935
FXUS63 KBIS 080843
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
343 AM CDT Tue Jul 8 2025

.KEY MESSAGES...

- Temperatures trend warmer through the middle of this week,
  peaking on Wednesday when widespread 90s are expected for
  daytime highs.

- Isolated severe thunderstorms are possible across most of
  North Dakota on both Wednesday and Thursday.

- Temperatures cool down for the end of the work week, before
  warming back up through the weekend.

&&

.DISCUSSION...
Issued at 343 AM CDT Tue Jul 8 2025

This morning, northwest flow aloft exists across the Dakotas,
over top a surface high pressure analyzed from the southern
Canadian Prairies into central North Dakota. The main weather
concern this morning is the development of fog, occasionally
dense, from the northwest through the southeast. As of 3 AM,
reduced visibilities extend across northwest North Dakota into
the northern James River Valley. We do have a Special Weather
Statement out for these areas until 445 AM CDT. Will continue
monitoring to see if the lowest visibilities get widespread
enough to warrant a headline, although high-res guidance has
been advertising that outcome for a few hours now.

Once fog dissipates, quiet weather is in the forecast today, as
a shallow ridge attempts to build to our west on top of a stout
upper high over the Four Corners region. Highs will be in the
upper 70s to upper 80s, maybe a touch cooler in the Turtle
Mountains area, and skies will be clearing after the fog and low
stratus of the early morning hours. Although one or two high-
res models bring in some scattered showers tonight from a weak
impulse aloft, blended POPs are generally 10 to 15 percent, if
that, so any precipitation is a low odds solution. Lows tonight
will be a bit warmer than normal, in the mid 50s to mid 60s.

Wednesday and Thursday are still being eyed for potential for
severe thunderstorms across the state. A closed low and
attendant trough will begin to move onshore in the western CONUS
through the day Wednesday, with nearly zonal flow aloft across
North Dakota. Low confidence in how the day will evolve on
Wednesday, as the synoptic scale forcing is pretty lacking, and
on top of a stout thermal ridge at 850 mb. Surface temperatures
are expected to be in the upper 80s to upper 90s, with generally
a 10 to 40 percent chance of exceeding 100 F across western
North Dakota. NBM currently has dew points ranging from the 40s
west to mid to upper 60s central and east, with max apparent
temperatures approaching 100 F. Held off on any heat headlines
for now, but will be something for next shift to consider
depending on how guidance trends.

Some forecast soundings do have parts of southwest and south
central North Dakota reaching convective temperature, which
matches with high-res longer range reflectivity advertising
convection developing in this area. The caveat we see at the
moment, besides the nebulous forcing mechanisms, is that bulk
shear is on the marginal side, around 20-30 knots. However,
instability is quite impressive, as are forecast DCAPE and lapse
rates. In previous events with a similar environment, we have
seen explosive thunderstorm development from the very high
bouyancy that is not long- lived due to the lack of shear, which
fits with the 00Z HREF showing numerous short max UH tracks in
an area from Dunn County to Hettinger County and east to the
Missouri River. Forecast soundings also occasionally show large
hail analogs from our area. We are carrying the mention of
isolated severe thunderstorms (level 1 out of 5) across the
majority of the forecast area, although the Storm Prediction
Center did mention consideration of an upgrade. Will bump up
hail size to ping pong ball and keep mention of 60 mph winds.

There is still a large amount of uncertainty on Thursday`s
severe threat, as North Dakota ends up in between two upper
troughs -- one passing through the southern Canadian Prairies,
and one in the South Dakota / Nebraska corridor. It is expected
to be another day of very high instability across the forecast
area, especially central and east, ahead of a cold front progged
to sweep through the area Thursday evening. Although mid- level
height falls look a bit more promising compared to Wednesday,
most guidance is not developing much of any robust convection.
Higher bulk shear does look to be offset from the strong
instability which could also limit the threat ceiling, and could
lead to storms being similar to Wednesday where they have
explosive initial development but are unsustainable due to shear
being only around 20 knots. NSSL and CSU machine learning
guidance still favor Thursday over Wednesday for when the
highest severe risk is, although worth noting it`s not overly
high, especially in CSU. Deterministic guidance on Thursday
does show weak enough flow that any storms that develop could be
quite slow moving, and with high PWATs, locally heavy rainfall
could be a threat. Like Wednesday, we are advertising isolated
severe thunderstorms (level 1 out of 5) across most of North
Dakota on Thursday, with highs in the lower 80s to lower 90s and
dew points in the 60s across the central and east.

Friday will be much cooler in the wake of the cold front, with
forecast highs only in the 70s. Blended POPs give a broad 20 to
30 percent chance of showers and thunderstorms from the cyclonic
flow aloft as the upper low shifts to our northeast. Ensemble
members then favor ridging beginning to build across the western
CONUS, with NBM temperature percentiles showing a warming trend
across the state through the weekend, bringing temperatures back
into the widespread 80s by Sunday. Near normal temperatures and
on and off chances for showers and thunderstorms continue next
work week.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1247 AM CDT Tue Jul 8 2025

Overall VFR conditions expected through the period, although fog
development is possible through the night and into Tuesday
morning. The mostly likely terminals to be impacted are KMOT and
KJMS where TEMPO group was included with this update, although
could potentially reach KXWA/KBIS, just too low of confidence to
include at those terminals for now. Outside of fog potential,
expect limited cloud cover and winds under 10 knots.

&&

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

&&

$$

DISCUSSION...Jones
AVIATION...Jones