484
FXUS63 KBIS 150600
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
100 AM CDT Tue Jul 15 2025

.KEY MESSAGES...

- Isolated strong to severe thunderstorms are possible through
  the early morning. Expected hazards include hail as large as
  ping pong balls and wind gusts up to 70 mph.

- Well below normal temperatures Tuesday through Thursday, with
  near-record cold highs in the 60s Tuesday and Wednesday.

- Medium to high chances for showers tonight through Wednesday.

&&

.UPDATE...
Issued at 100 AM CDT Tue Jul 15 2025

Scattered showers and thunderstorms are found over south western
and south central North Dakota at the time of this. One line of
storms are found along a quasi-stationary bound stretching from
Mercer County through Foster/Stutsman counties, and another is
oriented being a surface boundary draped between Bowman and
Grant counties. These storms have been fairly pulsey, with some
cells along the quasi-stationary becoming severe. A Severe
Thunderstorm is in effect for Stutsman and Foster counties
through the mid morning, though storms are already starting to
diminish at the time of this update. While mainly dry conditions
are found in northwestern and north central North Dakota,
showers and thunderstorms are starting to move into northeastern
Montana. These are expected to move into northwestern North
Dakota, expanding broadly across northern North Dakota through
the morning and much of the day today. Regarding updates, have
made some tweaks to the short term PoPs to account for slightly
faster development in the southwest.

UPDATE
Issued at 1007 PM CDT Mon Jul 14 2025

Thunderstorms have developed over parts of south central ND near
the SD border, or mainly over eastern Sioux, Emmons, and
McIntosh counties. These thunderstorms may expand a bit more in
coverage, with a few strong storms possible, before likely
weakening over the next couple hours. Additional development was
visually observed a fair bit north of the office and is
starting to produce radar returns. This west to east orientated
line of development is mainly along and near Highway 200. Per
the latest model guidance, this is the area most favored to
produce isolated strong to severe thunderstorms tonight.

UPDATE
Issued at 659 PM CDT Mon Jul 14 2025

Mostly sunny skies are present over southern and northwestern
ND with mostly cloudy skies over the northeast. A few showers
tried to develop an hour or so ago in the far southwest, but
were unable to sustain themselves. That said, showers and
thunderstorms are still expected to develop across much of the
state this evening and especially overnight. However, CAMs
continue to disagree moderately in regard to timing and
placement of thunderstorm development. A few severe storms
remain possible.

&&

.DISCUSSION...
Issued at 354 PM CDT Mon Jul 14 2025

Early afternoon surface analysis shows a quasi-stationary
surface boundary extending northeast from low pressure over
eastern Wyoming, with the wind shift/trough axis from around
Dickinson to Devils Lake to Grand Forks. Flow aloft has turned
zonal, with no waves of appreciable amplitude noted in the mid
to upper level height fields. A band of showers is moving east-
southeast across southern Canada and into far northeast North
Dakota, sandwiched between an upper jet to its north and a low
level baroclinic zone to its south. Temperatures across
southwest and south central North Dakota have soared into the
90s, while far northern areas remain stuck in the 70s.

From tonight through Tuesday, a series of deepening shortwaves
across southern Canada will force colder air into the Northern
Plains, squeezing the thermal gradient against the surface
boundary which would otherwise act as a warm front. The clashing
of these two air masses is likely to result in widespread
showers and scattered thunderstorms throughout the region over
the mentioned time period. Ensembles show a break in rain
chances, especially for central North Dakota, Tuesday night as
Canadian high pressure wedges drier air in from the
north/northeast. But this is now followed by guidance
consolidating on a higher-amplitude shortwave bringing another
round of rain across the state on Wednesday, with the highest
chances in southwest North Dakota. QPF threshold probabilities
and ensemble mean QPF have slightly decreased from previous
forecast iterations, but there are still high chances for at
least 0.25" and medium chances for at least 0.5" across western
and south central North Dakota. In contrast, north central parts
of the state only have medium odds for over 0.25" and low odds
for over 0.5".

