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722
FXUS63 KABR 172326 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
626 PM CDT Fri May 17 2024

.KEY MESSAGES...

- A cold front crossing the area this evening will bring 70%  chance
of showers and thunderstorms to north central South  Dakota, with
lower chances elsewhere. Some storms may become  severe over central
South Dakota, with gusty winds of 60-70 mph and quarter sized hail.

- Strong west to northwest wind gusts between 30-45 mph will be
possible on Saturday. Highest probabilities for the strongest gusts
are across our northern tier of counties along the ND border.

- Active pattern with additional rounds of showers/thunderstorms for
Sunday-Friday. Below normal temperatures Tuesday-Friday.

&&

.UPDATE...
-- Changed Discussion --
Issued at 624 PM CDT Fri May 17 2024

Strong to severe storms are currently moving toward Corson county
and will progress east through the evening. A severe thunderstorm
watch is in effect until midnight for portions of north central SD
with the main threat being strong winds.
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&&

.SHORT TERM /THIS EVENING THROUGH SATURDAY NIGHT/...
Issued at 257 PM CDT Fri May 17 2024

Expect significant changes to our current hot and dry weather
conditions. At 19Z temperatures were in the 80s across the entire
area, and mid 80s from MBG-ABR. Dewpoints remain moderate to low, in
the 40s to low 50s across much of the area. A string of upper 50s
dewpoints has shifted into portions of central SD from Harrold, HON,
to Redfield. Only a few fair weather cumulus clouds were evident
over mainly west central MN. Otherwise, our attention has bee to our
west. The surface weather map shows the quick moving surface low
over southwestern ND/far northwestern ND/southeastern MT. We`ve seen
showers and thunderstorms develop over eastern MT/western ND already
this afternoon, and will continue to monitor this area as the area
of low pressure and associated cold front sink east-southeast over
the forecast area this evening. Ahead of the boundary, DCAPE values
are in the 1300-1700 J/kg range, indicating a higher potential for
strong winds with the incoming storms. They will also be accompanied
by ML lapse rates of over 8C/km. High based, mainly dry
thunderstorms are expected. A few strong to severe storms will be
possible over north central South Dakota this evening. The strongest
storms could be capable of producing winds of 60 to 70 mph, along
with hail the size of quarters. Precipitation will be around for 2-4
hours at any site. The cold front will sink to our far eastern
counties by around 09Z Saturday. The passage of the cold front will
usher in strong winds out of the west to northwest with gusts of 30
to 45 mph through the day Saturday, or near the high end of forecast
guidance due to the strong pressure gradient.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 257 PM CDT Fri May 17 2024

When the period opens, mid-level WAA and a low level jet could be
combining to produce some isolated to scattered (15-45 percent)
elevated showers and thunderstorms across the CWA Sunday morning.
Once the best forcing/lift shifts north and east of the CWA, things
should clear out and, depending on the amount of sunshine seen for
the rest of the day on Sunday, there could be a severe weather
threat developing across the western third of the CWA by early
Sunday evening, where a surface frontal boundary (inverted sfc
trof?) is forecast to be. Along the boundary, CAPE over 1000J/kg and
deep layer shear over 40 knots is currently forecast. So, initial
indicators for strong to severe storms are there. Previously
mentioned, there will be a bit of thermal capping to overcome
though, for storms to initiate.

From Sunday through Friday, the upper level flow pattern over the
CWA is an active west-southwest progressive pattern for the most
part. Precipitation chances appear to line up appx every 36 to 48
hours. After Sunday/Sunday night chances (20 to 60 percent), the
best chances for rain right now appear to line up by Tuesday (25 to
50 percent) and Thursday/Thursday night (25 to 45 percent).

Depending on how strong the potential storm system is for
Tuesday/Tuesday night, wind gusts in excess of 30 mph may develop.
This will have to be monitored on future shifts for wind headline
potential.

With "climate normals" for the second half of May running generally
in the low to mid 70s for highs and mid 40s for lows, looking at the
majority of the extended temperature forecast showcasing readings a
little below normal (S.A. Table 850hpa thermal anomalies for NAEFS
and ECMWF). Sunday looks like it might be the warmest day in the out
periods. Then, the succession of low pressure systems, periods of
clouds and rain should help to suppress temperatures for much of the
rest of the period. Looking at probabilities for temperatures
falling to or below freezing during the period, right now it does
not appear that this is a threat. NBM box and whispers output shows
even values for low temperatures below the 25th percentile,
presently are not much colder than ~40 degrees.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
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Issued at 624 PM CDT Fri May 17 2024

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are expected except in the vicinity of
thunderstorms that will affect KMBG and KABR this evening.
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&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&

$$

UPDATE...Wise
SHORT TERM...KF
LONG TERM...Dorn
AVIATION...Wise