247
FXUS63 KABR 161726 AAC
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1226 PM CDT Tue Jul 16 2024

.KEY MESSAGES...

- Showers and thunderstorms will slide from northwest to southeast
  across the region through the first half of today. The overall
  severe weather threat is low, although areas south of US Highway
  14 are in a Marginal Risk (1 out of 5) for severe weather. The
  main threat will be 60 mph wind gusts and up to quarter sized
  hail. Precipitation should be winding down by early this
  evening.

- Below normal temperatures in the 70s to low 80s are anticipated
  today and Wednesday. Temperatures will continue to be at or
  below average for the end of the week into the weekend.

- 20 to 40% chance of precipitation late Thursday through Friday,
  with the highest chances over central SD.

&&

.UPDATE...
Issued at 1225 PM CDT Tue Jul 16 2024

See updated aviation discussion below.

UPDATE Issued at 1009 AM CDT Tue Jul 16 2024

An area of showers and thunderstorms currently over the far
southern part of the CWA will continue to drift south, and should
exit the area completely by midday or so. Still looking at the
potential for additional development over Jones and Lyman counties
later this afternoon or evening, but better chances will be to the
south of those counties. No changes made to winds or temperatures
at this time.

&&

.SHORT TERM /TODAY THROUGH WEDNESDAY AFTERNOON/...
Issued at 253 AM CDT Tue Jul 16 2024

At 2 AM CDT, much of the CWA is clear, but clouds were increasing
across the northern tier and far western counties as the PVA/WAA-
forced clouds/showers associated with the next area of low pressure
were working down out of North Dakota. Overall, surface pressure is
broad/baggy high pressure and surface winds are light and variable
as a result. Temperatures are cooling through the 60s, and in some
places are headed for the mid/upper 50s before the night is through.

Model guidance seems to have this current batch of showers working
down through eastern Montana and North Dakota and developing within
the Missouri River valley handled fairly well. These showers and
embedded weak thunderstorms should clear the southern edge of the
CWA by late morning/early afternoon, and depending on the amount of
clearing behind it, there could still be enough sunshine/daytime
heating to steepen low level lapse rates and generate a handful of
late day showers/storms (RAP model-based CAPE up to ~500J/kg in deep
layer shear potentially as high as 40 to 50 knots) across the
northern half of the CWA. Worth noting, the NAM model generates
something closer to 1500+J/kg CAPE out over portions of
central/south central South Dakota this afternoon/evening. Tough to
find a low level source of forcing out there for convection, but
thought the better instability/shear combo that potentially exists
out there into this evening was worth the mention. The timing of
today`s cloud-cover/shower-coverage makes the high temperature kinda
tricky. Seems like there should be plenty of time this afternoon for
some sunshine and temperature recovery, after being suppressed for
the first half of the day by clouds/precipitation. Based off the
latest HRRR-smoke output, there should be a bit of a reprieve from
smoke aloft today into tonight.

Pretty much all of the tonight/Wednesday forecast periods are dry as
more cool/dry Canada-sourced surface high pressure builds down over
the region, keeping winds light with a north/east component and
temperatures comfortably below normal in the 50s tonight and the 70s
to low 80s on Wednesday.

&&

.LONG TERM /WEDNESDAY EVENING THROUGH MONDAY/...
Issued at 253 AM CDT Tue Jul 16 2024

Main highlights for the long term will be below to around average
temperatures through early next week with occasional chances of
moisture. Not much has changed to the overall pattern as Clusters
have a good handle and continue to show an amplified ridge and mid
level high from the Rockies and westward with a troughing pattern
over the eastern Midwest into the Northeastern part of the US for
the end of the week. To the north of this trough, a large mid level
low sits over eastern Canada. This puts the Northern Plains in
ongoing northwest flow aloft. By the weekend we see more of a rex
block pattern as a mid level low will move in over the northern
Pacific as the low over eastern Canada sinks a bit south then
southeast early next week, with not much movement in the ridge at
all. So expect northwest flow aloft through the start of the weekend
with mid level winds turning more northerly late Saturday into
Sunday through early next week.

A large area of high pressure will be over the Northern Plains and
upper Midwest Wednesday night through Thursday, keeping the region
dry. The high will shift southeast early Friday as a surface trough
sets up over the central/western Dakotas and westward over the lee
side of the Rockies. Within this area of low pressure, several weak
surface boundaries are noted. However, winds aloft will only range
between 20-30kts, so not a lot of upper level support. Latest NBM
indicates pops of 15-25%, keeping it fairy isolated around and west
of the Mo River early Friday. Diurnal heating and instability, along
with a slight shift eastward on surface features (and upper level
shortwave), pops range from 20-40%, with the highest pops over south
central SD Friday afternoon into the evening. Much of the action
looks to stay to our west early Friday and south of the CWA Friday
afternoon and evening. This moisture will continue to shift east
early Saturday with overall dry weather expected behind it.
Ensembles do indicate a few weak shortwaves/ongoing shortwave pulses
moving over the crest of the ridge and southeastward into the
Northern Plains this weekend into early next week. This could bring
a chance of precip aided by this and diurnal heating. NBM pops
remaining minimal and broad brushed across the CWA from 15-20%,
making confidence low at this point in time in outcome. With
dewpoints in the upper 50s to the lower 60s, creating a moist
environment, and afternoon instability, strong to severe storms are
not out of the question each afternoon. Nothing has been highlighted
by the SPC as confidence remains low at this time.

Return flow Thursday will bring in "warmer air" (over central SD)
with 850mb temps 13-15C with the coolest temps over the eastern CWA
,per the high, within this cooler air mass. Surface highs will range
in the upper 70s to the upper 80s, warmest around and west of the Mo
River. Temps over the eastern CWA look to be around 5 degrees below
average. Slightly cooler readings in the mid 80s around and west of
the Mo River with temps up to 10 degrees below average over parts of
central and northeastern SD. For the weekend into Monday, temps will
be at or below normal, with highs in the upper 70s to the mid 80s
over the CWA. We do start to see warmer temps Tuesday over central
SD as the ridge could move slightly east with highs reaching the
upper 80s with warmer 850mb temps.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1225 PM CDT Tue Jul 16 2024

Terminals KABR,KATY,KPIR,KMBG

Will see scattered showers continue across mainly the southwestern
part of the area through the afternoon hours. Otherwise, VFR
conditions will prevail through the TAF period.

&&

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

$$

UPDATE...Parkin
SHORT TERM...Dorn
LONG TERM...MMM
AVIATION...Parkin