781
FXUS63 KBIS 140839
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
339 AM CDT Sun Jul 14 2024

.KEY MESSAGES...

- Isolated to scattered severe storms will be possible once
  again late this afternoon and into the evening.

- Hail to the size of tennis balls and damaging winds up to 70
  mph will be the main hazards. There is also a conditional
  threat for a tornado or two.

- After another very warm day today with highs mainly in the mid
  80s to mid 90s, we cool down through midweek before another
  warmup to end the week.

&&

.DISCUSSION...
Issued at 339 AM CDT Sun Jul 14 2024

Early this morning, western and central North Dakota sits under
the influence of subtle northwest flow aloft. Several waves
moving through the apex of a western US ridge have flattened the
flow to nearly zonal. The most recent of these waves continues
to move off to the east southeast across South Dakota, along
with an impressive complex of severe storms that will continue
to move away from our area through the morning.

The next wave will move into our area later this morning and
into the early afternoon and is currently located over southern
Saskatchewan. This wave will lead to the development of some
showers and perhaps a thunderstorm or two across the northwest
and north central. We do not expect severe weather with these
initial showers and storms early in the day.

The next stronger wave will then approach late in the afternoon
or in the evening. There is still some uncertainty regarding
the timing of this wave. One scenario would bring the wave in
earlier which would potentially lead to a greater severe weather
threat. The other scenario brings the wave into the area later
in the evening, which would perhaps limit the severe weather
potential. The latest HRRR runs have started to back off
significantly with an earlier convective initiation solution
and convection coverage in general, so it may be starting to
pick up on the delayed wave arrival. These trends will be
important to watch through the day.

A broad and weak surface low will develop in the afternoon
around the North Dakota/South Dakota/Montana tri-border area. A
warm front will extend to the east of this low and a surface
trough to the south. These features will be favored areas for
convective initiation once the mid level wave does start
approach.

If storms can get going, let`s talk worst case scenario. The
environment will be characterized by MLCAPE in the 1500-2500
range and strong deep layer shear in the 45 to 55 knot range.
Storm mode becomes a bit complicated as the deep layer shear
vector will be fairly parallel with the warm front but there
will be a clear perpendicular component to the surface trough.
Thus, depending on storm coverage we could end up with a mixed
mode: some bowing/line segments and some embedded supercell
structures. If we can get a discrete supercell or two, there
could also be a conditional tornado threat along one of the
boundaries around and after 00z given increasing storm relative
helicity. That being said, the main threats would be hail to the
size of tennis balls and damaging wind gusts to 70 mph.

Best case scenario is that the wave comes in later in the
evening and elevated convection develops mainly across the
north. Storms also may approach from northeast Montana and/or
Saskatchewan in the overnight hours. These storms would still
have a risk for some severe hail and damaging winds but the
coverage and magnitude of threats would likely be less. It will
be interesting to see how all of the CAMs progress over the next
12 hours. Either way, showers and storms will likely linger
across portions of the Devil`s Lake Basin and/or James River
Valley through Monday morning. We will then pretty much dry out
for the rest of the work week. The one exception may be on
Tuesday, when another weak wave will bring a slight chance of a
shower or thunderstorm to the south and portions of the central.

Regarding temperatures, we will have one more very warm day
today with highs ranging from the lower 80s in the vicinity of
the Turtle Mountains to the mid and upper 90s southwest. Monday
will then be much cooler in the wake of the aforementioned
surface low, with highs ranging from the lower 70s northeast to
the mid 80s southwest. Highs will remain similar through
Wednesday, but the western ridge will start to nudge in again
towards the end of the week and into the weekend, promoting the
next warmup and the potential return of some 90s to the
forecast.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1233 AM CDT Sun Jul 14 2024

VFR conditions are generally expected through the period at all
sites. However, more showers and storms will develop Sunday
afternoon, potentially lasting into the late evening. Storms
will be isolated to scattered with exact locations and tracks
uncertain. A few storms could become severe. Large hail to the
size of golf balls and damaging winds to 70 mph will be possible
with the strongest storms. If a stronger storm does move
overhead any particular site, brief MVFR to IFR visibilities
will be possible. Winds may become gusty and erratic in the
vicinity of any thunderstorms.

&&

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

&&

$$

DISCUSSION...ZH
AVIATION...ZH