717
FXUS63 KBIS 081445
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
945 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.

&&

.UPDATE...
Issued at 945 AM CDT Tue Jul 8 2025

Dense fog is found over portions of northwestern and central
North Dakota this morning. Before this update, we extended the
Dense Fog Advisory further south to the ND/SD border as
visibilities in Burleigh, Kidder, Emmons, Logan, and McIntosh
counties had dropped below 1/2 SM. The gradual lifting of the
fog is already evident at the time of this update, especially
across the north where cloud cover is low. With low stratus
moving over the fog in the south central, there may be a slight
delay in fog fully lifting this morning, but visibilities should
still steadily increase over the next hour or so. Thus, the
Dense Fog Advisory will be allowed to expire on time at 10 AM
CDT. Otherwise, the forecast remains on track at this time.

UPDATE Issued at 645 AM CDT Tue Jul 8 2025

Surface high pressure still analyzed over north central North
Dakota, with low stratus and areas of fog extending from
northwest to southeast across the forecast area. Dense Fog
Advisory is still in effect, with no expansion at this time.
Visibilities are reduced in areas outside of the advisory,
especially in the James River Valley, but not seeing anything
consistently under a mile outside of the advisory area. NDDOT
webcams show fog is extremely shallow in some areas and should
be burning off through the morning as the sun continues to rise.

UPDATE
Issued at 431 AM CDT Tue Jul 8 2025

Quick update for the issuance of a Dense Fog Advisory until 10
AM CDT for parts of northwest and central North Dakota, with
multiple automated sites reporting visibility under one quarter
of a mile, and NDDOT webcams showing significantly reduced
visibility across this area.

&&

.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 /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 945 AM CDT Tue Jul 8 2025

Areas of fog continue over parts of the forecast area this
morning, extending from the northwest through the James River
Valley. Visibilities are lowest across the north central and
into the northwest, impacting KMOT but not quite reaching KXWA.
Patchy fog is present at KJMS and KBIS. Fog is expected to
diminish through mid morning with a return to VFR conditions by
14 or 15Z. Winds will be light through the day, becoming
southerly around 10 knots tonight.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 10 AM CDT this morning for NDZ001>005-
009>013-021-022-035-036-046-047-050.

&&

$$

UPDATE...Adam/Jones
DISCUSSION...Jones
AVIATION...Jones