284
FXUS63 KABR 150513
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
1213 AM CDT Thu Aug 15 2024

.KEY MESSAGES...

- Showers and weak thunderstorms will wrap back into northeast
  South Dakota and western Minnesota Thursday afternoon
  (30 to 50 percent chance).

- 10 to 25 percent chance for afternoon and evening thunderstorms
  this weekend into next week. Timing and location are uncertain
  at this time.

&&

.SHORT TERM /THIS EVENING THROUGH THURSDAY NIGHT/...
Issued at 311 PM CDT Wed Aug 14 2024

An upper level trough will track across the area tonight and
Thursday, keeping some decent shortwave energy over the area. The
trough will exit to the east Thursday night as ridging begins to
build in from the west.

At the surface, a frontal boundary currently over western South
Dakota will become the focus for thunderstorms this evening. Central
South Dakota has seen a little bit of clearing this afternoon, which
has aided in some higher instability (1500-2000 J/kg of MUCAPE).
Already seeing the beginnings of some convective development across
north central South Dakota, and per many of the CAMS, this will
become a line of storms that will intensify and track eastward
across the CWA. Timing is one of the big questions with the line of
storms, along with where the strongest part of the line will go.
Latest model runs have shown decreasing amounts of shear available
this evening across the northern part of the CWA, but still
generally in the 25 to 35 knot range. Some of the CAMs are hinting
that the line of storms may drift a bit more to the south this
evening, while others track the line straight east across the entire
CWA. The better instability will definitely remain south, but the
shear may be enough to keep the line going across the north too. The
main threats with the line of storms will initially begin as large
hail and strong wind gusts, then will transition to more of a wind
threat vs hail. Heavy rain and lightning will also be threats
throughout its life span. The storms will exit the CWA to the east
during the early overnight hours, with the remainder of the night
being quiet. The low will wrap up over Minnesota on Thursday, and
may see some wrap around shower activity across the eastern CWA,
especially in the afternoon. High pressure will settle in Thursday
night, bringing a return to dry conditions.

Low temperatures tonight will be in the lower to mid 60s. High
temperatures on Thursday will range from the mid 70s east to the mid
80s along and west of the Missouri River. Lows Thursday night will
be in the upper 50s to lower 60s.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Issued at 311 PM CDT Wed Aug 14 2024

As the low pressure moves out of the area Friday evening into
Saturday, a ridge will start building in over the area and will stay
around till the end of the forecast period. Occasional development
(10-20% chance)of precipitation could occur along the edge of the
high pressure through SD. However, timing and location is difficult
to nail down with the difference in model guidance.

Model clusters all show ridge building and staying in area over the
forecast period, however there is some variance in strength and
amplitude. By day 5, one cluster with 25% of the Canadian members
and 50% of the GEFS members (24% of total members)show the ridge
being surpressed from a more northerly wave. The deterministic GFS
also shows a similar pattern which allows multiple shortwaves easier
travel along the ridge over the area. The deterministic models at
500mb show pockets of potential vorticity moving over the forecast
area once the ridge moves in. Those pockets of potential vorticity
as well as area of Warm and Cold air advection that move along the
edge of the high pressure shows where upper level forcings are
located to help with the development of precipitation. While drier
air moves in after the low at 700mb, there is some moisture in
the 700 and 850 mb levels that occasionally moves in to the area
over the forecast period. The locations and timing of this
moisture along with the timing and location of the other forcings
make it difficulty to nail down when and where precipitation will
develop.

Deterministic and ensemble models also show this variability with
very little consistency on when occasional pockets of precipitation
develops through SD along the top of the ridge. Some ensemble
clusters show occasional areas of higher CAPE and shear Friday
evening, Saturday afternoon and evening, and Sunday afternoon. This
shear and instability shows where development of storms could occur,
however the clusters also show a fair amount of CIN that could
inhibit development of severe weather making it harder to know if
it will happen.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1211 AM CDT Thu Aug 15 2024

Terminals KABR,KATY,KPIR,KMBG

MVFR/IFR CIGs still possible/likely across KABR/KATY during the TAF
period, with lesser chances of seeing this over KPIR/KMBG. By
Thursday afternoon, scattered -SHRA/SHRA expected across eastern SD,
possibly affecting KABR and KATY and will include a vicinity (VC)
mention at this time.

&&

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

$$

SHORT TERM...Parkin
LONG TERM...Vernon/SRF
AVIATION...Connelly