Crandall, South Dakota Weather Forecast Discussion

345
FXUS63 KABR 030835
AFDABR
Area Forecast Discussion
National Weather Service Aberdeen SD
335 AM 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.
- Near record high temperatures, in the 80s to lower 90s, will
continue through Saturday.
- Winds begin to increase today and will remain windy through Sunday
with gusts ranging from 30 to 40 mph, with localized higher gusts
possible.
- 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. The probabilities to measure in excess of 1" is limited
to along/west of a line from Mobridge to Hayes, ranging from 50% to
75%.
- Looking at localized frost potential Monday through Wednesday.
&&
.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 /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1222 AM CDT Fri Oct 3 2025
Terminals KABR,KATY,KPIR,KMBG
There will be a period of low-level wind shear (LLWS) overnight in
the KPIR region, with a much larger low-level jet and resulting wind
shear over the region Friday night. Included mention of this in the
TAFs. Otherwise, VFR conditions are forecast through the period,
with breezy/gusty southerly winds developing during the day
Friday.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Red Flag Warning from 1 PM CDT /noon MDT/ this afternoon to 8 PM
     CDT /7 PM MDT/ this evening for SDZ033-045-048.
MN...None.
&&
$$
SHORT TERM...MMM
LONG TERM...07
AVIATION...MMM

NWS ABR Office Area Forecast Discussion