The main concern for the next 24 to 30 hours is the potential
for strong to severe thunderstorms. There are still a variety of
outcomes being offered by CAMs, but some common themes are
emerging. First of all, it is increasingly unlikely that we will
see convective initiation this afternoon, as there does not
appear to be enough lift to overcome -50 to -100 J/kg MLCIN. If
an attempt at initiation is to be made, it would likely be along
the quasi- stationary surface boundary. As of 330 PM CDT, a
cumulus field was increasing in coverage and density over
southwest North Dakota, but satellite shows vertical growth to
be limited. The most likely outcome now appears to be for
convection to initiate, perhaps rapidly so, sometime around 9 PM
to midnight CDT along the baroclinic zone where strong low
level frontogenesis and modest low to mid level moisture
transport are forecast. The most likely location for this to
occur is between Highway 2 and Interstate 94. There are higher
odds for initial convection to blossom over central parts of the
state, but areas farther west could quickly fill in. There is
also a signal for a separate batch of convection with a plume of
mid level theta-e that could move from north central South
Dakota into the James River Valley.

All convection late this evening through tonight should be
elevated. Forecast MUCAPE ranges from as much as 1000-2000 J/kg
across southern North Dakota to less than 500 J/kg and
decreasing with time across the far north. In contrast, there is
much stronger shear farther north than south, the magnitude of
which will depend on the effective inflow layer. Using the 2-7
km layer as a proxy, forecast effective bulk shear ranges from
around 20-30 kts south to as high as 50 kts along the Canadian
border. While any part of western and central North Dakota could
see a strong to severe storm through tonight, the most
favorable combination of shear and buoyancy could be collocated
with the strongest mesoscale forcing. Having said all this, it
can sometimes be a struggle for elevated convection to realize
all of its available potential energy, and it would be a
reasonable outcome for there to only be weaker thunderstorms
through tonight. Still think that a scenario with at least a few
stronger to severe storms is the most likely outcome when
taking into account CAMs` reflectivity/UH output.

The colder air mass advecting down from Canada should push
instability/buoyancy off to the south on Tuesday. There is a low
probability that the unstable air mass may not clear the
southern James River Valley before thunderstorms become more
widespread early Tuesday afternoon, but there is not much model
support for this outcome.

The other major story for the forecast is unseasonably cold
temperatures, especially daytime maxima. Forecast highs in the
60s Tuesday and Wednesday are around 15 to 25 degrees below
normal for what should be the warmest time of the year.
Southwest North Dakota looks exceptionally cold, with higher
confidence in rainy conditions on Wednesday that could keep
daytime highs in the upper 50s. Record cold high temperatures
across western and central North Dakota are generally in the
lower to mid 60s, so there could be a few of these records
broken the next couple days. Dickinson in particular is forecast
to set new record cold daily maximum temperatures both Tuesday
and Wednesday. Low temperatures are forecast to mainly be in the
mid 40s to lower 50s over this time period, which is still
below normal but not to the same extent as high temperatures are
forecast to be.

A slow warming trend is expected to commence on Thursday,
lasting through the weekend and into next week when highs could
return to near or slightly above average. The latest ensemble
guidance has trended toward favoring more of an active quasi-
zonal pattern that includes a possible shortwave passage late
Thursday into Friday that is showing up in mean vorticity fields
across all ensemble clusters. The NBM has increased its PoPs
into the 30 to 50 percent range late Thursday night through
Friday afternoon. There may be enough CAPE and shear to support
a strong to severe storm threat over this time period, and CSU
machine learning guidance does paint low probabilities for
severe weather over southwest and south central North Dakota on
Friday.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 100 AM CDT Tue Jul 15 2025

Mainly VFR ceilings and visibilities are found at all TAF sites
at the time of this update. Scattered showers and thunderstorms
are found across southern North Dakota this early morning.
Another push of showers and storms are anticipated to move into
northwester North Dakota later this morning, though these should
generally become showers by the mid morning hours. MVFR to IFR
ceilings and visibility are anticipated if any storms manage to
move any terminal, though the confidence remains low at this
time. Thus, have generally added PROB30 groups for -TSRA for
KXWa, KBIS, and KJMS at the time of this update. A general
lowering to MVFR to IFR ceilings is anticipated through the the
early overnight period as showers fill in and become more
widespread across the forecast area. These showers will linger
through the day today and through the end of the TAF period.
Northwest winds are expected to become gusty through the
morning and afternoon, with sustained speeds up to 20 knots and
gusts up to 30 knots. Winds will then diminish through the
evening and the end of the TAF period.

&&

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

&&

$$

UPDATE...Adam/Telken
DISCUSSION...Hollan
AVIATION...Adam/Telken