839
FXUS63 KABR 031709 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1209 PM CDT Fri Oct 3 2025

.KEY MESSAGES...

- A Red Flag Warning has been issued for Stanley, Jones, and Lyman
Counties and goes into effect midday today through this evening.

- Upper 80s to mid 90s are expected today. Near record high
  temperatures will remain possible east of a line from Pierre to
  Ipswich on Saturday, where highs will be in the mid 80s to near
  90 degrees.

- Windy conditions Saturday and Saturday night will be east of a
  line from Vivian to Aberdeen, where winds out of the south will
  gust 30 to 40 mph. On Sunday the winds will be switching out of
  the northwest, with gusts of 35 to 45 mph with locally higher
  gusts.

- A cold front will bring rain Saturday night through Sunday
  morning. There is a Marginal Risk, level 1 of 5, for severe
  storms Saturday night. Damaging winds will be the main concern.
  Heavy rain or hail will also be possible.

- There is a slight shift westwards with the highest rainfall
  potential. There is a 50 to 75% chance of rain in excess of 1"
  along and west of a line from Mobridge to Hayes.

- Localized frost is possible Monday morning, Tuesday morning, and
  Wednesday morning.

&&

.UPDATE...
Issued at 1207 PM CDT Fri Oct 3 2025

Updated for the 18z Aviation Discussion below.

UPDATE Issued at 1117 AM CDT Fri Oct 3 2025

No significant changes were needed this morning to the ongoing
forecast. We continue the latest on the gusty southerly winds
today, strongest from south central to northeastern SD gusting 20
to 28 mph as of 11 AM.

&&

.SHORT TERM /TODAY THROUGH SATURDAY AFTERNOON/...
Issued at 323 AM CDT Fri Oct 3 2025

The main concern in the short term will be the windy conditions,
near record warm temperatures, and elevated fire danger concerns.
Zonal flow aloft will turn southwesterly today as a trough moves in
and sets up over the western CONUS. Through tonight and Saturday,
this trough will shift eastward with ongoing southwesterly flow
turning more southerly/southwesterly by Saturday evening. Its
surface low by 12Z this morning will be positioned over southeastern
MT/northeastern WY and the western Dakotas, only shifting slightly
east by 18Z. WAA winds will increase over the CWA ahead of this low
with 700mb winds ranging from 20-30kts out of the southwest and
850mb winds of 25-35kts out of the south by this afternoon, per
HREF. With steepening pressure gradients at the surface (~6-8 over
the CWA), gusty winds aloft, and higher daytime mixing levels,
sustained winds are forecasted out of the south between 15-25kts
with gusts 25-35kts, highest over central SD. With this being WAA
winds/pressure gradient combo and not CAA driven gusts, was hesitant
on going full NBM/NBM90, so blended 2 parts NBM 1 part NBM 90th to
show potential for a bit higher gusts. NBM wind gusts>40mph is 20%
or less with the exception of southern Lyman which is 35%.

As the low shifts closer to the CWA winds will continue to remain
gusty as a LLJ sets up this evening through the overnight with
speeds between 25-45kts at 850mb. Wind gusts at the surface will
range between 20-30kts. With this southerly/southwesterly wind
component, wind gusts over the Coteau, and along the western and
eastern slopes, gusts are forecasted between 30-35kts. Probability
of gusts>40mph is 30-50% over and along the Coteau. By Saturday
morning the elongated area of low pressure will stretch from
northeastern ND through southwestern SD, and its slow moving cold
front. By 18Z locations along and west of the Mo River will be
along or behind the fropa. Steep pressure gradients along with
daytime mixing, and wind gusts ahead of the front are forecasted
to range between 20-35kts, highest over east central SD and
portions of northeastern SD (including the Coteau). Probability of
gusts>40mph is about 25-45%, highest over east central SD.

It will feel more like July than the beginning of October!
Temperatures at 850mb this afternoon will range from +22 to +25C
(highest over central SD) which runs within the 97-99th percentile
range! NAEFs even indicates 500-700mb temps run about 1 standard
deviation above climo and 850mb temps 1-2 standard deviation above
climo through Saturday evening. Surface temps are forecasted in the
upper 80s to the lower 90s. This is about 20-25 degrees above
average with EC EFI between 0.6 to 0.9. High temps will run from
about 1 to 5 degrees near record highs with the closest being
Sisseton with a forecasted high of 89 and record sits at 90/1938. For
Saturday, ahead of the cold front, 850mb temps will still be about
+20 to +23C with surface highs still expected in the upper 80s to
around 90 east of the MO River with highs over north central SD
behind the front only in the 70s.

