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207
FXUS63 KABR 220909
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
409 AM CDT Sat Jun 22 2024

.KEY MESSAGES...

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- Light showers and weak thunderstorms possible (40-60%) this morning.
  Just a 20% chance for thunderstorms this evening...very low
  risk of severe weather.

- Periodic chances for showers and storms will be possible next week,
  especially late Monday/early Tuesday and again Thursday and
  Friday. Otherwise, dry conditions look to prevail with
  temperatures initially well above normal Monday into Tuesday
  before returning closer to seasonal normals the rest of the
  week.
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&&

.SHORT TERM /TODAY THROUGH SUNDAY AFTERNOON/...
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Issued at 407 AM CDT Sat Jun 22 2024

A couple of areas of rain and weak convection associated with a weak
wave thats embedded within upper flow that is transitioning to
zonal. That continues east through the morning, with CAMS showing
random weak convection but honing in on a solution that involves a
broad area of precipitation moving between essentially highway 12 and
14. CAMS also continue to show isolated late afternoon/evening
convection on a northwest to southeast trajectory as a northwest
flow regime develops. CAPE still only tops out around 1000j/kg with
northwest unidirectional shear. Northwest flow continues through
Sunday, supporting drying/clearing skies. 850mb temperatures remain
mild (+14 to +18) but 700mb temperatures are on the increase.
Surface dewpoints also remain around 60F up around Aberdeen however
across central/southern South Dakota, dewpoint pooling pushes those
values up into the upper 60s.
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&&

.LONG TERM /SUNDAY EVENING THROUGH FRIDAY/...
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Issued at 407 AM CDT Sat Jun 22 2024

This period begins Sunday evening with sfc high pressure drifting
eastward across the eastern Dakotas into Minnesota. This sfc high
will continue to drift east of our area on Monday, allowing for
return flow to set up which will draw in a more moisture rich air
mass into the area. An upper level ridge will shift eastward across
the Dakotas on Monday leading to a hot and humid day for most of the
forecast area. Guidance progs 850mb temps will top out between +25C
to near +30C Monday afternoon. NBM probabilities of reaching or
exceeding 90 degrees is very high(80-95 percent) across most of the
CWA, with the exception of locales east of the James Valley. The
75th percentile for Max T`s on Monday at Aberdeen, Mobridge and
Pierre is 100 degrees. We won`t be forecasting readings quite that
high, but mid 90s look probably for highs across parts of central
and northeast SD. Heat indices could approach 100 degrees in some
spots Monday afternoon.

One trend we will have to keep an eye on is convection potential by
late Monday afternoon into Monday night. An upper trough is progged
to trek across the Canadian Provinces with associated mid-level
shortwave energy riding over the top of the upper ridge in parts of
the Dakotas. Sfc low pressure will shift eastward across the
International border with a sfc trough extending southward into the
Dakotas and a trailing cold front farther to the west. A north-
northeastward moving warm front will track from southeast
SD/southwest MN into far northeast SD/southeast ND and central MN
toward the latter half of the day and then eventually moving farther
northeast Monday night. Favorable instability and deep layer shear
look to be present by Monday evening across our eastern zones. The
one caveat in all this is a capping inversion could be in place to
preclude any storm development in our area. 700mb temperatures are
progged to be +13C to +16C across our CWA Monday afternoon into
Monday evening with gradually cooling thereafter as the
aforementioned trough/cold front sweep through the area later Monday
night. SPC`s current Day 3 severe weather outlook highlights most of
our CWA in a marginal(1 out of 5) risk. At this point, still very
uncertain how any potential convection will play out, but our
eastern zones may have the best chance at seeing some storms Monday
night.

The upper level ridge is progged to build back in across the
Northern High Plains and Northern Plains toward the middle of the
week. This should lead to a couple of dry days for our area Tuesday
into Wednesday. The pattern could become more active by late next
week as guidance progs yet another upper trough to roll across the
northern tier of the CONUS and increase our precip chances Thursday
into Friday. Temperatures will cool off from Monday`s heat and
return to closer to seasonal normals the remainder of the period
with highs generally in the 80s and lows in the 60s.
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&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1225 AM CDT Sat Jun 22 2024

Terminals KABR,KATY,KPIR,KMBG

Guidance says to expect more MVFR/IFR conditions (cigs mainly) for
the rest of tonight into Saturday morning before conditions improve
to VFR from west to east. KPIR and KMBG should be back into VFR
weather by 18Z Saturday; KABR and KATY likely following suit by ~21Z
Saturday.

The east-component surface/near surface wind is likely generating
some upslope fog on the lee-side of the Prairie Coteau in northeast
South Dakota (fog/visby a potential concern at KATY) through ~15Z
Saturday.

Showers and weak thunderstorms are just starting to get going and
may affect any terminal in the CWA through the overnight to
morning hours Saturday.


&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Flood Watch until 7 AM CDT this morning for SDZ037-048-051.

MN...None.
&&

$$

SHORT TERM...Connelly
LONG TERM...Vipond
AVIATION...Connelly