960
FXUS63 KABR 211844
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
144 PM CDT Tue May 21 2024

.KEY MESSAGES...

- Strong north wind gusts of 45-55mph will persist late into this
  evening before diminishing overnight.

- An unsettled weather pattern continues with another shot of
  moisture possible Thursday into Friday and again Sunday into
  Monday.

- Except for a brief potential warm up on Thursday, temperature
  guidance remains near to below normal Friday through Monday.

- Chance of frost/freeze Friday and Saturday mornings with low temps
  near freezing.

&&

.SHORT TERM /THIS EVENING THROUGH WEDNESDAY NIGHT/...
Issued at 143 PM CDT Tue May 21 2024

At 1 PM CDT, a moderate to heavy rainfall event is ongoing across
far northeast South Dakota and west central Minnesota. Temperatures
under clouds and rain are holding in the 50s this afternoon. Further
west, where cloud cover is less/thinner and there is no rainfall
occurring, temperatures have been able to warm into the low to mid
60s. Across the wind advised region of the CWA, north winds have
increased, at times, into advisory criteria sustained winds (30mph)
and gusts (45mph or greater).

The current deformation-zone-forced precipitation occurring over
northeast South Dakota will shift off to the northeast, as the upper
circulation/lift support pulls away from the region. The ongoing
strong winds across the far eastern forecast zones will gradually
diminish late this evening into the overnight hours. So, for now,
will leave the expiration time at 11 PM CDT.

From late tonight through Wednesday night, the forecast goes dry, as
surface high pressure settle over the region. Wednesday night, the
surface high shifts away from the CWA, and return flow
southerly/southeasterly winds develop. There is a low level jet
progged to form over the CWA Wednesday night, but right now, it does
not appear that sufficient LLM recovers in time to support elevated,
nose-of-the-low level jet convection. Low temperatures tonight and
Wednesday night should be running close to, or perhaps a little bit
below, normal. If the HREF is correct, and there is more sun than
clouds on Wednesday, then high temperatures warming into the 60s and
70s seems achievable.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 143 PM CDT Tue May 21 2024

The long term period will have a couple chances for rain as some
lows roll through the region. The first will be Friday morning
through possibly Saturday morning. Deterministic models all have the
upper level low in approximately the same area of ND/SD. Since the
Canadian model has the low a little farther south, it stays in the
area a little longer (into early Saturday morning). In general, the
low moves northeast and out of the region by 7AM Saturday. The EC
and GFS have another low coming into the area late Sunday into
Monday. The upper level low passes over western and south central
SD. The end of the period shows a large ridge building to our west
and moving towards the region.

Thursday afternoon, ahead of the Friday system there is a chance (30-
80%) for rain and some storms. At the moment, SPC has the
southeastern portion of SD in a marginal (1 of 5) risk for severe
storms. While mid level lapse rates look pretty favorable across
deterministic models (between 6.8 and 8.4 C/km), CAPE is pretty
variable. The EC has anywhere from 100 J/kg of MLCAPE to 1000 J/kg.
The Canadian and GFS have the most MLCAPE in the risk area - between
1500 and 2000 J/kg. As for bulk shear, all deterministic models have
at least 35 kts, so fairly favorable for storm formation. Threats
are hard to nail down right now, but leaning towards hail. General
(non-severe) thunderstorms will be possible across the forecast
area. Rain chances (30-60%) continue into Friday morning. The next
chance of rain looks to be Sunday afternoon through the day Monday
(30-50%). It is possible that storms could form but being 5/6 days
out, severe potential is hard to determine.

Temperatures will be up and down during the period with the lows
bringing clouds and rain. The first day of the long term looks to be
around average with highs in the mid 70s. Then, for the holiday
weekend, temperatures look to be in the 60s to low 70s with those
rain chances. For the end of the period, temperatures look to warm
back up into the mid to upper 70s. NBM is starting to show a chance
for some overnight temperatures close to the freezing mark for
Friday morning and Saturday morning. We will be keeping an eye on
this, but Saturday morning looks a bit more likely for some frost or
a freeze, with around a 30% chance of temperatures at or below 32
degrees for areas of northern SD between Herried and Long Lake.
Winds could gust up to 35 mph in Corson and northern Dewey counties
Thursday afternoon, and then over the Coteau Friday afternoon.
Otherwise, winds stay around normal through the period.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1230 PM CDT Tue May 21 2024

Terminals KABR,KATY,KPIR,KMBG

KATY will be in and out of IFR conditions through late this
afternoon before conditions improve to prevailing VFR. But, VFR
conditions are forecast at KABR/KPIR and KMBG through the TAF
valid period. North winds for KATY have come up and will range
from 20 to 30 knots sustained, with gusts ranging from 35 to 45
knots through late this evening, before diminishing overnight.
Rain is expected to persist at KABR and KATY this afternoon. But,
after 00Z, TAFS for all four terminals should be dry.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Wind Advisory until 11 PM CDT this evening for SDZ007-008-011-
     019>023.

MN...Wind Advisory until 11 PM CDT this evening for MNZ039-046.

&&

$$

SHORT TERM...Dorn
LONG TERM...KK
AVIATION...Dorn