430
FXUS63 KABR 120839 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
339 AM CDT Mon Aug 12 2024

.KEY MESSAGES...

- Below average temperatures (5 to 10 degrees) continue today.

- 15 to 25 percent chance of showers and thunderstorms across
  central South Dakota for Tuesday.

- Additional chances for moisture in the form of thunderstorms run
  from late Tuesday through early Thursday. Severe storm potential
  looks limited to Wednesday with a marginal risk (1 out of 5).

&&

.UPDATE...
Issued at 339 AM CDT Mon Aug 12 2024

Added patchy fog wording for areas along and east of the Missouri
River as webcams around the area show some fog with several obs
at or close to 100% humidity. This is through 14Z.


&&

.SHORT TERM /TODAY THROUGH TUESDAY AFTERNOON/...
Issued at 247 AM CDT Mon Aug 12 2024

As of 2AM satellite imagery indicates scattered high clouds moving
eastward over northeastern SD through ND with lower clouds over
central SD. Temps are ranging in the upper 50s to the lower 60s.
Short term models indicate the shortwave, and its surface low,
continuing to push southeast and will be over the central Midwest
around 12Z this morning, leaving northwest flow across the Northern
Plains. Behind this low, a high pressure system will position itself
over the eastern Dakotas/western MN this morning and over central MN
this afternoon, keeping the area dry. Few of the CAMs do show
speckles of precip here and there but left that out of the grids for
now. Aloft, a ridge will build slightly over the Rockies/western
Plains through the day. To the west of the ridge, a shortwave
positions itself over the Pacific Northwest as a deeper trough moves
in off the Pacific, over the western CONUS. These waves look to come
together tonight into early Tuesday and shift east. This will also
push the ridge slightly east with the axis over much of the midwest
to the Northern Plains by midday Tuesday, as it amplifies a bit.
This will turn our winds aloft more zonal/slight northwest flow.
Latest HRRR smoke model looks to indicate another plume of smoke
aloft returning this evening over central SD, pushing east overnight.

By this evening into Tuesday, RAP indicates a lee side surface
trough/weak frontal boundary setting up over the western Dakotas as
as several shortwaves will track upwind and along the axis of the
ridge. Return flow will help 1000-500mb RH increase over central SD
and help dewpoints rise back into the lower 60s across the CWA. CAMs
indicates a few rounds of very spotty precip, in the form of showers
and thunderstorms, over central SD (with disagreement on location
and timing between the models) with NBM being very aggressive on
pops. So low confidence on exact outcome for now. For grids I went
with more of the CAMs/HREF solutions for pops which range from 20-
25% over central SD. As of now the SPC marginal risk stays to our
west.

Highs will range in the 70s to the lower 80s across the CWA, which
is still 5 to 10 degrees below average. Overnight lows will range in
the upper 50s to the lower 60s. Warmer for Tuesday with the ridge,
with highs in the upper 70s to the upper 80s, warmest around and
west river.

&&

.LONG TERM /TUESDAY EVENING THROUGH SUNDAY/...
Issued at 247 AM CDT Mon Aug 12 2024

From a 24 hours ago perspective, looks like a slight slowdown in
wave timing for late Tuesday and Wednesday. The southwest flow
regime doesn`t get into central SD counties until Tuesday night at
which point we`ll have about 1000j/kg MUCAPE and weak shear. NAM
PWATs are up over 1.5 inches with the NAEFS up closer to 1.75 (2
standard deviations above climo), with the GFS depicting a 30kt low
level jet overhead enhancing the moisture feed. NAM BUFKIT profiles
are essentially moist adiabatic, which should be expected this time
of year when you mix low level jet moisture with a plume of mixed
over Desert Southwest monsoon moisture aloft. Unsure about the NBM
60+ probability POP coverage for just about the entire CWA with the
lee low still out by Rapid City drifting towards south central SD by
mid day Wednesday, providing limited surface convergence even into
the afternoon particularly east river, but rainfall rates from any
storms that do develop should benefit from this high moisture
content and slow storm motion.  As we get into the day Thursday, the
weak surface trough has moved over the eastern CWA and should be out
of the CWA by the time peak heating has destabilized the low levels.
Profiles dry a little but remain essentially moist adiabatic with
light winds aloft.

Thursday night/Friday an upper ridge builds to the west but fails to
proceed east very rapidly, placing us in a northwest flow regime.
NBM POP trends continue to come down with better deterministic run
consistency and placement of features that are generally unconducive
to thunderstorm generation this time of year.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1219 AM CDT Mon Aug 12 2024

Terminals KABR,KATY,KPIR,KMBG

MVFR conditions currently at KPIR as satellite imagery indicates
scattered to overcast lower clouds over south central SD. Patchy
fog could be possible here through the early morning hours. KPIR
expected to become VFR with possible MVFR conditions for a few
hours late morning. Otherwise, VFR conditons prevail for the rest
of the TAF sites through the forecast period.


&&

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

$$

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