146
FXUS63 KBIS 040908
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
408 AM CDT Sat Oct 4 2025

.KEY MESSAGES...

- Windy with high chances for rain, heavy at times, across
  southwest and central North Dakota Saturday night into Sunday,
  with medium chances for rain northwest.

- A few strong to marginally severe thunderstorms are possible
  across south central into eastern North Dakota late Saturday
  afternoon through Saturday night.

- Much cooler for the first half of next week, with highs mostly
  in the 50s and lows in the mid 20s to mid 30s.

- Medium chances for a freeze across much of western and north
  central North Dakota Sunday night and Monday night.

&&

.DISCUSSION...
Issued at 201 AM CDT Sat Oct 4 2025

Early this morning, a split upper level trough was situated
over the western U.S. At the base of the trough an upper low
was situated over the Desert Southwest, with a northern stream
trough from western Canada into the Pacific Northwest. Broad
high pressure was situated from the southern Plains into the
southeast U.S. Ahead of the northern stream trough, upper level
jet energy extended from the northern Plains into Ontario
Canada. In our neck of the woods, a cold front extended from
northeast to southwest North Dakota. Isolated shower activity
was pushing from the northern High Plains into the western
Dakotas.

For today, shower activity is expected to slowly increase over
western and central ND today as the areas will remain in a
favorable area for lift, beneath the right entrance region of
the northern stream jet through the day, then within an area
of increasing upper level divergence this afternoon as the
southern upper low lifts into the Rockies. The initially very
dry lower atmosphere will keep the increase in shower activity
tempered, especially this morning. However, WV satellite and
especially the advected layer PW shows subtropical moisture
already lifting through Mexico and into the southern/central
Rockies, on its way to the Northern Plains. It`s just going to
take a while to get here. By 00Z and through 06Z NAEFS PW values
are at or above the 99th percentile, relative to climatology
centered on this date. The ECMWF SA page shows QPF for this
system is above the 90th percentile, with a shift of tails of 2,
from around the Bismarck area northeast towards the Devils Lake
Basin. The latest NBM qpf with this system has shifted a little
to the west over southern ND, to include more of southwest ND.
However the axis of highest probabilities still extends through
the Bismarck area northeast to the Devils lake Basin, just as it
did 24 hours ago.

There has been little change in the SPC marginal severe risk,
still highlighting south central through northeast North Dakota,
which includes the James River Valley. Latest Cams have been
advertising some stronger convection from very late afternoon
into the evening, and developing from northeast/east central ND
back into the south central, and then possibly a later round
lifting up from central SD into the far south central/James
River Valley as the main shortwave lifts into the area. The
latest SPC HREF shows some stronger UH tracks developing around
the northern JRV into east central ND around 01 UTC, and then
over north central SD, lifting into the far south central/JRV
very late evening and into the early overnight hours. Convection
is elevated so it makes it harder to determine the extent of
any hazards. However, utilizing NAM bufkit sounding you can
generate around 1000-1500 J/KG of elevated CAPE at Ashley and
Jamestown in the evening and early overnight hours, with some
decent hail cape as well. As you get west to Bismarck it more
like 500 J/KG of elevated cape and little hail cape. With very
strong bulk shear over the entire forecast area, pretty much any
updraft would have the potential to rotate, but again, the
greatest elevated instability should remain over the far south
central into the James River Valley. Thunderstorms can not be
ruled out across most of southwest and central ND, but the
threat for severe should remain south central into the JRV, with
the main hazards being quarter size hail and 60 mph winds.

The system also looks to have trended a little bit slower, so
precipitation is expected to linger through Sunday morning over
central ND as the west begins to dry out. Showers are expected
to end across the forecast area by around mid-afternoon.

It will be windy late Saturday night through Sunday behind the
exiting surface low, but at this time it looks like the
greatest pressure falls and strongest cold advection remain
south and east of the forecast area. We could see some near
advisory criteria winds southwest and south central Sunday
morning as the strongest gradient winds move through, but this
is an unfavorable timeframe, especially if you are lacking
strong cold advection and the isallobaric pressure fall/rise
couplet. Will continue to monitor though.

Once the system exits the area the upcoming work week looks to
be pretty quiet. Currently our given NBM pops are negligible
from Sunday night through the work week. That`s not to say we
won`t have a stray shower here or there, but overall, pretty
quiet.

The main concern behind the system is the potential for freezing
temperatures over a good portion of western and north central
ND, both Sunday night into Monday morning and again Monday
night into Tuesday morning. Latest guidance has warmed slightly
from 24 hours ago, and deterministically you can see there may
be some issues with timing of the surface high being in a
favorable position each morning, as well as issues with clouds
within a progressive, slightly cyclonic northwest flow pattern.
Will need to see how this plays out over the weekend. After the
cold start to the week (highs mainly in the 50s) temperatures
rebound back to near or slightly above normal temperatures in
the 60s to lower 70s.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1150 PM CDT Fri Oct 3 2025

A cold front is currently situated from Rolla through Beach and
will continue to move southeast overnight. North to northwest
winds already over northwest ND. Elsewhere, southerly winds
(strong south central into the JRV) will shift northerly with
the frontal passage. Very strong winds aloft at KJMS will
necessitate a mention of LLWS through 11-12 UTC. Expect VFR
conditions overnight with isolated showers, which are too
isolated in nature to mention in any one TAF.

There is a low chance that an area of MVFR ceilings could spread
across much of western and central North Dakota tonight into
Saturday morning. Confidence in these lower ceilings developing is
not high, so have limited to a SCT mention in the TAFs for now.

Chances for rain will increase from western into central North
Dakota through the day Saturday. Periods of heavier rain could
reduce visibility at times. This may be limited to the
afternoon hours in southwest North Dakota prior to Saturday
evening, when rain is expected to become much more widespread.
A few thunderstorms could also be developing in south central
North Dakota near the end of the forecast period.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Adam/TWH
AVIATION...TWH