496
FXUS63 KFSD 110528
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1228 AM CDT Mon May 11 2026

.KEY MESSAGES...

- Frost is expected to develop tonight, mainly along and
  northeast of a Huron, South Dakota to Sioux Falls, South
  Dakota, to Storm Lake, Iowa line. A Frost Advisory has been
  issued for this area and is in effect from 3 am to 9 am
  Monday.

- Low humidity and breezy winds will persist through Tuesday,
  continuing elevated fire danger each day. Tuesday has the
  highest chances for fire danger.

- Temperatures begin to warm through the upcoming work week, and
  by the end of the work week and weekend may further warm to
  the 80s.

- The upper level pattern remains uncertain for the end of the
  week and weekend. Chances for rain will depend on how the
  pattern evolves.

&&

.UPDATE...
Issued at 858 PM CDT Sun May 10 2026

A quiet but chilly night is ahead for the area. Winds have come
down as the sun has set and skies are mostly clear with the
exception of some high clouds streaming into areas west of I-29.
For tonight, did blend in some of the NBM 10th percentile to
areas which will see the lightest winds through the night
(mainly east of I-29) because last night, under fairly similar
conditions, parts of the area dropped as low as the 10th
percentile with how dry the air has been. Winds should be
slightly higher than last night overall, so did not go full
NBM10th, but temperatures are trending cold enough to warrant
an expansion of the Frost Advisory to include Cherokee and Buena
Vista Counties in northwest Iowa. Otherwise it goes unchanged
and runs from 3 am to 9 am Monday.

Only other thing to note about tonight is that southeasterly
winds will begin to increase towards daybreak over south-
central South Dakota and that`s where we will generally see the
warmest lows tonight, in the lower 40s. The coldest air tonight
will reside over southwest Minnesota and adjacent areas of
northwest Iowa and eastern South Dakota where temperatures drop
to around 33-34 degrees. Could see a few spots briefly drop to
32, but the expected duration and patchy nature of this
precludes the need for freeze headlines at this time.

&&

.DISCUSSION...
Issued at 153 PM CDT Sun May 10 2026

Partly clear skies persist this afternoon, allowing high
temperatures to warm to the 60s and 70s. Low humidity and marginally
breezy winds will keep elevated fire danger conditions going through
the rest of the afternoon hours. Temperatures tonight remain on
track to be on the cold side once again, falling to the low to mid
30s to low 40s. Thus, have issued another Frost Advisory for
locations along and northeast of a Huron, South Dakota to Sioux
Falls, South Dakota, to Orange City, Iowa line. The Frost Advisory
is in effect from 3 am to 9 am Monday.

An upper level trough will begin to push into the Northern Plains
from Canada on Monday. Warm air advection (WAA) will strengthen
ahead of this wave throughout the day. The WAA will push high
temperatures above average across the area with highs into the 70s
and 80s expected. Dew points will remain low though, resulting in
humidity values down to near critical to critical levels. The low
humidity along with breezy southerly winds with gusts up to 20-35
mph, strongest along and west of I-29, will result in another day of
elevated fire danger across the area. While conditions will be near
critical to critical, greening fuels continue to lessen the overall
fire danger. A cold front tied to this upper wave will push through
the area during the overnight hours. The low level jet (LLJ) will
strengthen ahead of the front, keeping breezy winds going through
the night. A few showers to perhaps a thunderstorm or two could
develop along the front as well. Severe weather is not expected as
instability will be quite weak, but perhaps some gusty winds could
be possible. Low temperatures will be much warmer, only falling to
the 50s overnight.

Tuesday and Wednesday look to remain warm across the area as upper
level ridging builds over the central CONUS. Tuesday will be the
cooler of the two days with high temperatures warming to the 70s.
However, winds will be quite breezy out of the northwest within the
post frontal cold advective airmass with gusts up to 30-40 mph.
Humidity values will be low across the vast majority of the area and
will hit critical thresholds. Despite recent greening of fuels,
Tuesday continues to have the highest fire danger potential with a
high GFDI. Wednesday will be a little bit warmer with highs in the
70s to low 80s. The low humidity will persist but winds will be much
lighter, keeping fire danger at bay.

There remains uncertainty regarding how the upper level pattern will
evolve for the rest of the work week and weekend. Medium range
guidance, including the machine learning guidance, continue to vary
on how the shortwave trough over the west coast progresses. The main
two camps that the models are split over is whether the upper low
slows down and potentially cuts off over the west coast or continues
eastwards as a more progressive shortwave. If the wave stays
progressive, then rain chances could increase beyond what they
currently are (20-30%). If the waves cuts off, then chances for rain
could diminish. Tough to say which solution is most likely at this
time but something that will be monitored over the coming days.
Aside from rain chances, Thursday and Friday continue to look very
warm with high temperatures warming into the 80s across the area.

The models are in slightly better agreement for next weekend with
zonal flow taking over. This could still change depending on how the
previously mentioned upper level low evolves but for now, it does
seem most likely that rain chances will increase across the Northern
Plains. This is supported by the ensembles as they show increasing
chances for rain, up to a 30-50% chance for exceeding a tenth of an
inch of rain. Sunday has the highest probabilities at this time.
High temperatures look to remain warm but a little bit cooler than
Thursday and Friday with highs only warming to the 70s and 80s.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1226 AM CDT Mon May 11 2026

VFR conditions expected through the period. Southeasterly winds
will be increasing through the day on Monday, gusting to 20 to
30 kts west of I-29 by the late morning and then gusting to
around 25 kts near and east of I-29 by the early afternoon.
Breezy conditions will continue into the evening as a cold front
approaches the area. This front will move into south-central
South Dakota at the very end of the period. Winds just ahead of
the front will decrease before increasing again and turning
northwesterly behind the frontal passage.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Frost Advisory until 9 AM CDT this morning for SDZ038>040-
     053>056-061-062-067.
MN...Frost Advisory until 9 AM CDT this morning for MNZ071-072-080-
     081-089-090-097-098.
IA...Frost Advisory until 9 AM CDT this morning for IAZ001>003-
     012>014-021-022.
NE...None.

&&

$$

UPDATE...Samet
DISCUSSION...Meyers
AVIATION...Samet