406
FXUS63 KABR 041555 AAB
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1055 AM CDT Fri Jul 4 2025

.KEY MESSAGES...

- Heat and humidity will continue today. However, heat indices are
  forecast to stay below 100 degrees this afternoon, with cooler
  temperatures and dewpoints on Saturday.

- Showers and thunderstorms are expected (55-75% chance),
  initially,over central South Dakota this afternoon with this
  activity slowly moving and being reinforced by additional
  thunderstorms (75-95% chance) across the eastern half of the
  state this evening through Saturday morning.

- Rainfall amounts of 1 to 2+ inches is possible this afternoon
  through tonight mainly east of the Missouri River. Localized
  areas could exceed 2 inches, especially over portions of north
  central through northeastern SD into west central MN.

- The weather pattern stays active into early next week with rain
  chances Saturday night, and again Monday afternoon/evening.

&&

.UPDATE...
Issued at 1046 AM CDT Fri Jul 4 2025

Satellite trends this morning indicate thickening clouds across
western and central South Dakota with some of these mid to higher
level clouds rolling into the James Valley. A couple of non-severe
storms are already firing and tracking northeastward in the
vicinity of a sfc trough across central SD. Expecting this
convection to only continue and develop across central SD late
this morning into the early afternoon. Main threats continue to be
strong winds and heavy rainfall. Can`t rule out some larger hail,
especially initially with some of the stronger cells that develop
across central SD and shift east toward the James Valley later
this afternoon/early evening. Made some minor adjustments to PoPs
to account for the convection coming in just a bit earlier than
expected across our far western zones.

UPDATE Issued at 648 AM CDT Fri Jul 4 2025

See below for an aviation forecast discussion for the 12Z TAFs.

&&

.DISCUSSION /TODAY THROUGH THURSDAY AFTERNOON/...
Issued at 430 AM CDT Fri Jul 4 2025

At 3 AM CDT, skies are mostly clear and temperatures are in the 70s.
Winds are southerly around 10 to 20 mph with gusts up to 30+mph at
times while a southwesterly low level jet of 30 to 45 knots happens
just off the surface.

The seven day forecast features an upper level ridge; currently
centered over the middle of the CONUS, but forecast to flatten a bit
over this CWA days 3 and 4 into zonal flow, before it pumps back up
over the western CONUS Tuesday/Wednesday and then propagates back
over the nation`s mid-section Wednesday/Thursday.

While the ridge remains overhead today, it`s looking like another
warm day, with high temperatures expected to warm up into the 90s
across much of the CWA. However, presently, guidance does not
introduce temp/dewpoints high enough to generate widespread apparent
T`s (heat indices) of 100F degrees or higher. As a result, not
starting the day off with a Heat Advisory. The day shift can throw
one out, if it starts looking like temp/dewpoint forecast are
getting off track.

So, aloft, there is a shortwave over the central high plains that is
forecast to rotate north and east around this upper level ridge over
the region. And, at the surface, the map shows two surface trofs
(one over western SD and one back over northeast MT/northwest ND).
Models generally agree on holding this western SD/lee-of-the-Rockies
surface trof in place over western/central SD through early this
afternoon, while gradually dropping the MT/ND boundary (a cold
front) south and east into the CWA by early this evening and running
it down out of the southeast corner of the CWA Saturday morning.
Expecting, with an environment that is weakly capped, CI should be
generally somewhere between 1 PM CDT and 4 PM CDT in/near this lee-
side surface trof across the far western forecast zones. ML CAPE
over 2000J/kg and deep layer shear at or less than 25 knots should
promote a storm mode of pulse to perhaps multi-cellular convection
this afternoon with a marginal hail threat. With a nearly saturated
sounding (high pwats) environment and (almost saturated) mid-level
lapse rates on the order of 5.5C to 7C/km, wind concerns do not
appear to come into play during the afternoon. But, perhaps
strong/damaging winds could be possible later in the
evening/overnight as drier air starts to entrain into the boundary
layer with any storms that develop along the cold front as it moves
through the CWA. Both the NAM and RAP indicate a brief uptick in
deep layer shear across the pre-cold frontal environment over the
eastern third of forecast zones this evening between ~02Z and 06Z.
During this time, 0-3km CAPE is forecast at or above 75J/kg and 0-
1km shear vectors increase from the southwest to ~15-25 knots, all
lending support to the notion that perhaps a wind threat could
materialize with thunderstorms after they cross over the James River
valley and head toward west central Minnesota. But, more than
anything, there is a growing sensitivity and concern that
thunderstorms today/tonight will be slow-moving and rather moisture-
laden, capable of generating excessive (1-2+ inches of rain and/or 1-
2 inches/hour) heavy rainfall and/or heavy rainfall rates. SPC`s Day
1 slight risk (level 2 out of 5) now extends down just a little bit
into this CWA, and WPC`s Day 1 ERO also maintains a slight risk of
excessive heavy rain across the northern tier counties of this CWA.

By mid-day Saturday, high pressure nosing into the region, along
with low level CAA/dry air advection, should be bringing any
lingering precipitation chances across the CWA to an end. However,
there is a circulation noted in Water Vapor this morning over Nevada
that is progged to make its way into the eastern part of
Wyoming/Montana by Saturday afternoon, initiating afternoon/evening
convection within a deep layer shear environment (40-50+? knots)
much more supportive of organizing into one or more bowing line
(strong wind) segments that could potentially reach all the way to
Pierre, SD Saturday night (sometime after 1 AM CDT Sunday). SPC`s
Day 2 marginal risk (level 1 out of 5) covers a portions of this CWA
far western forecast zones.

There could be another round of convection developing/moving over
the CWA by Monday afternoon. Otherwise, it looks like there will be
break in precipitation chances for a couple of days before showing
up again right at/just beyond the end of the 7-day forecast
period.

Cooler conditions are expected over the CWA Saturday and Sunday (and
possibly into Monday) before low level WAA can potentially set back
up Tuesday and Wednesday of next week.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 648 AM CDT Fri Jul 4 2025

Terminals KABR,KATY,KPIR,KMBG

Excluding thunderstorms this afternoon and evening, where heavy
rain may reduce visibility to less than 6SM, VFR conditions are
expected through tonight.


&&

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

$$

UPDATE...Vipond
DISCUSSION...10
AVIATION...10