564
FXUS63 KABR 291117 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
617 AM CDT Wed May 29 2024

.KEY MESSAGES...

- Windy conditions will develop today across the forecast area.
  Southeast winds will increase by midday and this afternoon with
  gusts expected to range from 25-45 mph. The highest gusts will
  likely set up across the Missouri Valley and West River.

- A 30-60 percent chance for showers and thunderstorms across
  central South Dakota, mainly after sunset tonight. This activity
  will track eastward overnight and into northeast South Dakota and
  west central Minnesota on Thursday where a 40-80 percent chance for
  precip will be possible.

- Precipitation chances continue to litter the extended forecast period.
  But, right now Sunday evening holds the highest probability of
  seeing showers and thunderstorms (35-75%).

&&

.UPDATE...
Issued at 610 AM CDT Wed May 29 2024

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

&&

.SHORT TERM /TODAY THROUGH THURSDAY AFTERNOON/...
Issued at 415 AM CDT Wed May 29 2024

The main forecast challenge in this period will revolve around an
incoming storm system that is expected to deliver a round of showers
and thunderstorms to the forecast area late tonight through
Thursday. More to come on those details shortly. In the meantime,
sfc high pressure sits across the Dakotas/Minnesota border region
giving us clear skies and light winds early this morning.
Temperatures will likely start off on the cool side prior to
sunrise with readings around 40 degrees in spots. The sfc high
will begin drifting east and away from us today. Shortwave ridging
aloft building across the Dakotas will give us a mostly sunny to
partly cloudy day with warming temperatures. The warm advection
process will boost 850mb temps to +10C to +15C across our eastern
zones to about +15C to near +20C across the Missouri Valley this
afternoon. We should have no issues reaching daytime readings into
the 70s to around 80 degrees.

The one caveat to today`s nice weather will be the strong winds. A
tightening pressure gradient between the sfc high to the east and a
developing lee side trough west of the region will lead to strong
southeast winds by midday and afternoon. The general feeling is that
our eastern zones(James Valley and points east) will see afternoon
gusts between 25-35mph. Locales farther west stand a better shot at
realizing stronger wind speeds. The latest suite of ensemble
guidance progs indicate highest probabilities of the highest
gusts(40+mph) across north central SD, in particular Corson and
Dewey Counties. BUFKIT profiles show the highest mixed-layer winds
across locales along and west of the Missouri. Forecaster confidence
not the highest in speeds reaching advisory crit; it could be a
borderline marginal event in those far northwest zones of ours. Our
dayshift will have to see how conditions trend as the day wears on.

Focus will turn to increasing chances for convection late tonight in
our west as a s/w trough crosses the Northern Rockies into the
Northern High Plains. As this disturbance shifts east, lee side
troughing deepens with sfc cyclogenesis expected. The sfc low is
progged to track eastward out of MT into ND late tonight and
Thursday morning. An associated warm front shift eastward from
western into central SD will help to generate showers and
thunderstorms by this evening west of our CWA. These are expected to
track eastward into our western zones after sunset tonight, perhaps
late tonight or closer to midnight. Some storms could be strong to
severe across our western zones late tonight, but the ingredients
aren`t the most favorable. There will be a narrow ribbon of
instability developing across western SD into our far western zones
with MUCAPE values around 1500 J/kg. Deep layer shear remains
lacking in conjunction with this however. The best shear doesn`t set
up until post fropa, after the quickly trailing cold front passes
through closer to sunrise Thursday morning. SPC has highlighted
western SD with a Slight Risk for severe weather where the best
parameters for severe storms exist. With the loss of daytime heating
and increasing stability, storms should loose their punch as they
attempt to track any farther east of the Missouri River. The main
threats with any of the strongest storms that get going will be
large hail and damaging winds.

Whatever may come of the initial convection late tonight is progged
to track east across the forecast area through the early morning
hours Thursday. Again, not anticipating any severe weather across
our central and eastern zones during this point in time. The sfc
cold front will sweep east during the day and generate more
convection by midday and afternoon across our eastern zones.
However, best instability looks to set up across our far southern
zones into southeast SD. There may be a couple of strong to severe
storms Thursday afternoon along and south of U.S. Highway 14 where a
Marginal Risk for severe weather has been posted.

&&

.LONG TERM /THURSDAY EVENING THROUGH TUESDAY/...
Issued at 415 AM CDT Wed May 29 2024

At the start of the period, showers and thunderstorms are supposed
to be ongoing, working east out of this CWA into Minnesota. Surface
high pressure builds into the region for Friday, possibly into
Saturday, before return flow sets up out ahead of a frontal passage
progged for Sunday. More high pressure builds in behind that front,
making things mostly dry again until perhaps Tuesday when another
cold front (3rd cold front in the 7-day forecast?) may be working
through the region.

Aloft, clusters suggest there is general agreement in the various
camps of solutions that the pattern flattens out with an occasional
transient shortwave/fropa possible. It`s possible that one such
shortwave, a somewhat stronger upper wave, will work across the
northern plains/far southern Canada Tuesday and Tuesday night.

A warming trend is still noted in the ensembles data, as well as the
deterministic solutions, for the out periods and beyond. 850hpa
temperatures warming to up 1.0 to 1.5 standard deviations above
climo normal implies there is potential for temperatures to warm, at
least, into the 80s across much of the CWA beyond day 3 (Friday)

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 610 AM CDT Wed May 29 2024

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are expected to prevail at all terminals through
this TAF valid period. Guidance suggests some MVFR cigs could be
creeping into the KMBG terminal after 09Z tonight. Otherwise,
southeast winds settle in this morning across central and north
central South Dakota, increasing to 20 to 30 knots by late this
afternoon. Gusts of 35 to 40 knots will be possible as well. These
conditions will gradually spread over into northeast South Dakota
later on today, with breezy to windy southeasterly winds
persisting tonight. Chances for showers and thunderstorms begin to
increase late this evening into the overnight hours at KPIR and
KMBG.

&&

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

$$

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