833
FXUS63 KABR 142321
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
621 PM CDT Fri Jun 14 2024

.KEY MESSAGES...

- 30-50% chance of showers and thunderstorms across central South
  Dakota this evening. There is a Marginal Risk for severe storms,
  mainly over south central South Dakota. The main threats are
  large hail and strong wind gusts.

- Shower and thunderstorm chances will spread eastward tonight
  (30-70%) through Saturday. Additional thunderstorm development
  is expected across north central South Dakota Saturday evening,
  where there is a Marginal Risk for severe storms. Large hail
  and strong wind gusts will be the main threats.

- Additional chances for moisture exist through next week thanks
  to an active pattern. The two systems at the start of the work
  week come with a 70-80% chance of measuring Monday morning, and
  a 50-70% chance of measuring Monday night/Tuesday morning.

&&

.UPDATE...
Issued at 621 PM CDT Fri Jun 14 2024

Thunderstorm activity has diminished over the past couple of
hours, with much of the significant activity remaining across
Nebraska. We will continue to monitor the trends with showers and
a few thunderstorms, and update the forecast as needed this
evening.

&&

.SHORT TERM /THIS EVENING THROUGH SATURDAY NIGHT/...
Issued at 305 PM CDT Fri Jun 14 2024

Upper level ridging currently over the area will get pushed east
this evening as a shortwave trough tracks across the Rockies and
over the central part of the country. Will see some decent energy
affect the southern part of the state this evening. The main trough
will track across the CWA on Saturday, with a more zonal flow
pattern setting up Saturday night.

At the surface, the evening period will start off with high pressure
to the east and low pressure to the west. Currently seeing some
shower and thunderstorm development along and west of the Missouri
River ahead of the approaching low, and will see this spread
eastward tonight into the day Saturday. May see some stronger storms
develop across south central South Dakota this evening in the
vicinity of the aforementioned shortwave energy, but do not expect
any strong to severe storms elsewhere. The eastern part of the area
will see the best chance for some lingering rain through the day
Saturday, so will see quite a bit of cloud cover, thereby resulting
in cooler temperatures there vs the rest of the CWA. The main low
center will stall out west of the region on Saturday, then looks to
be the focus for additional thunderstorm development Saturday
evening, mainly across portions of north central South Dakota. This
will be in an area where 1500-2500 J/kg of MUCAPE and 40-50 knots of
bulk shear will develop. This area is currently highlighted with a
Marginal Risk of severe weather by the Storm Prediction Center, with
large hail and gusty winds being the main threats. The chance for
storms looks to diminish by midnight.

Low temperatures tonight will be in the lower to mid 60s. High
temperatures on Saturday will range from the lower 70s across west
central Minnesota and far northeastern South Dakota, to the upper
80s along and west of the Missouri River. Lows Saturday night will
be in the upper 50s to mid 60s.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 305 PM CDT Fri Jun 14 2024

The upper level pattern will see only a slight transition during the
extended, with more or less a southwest flow regime as an upstream
longwave trough varies in intensity.  One shortwave is already on
the way out at the start of the period. The next subtle wave moves
through early Monday, followed by another weak wave late
Monday/early Tuesday. A third system crosses Montana/North Dakota
late Tuesday. Thereafter there are more subtle upper level features,
though models diverge on timing with overall poor consistency
between deterministic guidance and associated ensembles (with the
GEFS showing quite a bit of spread in 850mb temperatures and rather
random blips of QPF after the 18th)...so will really focus on the
Sunday-Tuesday timeframes` convective potential. Sunday should be
mostly dry as weak high pressure ridge extends out of the northern
Rockies into the Dakotas. The frontal boundary, shunted into
Nebraska/southern South Dakota transitions to a warm front as mid
level warm air ascent supports morning storms mainly across the
southern tier of the CWA. Convection during the day then re-focuses
across the eastern CWA (where CWASP ends up being the highest) in
the vicinity of an inverted trough. All that is followed by a
surface low early Tuesday lifting across the area into eastern North
Dakota.

There is some uncertainty as the placement of high pressure that
follows thereafter, but for the most part deterministic
GFS/Canadian/EC guidance placement should be in a portion for a
period of mostly dry conditions across northern and central South
Dakota, though the slightly farther north placement of the high in
the ECMWF means some NBM POPs are inevitable during mid-week (mainly
in the form of elevated convection on the warm advection regime
around this high).

So as for temperatures, initially Sunday will be mild with a surface
front across the area, with cooler/drier air by the afternoon across
the CWA. Northeast low level flow and convective cloud cover into
Monday will limit mixing/heating. Really, the greatest uncertainty
in temperatures is related to Tuesday`s system, and the track will
determine how far west the mid/humid air migrates, with a 12-14F
range between the 25th/75th percentiles for highs at
Mobridge/Pierre, and a 21-23F (between upper 60s to low 90s) range
for KABR/KATY!

Generally modest humidity for this time of year as well. NBM
dewpoints, while initially in the mid/high 60s Sunday from the James
valley and points east Sunday, are lower for the rest of the
forecast period. The probability of exceeding a 65F degree dewpoint
is limited to mainly across the southeast CWA with around a 40-80
percent probability from the James valley east on Tuesday. It then
remains nearly negligible until the end of the forecast period
Friday.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 621 PM CDT Fri Jun 14 2024

Terminals KABR,KATY,KPIR,KMBG

VFR conditions will start the period, with PIR/MBG falling into
the MVFR range around 12Z, and the ABR/ATY around 14Z. Expect
improving conditions back to VFR by around 18Z across central SD
(PIR/MBG), and ABR shortly before 23Z.

&&

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

$$

UPDATE...KF
SHORT TERM...Parkin
LONG TERM...Connelly
AVIATION...KF