772
FXUS63 KABR 270900
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
400 AM CDT Mon May 27 2024

.KEY MESSAGES...

- Continued unsettled conditions across northeast SD and west
  central MN today with a 30-60 percent chance for showers and
  thunderstorms. Storms will generally be weak with no severe
  weather expected.

- Windy conditions develop today with northwest winds between 15-
  30 mph.

- A 40-60% chance of precipitation exists Wednesday night, and a
  45-75% chance exists on Thursday. Beyond that, a general 20 to
  40% chance of rain remains in the forecast for Friday through
  Sunday.

&&

.SHORT TERM /TODAY THROUGH TUESDAY AFTERNOON/...
Issued at 357 AM CDT Mon May 27 2024

The weather pattern during most of this forecast period will
continue to reflect an unsettled theme as a couple of upper level
disturbances move across the region in a northwesterly upper flow
regime. The good news is it looks to finally dry out once the end of
the period arrives on Tuesday.

The first upper level low and it`s associated sfc reflection sit
across ND this morning. Models prog this system to track
southeastward across our CWA during the day today. There`s a few
leftover showers exiting our far eastern zones early this morning
from the sfc trough that pushed across central and northeast SD the
latter half of yesterday. More scattered showers persist underneath
the mid level low in ND this morning. That activity will shift east-
southeastward with time. Daytime heating and some modest instability
in combination with mid level energy and a back-door cold front in
our eastern zones will aid in the development of more showers and
weak thunderstorms during the day. Hi-res model guidance suggests
that most of this activity should be confined to areas east of the
Missouri Valley, mainly in the James Valley and east into west
central MN. So, we`ll continue to advertise a 30-60 percent chance
for showers and storms, mainly around the midday and afternoon
hours. The pressure gradient does tighten up with time through the
day, so expect increasing northwesterly winds that will gust
generally between 25-35 mph but parts of the Missouri Valley and
West River zones could see gusts between 35-40 mph. Guidance
indicates highest probabilities of winds gusting to 40mph will be
across our southwest zones(SW of Pierre) and those chances only
sit around 50%.

The second mid level disturbance is progged to work southward across
the region late tonight into early Tuesday morning. This will help
touch off another area of showers and a few thunderstorms. This mid
level trough axis will be mainly impacting our eastern CWA once
again with a low end 20-40 percent chance of precip. Sfc high
pressure will gradually build southward into the forecast area on
Tuesday which will help to return dry conditions to the area along
with more sunshine. Temperatures will continue to be near normal to
slightly below normal through this forecast term. This will largely
be driven by cloud cover and precip chances, especially today into
tonight.

&&

.LONG TERM /TUESDAY EVENING THROUGH SUNDAY/...
Issued at 357 AM CDT Mon May 27 2024

Ensemble clusters analysis seems to suggest that models have gotten
closer to yes, regarding how things shape up in the flow pattern
aloft from Friday through Sunday; leaning moreso toward a slightly
more progressive push east out of the region of a slightly less deep
upper level trough by the end of Saturday. The pattern appears to
flatten out some right at the end of the period.

Models are continuing to ratchet up the PoPs for Wednesday night (up
to 40-60% now) over the western/central tiers of counties in the
CWA. There is a model tendency to over-inflate precipitation
potential in these types of set-ups (upper level ridge overhead with
troffing to the west and a surface boundary to the west of the CWA
and a stout low level jet expected). All too often, models
(including multiple ensemble member solutions of multiple ensemble
systems?) bring precipitation too far east. They assign a push of
precipitation northward into NoDak, and rightly so, given the mean
storm motion in this environment. But, there is a tendency to over-
extend or smear qpf too far east. Not saying it won`t rain somewhere
in the CWA Wednesday night. And, not carving up the PoPs grids
either. Perhaps the greatest (subjective convective conceptual
model) probability of measurable precipitation is Wednesday evening
(between 00Z and 06Z Thursday), and not all the way to the
Interstate 29 corridor. Perhaps it is relegated to just the far
(west river) west counties in the CWA. If outflow boundary/cold pool
consolidation from convection in the neighboring CWA to the west
happens and a decent gust front is pushed east into the Missouri
River valley, perhaps convective potential lives to reach U.S.
Highway 83 in the CWA.

Models are also ratcheting up PoPs on Thursday (up to a 75% chance
now) and Thursday night (up to a 65% chance over and east of the
Prairie Coteau), which checks all the boxes for convection. Return
flow heading into Thursday should be plenty of time to draw a better
low level moisture feed up into the region (low level
instability/CAPE). There should be some sort of mid/upper level
lifting mechanism in the region, along with a surface boundary for
forcing. And deep layer shear is currently progged at ~25 to
30knots.

Despite the presence of surface high pressure over the region
heading into the weekend, the remaining mid-level baroclinic zone
over the region could become active at times if any additional
transient pieces of shortwave energy pass overhead in developing
zonal flow Saturday/Sunday.

Still eye-ing up the strong mixed layer winds out over Corson/Dewey
counties by the end of peak heating/mixing on Wednesday as a
possible candidate for a wind advisory. The strong low level jet
that establishes across the whole CWA Wednesday night is expected to
re-connect with the boundary layer on Thursday across the James and
Big Sioux River valleys over into west central Minnesota,
potentially re-centering advisory criteria southerly winds on
Thursday to those areas of the CWA.

Temperatures in the models and ensemble S.A. tables (for 850hpa
thermal anomalies) are beginning to highlight the potential for some
warmer (perhaps much above normal warmer) weather during the first
full week of June. For the purposes of this 7-day forecast, there is
a warming trend noted Saturday and Sunday, with some locations over
and west of the Missouri River valley expected to warm into the 80s
on Sunday (June 2nd).

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1241 AM CDT Mon May 27 2024

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are expected through Monday evening except in
heavier showers or thunderstorms tonight or Monday
afternoon/evening.

&&

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

$$

SHORT TERM...Vipond
LONG TERM...Dorn
AVIATION...Vipond