396
FXUS63 KABR 010221 AAB
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
921 PM CDT Mon Jun 30 2025

.KEY MESSAGES...

- Heat and humidity return by the end of the week with highs in
  the 90s and dewpoints back into the 60s. Heat indices may flirt
  with 100 degrees over portions of central SD on Thursday.

- 20 to 35 percent chance of isolated showers and thunderstorms Tuesday
  night through Wednesday. Severe weather threat remains low.

- A storm system will pass over the Northern Plains for the Fourth
  of July bringing a possibility of showers and thunderstorms
  (40-65%) Friday afternoon and evening.

&&

.UPDATE...
Issued at 920 PM CDT Mon Jun 30 2025

No changes planned to the tonight period forecast.

UPDATE Issued at 623 PM CDT Mon Jun 30 2025

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

&&

.DISCUSSION...
Issued at 243 PM CDT Mon Jun 30 2025

As of 230pm, cumulus clouds have developed over most of the CWA with
radar indicating a few isolated thunderstorms pushing southeast over
central MN. Temps range in the mid to upper 70s to around 80 with
dewpoints in the mid to upper 50s around 60. Current setup aloft is
that the Northern Plains is on the backside of this trough/right
side of ridge with weak shortwave energy riding over the eastern CWA
through this evening, per RAP. RAP indicates ongoing steep low level
lapse rates of ~8C with weak 700-500mb lapse rates of 5-6C in this
area with CAPE values up to 1000j/kg. So this may be enough to
produce some isolated showers/thunderstorms through this evening.
Several of the HREF members/few CAMs show this very spotty chance
grazing far northeastern SD into west central MN, so have a 15-20%
pop chances to cover this threat. RAP soundings in this area
indicate a inverted V sounding with lots of dry air at surface, so
precip could be more light rain/sprinkles or entirely a virga
situation. Any stronger cell would produce gusty winds (50 mph and
under) and possibly small hail given the cooler temps aloft. No
severe weather is anticipated.

This ridge will push slightly east Tuesday into Wednesday with
ongoing northwest flow aloft. By Wednesday evening and Thursday,
Clusters are in agreement that the ridge is forecasted to be
overhead where it will continue its track east Friday into the
weekend. As the ridge moves over the eastern CONUS Friday, a broad
low amplitude trough sets up over the western CONUS with embedded
shortwaves that will ride northeast, along the right side of the
trough, and over the Northern Rockies/Northern Plains turning winds
aloft to southwesterly for the end of week. At the surface, high
pressure will move in over the region this evening and remain over
the area through the day Tuesday before shifting southeast Tuesday
evening. A lee trough will also set up to our west Tuesday through
Wednesday, with the right side of trough expanding eastward over
much of the CWA by Wednesday evening. This lee trough extends
southward from a low that will be over central Alberta with its cold
front extending southeast and east over ND/MN by 00Z Thursday. A
secondary lee low looks to form over MT Thursday with the cold front
turning more into a stationary front over SD before this system (and
trailing cold front) tracks east Friday and Saturday.

With surface troughing expanding eastward Tuesday night/early
Wednesday morning and an increasing LLJ, with central SD on the
northern fringe of this, Cams/HREF do show the potential for showers
and thunderstorms moving in from the higher elevations and over
central SD, spreading east/southeast during this time. However,
timing, exact location/track of storms, and intensity does vary
quite a bit between the models. Latest NBM highlights a 15-25% of
pops along and west of the Mo River Tuesday night, increasing to 20-
30% over central to portions of northeastern SD through midday
Wednesday. So LLJ, steep lapse rates, CAPE up to 1500 j/kg, mainly
over central SD (highest over south central SD) and bulk shear
around 30kts does support isolated severe chances over south central
SD. However, the one caveat is that this is hardly any support aloft
for anything more widespread. CSU Machine learning highlights a 5-
15% chance for wind/hail reaching severe limits, mainly central to
western SD with CIPS keeping a 5-20% hail threat over the western
half of SD. SPC added a marginal risk over western SD with the
eastern edge of this risk clipping western Stanley and Jones. Main
threat would be up to quarter size hail and wind gusts around 60mph.

Ongoing slight pops (20-35%) continue Wednesday afternoon/night
mainly east of the James River being south of the cold front and
ongoing surface troughing. We will see shower and thunderstorm
chances increase late Thursday into Friday and continue through
Saturday as this low/cold front moves across the region and its
shortwave with the highest pops of 40-65% Friday afternoon and
evening right ahead of the cold front. With the warm moist air ahead
of the system and 700mb temps only about 11-13C Friday afternoon,
enough low level heating/moisture and instability should be enough
to break the cap and allow storms to fire up. However, the greatest
shear looks to be behind the cold front which would limit severe
potential. CSU machine learning indicates a 5-15% chance of severe
weather each day with CIPS highlight a 10-15% chance just on Friday.

With clear skies and dew points in the upper 40s and 50s, I
continued with the trend with a mix of NBM/NBM25th to allow for a
bit cooler temperatures, ranging in the mid to upper 50s. With the
CWA on the north/northwest side of the high Tuesday
afternoon/evening, 850mb winds will turn southerly/southwesterly and
bring in WAA with temps between 18 to 24C by 00Z Wednesday. Surface
highs are forecasted in the 80s over the Coteau and eastward and
upper 80s to the lower 90s west of here, highest over central SD.
For Wednesday, 850mb temps increase up to 27C over central SD with
surface highs across the CWA well into the upper 80s to upper 90s,
warmest over south central SD. This is when we really see the moist
air surge northward with dewpoints rising into the 60s. This warmer
air continues to spread eastward for the end of the week with temps
continuing in the upper 80s to the upper 90s and dewpoints in the
mid to upper 60s to even lower 70s during peak daytime heating
Thursday and Friday. As of now, apparent temps overall look to
remain below 100 degrees with just a few speckles of 100 over south
central SD middle to the end of the week. The cold front will bring
bring a relief to the heat and humidity for the weekend.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 623 PM CDT Mon Jun 30 2025

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are forecast during the next 24 hours. Winds will
diminish this evening and then pick back up again Tuesday
afternoon with gusts between 15-20kts.

&&

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

$$

UPDATE...10
DISCUSSION...MMM
AVIATION...10