FXUS63 KBIS 192346
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
646 PM CDT Fri Jul 19 2024

.KEY MESSAGES...

- Isolated thunderstorms (15 to 20 percent chance) are possible
  this afternoon and into the early evening hours. A few could
  become strong.

- Expect daily low to medium chances (20 to 40 percent) for
  showers and storms from Saturday through Monday.

- Smoke aloft from distant wildfires will return later today
  through the weekend (at least).

- High temperatures will mainly be in the 80s through Tuesday,
  but some 90s may return mid to late week.

&&

.UPDATE...
Issued at 636 PM CDT Fri Jul 19 2024

Thunderstorms continue to fire across the south central, but
weak instability and no shear has hindered thunderstorm
development. Some showers and thunderstorms will move into the
northwest tonight but they are dealing with even less
instability. Smoke aloft continues to filter down from Canada so
far there has been no surface visibility reductions but that
could change later tonight when an inversion sets up trapping
smoke at the surface. No updates needed at this time, PoPs may
be tweaked before the next update.


&&

.DISCUSSION...
Issued at 220 PM CDT Fri Jul 19 2024

Western and central North Dakota currently sits under a fairly
stagnant upper level pattern with a highly amplified ridge to
our west, placing our area under nearly meridional flow aloft.
One weak wave that rode down the ridge passed through earlier
this morning and brought some scattered showers and
thunderstorms to the south central. However, this wave has now
moved off well to the south over South Dakota. Another weak wave
should pass overhead later this afternoon, keeping isolated
showers and thunderstorms (15 to 20 percent chance) in the
forecast through early evening. SPC mesoanalysis trends suggest
that the best thunderstorm environment later this afternoon will
be over the south central, where we will likely see MLCAPE
values in the 1000 to 2000 J/kg. However, shear will be meager
at best, maxing out in the 20 to 30 knot range south central
(and pretty much negligible elsewhere). Thus, any storms that do
form will likely be of the pulse/single cell variety with maybe
a multicell cluster or two south central where the best shear
should be. While severe weather is not expected, small hail,
winds to 55 mph, and frequent lightning will be possible under
the strongest storm cores. Brief heavy downpours will also be
possible given slow storm motions (stagnant flow aloft) and high
PWATS (1 to 1.3 inches or in the 75th to 90th percentile for
this time of year).

The forecast will be very similar Saturday through Monday as the
western ridge barely budges. This will mean daily low to medium
chances (20 to 40 percent) for showers and thunderstorms,
mainly in the afternoon and early evening as subtle waves ride
down the ridge. The best chances will generally be across the
north Saturday, south on Sunday, and east on Monday. On Monday,
the ridge finally starts to break down a bit and nudge our way.
This pattern should lead to mainly dry conditions with warming
temperatures as the ridge axis moves overhead sometime midweek.
Highs will mainly be in the 80s through Tuesday, but we will see
some low to mid 90s creep back in on Wednesday with some upper
90s possible again across the west by Thursday. NBM model spread
for temperatures is relatively small in the mid to long term,
suggesting confidence is fairly high with regards to the
pattern evolution and warming temperatures next week.

Finally, we will be seeing the return of smoke aloft from
distant wildfires later today through much of the weekend (at
least). The HRRR-Smoke model does not bring a ton of near
surface smoke into the area, but we could maybe see some slight
surface visibility reduction over the north central tonight
depending on how things evolve.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 636 PM CDT Fri Jul 19 2024

VFR conditions will continue across the region while winds will
remain light out of the north. A few thunderstorms continue
along the North and South Dakota border moving south.
Thunderstorm chances return tomorrow afternoon across the
northern half of the state. FU may cause visibility reductions
tomorrow morning for the northern and western terminals.

&&

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

&&

$$

UPDATE...Johnson
DISCUSSION...ZH
AVIATION...Johnson