471
FXUS63 KABR 151707
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
1207 PM CDT Sat Jun 15 2024

.KEY MESSAGES...

- Shower and thunderstorms (40-90%) will affect parts of eastern
  and northeastern SD into west central MN through the afternoon.

- Additional thunderstorm development is possible across north
  central South Dakota this evening. There is a Slight Risk (2/5)
  that a few storms could become severe in this area. Main threats
  include large hail, ranging from quarter to golfball size, and
  wind gusts of 60-70 mph.

- Sunday night and Monday will bring severe storm potential to the
  region as the weather pattern stays active. Large hail will be
  the main threat Sunday night (southern portions of the region)
  with hail, strong winds, and heavy rain all being possible over
  a larger portion of the area on Monday.

&&

.UPDATE...
Issued at 1207 PM CDT Sat Jun 15 2024

Subtle adjustments to the forecast but overall the trends remain
the same with these 30 to 40`ish mph winds across the eastern half
of the CWA lingering into the early afternoon. Light showers also
persist across southeast counties, and continue to weaken as they
drift east-northeast. Main focus remains on severe potential for
later this afternoon. CAMS continue to generate convection between
20-22Z in far western South Dakota, moving into the far western
CWA around 23-00Z, with a noted weakening/diminishment in coverage
between 00-03Z (HREF 2-5km max updraft helicity also falls off
along the western border during that timeframe). NAM MLCAPE
continues to run around 2500j/kg with ~35kts 0-6km shear. DCAPE
runs around 1000j/kg with a noted dry layer around 700mb (16-20C
dewpoint depression at KMBG at 00Z) and strong mid level west-
southwesterlies supporting the SPC highlighted wind/hail threat
so long as storms can persist.


See below for update to the aviation discussion.

&&

.SHORT TERM /TODAY THROUGH SUNDAY AFTERNOON/...
Issued at 335 AM CDT Sat Jun 15 2024

HREF indicates the ridge continuing to push east today as a mid
low/shortwave moves in off the Pacific and over the Pacific
Northwest today and into the Northern Plains/central Canada this
evening into tonight as mid level flow increases. This puts the CWA
on the PVA side of the trough. This will also turn 500mb winds more
zonal this afternoon and evening. Down at the surface, a broad low
is forecasted to be over MT/WY/ND border with a warm front extending
over central SD around 12Z today. This low deepens and pushes
northeast this afternoon through the evening as a dryline sets up
over the western Dakotas, with southerly flow over the Dakotas on
the warm side of the low/trough and dew points in the 60s. The low
and cold front will track east/southeast this evening through the
overnight with the center of the low forecasted to be over
northeastern SD at 12Z Sunday with the cold front draped
south/southwestward.

Ahead of the warm front and area of ascent of current shortwave,
HREF/CAMs indicates rain and thunderstorms continuing to move in
from the southwest, per radar imagery. This will mainly skirt our
eastern/southeastern CWA (some CAMs keep it further southeast) as it
continues northeast through the afternoon. Pops in this area range
from 30-80%, highest over our extreme southeastern CWA. Depending
how fast it exists, lingering pops of 15-20% are in place this
evening but may need to be adjusted.

With the synoptic pattern mentioned above, MU/ML Cape across central
SD increases to 1500-2500 J/kg this afternoon and evening with bulk
shear 30-40kts, increasing to 50kts over parts of this area, out of
the west. HREF 2-5 UH>72ms2 paintballs hint at the possibility of
organized convection in this area with a probability of 10-30%,
highest over north central SD. UH>150 stays more in ND (however a
couple paintballs are over Corson/Dewey) with most of the action
staying in ND/MT. Looking at a few soundings across north central
SD, this looks to be mostly elevated convection (as a cap will in
place at lower levels). This indicates hail would be the main threat
as mid level lapse rates are between 7-8C, at 00Z Sat, with SHIP
around 1.3. Latest Cams indicate a north to south broken
line/cluster type convection hitting our western CWA this evening. It
loses juice once it passes east of the Mo River and begins to
dissipate. With this setup, the SPC has upgraded to a slight risk
(2/5) from north central to central SD for this evening with main
threat of hail, ranging from quarter to golfball size, along with 60-
70mph wind gusts.

With cloud cover over the eastern CWA, highs will be cooler ranging
in the 70s east of the James River. East of the Mo river highs will
range in the lower 80-mid 80s. Much warmer around and west of the Mo
River with highs in the upper 80s to possibly hitting 90 in some
areas.

&&

.LONG TERM /SUNDAY EVENING THROUGH FRIDAY/...
Issued at 335 AM CDT Sat Jun 15 2024

Things appear to stay rather active to start of the extended period.
Sunday night will be the first time frame of interest. Stationary
surface front looks to set up south of the CWA, stretching from
northeastern CO into southern MN. Weak mid-level impulse embedded
within the southwest flow aloft moves across the region and
interacts with plenty of elevated instability across southern SD
into portions of the southern CWA. Although, exact placement of the
stationary front will be key in determining how far north the most
unstable air makes it. It appears severe storms are certainly
possible over southern SD into southern portions of the CWA Sunday
night, with large hail being the main threat.

Will then shift focus to Monday as the frontal boundary shifts
northward into the CWA and a wave of low pressure rides along the
front. Moisture surges northward with 60 dewpoints perhaps reaching
the eastern CWA by late afternoon/early evening. PWAT values (25th-
75th percentiles) generally show 1.40-1.75in on GEFS/GEPS/ENS.
Instability and shear will increase across the region, setting the
stage for severe storm and heavy rain potential.

Things look to quiet down at least somewhat mid-week with surface
high pressure trying to build in. But, flow aloft stays
southwesterly and models indicate potential for more waves moving
northeast across the region towards the end of the week, with
increasing precip chances once again.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1207 PM CDT Sat Jun 15 2024

Terminals KABR,KATY,KPIR,KMBG

We have some intermittent MVFR CIGS for KATY, otherwise VFR
conditions. There is just a low probability for convection near
the KMBG/KPIR terminals around 00Z.

&&

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

$$

UPDATE...Connelly
SHORT TERM...MMM
LONG TERM...TMT
AVIATION...Connelly