through Friday with the Northern Plains in southwest flow aloft.
Within this flow, a shortwave will move southwest to northeast and
over the Northern Plains Friday afternoon and evening, where it will
continue in more of an easterly direction into MN Saturday. With
this setup aloft, the axis of the surface trough will hover over the
lee side of the Rockies through the central Dakotas this evening,
which lies south of a low that will move across Canada. Its cold
front will drape southwest from this low through MT. By Friday
morning the trough`s axis will extend through the central Dakotas
into western NE/KS as this low in Canada tracks northeastward. By
Friday evening, the cold front will have shifted a bit southeast and
sprawled from Ontario and southwestward through ND/MT. The surface
trough`s axis will extend from northeastern through central SD as it
becomes positive tilted. Finally the cold front will be halfway
through the state as it continues east and southeastward by Saturday
morning before finally exiting the CWA by Saturday midday/afternoon

Ahead of the cold front, all the CAMs/HREF ensemble paintballs are
in agreement of isolated to scattered thunderstorms firing up over
the central half of ND through NE Friday afternoon. There seems to
be a wide range of storm modes expected as CAMs indicate
cells/multicells to start and merging into some sort of line or
several broken lines as it pushes over the eastern half of the state
with additional formations of cells/mulitcells ahead and behind the
line. There is a bit of a difference in exact timing between the
models on the progression eastward with the convection. With this
uncertainty, the NBM does a good job showing the potential with
broadbrushed pops of 30-60% between 18Z-00Z, highest west of the
James River and 50-90% pops east of the Mo River, with 80+ pops
James River Valley and eastward between 00-12Z Saturday. The last of
the precip looks to exit the far eastern CWA by Saturday afternoon.

With the storms Friday afternoon into early Saturday morning, the
main concern will be the potential for heavy rain. We have low level
moisture in place already with dewpoints continuing in the upper 60s
to lower 70s at the surface and dewpoints at 850mb around 11-12C
during the day Friday, increasing to 16-17C James River and eastward
by the afternoon and evening. NAM soundings over this area show a
fairly moist to saturated column well through 500mb with the
freezing level between 12-14K feet! So the depth of the warm cloud
layer is quite large! NAEFs indicates mean specific humidity runs
around 2 standard deviations above climo over the entire CWA from
700-850mb and James River eastward at 925mb Friday evening into
Saturday morning with PWAT running around 2 standard deviations
above climo as well, with values of 1.75" mainly James River and
eastward. NBM probability of 1" or over is 40 to 60% in this area,
highest over far northeastern SD into west central MN with a
probability of 2" is 20-30%. WPC ERO has upgraded to a slight risk
over portions of north central to northeastern SD/MN with the
marginal risk still along and east of the Mo River due to this heavy
rain threat. Higher rainfall amounts of over 2" are possible
(especially in the slight risk) with any slower moving/stronger
storms or training of storms over the same location. This could lead
to a flash flooding and/or river flooding concerns, especially over
northeastern SD which has already dealt with heavy rain/flooding
recently. EC EFI is still holding onto values of 0.5 to 0.7 and a
shift of tails of zero east of the Coteau, highest over Roberts
County into MN. Even though we have the moisture, lift from the
front/trough, and moderate CAPE, shear will be weak (less than
30kts). Also with the high freezing levels any hail that does fall
will melt along the way or be smaller. The latest severe outlook per
SPC has expanded the marginal risk(level 1/5) westward to now cover
locations along and east of the Missouri River into MN. With the
various storm modes expected, the main threat will be the winds,
with gusts of 60 to even 70 mph if this convection can form into
more organized line(s). The increased chances of wind and hail
threat will luckily stay to our north where there is better
instability.

Temp wise for Friday, we will continue in southwest flow along and
east of the Missouri River (ahead of the trough`s axis). 850mb temps
will run between 20-22C with deterministic NBM surface temps ranging
from the upper 80s to the mid 90s. 25th-75th spread is 3-7 degrees
with the highest spread over far north central SD depending on
timing of trough`s passage. Heat indices look to remain below 100
degrees, however, if we overachieve on highs/dewpoints we could be
flirting with 100 heat indices especially over portions of central
and northeastern SD. With the CWA behind the fropa Saturday, this
will bring a relief to the heat and humidity as highs will range in
the upper 70s to upper 80s, warmest across south central SD and
dewpoints in the upper 50s to lower 60s.

Split flow pattern continues with another shortwave moving in from
MT Saturday night into Sunday, bringing the possibility of more
showers and thunderstorms with pops of 40-65% over central SD. A
large ridge builds over the western CONUS midweek or so and mid
level high underneath this ridge over the Southwest. We will
continue in an unsettled weather pattern and temps warming back up.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1227 PM CDT Thu Jul 3 2025

Terminals KABR,KATY,KPIR,KMBG

VFR conditions will continue through the TAF period. Low level
wind shear at 2000ft, out of the southwest of 40kts, is
forecasted at KMBG and KPIR between ~07-09Z Friday. Showers and
thunderstorms are not forecasted to develop over KPIR/KMBG until
the end of the TAF period or shortly after.


&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Heat Advisory until 8 PM CDT this evening for SDZ004>006-008>010-
     016>018-021-037.

MN...Heat Advisory until 8 PM CDT this evening for MNZ046.

&&

$$

DISCUSSION...MMM
AVIATION...MMM