679
FXUS63 KFSD 142334
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
634 PM CDT Sun Jul 14 2024

.KEY MESSAGES...

- High humidity with temperatures in the 80s and 90s will lead
  to heat index values of 95 to 105 degrees. Heat Advisory
  remains in effect for areas along and south of I-90 until 8
 PM.

- An area of thicker wildfire smoke can be seen on satellite
  advecting into south central SD. This moves east through the
  evening along the southern MO River Valley and northwestern IA;
  however, no surface impacts are currently expected.

- Showers and storms are possible tonight through late Monday
  morning, although confidence is very low in coverage and
  timing. Strong to severe storms are possible if storms develop,
  with all hazards possible.

- Unsettled pattern continues into mid/late next week with
  periodic low shower and storm chances. Starting Tuesday,
  temperatures will be near to below normal for this time of
  year.

&&

.DISCUSSION...
Issued at 236 PM CDT Sun Jul 14 2024

CURRENTS THROUGH MONDAY: Morning cloud cover has diminished/moved
east, although diurnal cumulus is developing across the region. Also
noting an area of thicker wildfire smoke over south central SD;
however, no surface impacts are expected at this time as it moves to
the southeast through the evening hours. Temperatures continue to
climb into the 80s and lower 90s. Despite being a bit cooler than
yesterday, dew points in the mid 60s to mid 70s raise heat indices
into the mid 90s to 105 degrees F. Maintained the on-going Heat
Advisory for areas along/south of I-90.

Now, attention turns to chances for showers and storms overnight
through Monday. Models continue to struggle this run in resolving
short wave trajectories over the area during this time, including
source region (ND v.s. western SD), timing (tonight v.s. mid
day Monday), strength, and number of waves. This leads to very
low confidence in convective chances through Monday afternoon.
In one camp of models, the main short wave ejects out of ND late
tonight bringing a complex of storms into portions of
southwestern/central MN as it collides with a surface boundary.
This scenario is mostly evident in the NAMNest, ARW, and some
runs of the HRRR today. The FV3 is in a similar camp, although
is much further to the west (bringing the storms to areas west
of I-29). Some of the guidance (a couple of HRRR runs and the
RAP) either don`t have this feature or shift it much further
east in MN. Another short wave is progged to move into the area
later Monday morning, and depending on where the boundary ends
up after any overnight convection, this may be a catalyst for
additional storm development in the late morning tomorrow
along/south of I-90. The NAMNest is the most aggressive with
this development in northeastern NE, quickly growing upscale
along the front into northwestern IA. Given all the uncertainty,
generally tried to use an average of the hi-res models and
previous forecast for pops. If storms are able to advect into
or develop over our area into late Monday morning, they could
quickly become strong to severe. MUCAPE is generally 1500 J/kg
or higher (at times approaching 3000+ J/kg), bulk shear of 35+
knots, and steep mid level lapse rates of over 8 deg C/km
support wind gusts to 70 mph and golf ball sized hail. Based on
last night/early this morning`s storms, would not be entirely
surprised if a stronger complex of storms produces wind gusts to
80 mph. Can`t rule out a tornado or two with the surface
boundary hanging around, low LCLs, and 0-1 bulk shear around 20
knots. Locally heavy rain is possible as PWATs sit between 1.5
and 2 inches. Not anticipating widespread flooding issues as
convection is expected to be fairly progressive.

Lows tonight in the upper 60s to lower 70s. Highs tomorrow will be
highly dependent on morning convection, cloud cover, and how far
south the boundary is. Seasonal temps expected with highs in the 80s
to lower 90s. High dew points push heat index values into the upper
90s to near 100 in the southern MO River Valley into northwestern
IA.

MONDAY NIGHT AND TUESDAY: As the boundary moves south Monday night,
CAA begins to filter in, bringing cooler temperatures. A couple of
weak waves bring some occasional precip chances to the area, but
severe weather is not expected. Lows in the upper 50s to mid 60s.
Highs Tuesday will be slightly below average thanks to the CAA
and cooler surface high pressure moving in. We`ll only warm into
the mid/upper 70s to lower 80s.

MID WEEK ONWARD: Surface high pressure meanders south around
the northern/central Plains mid week, sliding east into the Great
Lakes late week. Northwesterly flow regime and CAA to neutral
advection keep temperatures cooler than average. Highs in the
70s to mid 80s and lows in the 50s to lower 60s. A few weak
waves could bring some shower and storm chances to the region,
but probability is low (< 30%). Synoptic pattern becomes more
amplified later in the period as troughing digs in over the
eastern US and high pressure deepens over the Southwest.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 631 PM CDT Sun Jul 14 2024

Light and variable winds along with mainly clear skies begin the TAF
period early this evening. Winds are veering though and will settle
out of the southeast later this evening with speeds of 5-10 knots.
Uncertainty remains on shower and storm chances during the overnight
hours so have only included VCSH in KHON`s TAF as confidence is
highest in rain chances at this terminal. Shower and storm chances
will be closely monitored over the coming hours. Showers and storms
are possible during the morning and afternoon hours tomorrow but
confidence remains too low to mention in TAFs at this time.

A cold front will push through the area mainly during the morning
hours tomorrow. The front will turn the previously mentioned
southeasterly winds to out of the north with gusts up to around 15-
20 knots. The northerly winds will finish out the TAF period.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Heat Advisory until 8 PM CDT this evening for SDZ050-057>071.
MN...None.
IA...Heat Advisory until 8 PM CDT this evening for IAZ001>003-
     012>014-020>022-031-032.
NE...Heat Advisory until 8 PM CDT this evening for NEZ013-014.

&&

$$

DISCUSSION...SG
AVIATION...Meyers