174
FXUS63 KBIS 142359
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
659 PM CDT Mon Jul 14 2025

.KEY MESSAGES...

- Isolated strong to severe thunderstorms could develop this
  evening through tonight. 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 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 /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 659 PM CDT Mon Jul 14 2025

VFR ceilings and visibility are present across the state at this
time. However, widespread showers and thunderstorms are expected
to develop this evening and especially overnight. Showers and a
few rumbles of thunder are then expected for the day Tuesday.
Models remain in disagreement as to the timing of when any
thunderstorms will initiate, as well as exact location. As a
result, have used a large amount of PROB30 groups to illustrate
this uncertainty. With this system, IFR ceilings are expected to
drop down from the north tonight before improving from north to
south Tuesday afternoon.

&&

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

&&

$$

UPDATE...Telken
DISCUSSION...Hollan
AVIATION...Telken