313
FXUS63 KBIS 261935
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
235 PM CDT Fri Jul 26 2024

.KEY MESSAGES...

- Potentially thick near-surface smoke may return later today
  and through the night to much of western and central North
  Dakota.

- Daily low to medium chances (20 to 40 percent) for
  thunderstorms are expected through the start of next week.
  Some storms could be strong to severe over central North
  Dakota Saturday and Sunday.

- Temperatures remain at or above normal, with highs mainly in
  the mid 80s to mid 90s through next week.

&&

.DISCUSSION...
Issued at 235 PM CDT Fri Jul 26 2024

Painting the synoptic picture, western and central North Dakota
currently sits under the influence of southwest flow aloft as an
upper level trough is starting to nudge into the region. A stacked
low is located over northern Saskatchewan with a cold front
extending south into central and southwest North Dakota. The stacked
low and front will slowly move off east through the weekend, but
western and central North Dakota will remain in persistent
zonal/southwest flow for several days as broad western US troughing
settles in.

For the rest of today, we will see plenty of mid to high clouds
along the cold front as it moves east. Forecast soundings suggest
plenty of dry air near the surface so cloud bases are fairly high.
Thus, while we continue to see radar echoes all along this boundary,
it is likely that only a little bit of light rain is making it down
to the surface. Later this afternoon and into the evening,
instability will increase along and ahead of the cold front which
will also lead to an increase in shower and thunderstorm coverage
and intensity. That being said, it`s a little bit unclear if showers
and storms will be along or behind the front. The best chance for a
strong storm or two will generally be early this evening in the
vicinity of the James River Valley. MLCAPE along the front is
forecast to be in the 1000 to 1500 J/kg range with deep layer shear
in the 30 to 40 knot range. If storms were able to fire in the warm
sector, they would have quite a bit more instability to work with,
but it seems likely that substantial capping will keep this scenario
from happening. Either way, the parameter space will be sufficient
for some organized or semi-organized convection. The most likely
scenario is a strong storm or two over the James River Valley this
evening with some gusty winds to 50 mph and small hail. Storms will
generally move out in the mid to late evening hours with some
showers lingering through the overnight.

For Saturday, we will stay in southwest flow aloft but most of the
larger scale forcing will have moved off to the east. However, a
diffuse stationary boundary extending north northeast from a weak
surface low over northwest South Dakota and several outflow
boundaries from tonight`s convection will be lingering around,
likely leading to enough convergence to trigger some storms by the
late afternoon and evening. Models are currently having a hard time
deciding on how far west the instability axis will extend which will
have a big impact on the coverage of strong to severe storms on
Saturday. The most likely scenario is that we will see some isolated
to scattered severe storms across the central and into portions
of the Devil`s Lake Basin and James River Valley. The
environment here will be characterized by moderate instability
(1500 to 2500 J/kg MLCAPE) and deep layer shear around 35 to 45
knots. Thus, any storms that can get going here will have the
potential to become severe. Hail to the size of golf balls and
winds to 60 mph will be the main threats. The tornado threat
appears to be fairly low, but when there are plenty of
boundaries floating around, we cannot completely rule it out.
The main limiting factor will be the uncertainty regarding storm
coverage given generally weak forcing, but another fly in the
ointment (per some forecast soundings) could be some dry air
entrainment into updrafts. Storms will once again weaken in the
late evening hours, potentially giving way to some more showers
overnight.

The setup on Sunday doesn`t look all too different from Saturday as
far as parameter space goes, but maybe a bit further south and east.
However, we will have a stronger shortwave moving into the southwest
around 00z Monday, which may end up leading to some sort of
cluster/MCS moving across the state through the night. It`s a bit
early to talk specifics, but these storms could also be strong to
severe with a better wind threat potentially depending on how the
boundary layer evolves.

We will then continue to have daily low to medium chances (20 to 40
percent) for showers and storms Monday through Wednesday. CSU
Machine Learning guidance is also suggesting that low severe weather
chances may hang around Monday and Tuesday which seems reasonable
given the parameter space many of the deterministic models are
suggesting.

Regarding the heat, it will be another hot one on Saturday with
highs expected to be in the mid 80s to mid 90s. However, the area
with the highest dewpoints (east) will be cooler than today so for
now, there are no plans for further Heat Advisories. We will cool
down slightly into the 80s on Sunday before the next wave of heat
and humidity moves in Monday and through the week. The hottest
day of the period will be on Tuesday when highs will generally
be in the lower 90s to lower triple digits. Thus, more heat
headlines could be needed eventually for Tuesday. We don`t cool
down much through the rest of the week with plenty of highs in
the 80s and 90s expected through Friday.

Finally, the HRRR-Smoke model continues to be aggressive in brining
in some thicker near surface smoke to the area late this afternoon
and through the night. While smoke aloft is likely to hang around
for at least several more days, it looks like we may get a break
from near surface smoke after tonight.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1257 PM CDT Fri Jul 26 2024

VFR conditions are generally expected at all sites through the
period. However, we will see periods of isolated to scattered
showers and thunderstorms this evening and into the overnight
hours. If a stronger storm moves overhead, brief MVFR
visibilities may be possible. Winds also may become gusty and
erratic in and around any showers or storms. Finally, near
surface smoke from distant wildfires may bring periods of
reduced visibility through the night.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 9 PM CDT this evening for NDZ048-051.

&&

$$

DISCUSSION...ZH
AVIATION...ZH