Mandan, North Dakota 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

048
FXUS63 KBIS 262045
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
345 PM CDT Thu Jun 26 2025

.KEY MESSAGES...

- An isolated strong to severe thunderstorm could impact far
  northwest North Dakota this evening. Expected hazards include
  hail as large as quarters and damaging wind gusts as high as
  60 mph.

- Patchy fog is possible Friday morning over south central North
  Dakota into the James River Valley.

- Scattered severe thunderstorms (risk level 2 out of 5) could
  develop across central North Dakota Friday afternoon and
  evening. Expected hazards include hail as large as tennis
  balls, damaging winds as high as 70 mph, and a tornado or two
  possible.

- Near to slightly above average high temperatures in the 80s
  are forecast Friday through next week. Friday will also be
  humid for all but far western North Dakota.

&&

.DISCUSSION...
Issued at 345 PM CDT Thu Jun 26 2025

The northern Plains falls under the influence of a transient
upper level ridge passing through a much broader southwesterly
low pattern. Downstream of this ridge, a shortwave trough
continues to exit eastward into the Great Lakes region. This
shortwave, in conjunction with ample moisture flowing into the
region due to surface high pressure lingering over eastern
Canada, promoted a layer of low stratus across much of the
region earlier this morning. Along with the shortwave, this
stratus layer continues to move eastward this afternoon. With
thick cloud cover lingering across the eastern North Dakota,
high temperatures in this area are slightly lower, forecast in
the upper 60s and lower 70s, versus out west where clear skies
have help push highs into the mid 70s to mid 80s.

Later this afternoon, isolated to scattered thunderstorms are
expected to develop over portions of eastern Montana as another
weak shortwave and associated occluding low pressure system
slowly makes its way eastward. Some of these storms may survive
long enough to move into northwestern North Dakota later this
evening. With moderate amount of instability across western
North Dakota, with modeled MLCAPE values around 500 to 1000
J/KG, and borderline sufficient bulk shear values around 30 to
45 knots, a few of these storms may become strong to severe.
With how borderline these values are, and how disorganized they
become later in the evening, our expectation is that any severe
storms that do develop would be relatively short lived, and
would struggle to put down much more that base-line severe
hazards of quarter sized hail and wind gusts up to 60 MPH at
most. Clusters of showers and possible some thunderstorms may
then linger across northwestern and central North Dakota
overnight.

Otherwise, for tonight, weak south to southeasterly winds and
ample near surface moisture could promote patchy dog development
across portions of south central North Dakota into the James
River Valley. An interrogation of BUFKIT model soundings during
this period reveal a surface inversion very close to the
surface, thus any patchy fog that does develop may be fairly
shallow, and fairly quick to lift as we move into the mid
morning hours. Low temperatures Friday morning are forecast in
broadly from the mid 50s east up to around 60 west.

Now on to Friday. With the Gulf essentially wide open to the
northern Plains, the continued saturation the low to mid layers
across western and central North Dakota will promote an
increasingly unstable air mass Friday afternoon. With model
surface dewpoint values peaking into the upper 60s and lower 70s
across central North Dakota, MUCAPE values approach the 3000 to
4000 J/KG range by the mid to late afternoon hours. While a
strong forcing mechanism is not anticipated to present itself
during this period, most likely to be associated with a broad by
shallow shortwave trough lofting a occluding low pressure
system across North Dakota, the continued saturation of the mid
layer is expected to help erode any lingering CIN across the
forecast area, and thus CI can still be anticipated by the mid
to late afternoon. With such weak forcing, these initial storms
are anticipated to discrete in nature. Model shear values are
somewhat all over the place, but broadly range from the lower 40
knot range all the up to around 55 knots just behind these
initial storms. With this, supercellular development is entirely
possible which, along with the abundant cape across the area,
could promote hail up to the size of tennis balls (2.5 inches).
Another thing to consider is the potential for tornadic
development during this period. While CAMs continue to capture
more than sufficient near surface SRH values peaking into the
100-200 M2/S2 range tomorrow afternoon, less agreement can be
found regarding near surface shear. Even the RAP and NAMNEST,
which have been most aggressively championing the potential for
tornadoes, promote SFC-1km shear values just around 15 knots at
most which, while climatologically sufficient for tornado
genesis, is not very high. Other models, such as the HRRR and
HREF, are much more conservative with values around 10 knots or
so. Overall, I think that the overall message is that a tornado
or two is possible tomorrow afternoon, and would be associated
with any potential supercell. Otherwise, an interrogation of
BUFKIT model soundings reveals moderate DCAPE values across
central North Dakota in the 1000-1500 J/KG range late Friday
afternoon and evening, signaling the potential for strong wind
gusts during this period. This would especially be true if a
general conversion from a discrete storm mode into a more
clustered or linear mode occurs, which can be anticipated with
both the weak forcing mechanisms and is climatologically the
norm as we head into the late evening and overnight period.
Thus, we are also advertising wind gusts up to 70 MPH as well.
Storms are expected to continue pushing eastward through the
late evening and overnight, by which time it is expected to have
started diminishing and clustering together.

Beyond Friday, near zonal to slightly southwesterly flow is
expected to persist over the forecast area through the weekend.
With this pattern, near daily low to medium chances for showers
and possible some thunderstorms can be expected. CSU machine
learning continues to highlight southeastern North Dakota for
severe weather potential on Saturday, though this is likely the
remnants of the system passing through the northern Plains from
Friday night. Temperatures during this period are advertised to
be near to slightly above normal by the NBM, in broadly in the
80s, though this deterministic output remains around the 25th
percentile of the ensemble as a whole. Looking ahead into next
week, there is moderate to strong agreement in the ensemble in a
switch to northwesterly flow aloft as broad upper level ridging
builds in the from the west. In this pattern, we could
anticipate relatively dry weather during this period. The
aforementioned ridge does begin to squish down by the midweek,
turning flow more zonal and thus could allow for more chances
for widespread rain.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 345 PM CDT Thu Jun 26 2025

Low stratus is causing MVFR to IFR ceilings across the forecast
area at the time of this mid day update. As this stratus deck
continues to move eastward through the afternoon, ceilings are
expected to broadly improve to VFR conditions from west to east.
KJMS may remain under MVFR ceilings through the early evening
hours. Later this evening, chances for showers and thunderstorms
are expected to increase across northwestern North Dakota,
including around the KXWA terminal. Some of these storms may
become strong to severe, with large hail up to quarters (1 inch)
in size and wind gusts up to 60 MPH. These thunderstorms
expected to generally diminishing through the late evening into
the early overnight period, though scattered showers may linger
across the north. Confidence is too low to include mentions of
showers or thunderstorms anywhere except for KXWA at this time.
Friday morning, patchy fog is possible across portions of south
central North Dakota into the James River Valley. Have included
visibility reductions at KJMS with this update. Currently, this
fog is expected to be somewhat shallow, and should readily lift
by the mid morning hours. Otherwise, Light east to southeasterly
winds are anticipated throughout the TAF period.

&&

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

&&

$$

DISCUSSION...Adam
AVIATION...Adam