666
FXUS63 KBIS 171110
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
610 AM CDT Thu Jul 17 2025

.KEY MESSAGES...

- Well below average temperatures through today, with lows this
  morning in the lower to mid 40s and highs in the mid 60s to
  mid 70s this afternoon.

- Patchy smoke across much of western and central North Dakota
  this morning, with conditions improving from south to north
  through the day.

- Medium chances for showers and thunderstorms tonight through
  Friday, and again Saturday night through Sunday. A few strong
  to severe storms are possible both tonight and Saturday night.

- Temperatures warm back closer to average this weekend into
  early next week.

&&

.UPDATE...
Issued at 610 AM CDT Thu Jul 17 2025

Quiet weather is found across western and central North Dakota
this morning. Occasional drops in visibility have been observed
in north central North Dakota into the James River Valley as
patchy fog has developed. All fog is anticipate to lift soon
after sunrise. Otherwise, clear skies are found across much of
the forecast area, except in west where mid based clouds (north)
have lingered through the night, and a band low level clouds
have begun to push into southwestern North Dakota. These cloud
are anticipated to lift to become mid based clouds as they
expand to the northeast through the day today. Low temperatures
so far this morning have been in the lower to mid 40s, though a
few reports as low as 39 have come from in far south central
North Dakota and in the Turtle Mountains area. We have already
(unofficially) broken the daily low temperature record at the
KBIS climate site this morning, with an 24 hour low of 40
breaking the previous record of 42 from 1984. Regarding
forecast updates, have blended in the latest satellite
observations in the sky grids. Otherwise, the forecast remains
on track.

&&

.DISCUSSION...
Issued at 400 AM CDT Thu Jul 17 2025

Near southwesterly flow is found over the northern Plains this
morning as an upper level trough cuts across the southern
Canadian Prairies. Surface analysis reveals high pressure
lingering over far south central North Dakota, which has helped
limit cloud cover over western and central North Dakota. This
pattern is somewhat reminiscent of when we usually anticipate
very cool morning temperatures, namely when surface high
pressure is centered over Aberdeen. With that in mind, low
temperatures this morning are expected to be unseasonably cold,
broadly in the 40s across the forecast area. Some more local,
low-lying areas may even dip as low as the upper 30s when all is
said in done, with the most likely are being in the gullies of
the Missouri Plateau in southwest North Dakota. Otherwise this
morning, patchy near surface smoke lingers across western and
portions of central North Dakota, occasionally inducing minor
visibility reductions. As the high pressure near the surface is
displaced eastward through the day today, the highest
concentrations of smoke are expected to filter anti cyclonically
to our north. Additionally, light winds and clear skies will
help promote patchy fog across portion of north central North
Dakota and the northern James River Valley, though this is
anticipated to rapidly lift after sunrise.

A weak shortwave ejecting off the aforementioned upper level
trough is progged to cut across our southern counties. The
passage of this wave could promote low chances (<20%) for
isolated showers across central North Dakota this morning, with
these chances expanding across central North Dakota through this
afternoon. By this time, the upper level trough itself is
expected to start dipping into the northern Plains. A low
pressure system associated with this trough is progged to form
on the lee of the Rockies in Wyoming. As this low pressure
system cuts across southern South Dakota, chances (50 to 80
percent) for showers will increase across the forecast area
through this evening and overnight. With slightly warmer
temperatures forecast this afternoon in the wake of the
displaced center of high pressure, forecast broadly in the mid
60s to mid 70s, forecast dewpoints manage to eek up into the
upper 50s by the mid to late afternoon. With this, and with
moderate model MUCAPEs peaking around 1000 J/KG range this
afternoon and evening, thunderstorms are also expected through
much of this period. What`s a little more borderline today is
the potential for severe weather. A very strongly sheared
environment is expected to develop across western North Dakota
today, with model 0-6KM Bulk Shear values jumping well into the
50- 55 knot range. However, the imbalance between the
instability and the shear, the timing of the inverted surface
trough not making it to our western counties until the late
evening, and a rapid redevelopment of robust capping by the
early overnight period is expected help limit the chances for a
severe storm tonight through Friday morning. The main two
concerns are a) a supercell moving out of the better environment
in south eastern Montana and persisting long enough to cross
into western North Dakota or b) clustered strong to severe
thunderstorms developing along the ND/SD border along the axis
of better instability. With these scenarios in mind, there will
be a brief window where large hail up to the size of ping- pong
balls and damaging wind gusts up to 60 MPH are possible. An
interrogation of BUFKIT soundings does reveal what could be a
somewhat decent environment for tornadoes, with high near
surface SRH values and a significantly curved hodograph.
However, with CAPE being very lacking across the forecast area
throughout this whole period, and with CAPE being elevated above
a layer of high MLCIN, tornadic development is currently not
anticipated today or tonight. As it stands, SPC has placed much
of southwestern and portions of central North Dakota into a
Marginal (level 1 of 5) risk for isolated severe thunderstorms
today, with a small area of a Slight (level 2 of 5) Risk for
scattered severe thunderstorms in the far southwest. The CSU
machine learning algorithm is similar, highlighting much of
southwestern North Dakota for hail potential today.

