543
FXUS63 KABR 171904
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
204 PM CDT Tue Jun 17 2025

.KEY MESSAGES...

- Isolated weak storms continue through the afternoon/evening (20-
50% chance). Severe weather unlikely.

- There is a Marginal risk (level 1 out of 5) for severe
thunderstorms Thursday night.

- Temperatures will be heating up into the 90s on Friday and
Saturday, or about 10 to 20 degrees above normal. The hottest day is
predicted to be Saturday, with a probability of 20% to 60% of
exceeding 100 degrees.

&&

.DISCUSSION...
Issued at 203 PM CDT Tue Jun 17 2025

Radar just got active around the lunch hour, but cells have been
fairly small and short lived. This matches the MO for the
environment, as NAM BUFKIT profiles indicate some skinny CAPE and
weak shear. There is a subtle mid-level trough staged over the
western Dakotas helping to support this. That feature continues east
overnight into early Wednesday, with a ridge aloft upstream and
gradually increasing 500mb heights. Height increases continue into
Thursday, at which point we begin to see a surge in mid level warm
air under the ridge. 850mb/700mb temperatures respectively increase
to +20C to nearly +30C / +8C to +13C from northeast to southwest
Thursday afternoon - a standard deviation above climo. Friday, those
numbers increase about 2-5C and about ~6C between 850mb/700mb
respectively, now up to about the 2 standard deviation level. The
heat increases incrementally for Saturday, with 700mb temperatures
up to 20C. Then Sunday, a frontal feature brings relief to parts of
the state (western), with uncertainty how far east the feature will
migrate before the day closes. 700mb temperatures ahead of this
feature remain 2-3 standard deviations above climo. How to best put
the extremes of the uncertainty in temperatures into perspective,
the 10th and 90th percentiles range for Aberdeen is 100 and 76
degrees - a range of nearly 25F - albeit only 10 degrees range for
the 25th/75th percentiles.

Its also important to note NBM deterministic temperatures,
originally a little cool in comparison to the 50th percentiles, have
bumped up closer to the mean. Thus, the forecast is in better
alignment with expectations with regard to the heat wave. Still some
wiggle room when it comes to how hot and humid each community gets
during this period of heat however, with a lee low forming over
central South Dakota, presenting us with less favorable mixing
conditions under the CAP on its northeast side with easterly low
level flow. On its backside a trajectory less favorable for moisture
advection will constrain the dewpoints and thus limit the extremes
in heat index values... thus still more details to be worked out
when it comes time for any early headline issuances.

As for storm chances during all this, we will be effectively capped
during the Thursday-Sunday timeframe with regards to surface based
convection. Low level flow ahead of the core of warmest air
increases with decoupling both Thursday night and Friday night, and
there is evidence in deterministic models for ridge riding waves for
both nights. Thus, could be a few rounds of elevated storm activity
during mainly the overnight/early morning hours.

As for the frontal passage, southwest flow aloft persists into next
work week, though with cooling temperatures aloft late Sunday into
Monday. Deterministic guidance moves this front ahead of the cooling
aloft, meaning profiles will not destabilize quickly enough for
surface based convection, though elevated convection late on into
Monday morning is a possibility as the front moves south and
southwest flow aloft pushes convection northwards off the front.
Still quite a bit of time between now and then however to iron out
details.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1224 PM CDT Tue Jun 17 2025

Terminals KABR,KATY,KPIR,KMBG

VFR conditions for all terminals. Cant rule out a weak storm at
any of the TAF sites, however probabilites are too low to include
in the near term of the TAFS. Winds are generally northerly,
though with quite a bit of variability under this weak pressure
pattern.


&&

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

$$

DISCUSSION...07
AVIATION...07