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331
FXUS63 KFSD 220900
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
400 AM CDT Sat Jun 22 2024

.KEY MESSAGES...

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- Light showers and thunderstorms continue over southwestern
  Minnesota and northwestern Iowa. These are expected to move to
  out by late morning

- A low pressure system and cold front will trigger additional
  showers and thunderstorms this morning over central South
  Dakota. These showers will move eastward through the day and
  be east of the area by late afternoon/early evening.

- Ongoing flooding may worsen as the runoff from the last 24
  hours makes its way to the waterways. Record river flooding
  is likely on several basins.

- Conditions will quiet down through the upcoming weekend into
  early next week. Temperatures remain near seasonal normals.

- Pattern through next week doesn`t favor any long duration
  rain, but several brief risks for passing convection exist.
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&&

.DISCUSSION...
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Issued at 355 AM CDT Sat Jun 22 2024

TODAY: Lingering showers and thunderstorms over northwestern Iowa
and central Minnesota will continue to push off to the east this
morning. Another round of showers and thunderstorms is possible as a
surface low and associated cold front move through late this
morning. The better environment for thunderstorms is located over
central Iowa. However, there is 500-800 J/kg of elevated
instability to work with. If convection does initiate, the main
threats will be moderate to briefly heavy rainfall, possibly
some small hail, and wind gusts to 50 mph. These storms should
be east of the area by late afternoon. Clouds will decrease from
west to east and we may catch a few peaks of sunshine before
sunset. Highs for this afternoon look to be in the mid to upper
70s with a few 80s along the Missouri River counties. A
pleasant overnight follows with mostly clear skies and lows in
the lower 60s.

SUNDAY: For Sunday, a weak high pressure ridge builds in from the
west. With rising heights we can expect a sunny day with warm
temperatures in the 80s, with the warmest temperatures again along
the Missouri River counties. Lows will be warm in the mid to
upper 60s. Late Sunday into early Monday, there is a low (<30%)
probability of some light showers. Confidence is low due to low
agreement in guidance. If showers develop, they will remain
light, producing a trace to a tenth or two.

MONDAY: Flow aloft becomes more zonal for Monday. Strong WAA and
southwesterly winds warm the 850mb temperatures into the upper 20s
Celsius! Good mixing will kick the highs up into low to mid 90s F at
the surface. Along with good mixing come gusty winds. Look for winds
to be southerly becoming southwesterly sustained at 15-20 mph with
gusts 25-30 mph by afternoon. A subtle mid-level wave and associated
cold front moves through late Monday into early Tuesday bringing a
chance for some showers and thunderstorms. Elevated instability is
sufficient to produce a few storms that could become strong to
severe. At this time model agreement is low, and therefore
confidence in thunderstorm development is low. Monday night lows
will be warm, in the upper 60-70s.

TUESDAY-SATURDAY: A series of short waves bring multiple rounds of
showers through Thursday. An upper trough approaches from the west
Thursday afternoon bringing our next chance for strong to severe
thunderstorms. Models are in fairly good agreement in the
development of the low pressure system, but they differ greatly in
timing and track. Definitely one to keep an eye on, especially
after the recent rains.
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&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1235 AM CDT Sat Jun 22 2024

Showers and thunderstorms continue over southeastern South Dakota,
southwestern Minnesota, and northwestern Iowa this morning. Expect
these showers to push east through the overnight. Showers are
expected to be clear of the area by the afternoon.

Current ceilings are a mixture of VFR west of I-29 to MVFR-LIFR over
southwestern Minnesota and northwestern Iowa. As the showers push
off, expect ceilings to lift to IFR. Skies will clear from west to
east as we approach the evening. VFR conditions are expected to
prevail for the rest of the period.

Winds will become light and variable after storms clear. By mid-
morning winds will become north-northwesterly around 10 kts.

&&

.HYDROLOGY...
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Issued at 244 PM CDT Fri Jun 21 2024

The flood watch has been extended for portions of southeastern
South Dakota, southwestern Minnesota, and northwestern Iowa.
Additional showers and thunderstorms are expected to develop
this afternoon and push east over an area already experiencing
significant flooding. Additional rainfall totals of 0.25 to 0.5
inches are expected. Though these totals are not considered
heavy rainfall, the situation over this area is already such
that any additional rainfall over a few tenths will exacerbate
an already serious situation.

In addition, river levels are expected to continue to rise over the
next 12 to 24 hours as the rainfall drains from the surrounding area
into the water ways. Widespread moderate to major flooding is
expected with some river basins seeing potently record breaking
peaks.
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&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Flood Watch until 7 AM CDT this morning for SDZ038>040-050-
     052>071.
MN...Flood Watch until 7 AM CDT this morning for MNZ071-072-080-081-
     089-090-097-098.
IA...Flood Watch until 7 AM CDT this morning for IAZ001>003-012>014-
     020>022.
NE...Flood Watch until 7 AM CDT this morning for NEZ013.

&&

$$

DISCUSSION...AJP
AVIATION...AJP
HYDROLOGY...AJP