893
FXUS63 KFSD 272334
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
634 PM CDT Thu Mar 27 2025

.KEY MESSAGES...

- Very mild temperatures for Friday as temperatures rise into
  he upper 70s and 80s. Some locations may approach or exceed
  record high temperatures.

- Gusty winds, low relative humidity and dry vegetation will
  result in fire weather concerns on Friday afternoon and early
  evening. A Fire Weather Watch is in effect for portions of
  northwest Iowa and adjacent far southeast South Dakota,
  northeast Nebraska, and southwest Minnesota.

- Rainfall onset Friday night is delayed, but still looking at
  moderate (50-70%) probability for rainfall/liquid equivalent
  exceeding 0.50" over the weekend (Saturday-Sunday). Some of
  this will fall as snow with areas north of I-90 and into south
  central SD more favored to see light accumulations.

- A second round of precipitation (rain with snow possible)
  comes midweek next week. More uncertainty in details with this
  system, but again seeing moderate (40-50%) probability for
  more than 0.50" rain/liquid equivalent in some areas.

&&

.DISCUSSION...
Issued at 231 PM CDT Thu Mar 27 2025

REST OF TODAY: A rather pleasant rest of the afternoon as
temperatures across the region top out in the mid 60s to mid 70s
with winds generally less than 15-20 mph.

Fairly stout theta-e/WAA push as we head into the evening and while
CAMs don`t show much in the way of shower/storm activity along it in
our area, have opted to leave sprinkle mention east of I-29 given
favorable pattern for some shallow convective clouds that can
occasionally overachieve model guidance.

TONIGHT: Southerly return flow quickly ushers in dewpoints in
the upper 40s to lower 50s after midnight with forecast
soundings split on whether this manifests as a low stratus deck
or perhaps a northward advecting fog. Have added mention of
patchy fog with this forecast package and will allow future
shifts to evaluate the need to increase/decrease coverage
wording. Overnight lows will hang very near normal high
temperatures for this time of year.

FRIDAY: Wave traversing the Northern Plains cuts into the upper
level ridge for Friday and will set up a very warm day across
the region with high temperatures soaring into the upper 70s and
80s. This would put several locations into record temperature
territory and certainly a taste of summer.

At the same time, initial southerly winds will take on a more west
to northwesterly direction across our western counties by the
afternoon hours as a front works in while remaining out of the
southwest ahead of this boundary. Over northwest Iowa and adjacent
portions of South Dakota, Nebraska and Minnesota, wind gusts in the
30-40 mph range are expected. This will result in fire weather
concerns discussed further in the Fire Weather Section.

FRIDAY NIGHT-SATURDAY MORNING: Surface cold front will be
pushing through the southeast portions of the forecast area
Friday evening, stalling just southeast/south of the forecast
through the overnight into Saturday morning while awaiting the
low pressure developing in the central Plains. Challenge for
this period will be moisture availability as latest models are
showing a relative void of low-mid level moisture along the cold
front Friday evening which persists behind the cold front as it
settles to our south later Friday night-Saturday morning. This
has resulted in a delayed start to any significant rainfall
until Saturday, especially toward Saturday afternoon, with most
areas seeing only a few hundredths to perhaps 0.10" through
midday Saturday.

One thing to monitor will be a potential for a stronger storm
if storms develop along or just behind the front in northwest
Iowa Friday evening. Chance for strong-severe surface-based
storms along the front looks low given displacement of greater
instability near/ahead of the front from the greater deep layer
shear behind the boundary. However, if these parameters come
together right along the boundary cannot rule out an isolated
strong-severe storm with marginally large hail or gusty winds.
As the boundary drops south, shear does increase through the
latter half of the night, though with decreasing instability.

SATURDAY AFTERNOON-SUNDAY: By Saturday afternoon, the focus
shifts to the wave lifting northeast across the area. Low level
boundary remains south of our forecast area, which will keep us
on the cooler side through this period, with the main question
being when/where will low level temperatures be cold enough for
snow vs rain. Still some disagreement among the various model
solutions in this regard, though with modest consensus that our
elevated areas (Buffalo Ridge in southwest Minnesota as well as
west of the James River toward south central South Dakota) will
be more likely to see cooler temperatures and a greater chance
of accumulating snow. That accumulation will be mostly focused
in the nighttime hours Saturday night-early Sunday, as with a
growing sun angle, it will be more difficult to see daytime
accumulations without heavier snow rates to overcome the warm
ground temperatures. That said, Could see an inch or two of
accumulation in the aforementioned higher elevations, with
amounts around a half inch or less more favored in our valley
areas.

Regardless of precipitation type, ensembles/NBM are showing
moderate (50-70%) probabilities for QPF exceeding 0.50" across
most of the forecast area from Saturday through Sunday, with the
bulk of this QPF coming Saturday afternoon/evening when a mid
level front could focus more intense precipitation rates across
portions of southeast SD-southwest MN.

MONDAY-THURSDAY: Will see a brief reprieve from precipitation as
we start the work week Monday, but another system quickly moves
in toward midweek, bringing another round of rain and/or snow to
the region. Details on this system are more uncertain given much
greater variance in timing/track/strength, but NBM again shows
a moderate (40-50%) probability for QPF exceeding 0.50" across
portions of the forecast area from Tuesday through Wednesday
night.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 628 PM CDT Thu Mar 27 2025

VFR conditions will persist for the rest of the TAF period.
Taking a look across the area, an abundance of sunshine
continues this evening with marginally breezy southeasterly
winds. Expect our winds to gradually decrease after sunset with
the potential for some increasing stratus over southwestern MN
overnight. Otherwise, could see a few isolated showers develop
by Friday afternoon as a cold front swings through the area with
breezy southwesterly winds becoming more northwesterly behind
the front to end the TAF period.

&&

.FIRE WEATHER...
Issued at 231 PM CDT Thu Mar 27 2025

Gusty southwesterly winds ahead of an approaching front will
gust in the 30-40 mph range across northwest Iowa and
immediately adjacent portions of southwest Minnesota, northeast
Nebraska and far southeast South Dakota. A stripe of lower
dewpoints within the pre-frontal trough underneath a broad area
of very mild temperature will drive afternoon relative humidity
values below 25% from southeast South Dakota to far southwest
Minnesota. The biggest question will be if there is an overlap
in the strongest winds and lowest RH or if they are just enough
offset to avoid critical fire weather conditions. Leaning more
heavily on HRRR/RAP guidance, and HREF probabilities, suggest
there will be a narrow stripe a couple counties wide. Given this
fact, and the cured pre-greenup vegetation in place with gusty
winds, have opted to issue a Fire Weather Watch for Friday
afternoon and early evening and will allow future shift to
further evaluate this overlap in conditions. There is also some
uncertainty on how quickly northwest winds pick up behind the
wind switch which may shift a threat area further west than the
current watch area (closer to the current Day 2 Elevated Fire
Weather Outlook).

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Fire Weather Watch from Friday afternoon through Friday
     evening for SDZ070-071.
MN...Fire Weather Watch from Friday afternoon through Friday
     evening for MNZ080-081-089-090-098.
IA...Fire Weather Watch from Friday afternoon through Friday
     evening for IAZ001>003-012>014-020-021-031.
NE...Fire Weather Watch from Friday afternoon through Friday
     evening for NEZ013-014.

&&

$$

DISCUSSION...JH/Kalin
AVIATION...05
FIRE WEATHER...Kalin