161
FXUS63 KFSD 052321
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
621 PM CDT Fri Jul 5 2024

.KEY MESSAGES...

- Diurnal showers/weak storms will rotate southward across the
  area this afternoon, dissipating by sunset. Rainfall will be
  spotty and light, but isolated lightning may impact outdoor
  activities.

- Unsettled weather continues Saturday-Monday, with periods of
  scattered showers/storms, mainly focused during the afternoon
  to early evening. A few strong to severe storms are possible
  Saturday afternoon, with large hail/damaging winds the primary
  threats.

- Cooler than normal temperatures for early July through the
  middle of next week, but trending closer to normal by the end
  of the week.

&&

.DISCUSSION...
Issued at 240 PM CDT Fri Jul 5 2024

An upper level low continues to spin over eastern WI this afternoon.
Relatively cool air aloft on the backside of the low has resulted in
weak instability (MLCAPE analyzed around 500-1000 J/KG) across the
region, and this had triggered scattered showers east of Interstate
29. Have yet to see any lightning strikes with the activity, though
cannot completely rule this out into mid evening as instability
increases a bit more as surface temperatures hit their peak for the
day. Bulk shear is nearly non existent over the region, so not
expecting any strong to severe storms. Any showers/storms will
quickly dissipate by late evening as heating of the day is lost and
the atmosphere becomes more stable. Otherwise, a weak surface high
slides across the region overnight. With that, winds will drop off
to nearly calm. Look for lows in the mid and upper 50s.

Our area remains under the influence of an upper level trough on
Saturday and Saturday night. Models indicate an upper level
shortwave tracking over our area on the northwesterly upper level
flow during this time frame. This will bring a better chance of
showers and thunderstorms to the region for Saturday afternoon and
evening. There is a low end potential for isolated strong to severe
storms with MUCAPE of 1000-2000 J/KG, this in conjunction with bulk
shear of 30-40 kts (focused mainly across the southern portions of
the CWA). Even so, mid level lapse rates are on the weaker side - 5
to 6 C/KM, so expect stronger storms to remain isolated, which is
supported well by an SPC Day 2 Marginal (1 out of 5) convective risk
for the southern portions of our area. As for rainfall amounts, most
places will receive a quarter inch or less - though higher amounts
are of course possible in a heavier storm. With the anticipation
that there could be more convective activity over southwestern MN,
total rainfall amounts (focused on Saturday afternoon through
Saturday night) may be higher over that area, with the 12Z HREF
indicating a 50% probability of that area receiving 0.50" or greater
during that time frame. Highs on Saturday remain just below normal
for this time of year - in the mid 70s to lower 80s.

Low probability (20-30%) rainfall chances continue on Sunday as a
weak cold front swings through the area. Severe weather is not
expected in the absence of any significant bulk shear along with
weak mid level lapse rates.

For next week, models continue to show our area remaining under the
influence of the upper level trough through at least midweek. Toward
the end of the week, a broad upper level ridge over the western
CONUS will try to build eastward into our area. Even so, there is
uncertainty on how much eastward progression the ridge will achieve -
 dependent on the evolution/track of tropical system Beryl which is
expected to push into the Southern Plains/Lower Mississippi Valley
by early/midweek. Next week does appear to be a drier period, with
ensembles suggesting a 15% or less probability of our area receiving
0.25" of precipitation in any one 24 hour period for Monday through
Thursday. Temperatures look to remain just below normal through at
least the middle of the week, perhaps creeping closer to normal by
the end of the week.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 616 PM CDT Fri Jul 5 2024

Scattered showers and isolated storms continue through sunset
this evening. Have included VCSH mention at all three sites for
a couple of hours, with confidence low enough in lightning
potential to preclude TS mention. An outflow boundary associated
with the showers/iso. storms has been moving west toward
KMDS/KFSD/KSUX, which would shift winds from more northwest to
northeast for a brief period. Unsure if it will reach KSUX, so
omitted the wind shift at this site.

Winds tonight into Saturday morning will be light and variable.
Additional showers and storms are expected through the day and
into the evening Saturday. Included VCSH mention for the highest
confidence periods (at this time), with continued PROB30 for TS
chances.

Outside of any convection, VFR conditions expected. Winds
Saturday out of the southwest.

&&

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

&&

$$

DISCUSSION...JM
AVIATION...SG