Looking ahead, flow aloft is expected to turn northwesterly on
Friday ahead of an upper level ridge being displaced eastward
across the southern Canadian Prairies. With this, chances for
showers from the night before will clear from west to east
through the early Friday morning, leaving dry conditions across
North Dakota through Saturday afternoon. Our warm up is also
anticipated to continue, with highs broadly back into the 70s to
lower 80s both Friday and Saturday. Through the day Saturday, a
a longwave trough ejecting off of an upper level low in western
Canada will displace the ridge further to the east through the
afternoon. With this pattern, chances for showers will increase
from from west to east through Saturday afternoon and evening.
At the time of this forecast, some of long term global models
are starting to highlight the potential for severe weather
across portions of far western North Dakota. As it is, the CSU
Machine learning algorithm has a low probability highlight
across our far western counties, while SPC has placed a similar
region under a Marginal (level 1 of 5) Risk for isolated severe
thunderstorms Saturday night through Sunday. Cluster analysis
reveals two scenarios as this time. The first scenario is more
favored by the ensemble (~75% memberships), and keep the main
axis of instability further to the west of the forecast area,
mainly in eastern Montana. The CSU algorithm currently reflects
this scenario, with a higher probability highlight found in
eastern Montana at the time of this forecast. The second
scenario is has less memberships (~25%), an instead drapes the
axis of instability across the ND/MT border, which would elevate
the potential for severe weather Saturday night into Sunday. In
any case, we will need to continue to monitor forecast trends
over the next few days.

With the longwave trough continuing to sink deeper into the
Great Plains Sunday through early next week, near daily chances
for showers and thunderstorms will continue through this period.
Long deterministic guidance continue to highlight portions of
North Dakota will sufficient instability and shear to promote
the develop of strong to severe thunderstorms most days through
this period. The CSU machine learning algorithm reflect this,
painting much of the forecast area with at least low probability
for severe weather each day through the early week. This
coincides with the warming trend continuing through this period,
bringing much of the forecast area well into the 80s and
possibly even the lower 90s each day Sunday through Tuesday.

As we head into the middle of next week, the ensemble becomes
increasingly discordant depending on rate at which the longwave
troughing becomes absorbed into a more general northwesterly to
near zonal flow. With the majority of model members (~85%)
favoring a slower absorption of the trough, the deterministic
NBM continues to advertise near daily low to medium chances for
showers through Thursday. With this setup, at least minimally
elevated potential for severe weather would likely persist
through Thursday as well. A minority cluster instead favors a
return to near zonal to northwesterly flow, which would help dry
us out a little earlier. In either scenario, a brief cooldown
is anticipated through the later half of the workweek as
northwesterly flow takes hold, though warming weather can then
again be anticipated through the weekend as more broad, upper
level ridging is somewhat favored to move over the northern
Plains.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 610 AM CDT Thu Jul 17 2025

Mainly VFR ceilings and visibility are expected at all
terminals throughout the 06Z TAF period.

Patchy fog is possible over portions of north central North
Dakota and the northern James River Valley this morning, but is
generally expected to lift soon after sunrise. This fog may
occasionally reduce visibility at KJMS and KMOT this morning,
thus have included a TEMPO for 5SM BR over the next hour. MVFR
ceilings have begun to move into southwestern ND this morning,
but are anticipated to lift and become VFR as they expand across
the forecast are from southwest to northeast.

Isolated showers are possible across western and portions of
central North Dakota through the morning and afternoon, though
confidence is too low to include at any terminal with this
update. This evening, medium to high chances for showers are
expected to expand across much of the forecast area, though may
not make it to the James River Valley by the end of the TAF
period. Have included prevailing -SHRA at all terminals, except
for KDIK where a PROB30 group for -SHRA has been included due to
lower confidence. Some thunderstorms are possible later this
evening and overnight, though confidence in locations remains
too low to include mentions with this update. A few storms may
become strong to severe this evening through the early overnight
hours, with damaging winds and large hail possible with any
severe storm.

East southeasterly winds are expected to remain generally light
across central North Dakota through the TAF period, though the
west is forecast to become breezy with sustained speeds up to 15
knots and gusts up to 25 knots through the late morning and
early afternoon, before diminishing through the evening and the
end of the TAF period. Where showers and/or storms do develop,
gusty and erratic winds are possible.

&&

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

&&

$$

UPDATE...Adam
DISCUSSION...Adam
AVIATION...Adam