105
FXUS63 KBIS 040602
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
102 AM CDT Fri Jul 4 2025

.KEY MESSAGES...

- Isolated to scattered severe thunderstorms tonight. The main
  hazards are golf ball size hail, damaging winds up to 70 mph,
  and a tornado or two possible.

- Thunderstorm chances will continue Friday with an isolated
  chance for severe weather in the southeast.

- Hot and humid conditions this afternoon and Friday with a
  cooling trend through the rest of the weekend. Daily
  thunderstorm chances will carry over into early next week.

&&

.MESOSCALE...
Issued at 1017 PM CDT Thu Jul 3 2025

The evolution of convection late this evening remains difficult to
discern. The boundary layer is becoming increasingly stabilized as
we enter the nighttime hours, but an elevated mixed layer continues
to promote very strong buoyancy on the order of 4000-5000 J/kg
MUCAPE. While there is certainly no shortage of that ingredient,
other ingredients for severe convection remain marginal at
best. A dry LFC-LCL layer has impeded convective growth thus
far, and this does not change downstream. While some modest
synoptic scale lift is present in the mid to upper southwest
flow, the strongest DCVA is just now approaching the southwest
corner of the state. Furthermore, effective bulk shear is only
around 30 kts west of Highway 83. This keeps the near-term
convective outlook for the next few hours very unclear. Dominant
hazards will likely be dictated by storm mode, though there was
a severe gust with a collapsing supercell near Dickinson. One
trend to monitor is that the convection moving up from northwest
South Dakota is riding a strong DCAPE gradient with downstream
maximum as high as 1800 J/kg.

Meanwhile, a complex of very intense thunderstorms has moved from
southeast Saskatchewan into southwest Manitoba. These storms have
been flirting with a right turn, which would follow the Corfidi
vectors and bouyancy gradient. If a transition takes place to a
southeastward storm motion by 11 PM CDT, the Turtle Mountains area
would see an increased risk of damaging wind gusts between then and
midnight. This appears to now be the highest conditional threat
ceiling across our forecast area.

MESOSCALE
Issued at 818 PM CDT Thu Jul 3 2025

Sustained strong to severe convection appears to be struggling in
southwest North Dakota due to greater MLCIN. However, synoptic scale
lift is increasing and downstream propagation would take these
storms into a more buoyant and highly sheared environment, and also
into a tongue of lower to mid 70s dewpoints with easterly surface
flow. DCAPE is analyzed around 1500 J/kg, and shear vector
orientation to the initiating boundary would favor a quicker
transition to a linear mode. Our expectations for the southwest are
that severe wind gusts will be the main hazard, but it may be until
closer to 8 PM MDT until this threat develops.

Convection north of I-94 is likely not being impeded by MLCIN per
SPC mesoanalysis, but is farther displaced from the highest boundary
layer moisture (though dewpoints are still in the 60s to lower
70s) and also farther displaced from strong synoptic scale lift.
If strong to severe convection does become sustained in the
north, they would be more likely to remain discrete for longer
duration, leading to large hail being the main hazard.

The tornado threat for all areas is low, but greater than zero IF
storms become severe. A strengthening low level jet will increase 0-
1 km bulk shear/SRH through the evening. The corridor with the
highest relative probability of a tornado is likely along the nose
of the low level jet which also coincides with the highest surface
dewpoints and weak but shifting surface winds. This is roughly from
around south of Dickinson to north of Bismarck.

&&

.UPDATE...
Issued at 100 AM CDT Fri Jul 4 2025

Storms continue across the west, and now north central. The only
severe storm is entering Ward County. This storm has a history
of 90mph winds. General thunderstorms continue in the southwest.
Storms will continue to move northeast for the next few hours.

UPDATE
Issued at 718 PM CDT Thu Jul 3 2025

Attempts at sustained convective initiation are becoming more noted
on satellite imagery along a surface trough from near Kenmare to
Baker, MT. The environment has become increasingly unstable across
western and central North Dakota, with SBCAPE around 4000-5000 J/kg.
Some residual MLCIN does remain, but it is very meager. Effective
bulk shear is increasing per SPC mesoanalysis trends, and is now up
to around 30 to 40 kts immediately downstream of where convection is
growing. A Severe Thunderstorm Watch has been issued for much of
western and central North Dakota until 2 AM CDT.

&&

.DISCUSSION...
Issued at 346 PM CDT Thu Jul 3 2025

An upper level ridge axis is located over the Northern Plains.
High temperatures have climbed upper 80s into the 90s across
the western and central North Dakota. In addition, a north south
orientated surface pressure gradient will bring forth a low
level jet around 20 mph that will pull in upper 60s to lower 70s
dewpoints across the state. High dewpoints and high
temperatures has lead to hot and muggy conditions. Breezy winds
may keep temperatures feel a few degrees cooler.

Surface low pressure and an upper level wave is forecast to move
in from northeastern Wyoming to eastern Montana. This wave
will lead to the potential for thunderstorms. Today`s
environment supports a chance for isolated to scattered severe
storms in the late afternoon into the overnight hours. MUCAPE is
forecast to sit around 2500-3500 j/kg with around 20-30 kts of
0-6 km bulk shear. The shear is on the lower end which would
support cluster development off of outflow boundaries. Forecast
soundings are uncapped. The aforementioned upper level wave and
convective temperature could play a roll in storm initiation
this afternoon with the low level jet supporting storms later
tonight. The mode of the storm could start out as discrete
supercells in southeastern Montana congealing into a cluster of
storms as it moves into western North Dakota. The wind threat
will be the highest overnight. The main hazards are golf ball
size hail, 70 mph winds, and a tornado or two are possible with
the supercells early on.

The upper level ridge axis is forecast to move across eastern
North Dakota and eastern Minnesota Friday. This will lead to
another round of hot and muggy temperatures across the eastern
half of the state. An upper level wave is forecast to move
through the region bringing in chances for thunderstorms. In
addition precipitable water is forecast to increase across the
eastern half of the state ranging from 1.7 in Bismarck to 1.9 in
Jamestown which could lead to the heavy rain potential. The
heavy rain will be more localized as the NBM probabilities of an
inch or more of precipitation are low through Saturday. The
CAMs are picking up on an axis of storms forming across the
James River Valley tomorrow afternoon slowly pushing into the
Red River Valley tomorrow evening. There is an isolated risk for
severe weather out east Friday afternoon clipping the southern
James River Valley. The environment tomorrow has around 2000
j/kg of MUCAPE could lead to gusty winds and large hail tomorrow
afternoon.

An upper level trough will pass across the region Saturday
leading to increased rain chances and cooler temperatures. The
wrap around precipitation from the upper level low is forecast
to bring in showers and thunderstorms Saturday morning with
another wave following suit Sunday. Temperatures will drop back
down into the upper 70s to lower 80s this weekend. Next week we
could see a return of severe weather as the upper level pattern
returns to zonal flow with multiple waves moving through the
region. CSU machine learning program is pegging Monday and
Tuesday for having low chance of severe weather.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 100 AM CDT Fri Jul 4 2025

VFR where thunderstorms are not present, MVFR possible in the
thunderstorms along with erratic winds. Strong to severe
thunderstorms are possible through 07z. Wind shear is possible
in KBIS and KJMS tonight at around 1200ft. Friday late morning
through most of the day will be scattered showers and
thunderstorms. PROB30 was used in locations with more
uncertainty.

&&

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

&&

$$

MESOSCALE...Hollan
UPDATE...Smith
DISCUSSION...Johnson
AVIATION...Smith