352
FXUS63 KABR 230918
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
418 AM CDT Thu May 23 2024

.KEY MESSAGES...

- A slight risk for severe storms (2 out of 5) this afternoon.
  Threats include damaging wind (~60-70 mph), large hail (up around
  the size of golfballs) as well as a low tornado probability.

- Showers and weak storms continue into Friday (30-70%) with
  rain chances diminishing southwest to northeast through Friday evening.
  The unsettled weather pattern continues with additional chances
  of moisture Saturday into Monday (30-50%).

- Temperature will be around or slightly below average Saturday-Monday,
  in the upper 60s to lower 70s.

&&

.SHORT TERM /TODAY THROUGH FRIDAY AFTERNOON/...
Issued at 412 AM CDT Thu May 23 2024

Main focus is severe weather potential this afternoon/evening.
Right now we are seeing widespread light returns associated with mid
level warm advection/elevated convection. As the day progresses, low
pressure develops in central South Dakota, with a dry line extending
to the south, and a warm front along the ND state line. The focus
area for CAPE is between the Missouri and James valleys where CAMS
generate a line of convection around the Pierre area and north
associated with that dry line, with more isolated cells scattered
across the forecast area near the warm front. NAM MLCAPE peaks
around 1500-3000j/kg along this axis where 0-6kt shear is between
30 and 50kts with the 0-6km shear gradient running from south to
north respectively. This ribbon of higher uncapped instability
depicted within the NAM is fairly close to those in the
CAMS...which generally wiggle between the James and Mo valleys.
BUFKIT profiles show a nice looping hodograph with strong
unidirectional shear above the mixed layer and 60-70kts of flow at
300mb. NAM DCAPE also runs about 1000j/kg. So looking at
storms with occasional supercell characteristics and wind and
large hail threats. Everything pushes east in the evening though
weak convection continues under the low through the late evening
with wrap around showers into Friday morning across the northern
tier of the CWA.

On the backside of the system, 1/2km winds increase to 40kts with a
8-10mb pressure bubble coming in from the west. Mixed winds for
Philip top out at 40kts, however for Pierre its only in the 30s so
some question how well these winds mix down and whether we will
see advisory criteria. CAM ensembles only show around a 10-15%
probability of exceeding 45mph so for now will hold off on any
wind related headlines late in the short term.

&&

.LONG TERM /FRIDAY EVENING THROUGH WEDNESDAY/...
Issued at 412 AM CDT Thu May 23 2024

Clusters agree on a troughing pattern continuing over the western
CONUS (which has moved slightly east since Friday) as the shortwave
departs the area and tracks northeast, with the axis over northern
MN/southwestern Ontario (along with the 850mb/surface low) around
12Z Saturday. An active pattern continues as another shortwave
swings down from western Canada and over the Pacific Northwest
during this time as well. Little bit of a difference in the strength
of the trough between the Clusters. Through the day into Sunday this
wave pushes east/southeast with the southern trough pushing east.
Ensembles indicate these system merge together over the Rockies
~Sunday morning. Sunday evening into Monday this wave will push east
but quite a bit of variability between the Clusters on the location
of the axis and strength. Clusters do agree on an amplifying ridge
over the western CONUS, creating a +PNA pattern, early next week.
This ridge moves east and over much of the central parts of the
country midweek or so. Again, timing and intensity vary between the
ensembles.

Behind this departing low, models do show some lingering moisture
with EC showing this only over extreme northeastern SD/western MN.
Latest NBM indicates this well with 15-20% pops in this area between
00Z-06Z Saturday. With this next wave over the Rockies Saturday
morning, the ensembles indicate we could see light moisture from
this across central to south central SD (NBM pops 20-30%) then
spreading northeast across the CWA through the afternoon and evening
as a Colorado low forms on the lee side of the Rockies from 850mb to
the surface. NBM pops of 20-40%, highest over south central SD, are
forecasted Saturday afternoon and evening. Sunday this low will track
east then northeast. It appears this low will track further away
from our CWA than the previous two but still could bring moisture to
the area. Another system will form over the northern Rockies at this
time as well which could bring additional across parts of the
central and western CWA. NBM pops Sunday will range 30-50% with
chances decreasing west to east through Monday. Dry weather then
expected Tuesday though midweek as the low departs and ridge moves
in, along with a surface high. Possible moisture could return for the
end of the week with another low/shortwave.

Cool temps forecasted Friday night into Saturday morning as the high
moves in with temps dipping into the upper 30s to the lower 40s.
Highs for the weekend will be at or below average ranging in the
upper 60s to the lower 70s. Temps warm back into the 70s/80s midweek
with the ridge overhead.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1223 AM CDT Thu May 23 2024

Terminals KABR,KATY,KPIR,KMBG

VFR conditions will prevail across the area overnight and through
the day Thursday. South to southwesterly winds will increase into
the 15 to 30 knot range late Thursday morning and Thursday
afternoon. There is a chance for thunderstorms to affect the entire
area Thursday evening. Periods of MVFR vsbys will be possible with
the thunderstorms.


&&

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

$$

SHORT TERM...Connelly
LONG TERM...MMM
AVIATION...Connelly