917
FXUS63 KABR 261728 AAC
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1228 PM CDT Sun May 26 2024

.KEY MESSAGES...

- A couple more shots at precipitation will be possible the
  remainder of the Memorial Day holiday weekend. There`s a 30-60
  percent chance for showers and thunderstorms today into
  tonight. A 20-50 percent chance is possible Monday and Monday
  night, mainly east of the Missouri Valley.

- Temperatures will remain around seasonal normals for the rest of
  the holiday weekend and on through the end of May. Stronger
  northwest breezes will kick in on Monday with gusts peaking
  between 25-35 mph.

- At this point, later this week, thunderstorm chances (30-60%)
  look the best on Thursday afternoon through Thursday night.

&&

.UPDATE...
Issued at 1225 PM CDT Sun May 26 2024

See updated aviation discussion below.

UPDATE Issued at 1008 AM CDT Sun May 26 2024

Just a few light returns showing up on radar this morning across
parts of north central South Dakota. Timing for additional shower
and thunderstorm activity still looks to begin across central
South Dakota during the mid afternoon hours before spreading
eastward late this afternoon into tonight. No changes made to
winds or temperatures at this time.

&&

.SHORT TERM /TODAY THROUGH MONDAY AFTERNOON/...
Issued at 411 AM CDT Sun May 26 2024

A couple more rounds of precipitation chances will remain possible
across this forecast area through the remainder of the holiday
weekend. The first round is anticipated to arrive later today and
persist into tonight and the second round will be during the daytime
on Monday.

Weak sfc high pressure remains in the vicinity of the forecast area
early this morning leading to relatively quiet conditions. The last
of Saturday`s rainfall has exited east into MN and now we`re just
seeing a partly to mostly cloudy sky. Fog is beginning to develop
across parts of our southwest zones. This is evident on satellite
and from webcams positioned across parts of Jones, Lyman, Hughes,
Hyde and Hand Counties. Expecting this fog and low stratus will
continue to expand through the remainder of the pre-dawn hours in
our southern zones as well as parts of the James Valley. Hi-res
guidance shows it will fade away by mid-morning. The next system
will be poised to our west by then. Mid-lvl s/w trough energy
working around the base of the main mid-lvl low positioned over
central Manitoba will track across the Dakotas later today into
tonight. Sfc low pressure and an associated trough is progged to
track across the region kicking off showers and elevated
thunderstorms by late this morning into the mid afternoon hours
across the Missouri Valley. This activity will shift east into the
James Valley by late this afternoon and early evening before moving
into west central Minnesota tonight.

We aren`t expecting much in the way of organized severe weather with
this system. There will be some modest instability for storms to
feed off of as some models do prog MUCAPE values to reach upwards of
around 1000-1500 J/kg. Bufkit forecast soundings show skinny CAPE
soundings during the afternoon. Steep low level lapse rates look
favorable and to a certain extent mid level lapse rates are
respectable. However, deep layer shear is lacking however during the
afternoon into the evening when CAM solutions depict a scattered
line of convection crossing west to east across the CWA. Still,
can`t rule out a strong storm or two, but again our forecast area is
not outlooked for organized severe storms. This activity should be
waning once it arrives in our eastern zones by late evening and
early overnight. There should be somewhat a lull in the precip
through the early to mid morning hours on Monday, but we reset
things as we get into the daytime heating hours. The aforementioned
sfc low will be positioned northeast of our area by then with the
that mid-lvl trough axis working southward across the region helping
to push a sfc cold front through. Stronger northwesterly flow at the
sfc and aloft along with some cold air advection will help kick off
more scattered showers and storms by midday Monday and Monday
afternoon. This activity should remain mainly east of the Missouri
Valley. A tightening gradient during the day will lead to increasing
northwest winds that could gust between 25-35 mph.

&&

.LONG TERM /MONDAY EVENING THROUGH SATURDAY/...
Issued at 411 AM CDT Sun May 26 2024

When the period opens Monday night, models prog the upper low now
straddling the Manitoba/Ontario border to warble around and swing
southward across the region, bringing PVA-influenced showers south-
southeastward across the CWA. Loss of daytime heating may weed out
the weaker bits of convection, but there could be showers ongoing
for several hours into the overnight Monday night.

With the push of that upper circulation south and east away from the
area on Tuesday, enter the upper level ridge that`s been forecast
for several days now to push east across the CONUS`s mid-section
Tuesday through Thursday.

Overall, the steering flow pattern in the out periods has not
changed all that much in 24 hours. The upper ridge axis continues to
be forecast to be east of the CWA heading into Thursday morning.
Models depict a "warm tongue" (700hpa temps ~+7C to +9C) aloft to
march across the region with this upper level ridge. This may be
enough of a cap to keep convection off to the west and north
Wednesday afternoon and night. There is a low level jet that
develops/spreads across the CWA Wednesday night. But, the nose of
this LLJ is well off to the north/west of the CWA, and without
something on which to focus (a low level forcing mechanism)
convective potential, seems the LLJ and steepening mid-level lapse
rates will be mostly academic. By Thursday afternoon, however, a
surface frontal boundary is forecast to be working into central
South Dakota, while mid-level temperatures begin a subtle cooling
trend. Thursday afternoon through Thursday night appear to hold a
decent chance for thunderstorms (30-60% chance of precipitation).

Models continue to work toward a final solution (Ensemble Clusters)
for Friday and Saturday steering flow winds and how to bring the
next longwave trof through the central CONUS (progressive or not-so-
progressive). For now, 20-30% chances for precipitation are
smattered over Friday and Saturday while the uncertainty remains.

Ensemble S.A table 850hpa temperature anomalies continue to support
generally "near normal" temperatures throughout the period after
Tuesday. While in northwest flow on Tuesday in the wake of that
upper low, cooler air over west central Minnesota into far northeast
South Dakota may make it feel a bit chilly over that area, with
daytime highs Tuesday only topping out in the low to mid 60s. Expect
temperatures to be a little bit warmer Wednesday through Saturday
with highs generally warming into the 70s for much of the time
throughout the CWA.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1225 PM CDT Sun May 26 2024

Terminals KABR,KATY,KPIR,KMBG

Scattered showers and thunderstorms will develop across central
South Dakota late this afternoon, then will gradually track
eastward through the evening hours. Due to the scattered nature,
will just mention VCTS in the TAFS for now. Other than the
potential for some MVFR vsbys with any thunderstorms, VFR
conditions will prevail across the area through the TAF period.
Look for northwest winds to increase into the 15 to 30 knot range
Monday morning.

&&

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

$$

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