807
FXUS63 KBIS 172326
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
626 PM CDT Tue Jun 17 2025

.KEY MESSAGES...

- Active pattern with periodic chances for showers and
  thunderstorms through the work week and into the weekend. A
  few severe storms are possible, more likely later in the week.

- Overall temperatures remain around normal to slightly above
  normal for this time of year.

&&

.UPDATE...
Issued at 625 PM CDT Tue Jun 17 2025

The thunderstorms in the southwest have finally dissipated,
with only some lingering high cirrus and fair weather cumulus
across the area this evening. The forecast remains on track for
now. In northeastern Montana, a thunderstorm complex has
developed underneath a shortwave, slowly moving eastward. This
may reach northwestern North Dakota in an hour or two, so we`ll
continue to monitor the development of these storms.

&&

.DISCUSSION...
Issued at 312 PM CDT Tue Jun 17 2025

This afternoon, surface high pressure was centered over eastern
Montana and western North Dakota, with broadly zonal flow aloft
that is expected to turn more northwesterly through the
evening.

A vort max aloft has been slowly tracking along the North
Dakota / South Dakota border, with persistent, isolated showers
ongoing for the past few hours. Lightning has already been
observed with this activity, with SPC mesoanalysis page showing
500-1000 J/kg of MLCAPE, but bulk shear is very low which limits
potential for storms to become strong to severe, although the
initial pulse up could produce some small hail. We did get a
report of a very brief, weak landspout tornado a few miles north
of Hettinger, and additional funnels / landspouts cannot be
ruled out, although the non- supercell tornado parameter is not
showing anything in this area. Elsewhere, fair weather cu is
widespread, with a touch of a breeze across northern North
Dakota. Highs this afternoon will be in the 70s to around 80 F.

The activity in our southern tier of counties is expected to
diminish through the late afternoon, while a weak embedded
shortwave aloft brings a chance for isolated showers across
northwest North Dakota this evening into the overnight hours.
CAMs are a little scattered on start time and duration, but the
signal is strong enough to carry a 15 to 20 POP. Lows tonight
will be in the 50s.

On Wednesday, a shallow ridge attempts to build over the
Northern Rockies, with continued northwest flow over the
Dakotas. A surface trough and trailing cold front are progged to
drop south during the afternoon and evening, with scattered
showers and thunderstorms likely. We are still seeing potential
for isolated severe thunderstorms (level 1 out of 5; Marginal
Risk), with broadly 1000-1500 J/kg of instability available, but
only 20-30 knots of 0-6km shear. Will continue advertising hail
up to the size of quarters and wind gusts up to 60 mph.

Rinse and repeat for Thursday, although flow aloft turns much
more zonal as the ridge is flattened. SPC continues to advertise
isolated severe thunderstorms possible (level 1 out of 5) on
Thursday as well. The main concern with Thursday is that
deterministic guidance is advertising rising heights across the
majority of the states, so capping might be too robust for any
convection to develop, especially with no strong synoptic
forcing.

A deepening low off the Pac NW coast will move onshore and help
turn flow more southwesterly across the Dakotas Friday and
Saturday, leading to plentiful moisture advection and likely dew
points in the 60s F. CSU and NSSL machine learning guidance
continue to show heightened probabilities for severe weather on
these days, with deterministic models already advertising strong
instability and very strong shear overlapping across much of
the forecast area. Highs on Friday and Saturday will be in the
mid 70s to mid 80s.

Cluster analysis shows an embedded closed low moving through
the mean southwest flow on Sunday and Monday, with a front and
cooler air filtering into the region. The latest NBM gives a
broad 20 to 40 percent chance for showers and thunderstorms on
Sunday, with some low potential for strong to maybe severe
storms across eastern North Dakota on Sunday, before highs in
the 60s on Monday limit thunderstorm potential.

Seasonably cool temperatures continue through midweek, but
start slowly warming up day by day. By late next week, machine
learning begins to highlight increasing probabilities for severe
weather again, with some uncertainty in the overall synoptic
pattern but some broad consensus on zonal to southwest flow
aloft across the region.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 625 PM CDT Tue Jun 17 2025

VFR conditions are present and are expected to prevail through
the TAF period. Fair weather cumulus will dissipate tonight,
with some higher clouds moving in. Winds will become light and
variable overnight, then becoming westerly Wednesday. A few
thunderstorms have developed in northeastern Montana, moving
east towards KXWA. Confidence is low regarding whether or not
these storms will hold together and reach KXWA within the next 3
hours.

&&

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

&&

$$

UPDATE...Besson
DISCUSSION...Jones
AVIATION...Besson