957
FXUS63 KBIS 172012
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
312 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.

&&

.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 /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1235 PM CDT Tue Jun 17 2025

VFR conditions are expected at all terminals through the TAF
period. Winds are generally from the north to northwest
this afternoon, becoming light and variable overnight before
shifting to be southwesterly on Wednesday.

&&

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

&&

$$

DISCUSSION...Jones
AVIATION...Jones