085
FXUS63 KFSD 280808
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
308 AM CDT Tue May 28 2024

.KEY MESSAGES...

- Scattered showers with isolated thunder through late morning
  east of the James River. Seasonal temps and slightly breezy
  east of I-29, with dry conditions this afternoon.

- Dry on Wednesday. Multiple chances for showers and
  thunderstorms starting late Wednesday night and continuing
  through the weekend.

- Near normal temperatures prevail with periodic breezy
  conditions into early next week.

&&

.DISCUSSION...
Issued at 304 AM CDT Tue May 28 2024

TODAY/TONIGHT: Watching the next wave dive southeast this morning
from ND, bringing some light showers to the area through the
overnight hours through mid morning. Can`t rule out a few rumbles of
thunder with a couple hundred Joules of CAPE. Severe weather is not
expected, and should see rainfall amounts of a tenth of an inch or
less. Lows tonight will be in the 40s to near 50, with increasing
clouds as the wave moves through.

Isolated sprinkles are possible in the afternoon hours across
southwestern MN and northwestern IA as the wave swings through the
eastern portion of the forecast area. However, with so little low
level moisture to work with, will keep the forecast dry for
now. Highs in the mid 60s to mid 70s, coolest across southwestern
MN where cloud cover and stronger northwesterly flow/CAA prevail.
Winds today will be breezy as we mix into the stronger winds
and cooler air aloft. Northwesterly winds will be sustained
around 10-20 mph (strongest in southwestern MN) with gusts near
30 mph.

Weak and quick moving ridge begins to slide into the western portion
of the forecast area by late tonight, bringing clearing skies and
winds shifting to the south. Lows tonight fall into the mid 40s.

WEDNESDAY: Aforementioned ridge and surface high slide across the
area tomorrow, ahead of the next system developing over the Rockies.
Winds increase through the day west of the James River, where
this surface pressure gradient begins to compress between the
surface high and developing low to the west. South to southeasterly
flow brings in relatively warmer air, although highs remain near
average for this time of year (in the 70s). West of the James,
winds of 15 to 20 mph will gust around 30 mph. Lighter winds
with gusts 15-20 mph expected elsewhere.

WEDNESDAY NIGHT ONWARD: Trough deepens and slides through the
Rockies Wednesday night into Thursday, with a leading short wave and
weak surface low ejecting into the western Dakotas and NE Panhandle
overnight. This begins the increase of shower and storm chances from
west to east overnight Wednesday into Thursday, with showers/storms
continuing through the day Thursday. Models are varying in how much
and at what level the greatest instability will be at, and during
what time. There looks to be enough for at least some rumbles of
thunder, although severe weather is currently not expected with the
greatest instability off to the west (Thursday) and south (Friday).
Trough axis swings north of the area on Friday, with another weak
short wave ahead of it, although this wave may stay largely to our
south. This keeps at least scattered activity around through the end
of the week. Areas across south central SD through Friday have high
probabilities (> 60%) of over 0.25" of rain, with moderate to high
(> 40%) chances of over 0.50" of rain in a 24 hour period. Ensembles
also show a low (< 20%) chance of over an inch of rain. Will have to
keep an eye on trends, but generally think flash flooding risk is
low given 1 hour flash flood guidance near/above 2 inches in most of
this area.

Next and possibly stronger short wave/trough axis swings across the
northern and central Plains Saturday into Sunday, although models
vary on details of this feature as well as trailing wave through
the weekend. Ensemble guidance this morning shows low to moderate
(< 40%) chances of exceeding 1500 J/kg of CAPE, with moderate to
high chances (40%+) of this occurring Sunday. Locally heavy rainfall
is possible with PWAT values likely (> 60%) over 1". Again, with
models varying in the details, there remains quite a lot of
uncertainty, but folks without outdoor and/or travel plans should
keep an eye on the forecast for the weekend.

Periodically breezy with near normal temperatures late this week
into early next week. More chances for rain possible to start
next work week.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1026 PM CDT Mon May 27 2024

VFR throughout the period. A 30% chance for scattered showers and
thunderstorms exists overnight into Tuesday morning for areas along
and east of a line from Huron, SD to Sioux Falls, SD to Storm Lake,
IA. Have included tempo groups for both KHON and KFSD, though
impacts should remain minimal. Otherwise, expect light and variable
winds between westerly and northerly overnight, with semi-
breezy N/NW winds developing throughout the morning hours on
Tuesday.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.

&&

$$

DISCUSSION...SG
AVIATION...APT