999
FXUS63 KABR 202000
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
300 PM CDT Tue May 20 2025

.KEY MESSAGES...

- Rain continues tonight and will diminish through Wednesday.
Additional rainfall amounts range from a couple hundredths over
central South Dakota, up to a half inch over far northeastern South
Dakota and western Minnesota.

- Below normal temperatures, by 15-25 degrees continue through
Wednesday before a slight warmup into the upper 50s and 60s for the
end of the week.

&&

.DISCUSSION...
Issued at 259 PM CDT Tue May 20 2025

As of 2pm widespread rain showers continue over northeastern SD into
west central MN in a counterclockwise fashion on the northwest side
of a mid level vort/low spinning over southern MN. There is also
spotty rain showers over central SD from an ongoing mid level low
currently spinning over the central parts of the state. Temps have
remained cool ranging in the mid 40s with low stratus.

Rap/water vapor imagery indicates this ongoing broad circulation
aloft over the Upper Midwest and Northern Plains with at least three
ongoing little vorts/lows (seen in water vapor imagery) that will
continue to spin around each other. They will congeal into a main
circulation over ND/SD/MN border this evening. As what the previous
shift said, this low will then "spaghettify" from northeastern SD
through northwestern ND overnight through Wednesday evening. Its
occluded surface low will be over IA/IL this evening as the inverted
trough stretches northwest from the low, mainly over the eastern
half of the state into MN tonight through Wednesday morning with
more of a surface troughing pattern over northern SD into ND. With
this setup at the surface and energy/lift aloft from the mid level
features, along with ongoing high RH`s, this results in continuing
rain showers over the CWA through Wednesday evening. CAMs indicate
the bulk of the precip falling over northern to northeastern SD into
west central MN through Wednesday where were the upper low lies and
best forcing. As the system falls apart aloft and surface system
shifts east, rain will diminish from southwest to northeast over the
CWA Wednesday with the last of the precip mainly east of the James
River by the evening. Additional rainfall from 00Z Wednesday to 00Z
Thursday is a few hundredths over south central SD to another 0.20
to 0.45" highest over far northeastern SD into west central MN.

Being on the backside of this system, CAA continues to
filter in as 850mb temps early Wednesday morning will range from 0
to +1C over the CWA! This is below the 10th percentile which is
+2.8C per ABR sounding climatology. NAM bufkit sounding at KMBG/KABR
still indicate the possibly of a rain/snow mix or a changeover to
snow as Ptype as soundings show lift and saturation within the DGZ
to the surface. NBM is still on board with this, mainly over north
central SD and southward to possibly Hyde/Hand Counties and possibly
the higher elevations of the Coteau, however, latest run has kept
ptype here as rain. EC meteograms also keep rain as ptype for
ATY/8D3 with soundings here showing surface temps should stay above
freezing. As of now, NBM min temps range from the mid to upper 30s
with about a 4-5 degree spread between the 25-75th percentile
(ranging from upper 20s to mid 30s). So, the caveat is with overall
cloud cover tonight and some wind, temps may not drop as low as NBM
suggests which would make the ptype stay all rain. As temps rise
through the morning, PTYPE will change back to rain if we do get a
little snow or mix. No accumulation is expected however higher
elevations of the Leola Hills may see a dusting at most!

Otherwise behind the system, a low amplitude ridge builds over the
area for the end of the week with a weaker trough setting up over
the western Conus as Clusters shows this. This trough will shift
northeast over the northern Rockies, becoming positive tilted, as a
ridge amplifies behind it over the western CONUS. Sunday into early
next week, we see differences in intensity of the position of these
features between the ensembles. High pressure will keep the area dry
Thursday with a lee low forming Friday which could bring the return
of pops (40-60%) mainly over central SD. Additional precip looks to
be possible for the Memorial Day weekend per shortwave aloft,
downwind of the ridge, and its surface system. As of now, severe
weather is not anticipated.

Temps will continue to be 20 to 25 degrees below average for
Wednesday ranging in the mid to upper 40s to mid 50s. EC EFI shows
values between -0.8 to -0.9 with a SOT of zero over much of the CWA
for MaxT. Patchy to areas of frost is possible mainly along and west
of the Mo river early Thursday morning due to clearing skies and
light winds and temps in the low to mid 30s here. Clouds will limit
frost chances further east. It will finally warm up a bit Thursday
into the upper 50s to the mid 60s. This is still about 5 to 10
degrees below average. Friday through Monday temps will range in the
upper 50s to the mid 60s which is still 5 to 15 degrees below
average.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1148 AM CDT Tue May 20 2025

Terminals KABR,KATY,KPIR,KMBG

Rain showers over the Northern Plains will linger through the TAF
period, bringing widespread IFR ceilings and MVFR visibilities.
Ceilings may occasionally dip down to LIFR conditions, coinciding
with the heaviest rain showers. Showers will be more intermittent
over KMBG and KPIR, so tempos have been put in as appropriate.
However where showers aren`t present, mist is still expected and
will reduce visibilities. During the early morning hours,
precipitation type may become an issue with rain showers potentially
becoming mixed with snow. Precipitation is expected to return to all
rain shortly after daybreak. Winds will remain out of the north to
northeast through the TAF period, occasionally gusting up to 25
knots.


&&

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

$$

DISCUSSION...MMM
AVIATION...BC