013
FXUS63 KFSD 051115
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
615 AM CDT Wed Jun 5 2024

.KEY MESSAGES...

- Very breezy west-northwest winds with gusts 40 to 50 mph likely
  early this afternoon into the late afternoon hours behind a
  frontal boundary. Strongest winds are expected along and north
  of the I-90 corridor, with a wind advisory issued for
  counties where gusts at or above (AOA) 45 mph are expected.

- Another breezy day expected for Thursday, with gusts up to 40 mph
  possible.

- Pattern shift to northwesterly flow aloft continues into next
  week. This pattern favors only modest precipitation chances
  (Saturday), but higher confidence for below normal
  temperatures and below normal precipitation across the 6 day
  period of time.

&&

.DISCUSSION...
Issued at 401 AM CDT Wed Jun 5 2024

Currently between a strong surface low pressure to our north and a
surface high pressure to our south, surface winds will quickly
strengthen during the morning hours as the inversion weakens. Aloft,
an associated upper-level vorticity lobe moves across portions of
the area north of I-90 during the morning hours from west to east.
While this may spark a few showers, dry air below 10 kft will
evaporate most of the rain resulting in mostly sprinkles expected
down by the surface. However, with winds at 600 mb AOA 60 knots,
even weak showers may be capable of producing wind gusts in excess
of 45 mph. These stronger winds continue to move down in the
atmosphere as the front moves through, and as we mix higher up
behind the front we`ll be able to bring down a portion of the 50+
knot winds found at the top of the mixed layer. Thus, am expecting a
period of 40 to 50 mph winds during the early to late afternoon
hours. This has synoptic support from ensemble situational awareness
tables (ESATs), which show wind speeds at 850mb are above the 90th
percentile of climatology, giving weight towards leaning on higher
wind gusts for today. On the bright side, afternoon highs in the mid
70s to mid 80s are still expected.

As the front continues to slide southeastwards throughout the
afternoon hours, a few scattered showers and very isolated
thunderstorms are possible east of I-29, where up to 200 J/kg of
CAPE looks to be available. As the surface inversion strengthens
during the evening hours, surface winds will weaken into the
overnight hours. However, as the surface pressure gradient remains
elevated while a surface high pressure slides southwards west of the
area, winds will remain semi-breezy with gusts in the teens and
possibly lower 20s. During the morning hours Thursday, the inversion
will again weaken and allow for stronger winds aloft to be mixed
down to the surface. Currently expecting wind gusts to 40 mph again
to be possible, but as the ESATs again show winds at 850mb at the
90th percentile of climatology, would not be surprised to see winds
come in higher with additional model runs. Temperatures in the lower
70s to lower 80s expected.

Friday will see the surface ridge traverse the region, though model
guidance does still have some timing differences, which will swing
the winds around to become out of the southeast. As a weak surface
low pressure develops quickly on the backside of the ridge, we may
see light showers possible along the Missouri River Valley
throughout the day. Otherwise, afternoon temperatures remain in the
mid 70s to lower 80s. As was the case with the previous discussion,
model guidance remains poor on the details in the extended as they
struggle to resolve the ridge breakdown in similar fashions.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 600 AM CDT Wed Jun 5 2024

VFR conditions expected throughout the period. Winds will be the
main aviation concern, and will start out the day from the
southwest. Throughout the morning hours, winds turn westerly ahead
of frontal passage as they increase in strength, with winds becoming
west-northwesterly behind the front. Winds will be strongest behind
the front, gusting 40 to 50 mph before decreasing during the evening
hours. While surface winds weaken, winds aloft remain strong,
introducing LLWS across the area overnight into Thursday.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Wind Advisory from 11 AM this morning to 7 PM CDT this evening
     for SDZ038>040-050-052>067.
MN...Wind Advisory from 11 AM this morning to 7 PM CDT this evening
     for MNZ071-072-080-081-089-090-097-098.
IA...Wind Advisory from 11 AM this morning to 7 PM CDT this evening
     for IAZ001>003-012>014.
NE...None.

&&

$$

DISCUSSION...APT
AVIATION...APT