739
FXUS63 KABR 010902
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
402 AM CDT Tue Jul 1 2025

.KEY MESSAGES...

- Scattered showers and thunderstorms (40-60% chance) expected
  across the region overnight into early Wednesday morning, with
  small hail up to around quarter size being the main threat.

- Heat and humidity return to the region Wednesday through
  Friday, with highs in the upper 80s and 90s, and dewpoints in
  the 60s to low 70s. Heat indices flirting with 100 degrees over
  central SD.

- A system late Friday/early Saturday will bring relief from the
  heat and humidity in the form of storms (50-70% chance eastern
  SD/western MN). Main concern is the potential for heavy
  rainfall.

&&

.SHORT TERM /TODAY THROUGH WEDNESDAY AFTERNOON/...
Issued at 401 AM CDT Tue Jul 1 2025

Surface high pressure over the region early this morning is
providing for clear skies, light winds, and temps falling
into/through the 50s. As the day progresses, this high center will
gradually shift southeast and eventually allow for increasing
southerly winds over central SD, while warm air advection also
overspreads the area. Thus, highs today will be a bit warmer than
Monday, with areas along and west of the James River rising into the
upper 80s to low 90s. Skies look to remain sunny today as well.

Overnight, we continue to see the development of a 35-40kt low-level
jet nosing into the CWA. Mid-level atmospheric dewpoints begin to
increase as well within the broad return flow across the Northern
Plains. HREF mean MUCAPE values generally range from 500-1000 J/KG,
with 30-35kts of effective shear. HREF composite reflectivity >40dBz
ensemble paintballs show rather good consistency in showing
convective development across north central SD around 05Z-06Z, then
spreading continued development/movement of convection southeast
towards KATY/KBKX by 10Z-11Z. Given the good signals, and basically
all CAMs showing convection across the CWA, increased PoPs above NBM
to likely where the paintballs were showing highest confidence.
Small hail, perhaps up to quarter size, seems to be the main threat
with any storms that develop overnight. Some of this activity may
linger into Wednesday morning across the eastern CWA and have small
PoPs (20-30%) for this.

Dewpoints in the 60s look to make a comeback by Wednesday as
temperatures remain warm to hot across the region. Hottest area
looks to be over the southwest CWA where 850mb temps rise to between
+20C to +25C. Highs in the mid 90s seem likely, with heat indices
flirting with 100 degrees.

&&

.LONG TERM /WEDNESDAY EVENING THROUGH MONDAY/...
Issued at 401 AM CDT Tue Jul 1 2025

Wednesday night the ridge axis moves overhead, with southwesterly
flow and warm air advection in the mid-levels. 700mb temperatures
still appear to only top out around +11 to +14C, roughly a standard
deviation above climo. Thursday`s surface setup includes a lee low
over eastern Wyoming and light easterlies prior to an early morning
warm frontal passage, which becomes more of an inverted trough
extending to the east northeast, and primarily southerly flow, with
just a slight easterly component (170-160 degrees). The lee low
lifts northeast through the overnight Thursday, into central North
Dakota by Friday morning. A cold front is then set up by 00Z
Saturday along the Missouri valley. This will mean surface flow for
Friday may take on a more westerly component east river (190-200
degrees).

With regard to temperatures both days, NBM 25th/75th percentile
range is about 5 degrees, though its important to note that
deterministic NBM is closer to the 25th percentile. As for
dewpoints, given the time of year and past experience, the NBM is
underdone for Thursday with the lower mixing potential wind
direction but on par with most deterministic guidance. The NAM does
show a slug of +70 rich air moving overhead during the early part of
the day but its mostly associated with the warm front with
moderation into the 60s during the day. For Friday, with the slight
southwest component we could see more mixing potential, although
pooling along the front later could likewise add to surface
humidity. Thus, its a low/moderate confidence forecast when it comes
to heat index values for Thursday/Friday with any headline
potential.

Then we have to address severe weather potential for later Friday,
with the hot and humid airmass in place, and the slow eastward
progression of the frontal system as it moves into eastern
SD/western MN. Mean NBM CAPE is just above 2000j/kg. GFS BUFKIT
profiles indicate quite a bit of warm air through the column
limiting CAPE (6 to 7C/km above the mixed layer). This is a pretty
moist column however, with NAEFS PWATs up in the 1.5-1.75 range or 2
standard deviations above climo. Flow aloft is relatively weak, with
mid level winds only about 20-40kts and 0-6km shear ranging between
10 to 30kts. Weak mid level flow and high PWATs means the concern is
more in regards to heavy rainfall than severe weather.

A weak upper trough will be in place over the weekend, with cooler
mid/low-level temperatures. The wave train continues however, so
additional rounds of weather can be anticipated through the weekend
and into next week.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1235 AM CDT Tue Jul 1 2025

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are forecast during the next 24 hours. A few
thunderstorms are expected Tuesday night, possibly starting out
near KMBG, before spreading southeast toward KATY. Much of this
activity looks to be between 06Z and 12Z Wednesday, so will
address this for the 12Z TAFs later this morning.


&&

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

$$

SHORT TERM...TMT
LONG TERM...07
AVIATION...TMT/10