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934
FXUS63 KABR 251138 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
638 AM CDT Sat May 25 2024

.KEY MESSAGES...

- Seasonal temperatures return this weekend with daytime readings
  back into the upper 60s to mid 70s.

- Unsettled pattern continues with a 20-50% chance for showers and
  thunderstorms south and east this afternoon and evening. Some
  storms could be strong to severe late this afternoon, especially
  across south-central SD.

- 20-55% chance for rain Sunday night and Monday. 20-40% chance for
  rain Wednesday night through Friday.

&&

.UPDATE...
-- Changed Discussion --
Issued at 625 AM CDT Sat May 25 2024

See below for an aviation forecast discussion for the 12Z TAFs.
-- End Changed Discussion --

&&

.SHORT TERM /TODAY THROUGH SUNDAY AFTERNOON/...
Issued at 417 AM CDT Sat May 25 2024

The main concern in the short range is storm chances the next couple
of days and whether or not our forecast area will see any strong to
severe storms out of the deal. More to come on that in a moment.

For the time being, our weather across the forecast area remains
relatively quiet early this morning. Partly to mostly cloudy skies
are the prevailing sky condition with rather cool temperatures in
the upper 30 to low 40s north to upper 40s to low 50s south. A few
showers remain across our northeast zones thanks to a little subtle
vort energy working through a quasi-barotropic zone set up basically
in the vicinity of the ND/SD border. These will exit the CWA by
daybreak. Dry conditions will be the rule at least until around
midday or so before a frontal boundary or sfc trough nudges east and
north across the southern part of SD. This in combination of mid lvl
s/w energy working through the region will aid in shower and
thunderstorm development this afternoon. By late afternoon/early
evening across our far southern zones, increasing instability on the
order of 1000-1200 J/kg of MLCAPE, 40-50kts of 0-6km bulk shear and
steep low to mid level lapse rates will lead to the potential for
seeing strong to severe thunderstorms. Several CAM solutions depict
storms developing after about the 5-6 PM CDT hour across the I-90
corridor of Lyman County in our forecast area and moving east to
northeast into the evening hours. SPC`s Day 1 severe weather outlook
nudged the Marginal Risk(1 out of 5) northward to include the
southeastern tip of Lyman County This activity looks to persist in
our south and east until mid-late evening before shifting out of our
area.

We`ll see a break from the precip chances overnight into Sunday
morning before another disturbance shifts into the region by Sunday
night. Could see some patchy fog in parts of the Missouri Valley
including the Pierre area thanks to an increase in boundary layer
moisture and an easterly wind fetch just off the sfc and light sfc
winds. Another s/w trough will work east-southeastward from the
Northern High Plains by Sunday afternoon. A sfc trough or cold front
is progged to shift east across the Dakotas Sunday afternoon into
Sunday night. This will lead to another round of scattered
thunderstorms that look to impact the Missouri Valley as soon as
early-mid afternoon Sunday. At this point, instability and shear
aren`t quite as favorable as today`s set up, so we aren`t expected
any organized severe weather, but it will be something to keep an
eye on going forward. Temperatures will return closer to seasonal
normals for late May today and tomorrow with highs in the upper 60s
to mid 70s. Overnight lows tonight won`t be quite as cool with
readings in the mid 40s to around 50 degrees.

&&

.LONG TERM /SUNDAY EVENING THROUGH FRIDAY/...
Issued at 417 AM CDT Sat May 25 2024

Not a ton of change in the mass fields from 24 hours ago in the out
periods. Still dealing with the formation and translation eastward
over the region of an upper level ridge (ensemble clusters analysis)
mid-week. Until then, the pattern takes on a northwest flow look and
feel, scouring out any lingering shortwave energy Sunday night and
Monday (25-55% chances of rain), and quite possibly into Tuesday.

After a dry period as the ridge moves across the region, return flow
southerly low level winds and west-southwest winds aloft set up by
Wednesday evening, and usher a return to low PoPs in the forecast
from Wednesday night through the end of the period (a general 20-40%
chance which is almost climo for this time of year; ie...no strong
signal to hang a hat on right now).

Typically, the better set up for convection shows up after mid-upper
level heights have a chance to fall some and warm mid-level
temperatures cool a few degrees. Perhaps the best chance for rain
will come by the end of peak heating on Thursday, with the door
remaining open for additional WAA-forced rain chances within a mid-
level baroclinic zone that sets up across the region into Friday.

There are still some wrinkles that need ironed out in the models for
timing/strength/track of the main upper circulation within the
longwave trof out west that develops in the wake of the upper level
ridge working across the region mid-week. The faster, more
progressive envelope of solutions have the region going dry by
Saturday as a weaker, more transient upper circulation sweeps
eastward through the region. The slower, stronger camp of solutions
would have the upper circulation slowing down and undergoing
cyclogenesis over the central/northern plains on Saturday, turning
the aforementioned baroclinic zone into a deformation zone with
additional precipitation chances persisting beyond the range of the
7-day forecast.

It does appear as though Thursday could hold some rather strong (25
to 35+mph with higher gusts) southerly winds. It also still looks as
though temperatures throughout the extended will remain anchored
within ~5 to 10 degrees either side of climo normal (ie...no
extremes in temperature noted in the models in the out periods).

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
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Issued at 625 AM CDT Sat May 25 2024

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are forecast to prevail through the entire forecast
period. There could be some elevated rain shower activity at/near
the KPIR and KATY terminals this afternoon into this evening.
Between these two terminals, there could isolated to scattered
thunderstorms from late this afternoon through late this evening.
Whether or not any thunderstorms get within 5 miles of a terminal
remains unclear at this time. Toward the end of the TAF period,
the boundary layer set-up appears to promote some patchy fog or
low stratus potential, particularly along the upslope wind-
favored portions of the forecast area.
-- End Changed Discussion --

&&

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

$$

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