186
FXUS63 KABR 261120 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
620 AM CDT Sat Apr 26 2025

.KEY MESSAGES...

- Showers and thunderstorms expected across the area into Monday.

- Severe weather threat includes a Marginal Risk (1 out of 5) increasing
  to Slight Risk (2 out of 5) for Sunday evening through Monday
  afternoon. The risk for severe weather migrates into Minnesota
  by late afternoon Monday.

&&

.SHORT TERM /TODAY THROUGH SUNDAY AFTERNOON/...
Issued at 321 AM CDT Sat Apr 26 2025

Cloud cover under the ridge will help keep temperatures around or
slightly below average today. Moisture will surge north today on
southerly return flow as the sfc high shifts east. Some spotty
showers have developed on the warm side of this moisture and are
expected to continue through the day. A 35 to 40 kt llj develops by
21z and may interact with increasing shortwave flow in the upper
ridge this evening setting the stage for a few isolated strong to
severe thunderstorms. This activity would be co-located with the mid
level moisture so likely east of the James Valley after sunset.

On Sunday, there`s a break in the morning. A Colorado low begins to
move into the Plains late Sunday afternoon. Upper level energy
increases and converges with warm sector air ahead of the low after
21z Sunday. There is a marginal risk (1 out of 5) for severe storms
across the forecast area for this time period.

&&

.LONG TERM /SUNDAY EVENING THROUGH FRIDAY/...
Issued at 321 AM CDT Sat Apr 26 2025

Opening Sunday evening/overnight, an elongated lee/surface low is
situated up across the High Plains with strong south/southeast low
level flow across the eastern Dakotas/western Minnesota. This will
result in a near continuous link to Gulf moisture and PWATS
increasing to two standard deviations above climo. The GFS shows by
06Z Monday, the low level jet across the Central Plains terminates
across eastern South Dakota, providing a hint at the location for
elevated ascent as the low tracks into central South Dakota. MUCAPE
values are close to 3K in the NAM and closer to 2K/1500j/kg in the
GFS. 0-6km shear within this instability is 35-55kts, so storms that
persist from western SD/NE or those that develop later along the mid-
level warm advection nose will be presented with a favorable shear
environment to potentially continue the severe weather threat,
though with stabilizing conditions overnight in the low levels, that
pretty much leaves us with a primarily hail/heavy rain threat as
flow aloft is unidirectional from the south southwest.

As the system continues east through the course of Monday morning,
so goes the area of instability, with a dry line and then cold front
stabilizing the surface. Deterministic guidance has the dry line to
the MN/SD state line by 18Z with westerly low level flow, with the
cold front in north central South Dakota.   TROWAL/wrap around
moisture follows the cold front, continuing chances for moisture
well into Monday.

The upper low/trough continues east with a ridge aloft folding down
into the region Tuesday while a cut off develops over the 4-Corners
region. That re-integrates for late Wednesday with a northern stream
trough moving overhead. That upper trough passage, and essentially a
decaying cold front will give us the next round of light showers.

As for temperatures, pretty mild with the warm air streaming up into
the region for the start of next week, but the cold front that
follows, with high pressure overhead Tuesday morning could send us
back to below freezing (NBM probability 20-60%). Thereafter its much
closer to average for the rest of the work week.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 615 AM CDT Sat Apr 26 2025

Terminals KABR,KATY,KPIR,KMBG

VFR conditions will deteriorate after 21z with MVFR cigs as a low
level jet develops across the region. Southerly winds gust to 30
kts today, drawing moisture into the area. Showers and/or isolated
thunderstorms may develop this evening in the llj.

&&

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

$$

SHORT TERM...20
LONG TERM...07
AVIATION...20