234
FXUS63 KABR 201513 AAB
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1013 AM CDT Tue May 20 2025

.KEY MESSAGES...

- Rain continues today and diminishes through Wednesday. Ranges
  run from a few tens of inches in south central South Dakota, to
  in excess of an inch across the northeast South Dakota and
  western Minnesota.


- Below normal temperatures, by 15-25 degrees, continue through
  Wednesday before we see a warming trend toward normal (upper 60s
  to mid 70s) for the weekend that lasts into next week.

&&

.UPDATE...
Issued at 1008 AM CDT Tue May 20 2025

Current radar continues to show widespread rain and fog/low
stratus from the James River Valley and eastward and more widely
scattered rain/drizzle over central SD as the upper low continues
to spin overhead and surface low over IA/MO. Current temps are
only in the lower to mid 40s with winds not as gusty as
yesterday, between 10 to 20 mph. I did decrease the pops a bit
over central SD (used HRRR/HREF), otherwise the forecast remains
on track.

UPDATE Issued at 621 AM CDT Tue May 20 2025

See below for an aviation forecast discussion for the 12Z TAFs.

&&

.SHORT TERM /TODAY THROUGH WEDNESDAY AFTERNOON/...
Issued at 311 AM CDT Tue May 20 2025

Scattered rain showers continue across much of the CWA early this
morning, with low stratus and pockets of fog. Winds are a bit
reduced in comparison to 24 hours ago as well.  The upper level low
sits overhead through the day and into tonight before
spaghettifying. During that time a shortwave gets pulled up from the
southeast, which will translate into another bout of rainfall
lifting into western Minnesota/eastern South Dakota by mid to late
morning. That will also enhance mid/low level cold advection, with
850mb temperatures dropping to something on the order of -4 to -1C
or nearly 2 standard deviations below climo. The result is
temperatures stalled or falling through the day, so low in fact
that profiles are leaning towards the introduction to snow as one
of the possible p-types overnight. HREF probability of actually
accumulating (rather than melting on contact) is about 50/50 for
far north central SD and the higher terrain of northeast SD so
wouldn`t be totally surprised if we get a few snapshots of a light
wet accumulation on elevated surfaces Wednesday morning. We do
finally start to see a western edge of stratus and light
precipitation in some of the CAMS coming towards the CWA from
southwest South Dakota late Wednesday. Overall QPF is still
running around an inch plus in the northeast to just a tenth or
two in south central South Dakota.

&&

.LONG TERM /WEDNESDAY EVENING THROUGH MONDAY/...
Issued at 311 AM CDT Tue May 20 2025

When the period opens Wednesday night, seeing the last of upper
level low pressure being sheared apart as upper level low pressure
deepens/widens across the eastern CONUS and upper level ridging
begins to overwhelm the middle of the CONUS. This large/blocking
upper low over the east will force any additional systems working in
from the west to either have to turn southeast and go around, or
undergo significant shearing aloft as it gets shunted northward into
an upper level ridge. Much of the period will see some form of
mid/upper level ridging (ensemble clusters heights analysis),
interrupted occasionally by these previously alluded-to systems. Per
ensemble clusters qpf analysis, an initial (weak) system looks to
try to bring some precipitation potential back into the CWA late
Thursday night and during the day Friday. Perhaps the
western/southwestern third of forecast zones may see a bit of
precipitation. An additional system still showing up in the models
is progged to move from the intermountain west out onto the plains
states over the weekend, with this CWA perhaps seeing some
precipitation chances Saturday night into Sunday. There are still
some timing/placement issues surrounding this scenario.

At the surface, high pressure is sitting over the region for much of
the forecast period. If the western forecast zones clear off
Wednesday night (currently guidance suggests this is a possibility),
when winds are light and variable, surface temperatures would be
cool enough to support some frost potential. As such, frost in the
grids continues to be advertised across the western forecast zones.
Otherwise, it appears there is enough insolation-based low level
warming each day in the extended that temperatures should be
clearing the well below normal hurdle by Thursday, and settling into
a period of near to slightly below normal temperatures for Friday
through next Tuesday.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 621 AM CDT Tue May 20 2025

Terminals KABR,KATY,KPIR,KMBG

IFR CIGS and intermittent MVFR VISBY in -SHRA/DZ will be the main
themes for the TAFS with little if any improvement expected for
the next 24 hours. Late in the TAF valid period, at KMBG, rain
p-type may mix with or briefly change over to light snow. Winds
are mainly northeast with occasional gusts up to 25 to 30 knots,
gradually shifting to the north.


&&

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

$$

UPDATE...MMM
SHORT TERM...07
LONG TERM...10
AVIATION...10