565
FXUS63 KFSD 121110
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
610 AM CDT Sun May 12 2024

.KEY MESSAGES...

- Another day with temperatures 10+ degrees above normal on Sunday.

- Scattered thunderstorms will be possible by mid-late
  afternoon ahead of a cold front. Severe weather risks remain
  very low, but some stronger wind gusts are possible. Those
  with outdoor plans should stay weather aware.

- Potential for wildfire smoke to move southward into the area
  Sunday evening into Monday. Some minor visibility reductions
  may be possible.

- Temperatures cool slightly, but remain above normal for much
  of the upcoming week.

- Scattered thunderstorm risks increase by late Tuesday through
  Wednesday. Outside of a small window Tuesday evening, most of
  the thunderstorms will stay well below severe limits.

&&

.UPDATE...
Issued at 402 AM CDT Sun May 12 2024

One quick addition to the forecast not previously mentioned in
earlier discussion. Northerly winds behind the late afternoon
frontal passage are likely to transport smoke from wildfires
across southern Canada into the Tri-State area. Good agreement
from RAP/HRRR smoke guidance in the potential for some sky
obstructions later this evening and into Monday. However, good
signals for subsidence pushing smoke down to the surface after
dark and into at least early Monday afternoon. This could
produce some marginal visibility reductions (AOA 5SM at times)
and reductions in air quality. Have added smoke to the grids
and increased sky cover to 30% into Monday.

&&

.DISCUSSION...
Issued at 259 AM CDT Sun May 12 2024

THIS MORNING:  Light southerly winds continue to keep morning
temperatures in the 50s in most locations.  Scattered mid to high
level clouds have develop in response we weak warm advection moving
through the region.

TODAY:  Another very warm day is expected on Sunday, with
temperatures rising a couple degrees warmer than on Saturday.  The
warmup is expected ahead of a slowly advancing cold front that will
be entering the far northwestern portions of the CWA by mid-morning
and then bisect the CWA from southwest to northeast by 21Z. Weak
surface convergence along this boundary is expected to lead to
a narrow band of scattered thunderstorms that will slowly drift
southeast into the evening. Instability along and ahead of the
front will be highly dependent on the quality of surface
moisture that moves into the area from the southwest. Some
models such as the RAP are pushing dew points into the upper 50s
and lower 60s by late this afternoon (resulting in nearly 1500
J/KG MLCAPE). Most other models are much more pessimistic with
surface dewpoints only in the lower 50s resulting in only 500 to
1000 J/KG MLCAPE. This seems more realistic given the deep
mixing up to nearly 8000 ft AGL, and the fact that dew points in
southern Nebraska and northern Kansas are only in the lower 50s
this morning. The general severe weather threat remains low,
given effective shear only around 10 to 15 knots, and a more
thin CAPE profile. However the high-base activity does present
some risk for localized weak downbursts as DCAPE values are
pushing 1500 J/KG. Some high resolution CAMs are suggesting this
potential with simulated pockets of 40 to 45 knot gusts
associated with weakening convection. QPF should remain light in
most areas, but did blend in some PMM numbers from the HREF
which would suggest some potential for very localized 0.50-0.75"
totals.

TONIGHT: While the majority of convection will weaken as sunset
arrives, a portion of the convection may continue into the early
overnight hours as weak dPVA moves in from the northwest and
secondary band from the southwest.  This area would mainly be in
eastern Nebraska and northwestern Iowa. Elsewhere, temperatures will
fall and dew points should drop quickly overnight, leading to a
cooler start to Monday morning.

MONDAY: Mid-lvl shortwave ridging moves in for Monday, and
temperatures will again rise a few degrees above normal.  Winds
should stay rather light under a passing surface ridge of high
pressure.

TUESDAY: A shortwave crosses the Northern Rockies into the Dakotas
early Tuesday.  There seems to be some agreement in surface low
development over southwestern South Dakota which then moves towards
central South Dakota by the evening. While most of the convection
may remain across the far western and northwestern portions of the
state in the evening, there are hints that depending on surface
heating and boundary layer moisture quality, we could see a risk of
convection into south central South Dakota in the evening.   The NAM
seems to be the most aggressive with convection, with other
models showing a stubborn EML that would hold any convection
from developing. Have nudged temperatures up slightly given less
signal for cloud cover and deeper mixing.

WEDNESDAY:  Any overnight convection will push cloud cover, along
with a weak surface boundary, eastward for Wednesday. This
should lead to slightly cooler temperatures and a few lingering
showers. A secondary wave approaches in the middle of the day,
likely leading to renewed scattered showers though the signal
for widespread activity continues to trend lower. The lack of
instability will preclude any severe weather risk.

THURSDAY-SATURDAY: The sharpening upper trough slides through the
region on Thursday, and could produce some widely scattered
afternoon sprinkles or showers.  However temperatures will remain
near seasonal normals.  We`re stuck in an active northern stream
flow through the upcoming weekend with one trough passing through
the Dakotas Friday and a second arriving towards the end of the
weekend.  At this point, with the lack of moisture advecting back
northward, the severe weather risk should remain very low.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 606 AM CDT Sun May 12 2024

VFR conditions are likely through most of the day. A frontal
boundary will sink southeast slowly this morning, stalling from
Gregory to Marshall by mid-afternoon. High based CU will develop
later this afternoon along and ahead of the front, with a few
scattered thunderstorms developing and moving southeast into the
evening. These smaller storms could produce scattered strong
wind gusts.

Secondary area of high based clouds expected to move northeast
out of Nebraska by mid-afternoon and could produce a few
sprinkles by 21Z near Sioux City.

Eventually this front and associated showers/storms will move
south of the Highway 20 corridor late this evening with a broken
mid-lvl cloud field into Monday morning.

A secondary concern will be the potential for elevated smoke to
move south later this evening. Some uncertainty on if there will
be ground impacts, and later TAFs will address potential smoke
inclusion in TAF if needed.



&&

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

&&

$$

UPDATE...Dux
DISCUSSION...Dux
AVIATION...Dux