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769
FXUS63 KABR 141155 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
655 AM CDT Fri Jun 14 2024

.KEY MESSAGES...

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- 20-40% chance of showers and thunderstorms from north central
  to south central SD today through this evening. There is a
  marginal risk (1/5) for strong to severe storms, mainly over
  south central SD, this afternoon and evening. Main threats are
  hail, up to the size of quarters, and 60 mph wind gusts.

- Shower and thunderstorm chances will spread eastward tonight (30-
  75%) through Saturday with chances diminishing west to east.

- Multiple chances for precipitation in the extended period in
  what appears to be an active pattern setting up. As of now,
  best chances for severe storms look to be Sunday night and
  Monday afternoon.
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&&

.UPDATE...
-- Changed Discussion --
Issued at 646 AM CDT Fri Jun 14 2024

Aviation discussion updated below for the 12Z TAFs.
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&&

.SHORT TERM /TODAY THROUGH SATURDAY AFTERNOON/...
Issued at 342 AM CDT Fri Jun 14 2024

HREF indicates split flow with the northern pattern consisting of a
ridge moving in overhead today, which will turn the 500mb winds more
zonal this afternoon. A shortwave will be moving in over the
Northern Rockies into western SD through the day into this evening.
At the surface, a high pressure system will be dominant over much of
the CWA early then shifting eastward as the wave`s surface low is
forecasted to be centered over MT/WY at 12Z, with the warm front
extending southeastward through WY into CO. HREF and most of the
CAMs indicate scattered moisture moving in over our southwestern CWA
today and spreading north/northeastward through the
afternoon/evening (ahead of the warm front). They do differ a bit on
timing and location as this moisture will be more
scattered/clustered. NBM does well with combing all the solutions
with pops ranging from 20-40% from north central to south central SD
through 00Z Saturday. Highest pops lie over the southwestern CWA.
Between 00-12Z Saturday as the low/front shifts east to northeast,
so do the pops, ranging from 30-75%, over south central SD where the
better moisture and instability lies

HREF`s MUCAPE increases to 1000-1500 J/KG, mainly west/southwest of
our CWA, but does clip parts of our southwestern counties late this
afternoon and evening, creating "better" instability. Wind shear is
forecasted to be between 30-40kts along with mid level lapse rates
around 7C in this area. WAA/afternoon heating will allow dew points
to rise into the mid to upper 50s by the afternoon along with highs
in the 80s. With this marginal instability, thunderstorms are
possible. However, HREF 2-5km UH>75m2s keeps any "organized
convection" mainly to our west and southwest of the CWA. A marginal
risk (1/5) is in place from SPC from western SD to south central SD,
clipping our extreme southwestern CWA (mainly Jones County) this
afternoon and evening. The main threat will be more elevated with
hail, up to the size of quarters, and 60mph wind gusts. General
thunderstorms are expected everywhere else over the CWA. CAPE values
decrease towards sunset, however, a LLJ strengthens (between 30-
40kts over central SD) out of the south/southwest overnight and
pushes eastward through morning (along with dew points still in the
mid/upper 50s). This will continue the threat for general
thunderstorms.

By 12Z Saturday, the low is forecasted to be over MT/ND border with
the warm front extending through central SD. Shower and thunderstorm
chances continue ahead of it with pops between 30-70%, highest along
and east of the James River. Behind the warm front, temps will rise
into the mid-upper 80s around and west of the Mo River. Highs in the
70s to lower 80s are forecasted east of here.

&&

.LONG TERM /SATURDAY EVENING THROUGH THURSDAY/...
Issued at 342 AM CDT Fri Jun 14 2024

Rather active pattern looks to be setting up across the
central/northern Plains during the extended period. Starting off the
period Saturday night, it appears we`ll be watching two areas. First
will be the mid-level shortwave moving eastward across southern
SD/NE into southern MN/IA, and the precipitation associated with
that. Next area is to the north, where an advancing cold front looks
to also be a focus for showers and thunderstorms mainly over ND into
northern SD. Given the tracks of these features, and model output of
precip, our CWA may in fact be missed by the most impactful weather
from these systems. In support of this thinking, NBM PoPs show
generally 30-40% chances along the eastern and northern fringes of
the CWA Saturday night, with much of the area with either small (20%
or less) or no chances for precipitation. Best severe parameters are
generally outside of the CWA as well for Saturday night, and SPC Day
2 outlook shows the CWA split between two threat areas.

Sunday looks to be mostly dry across the CWA, but will then be
watching a frontal boundary getting splayed out near/south of the
area Sunday night into Monday, providing our next opportunity for
rainfall. Models are indicating precip north of the front, with
convection also possible with sufficient elevated instability and
also a mid-level speed max parallel to the surface front. Hail-
producing convection seems possible, and Day 3 SPC outlook does have
the area included in a Marginal risk for severe.

The rest of the extended period looks to remain fairly active, with
PoPs littered throughout. Surface boundary may wobble north and
south through the period, with mid/upper level southwest flow over
the region with the likelihood of several shortwaves moving
northeast through the region. Taking a look at joint probability
(CAPE>500 J/KG, CIN>-25 J/KG, 0-500mb bulk shear>30 kts) to find any
time ranges for greatest severe storm threats, and Monday shows up
as potential, with unstable air looking to organize over the eastern
CWA. With models showing a subtle weak shortwave moving through the
region, stage could be set for strong to severe storms over eastern
areas Monday afternoon.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
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Issued at 646 AM CDT Fri Jun 14 2024

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are forecast through the TAF period. The potential
for isolated/widely scattered -SHRA/-TSRA across the region this
afternoon and evening warrants a VC (vicinity) mention. LLWS
(low-level wind shear) looks to be an issue overnight and have
inserted mention of this when/where appropriate. There are some
indications of MVFR/IFR CIG potential across KPIR/KMBG by around
12Z Saturday, but will await higher confidence before inserting
this into the TAFs.
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&&

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

$$

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