874
FXUS63 KABR 260208 AAB
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
908 PM CDT Fri Apr 25 2025

.KEY MESSAGES...

- Rain chances increase through the weekend (40 to 70 percent)
  with the highest chances east of the James Valley Saturday
  night.

- The next chance of a quarter inch of rain (50 to 90%) will be
  for Sunday night into Monday. There is a marginal risk (level 1
  out of 5) for severe storms Sunday night. There is a 15% chance
  for severe storms east of the James River Monday.

&&

.UPDATE...
Issued at 901 PM CDT Fri Apr 25 2025

No changes planned to the rest of the tonight period. Light
returns noted developing across parts of southwest and south
central South Dakota where, currently, the best low/mid-level
moisture and mid-level WAA is in place. Maybe some sprinkles or
very light rain-shower potential off and on overnight across parts
of central/north-central South Dakota as the leading edge of this
moisture/warm air advection advects up across the region.

UPDATE Issued at 618 PM CDT Fri Apr 25 2025

See below for an aviation forecast discussion for the 00Z TAFs.

&&

.SHORT TERM /THIS EVENING THROUGH SATURDAY NIGHT/...
Issued at 315 PM CDT Fri Apr 25 2025

Upper level ridging will build over the CWA tonight and Saturday,
then gets shunted slightly to the east Saturday night, with some
shortwave energy riding up the west side of it and over the Northern
Plains.

At the surface, high pressure will remain dominant over the region
tonight. The high will slide east of the area on Saturday, with the
CWA becoming situated between it and low pressure over the Rockies.
A tightening pressure gradient will allow southerly winds to
increase into the 20 to 35 mph range on Saturday, with the highest
gusts expected to occur across central South Dakota. This southerly
flow will begin to usher moisture northward into the region, and
cannot rule out a few rain showers during the day. These chances
will increase across eastern South Dakota and west central Minnesota
Saturday night as a 35 to 45 knot low level jet develops in
conjunction with the aforementioned upper level energy and
increasing moisture. Instability will be fairly lacking, but 35 to
45 knots of 0-6km bulk shear may be enough to result in a few
thunderstorms Saturday evening, mainly east of the James River
Valley. At this time, no severe weather is anticipated.

Low temperatures tonight will be in the upper 30s to lower 40s. High
temperatures on Saturday will be in the mid 50s to lower 60s. Lows
Saturday night will be in the mid to upper 40s.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 315 PM CDT Fri Apr 25 2025

A surface low pressure starts to move northeast over CO and towards
SD Sunday, with it looking to move over the state during the late
evening and through the day Monday. The location and timing of the
surface low will be a big factor in the chance for severe storms to
develop Sunday and Monday. The models are suggesting CAPE values of
500+ J/kg over western and central SD Sunday afternoon/evening
overnight into Monday, with potentially higher amounts in locations.
There is also a lot of warm, moist air moving into the warm sector
of the surface low that reaches into SD. As a boundary moves into
this area of instability and warm moist air, storms have the
potential to develop into supercells. The biggest hurdle the storms
need to overcome will be the cap, and the CIN values in models vary
quite a lot. NAM CIN values are a lot lower than the ECMWF and the
clusters. Sunday evening, the CIN values drop slightly and then they
drop again Monday afternoon. If the surface low and boundary move
faster, then the storms will be trying to develop in an unfavorable
environment for severe storms. However, if the low and boundary move
slower, then the storms have a higher potential to develop and
become severe in a more favorable environment.

Even if severe thunderstorms dont develop, there is still the
chance for rain. The clusters show a 30-70% chance for a half inch
of rainfall by Monday evening, mainly north of highway 212.
Additionally, there is currently a 30-50% chance for more than three
quarters inch of rain over the northern SD counties, though this
will also depend on the location of the surface low. Winds will also
be stronger and a threat as a low-level jet and higher lapse rates
develop over central and eastern SD Sunday afternoon, as well as
Monday afternoon behind the surface low as cold air advects into
central and eastern SD. There is the potential for widespread gusts
over 25kts and gusts of 30+ kts over the James River Valley Sunday.
Additionally, there is the potential for gusts above 30kts west of
the Prairie Coteau Monday afternoon.

Tuesday morning, a surface high pressure moves over central and
eastern SD, which keeps the precipitation out of the area through
Wednesday. After that, there is the potential for another surface
low to move through SD Thursday along with an upper-level trough
moving through the state. However, there is a lot of variability in
the models as to the location of this low and the precipitation that
could come along with it. Winds and gusts after Monday look to calm
down slightly and stay below 25kts through the long term forecast
period.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 618 PM CDT Fri Apr 25 2025

Terminals KABR,KATY,KPIR,KMBG

VFR conditions will prevail across the area through Saturday
afternoon. Southeasterly winds will increase into the 15 to 30
knot range Saturday morning.

&&

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

$$

UPDATE...10
SHORT TERM...Parkin
LONG TERM...12
AVIATION...10