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797
FXUS63 KABR 210511
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
1211 AM CDT Tue May 21 2024

.KEY MESSAGES...

- Mainly rain showers possible through late this evening (20-40%).

- A strong system will spread a swath of precipitation (40-100%)
  across the forecast area late tonight into early Wednesday.
  Total rainfall amounts could range from a few hundredths of an
  inch across north central SD up to 1 to 2 inches over far
  northeastern SD into west central MN.

- Another shot at moisture is possible during the Thursday -
  Friday timeframe.

- Except for a brief potential warm up on Thursday, generally at
  or below normal temperatures are expected for the next several
  days.

&&

.UPDATE...
Issued at 901 PM CDT Mon May 20 2024

Radar continues to show areas of light to moderate rain moving
northeast across portions of the CWA. Updated PoPs to better align
with radar trends. Much larger area of rainfall upstream (to the
south/southwest) that will eventually move in later tonight and
overspread at least the southern and eastern CWA through tomorrow
morning.

&&

.SHORT TERM /THIS EVENING THROUGH TUESDAY NIGHT/...
Issued at 205 PM CDT Mon May 20 2024

At 2 PM CDT, skies were partly to mostly cloudy, and a band of
southwest to northeast-oriented rain showers were extending from
south central South Dakota up into northeast South Dakota. The whole
line was slowly translating east across the region. North-northwest
winds of 10 to 20 mph with gusts up to 30 mph have been advecting
cooler air into the CWA today. That and the clouds and rain have
kept the lid on temperatures, with most of the CWA registering
readings in the 50s and 60s.

Until the deformation zone associated with the low pressure system
out over the Rockies begins to set up late tonight/early Tuesday
morning, the mid-level baroclinic zone (the cause of the current
banded rain showers) in place over the region is expected to remain
active through late this evening, with one or more bands of rain
(perhaps some embedded thunder) forecast to set up across the region
and gradually work east-northeast. But, once the deformation zone
sets up, periods of moderate to heavy rainfall will be possible from
late tonight through late Tuesday night. It still looks like there
will be a notable gradient in the amount of precipitation the CWA
receives with this next low pressure system. SuperEnsemble plumes
indicate less than a half inch of qpf is appropriate at KMBG. But,
from KPIR eastward to KETH, the plumes trend considerably up, with
the mean at KABR just over an inch and close to two-and-a-half
inches at KETH by Tuesday night. Not sure why the qpf guidance for
the forecast continues to remain on the conservative side, but at
least the amounts have been increased some over what the mid-shift
was given to use as a starting point.

Plenty of clouds and rain around on Tuesday, with cloudiness
expected to stick around Tuesday night. Should yield high
temperatures only in the 50s across much of the CWA. But, the
cloudiness Tuesday night should help "hold in the heat" and keep
temperatures from falling below 40F degrees.

Wind speed/gusts are also a concern on Tuesday. Soundings and
ensemble guidance indicate there is a strong signal for wind
advisory strength conditions across the eastern third of the CWA
(Prairie Coteau eastward into Minnesota) by the time late Tuesday
morning rolls around, persisting into Tuesday evening before the
pressure gradient relaxes and winds begin to diminish. Issued a Wind
Advisory, as such, for far northeast South Dakota and west central
Minnesota.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 205 PM CDT Mon May 20 2024

The forecast period begins on Wednesday with a surface low pressure
system departing the region to the northwest, with perhaps light
showers over the far NE corner of the CWA. Most of Wednesday and
through the first half of Thursday appears to be mostly dry, with
perhaps some WAA pcpn Thursday morning. The WAA should produce
seasonal temperatures with highs in the 70s on Thursday. An area of
low pressure and associated frontal boundary should cross the region
Thursday afternoon through Friday morning, bringing the potential
for widespread showers and thunderstorms. Models and ensembles vary
some, with a mix of a drier or wetter storm passage. It does appear
as though North Dakota may see the heaviest pcpn. The storm system
should depart the region sometime of Friday, leaving behind a period
of dry conditions until perhaps Saturday night, or moreso Sunday
afternoon. This is when another storm system should cross the
region, bringing more showers and storms. Timing and placement of
the late weekend storm is still a little unclear, causing more of a
broad brush approach to pops Sunday through Monday.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
-- Changed Discussion --
Issued at 1211 AM CDT Tue May 21 2024

Terminals KABR,KATY,KPIR,KMBG

CIGs will gradually lower to MVFR/IFR into Tuesday morning as
RA/SHRA expand across the region overnight. In areas of heavier
precipitation, MVFR/IFR VSBY is possible. Strong northerly surface
wind gusts around 40 knots or higher are possible at KATY by Tuesday
afternoon and early evening.
-- End Changed Discussion --

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
SD...Wind Advisory from 11 AM this morning to 11 PM CDT this evening
     for SDZ007-008-011-019>023.

MN...Wind Advisory from 11 AM this morning to 11 PM CDT this evening
     for MNZ039-046.
-- End Changed Discussion --

&&

$$

UPDATE...TMT
SHORT TERM...Dorn
LONG TERM...SD
AVIATION...Connelly