So with the combination of warm temperatures and gusty winds,
minimum RH values by this afternoon are forecasted between 25-30%
over portions of south central SD. The Grassland Fire Danger Index
(GFDI) is in the High category here, which includes from Stanley,
Sully, Hyde Counties and southward. The drying of fuels and gusty
winds (25-30kts) will result in the potential for elevated fire
weather conditions for this area. Wind gusts do reach RFW criteria
and just shy of RH criteria, however, to err on the side of caution
a RFW has been issued for Stanley, Jones, and Lyman Counties from
18Z-01Z. For Saturday the GFDI will be in the High Category with
more of an eastward shift over portions of south central and east
central SD. RH values are not expected to be as low ranging between
35-40%.

&&

.LONG TERM /SATURDAY EVENING THROUGH THURSDAY/...
Issued at 323 AM CDT Fri Oct 3 2025

Overall not much change with the setup Saturday evening/overnight
into Sunday with severe weather setup and precipitation amounts.

NBM deterministic 24-hour QPF is on the order of 1-2 inches with a
bullseye across north central/northwest South Dakota, essentially on
our northwest border. There is a tight gradient, with a significant
drop to the south and east, with a deterministic QPF of only about a
1/4 inch for Pierre and maybe a few hundreds for Aberdeen areas.
There is also a fairly large 25th-75th percentile range even within
this area of higher QPF, with western Corson county`s range on the
low end of 0.35 to a higher range of 1.88 ... thats and 1.5" range.

As for the severe weather potential, the environment features high
shear but limited instability. Essentially skinny CAPE and inverted
V soundings with high LCLs. Mid level temperatures to the east of
the surface low are also going to effectively cap the warm sector.

Thereafter the focus shifts to frost potential. 1025mb surface high
pressure moves overhead during the day Monday, so a bit too early
for Monday morning frost, except maybe in the far west. Will also
contend with some high clouds across the southern half of the CWA to
help inhibit temperature drops. Probabilities of 36 degrees or lower
limited to north central South Dakota between 30 and 70 percent,
though probability of less than 32 is down around 10-20%. Tuesday
would appear the more logical setup for frost, with the high
departing. Low level flow shifts to west southwesterly, and the
gradient is light. NBM probabilities have shifted lower however,
down to between 20-50% for Tuesday morning confined to western
Corson and northern Campbell. Uncertain as to the cause, with a lack
of low level moisture or gradient winds. A backdoor front is
evident, but that doesn`t come in till later Tuesday. And while
there is a re-enforcing shot of cooler air backing in, the surface
high remains to the northwest so gradient winds (northeasterlies)
may also preclude a widespread frost. So for Wednesday morning, NBM
deterministic has backed down slightly from the previous run
coverage for frost mention, however probabilities run from 20-30%
across the southern tier of the CWA to 40-60% along the ND/SD state
line... and its important to note the high range of uncertainty in
low temperatures with a 10 degree range in the 25th-75th
percentiles.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1209 PM CDT Fri Oct 3 2025

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are expected this afternoon through Saturday morning.
Winds this afternoon and evening will be from the south, gusting up
to 25-30kts at all terminals. A low level jet moves over eastern
SD tonight, which helps to keep winds over KATY and KABR gusting up to
20kts to slightly below 30kts though the night. At the same time, winds
over central SD weaken slightly, to be gusting below 15kts. With the low
level jet overhead having much stronger winds from the southwest,
there is an area of low level wind shear starting after 01z that continues
into the early morning hours over all the terminals. Winds
then strengthen again mostly over KATY and KABR during Saturday
morning into the afternoon, gusting up to 25-35kts.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Red Flag Warning until 8 PM CDT /7 PM MDT/ this evening for
     SDZ033-045-048.

MN...None.
&&

$$

UPDATE...12
SHORT TERM...MMM
LONG TERM...07
AVIATION...12