697
FXUS63 KFSD 120333
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1033 PM CDT Sat May 11 2024

.KEY MESSAGES...

- Some high clouds will be present aloft, but sufficient viewing
  conditions are still expected for seeing the Aurora tonight.

- Scattered showers and storms are looking increasingly likely
  near and south of the I-90 corridor tomorrow afternoon and
  evening. Severe weather is not expected but some storms could
  produce gusty winds.

- Temperatures will be closer to seasonal next week with the
  coldest highs focused around Wednesday.

- Rain chances late Tuesday through Wednesday and potentially
  continuing through Thursday and Friday. Severe weather risks
  are low but additional meaningful rainfall is possible.

&&

.DISCUSSION...
Issued at 332 PM CDT Sat May 11 2024

Beautiful conditions persist across the area this afternoon,
characterized by high temperatures in the 70s and marginally breezy
winds. These conditions will continue for the rest of the afternoon
hours so get out there and enjoy the nice weather!

Remnant coronal mass ejections (CMEs) continue to make their
presence known as they bring another chance to view the aurora
tonight. Tonight`s view is remains solid to view the potential
Aurora but mid level warm air advection (WAA) may result in some mid
level clouds. On top of the mid level clouds, literally, high level
cirrus streaming in from the northwest may thicken a bit aloft as an
incoming upper level wave pushes southwards through Canada to the
international border. While this won`t completely obscure the sky,
it may make viewing the aurora a little bit more difficult. As of
now, locations along the highway-14 corridor look to see the
thickest cirrus aloft. Good news is that the cirrus will not last
all night so there should be sufficient viewing potential during the
overnight hours. A cold front tied to the previously mentioned upper
level wave will reside in a surface pressure trough which will
tighten the surface pressure gradient a bit. With a tighter gradient
in place, slightly elevated southwesterly winds with gusts up to 10-
15 mph are expected tonight. The elevated winds will keep low
temperatures a bit on the warm side only falling to the 50s
overnight.

The previously mentioned cold front will slide through the forecast
area on Sunday, setting the stage for shower and storm development.
850 mb temperatures will warm to about +15 C aloft. Mixing this to
the surface will result in high temperatures up to the 80s across
the area. Dew points will only moisten to the mid 50s at the best as
southwest flow ahead of the incoming front will not provide the best
moisture return. With moist neutral mid level lapse rates in place,
some instability will be generated, up to 1,000 J/kg of CAPE. With
the best mid and upper level winds residing along the international
border, little to no wind shear is expected. This will keep any
severe storm potential at bay. Soundings do show a dry, inverted-v
structure in the low levels so there could be some gusty winds with
any storms that develop along the front. Light rain chances look to
continue through the overnight hours across northwest Iowa. Low
temperatures are expected to fall to the low 50s overnight.

Low rain chances (<= 30% chance) hang across parts of northwest Iowa
tomorrow as a vertically stacked low pressure system slowly exits
the central plains. Light rain may wrap back around the low which
would only produce minor rain accumulations. Otherwise, Monday will
be a quiet day with breezy northeast winds with highs up to 70s and
lows down to the 40s.

Medium range guidance begins to vary in how the upper level pattern
evolves through the middle of the week and end of the week. Tuesday
will be a quiet day as large scale descent resides over the forecast
area with highs again into the 70s. Ensembles are a bit more
consistent on a trough moving into the Northern Plains on Wednesday.
As of now, lapse rates look to be less then moist neutral so little
instability looks to be present. This is further supported by the
ensembles as they show only a 0-30% chance for CAPE values to exceed
500 J/kg. However, ensembles show higher probabilities up to a 30-
60% chance for exceeding a tenth of an inch of rain with this
system.

An active pattern looks to continue aloft which could result in more
rain chance for the end of the week. Details remain uncertain at
this time so have stuck with model blended PoPs for the end of the
forecast period. Highs will remain in the 70s with lows falling to
the low 50s.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1027 PM CDT Sat May 11 2024

VFR conditions will prevail through at least early Sunday
afternoon. Light west winds will weaken overnight and turn
southwest. A cold front slides in Sunday afternoon and evening,
turning winds to northwesterly behind the front. Moderate chance
of scattered showers and storms ahead (south) of the front from
21z Sunday afternoon through Sunday evening, which is expected
to settle in near the I-90 corridor Sunday afternoon. Added a
PROB30 group for this at Sioux Falls and Sioux City.

&&

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

&&

$$

DISCUSSION...Meyers
AVIATION...BP