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152
FXUS63 KABR 200527 AAC
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1227 AM CDT Fri Sep 20 2024

.KEY MESSAGES...

- Windy conditions are expected again Saturday morning into the
  afternoon, with peak gusts reaching over 30 mph in areas west of
  the James River Valley.

- Near normal to slightly below normal temperatures return Saturday
  and continue into next week.

&&

.UPDATE...
-- Changed Discussion --
Issued at 1224 AM CDT Fri Sep 20 2024

See updated aviation discussion below.

UPDATE Issued at 852 PM CDT Thu Sep 19 2024

Winds have subsided across the region as skies remain clear for
the overnight hours. With the continued light winds overnight and
clear skies, did knock just a couple degrees off low temps for
some locations, closer to MET/MAV guidance. Otherwise, forecast is
on track for the overnight hours.
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&&

.SHORT TERM /THIS EVENING THROUGH FRIDAY NIGHT/...
Issued at 149 PM CDT Thu Sep 19 2024

The current surface weather map shows the low over much of Manitoba
with the cold front extending across eastern MN and a secondary
trough over far eastern SD/west central MN. Yet another cold front
was set up from the low through northern MT. The strong low in
Manitoba Canada is stacked up through 500mb, with plenty of clouds
extending through much of ND and our north central SD counties. High
pressure building across NE and southwestern SD is allowing the
tight pressure gradient, that had been overhead much of the day, to
relax. Winds will continue to slowly diminish through the overnight
hours. Much of the cloud cover will diminish with the loss of
daytime heating.

Expect the clear sky to continue through the day Friday as the
surface high continues to track east across NE and extend a ridge
over eastern SD and southwestern MN from 12-18Z before exiting east.
Behind the ridge, warmer air will surge back north with temperatures
topping out in the 80s. A few 90 degree readings will be possible
over our southwestern counties as 850mb temperatures rise in the 21-
16C range. This will also be where winds out of the south will
increase to around 10-20mph with gusts 25-30mph in the afternoon.
Relative humidity values will be a little lower, in the 20-25% range
for much of the area west of the MO River. Winds just above the
surface will be on the increase across the entire forecast area
Friday night, with an inversion limiting most of these winds from
making it to the surface. While mainly dry weather will continue,
there is a 20% chance of showers and thunderstorms Friday night over
far northeastern SD/west central MN associated with a strong cold
front and warm air advection out ahead of it. This is the same cold
front currently set up over northern MT that will be enhanced by
another area of low pressure surging northeast along it across
eastern SD.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 149 PM CDT Thu Sep 19 2024

The clusters and deterministic models are fairly consistent with
moving a 500mb low out of Colorado on Saturday which then interacts
with a trough to the north over Manitoba. This interaction causes
the associated jet streaks to push against each other, creating
zonal flow over SD into Saturday evening. With this zonal flow, the
mid-levels see drier air over northern SD and moist air over
southern SD. The surface low beneath the Manitoba trough will not be
moving as far south as previous models suggested, causing the front
attached to surface low to move east of SD before Saturday morning.
With the lack of mid-level moisture, as well as lacking a source of
lift, precipitation chances in northern central and eastern SD have
decreased below 15% for Saturday. The main hazard being looked at
now is the chance for strong winds in the counties west of the James
River Valley. Models display stronger lapse rates occurring Saturday
morning into the afternoon, which indicates that there could be
stronger 0.5km winds mixing down to the surface. The clusters show a
similar story, with wind gusts around 30 mph noted over the same
area. Additionally, the NBM displays strong wind gusts at the same
time, west of the James River Valley, potently reaching over 33mph.

While the front will not help with the development of precipitation,
it does help to move colder air into SD. The CAA in the mid-levels
and at the surface behind the front will help to decrease
temperatures this weekend. This will lead to maximum temperatures
dropping down 5 to 10 degrees below normal on Sunday.

As a ridge over the Pacific Northwest starts to move east after the
weekend, drier air in the mid-levels will be advected over SD from
the north/northwest flow. This lack of mid-level moisture greatly
decreases the chances of precipitation next week. Additionally,
occasional pockets of mid-level WAA will start to warm temperatures
a bit at the surface during the week, allowing temperatures to be
around normal for this time of the year.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
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Issued at 1224 AM CDT Fri Sep 20 2024

Terminals KABR,KATY,KPIR,KMBG

VFR conditions will prevail across the area overnight and through
the day Friday. Low-level wind shear is forecast over KABR
through the overnight hours, and to develop over the KATY region
late in the TAF period.
-- End Changed Discussion --

&&

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

$$

UPDATE...TMT
SHORT TERM...KF
LONG TERM...Vernon
AVIATION...Parkin