055
FXUS63 KABR 211943
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
243 PM CDT Sat Sep 21 2024

.KEY MESSAGES...

- Near normal to slightly below normal temperatures through early
  next week. Above normal temperatures return Wednesday and stay
  around for the rest of the week.

&&

.SHORT TERM /THIS EVENING THROUGH SUNDAY NIGHT/...
Issued at 242 PM CDT Sat Sep 21 2024

Gusty northwest winds will diminish quickly this evening as sfc high
pressure builds in from the northwest. The upper trough will keep
temperatures seasonable through Sunday. Pretty quiet short term
forecast with the high keeping conditions dry, as well. The one
thing of note will be low temperatures. There is a high spread among
ensemble members, but with dewpoints in the upper 30s and 40s, lows
could tank quickly tonight as winds die down. Clear skies will help
support the radiational cooling. Could potentially see more areas
than just north central drop into the 30s tonight. A slightly
stronger pressure gradient Sunday night will likely keep winds up
just enough to stave off the best cooling, especially with the upper
ridge and some waa transitioning in from the west.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 242 PM CDT Sat Sep 21 2024

An upper-level jet, positioned along the eastern side of a ridge
over the Pacific Northwest, pushes east over western and central SD
late Monday evening. Around the same time, mid-level CAA moves into
western SD and continues to move southeast until Tuesday afternoon.
This CAA is located along a surface cold front moving across SD late
Monday evening into Tuesday. Additionally, the mid-levels have a
pocket of dry air that moves in just before the cold front. Because
of this dry air, the cold front will have very little chance to
develop precipitation as it moves through the state. The models are
also suggesting that stronger winds could occur along and behind the
front, with 0.5km model winds showing 30+ kts winds and stronger
lapse rates mixing these winds down to the surface. On the other
hand, ensembles do not show these winds occurring. With these
differences, more details will be investigate in future ensemble and
model runs to determine what will happen.

Models begin to differ from each other Wednesday morning. This
starts in the upper levels where the ECMWF and Canadian models
depict the ridge moving east, cutting off an area of low pressure
from the trough in front of the ridge. The cut-off lows stay over OK
and KS through the rest of the forecast period, pushing the high
pressure to the north, and expanding the influence of the ridge. The
GFS on the other hand does not have this happening, which causes the
ridge to appear weaker and faster. This contrast between models
creates a difference in flow patterns, as well as mid-level moisture
over SD. The GFS tends to move more mid-level moisture through SD
with north/northwest flow, while the Canadian and ECMWF show drier
air moving in from northeast/east flow. By Thursday morning, all the
models have dry air in the mid-levels over SD. With the dry air
aloft, there is a very low chance for precipitation to occur during
the rest of the long-term period. While they do vary on the timing,
the models have mid-level WAA occurring Wednesday into Thursday and
then some CAA happening Friday into Saturday. This is helping
surface temperatures warm up Wednesday onward, with temperatures
being 10 to 15 degrees above normal for this time of the year. With
the WAA occurring, Thursday will see the warmest temperatures, and a
slight decrease Friday and Saturday from the CAA.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1209 PM CDT Sat Sep 21 2024

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are expected through Sunday morning. Gusty
northwest winds will diminish quickly this evening.


&&

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

$$

SHORT TERM...Wise
LONG TERM...Vernon
AVIATION...Wise