715
FXUS63 KABR 101117 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
617 AM CDT Thu Oct 10 2024

.KEY MESSAGES...

- A mostly light concentration of smoke aloft to continue across
  the Dakotas today, gradually diminishing on Friday.

- High to Very High fire danger today across north central South
  Dakota where southwest wind gusts out ahead of a cold frontal
  passage are expected to reach as high as 25 mph at the same time
  that relative humidity will be less than 20 percent.

- Dry conditions are expected to continue through the weekend.
  Temperatures peak today with highs in the mid to upper 80s,
  including potentially as high as the low 90s for some locations.
  These temperatures are about 20 to 30 degrees above normal.

- Temperatures are forecast to gradually cool from Friday through
  early next week, and confidence remains moderate to high on
  readings cold enough to end the growing season early next week.

&&

.UPDATE...
Issued at 613 AM CDT Thu Oct 10 2024

See below for an aviation forecast discussion for the 12Z TAFs.

&&

.SHORT TERM /TODAY THROUGH FRIDAY AFTERNOON/...
Issued at 405 AM CDT Thu Oct 10 2024

At 3 AM CDT, skies are clear. If winds aren`t light and variable,
they have a southerly component generally under 10 mph. Temperatures
have cooled into the 40s and 50s for most areas. A downslope wind
event is happening off the Prairie Coteau, as Sisseton is showing a
southwest wind and a temperature of 66 degrees. The HRRR Smoke model
also indicates that a layer of low concentration smoke aloft
persists over the CWA this morning.

Similar to yesterday`s guidance, deterministic and ensemble-powered
guidance this morning highlights a cold frontal passage today into
tonight, moving through north central South Dakota during peak
heating/mixing today. Prior to fropa, conditions across portions of
north central South Dakota will come close to meeting Red Flag
Warning criteria. Confidence in this happening is not overly high,
given that southwesterly wind gusts are expected to be marginal, at
best, with gusts up to 25 mph being possible at times. To raise the
bar of awareness, a Special Weather Statement (SPS) has been issued
highlighting the high to very high fire danger that today`s weather
conditions will create, in lieu of issuing a fire weather headline.
The HREF also shows a gradual increase in high cirrus clouds today.
However, the amount of dry warm air in place today on southwest
mixing layer winds out ahead of an approaching cold front is
expected to cause high temperatures to over-achieve some, in terms
of what guidance supports (mostly mid 80s). Portions of the CWA have
the potential of seeing high temperatures bump up into the low 90s.

Notable low level CAA follows the frontal passage, which will
continue to surge southeast across the rest of the CWA this evening
into the early overnight hours, with post-frontal northwest winds
gusting to, at least, 25 to 35 mph. HREF cloud progs suggest
overcast coverage of mid/high clouds over the CWA tonight, which
should partially offset the CAA on these northwest winds. Surface
high pressure will also be building down across the CWA tonight and
during the day Friday. Todays 925hpa temperatures in the mid to
upper 20s celsius will cool down to ~+10C to +16C on Friday, which
translates into temperatures on Friday being about 20 to 25F degrees
cooler than today.

&&

.LONG TERM /FRIDAY EVENING THROUGH WEDNESDAY/...
Issued at 405 AM CDT Thu Oct 10 2024

Starting out the long term, ensembles have a good handle on a couple
of shortwaves merging together over Canada and riding southeastward
down the ridge and over northeastern ND into MN Saturday night into
Sunday morning. At the surface, the high pressure system pushes
eastward as the surface low, associated with the shortwave, will
position itself over ND and the Canadian border by 12Z Saturday with
the cold front extending southwestward through western SD. Ahead of
the front, the CWA will be in WAA as winds at the surface will be
light out of the south/southeast. As the system tracks southeast,
the cold front will continue to pass over the CWA through the day
with models agreeing the exit of the front by the evening/early
night timeframe or so. Behind the system, an elongated high
(positioned in Canada) will be the dominant weather pattern Sunday
into Monday, with the high sinking southward and and over the
Northern Plains Tuesday. It then pushes southeast midweek as the
next possible shortwave and low move set up to our northwest for the
end of the week. The ridge will continue its path eastward (and
becoming more positive tilted as well) with differences between the
ensembles further out in time you go.

ENS is still trying to hold onto moisture skirting over northeastern
SD into west central MN Saturday morning (ahead of the low) with
GEFS/GEPS indicating nothing with models now all agreeing on the
moisture staying northeastward over ND/MN, closer to the center of
low, through Saturday evening. As a result NBM took out the 15%
chance that was over northeastern CWA. Otherwise, no indication of
moisture through at least the middle of next week. Steeper pressure
gradients behind the front, along with mixing, will lead to gustier
winds to reach the ground as several soundings suggest this over
north central to central SD during the afternoon hours/evening on
Saturday with the gustier winds spreading eastward over the CWA into
Sunday as the system tracks southeast. With collab we decided to use
a NBM/NBM90 blend to show for this potential. This leads to gusts of
25 to 30kts, highest over central SD and then over/along the Prairie
Coteau.

Temps will still range between 5 to 10 degrees above average
Saturday with highs in the mid to upper 60s to mid 70s with the NBM
25-75th spread being about 5 to 7 degrees. Sunday through Tuesday,
however, there is still a difference between the ensembles on 850
temps. For example, our coolest day looks to be Monday with 850mb
temps in the afternoon ranging from +1 to +10 GEFS and -1 to +6C
ENS. With this, Monday`s highs has a NBM spread of 9 to 12 degrees
with even more of a spread (13 to 20 degrees!!) on Tuesday. For
example, the spread for KABR Tuesday`s highs is upper 50s to the
lower 70s. Tuesday GEFS has the warmer air from the under the ridge
moving in faster than the EC, which keeps the cooler air around
longer. Latest NBM has warmed the lows for early next week a bit
with the 25-75th spread for Min Temps Monday morning ranging from 4-
6 degrees, with the greatest spread over our northwestern CWA. The
spread increases to 9-13 degrees Tuesday morning. So again, KABR
could be in the lower 20s or mid 30s. NBM probability of 32 degrees
and below is 8 to 90% Monday morning and 20-75% Tuesday, highest
over the James River Valley. Being on the southern side of the high
Monday morning and western side Tuesday morning, NBM25th percentile
could be what is observed. So medium to high confidence on the end
of the growing season for early next week.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 613 AM CDT Thu Oct 10 2024

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are forecast at all terminals through this
forecast period. Low to moderate concentrations of wildfire smoke
will continue to drift across the area through tonight. A cold
front will move through central and north central South Dakota
this afternoon and northeast South Dakota later this evening,
switching winds from a south-southwest direction to a northwest
direction.

&&

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

$$

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