275
FXUS63 KBIS 031745
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1245 PM CDT Wed Jul 3 2024

.KEY MESSAGES...

- Low to medium chances (20 to 40 percent) for showers and
  thunderstorms beginning this afternoon and lasting into the
  night, with the highest chances in the southwest. An isolated
  strong storm is possible this evening in the southwest as
  well.

- Scattered showers and thunderstorms are likely on Independence
  Day, but the entire day should not be a washout.

- Slightly below normal temperatures and chances for showers and
  thunderstorms will continue through the holiday weekend, with
  highs mainly in the 70s.

&&

.UPDATE...
Issued at 1241 PM CDT Wed Jul 3 2024

A few showers and thunderstorms have formed in the diurnal
cumulus in the northwest, so we have adjust PoPs to include that
since the NBH did not have convection this early. Sky cover was
also updated because the NBM again did not have clouds.
Convection is also started in the eastern Montana that might
move into western North Dakota.

UPDATE
Issued at 931 AM CDT Wed Jul 3 2024

Fog has dissipated around the Turtle Mountains so we have taken
the fog out of the forecast. Showers and thunderstorms look to
form in the west and southwest around 3PM CT.

UPDATE
Issued at 623 AM CDT Wed Jul 3 2024

Minimal changes were made to the forecast for this update. Some mid-
level clouds continue to linger around across the west, so we`ve
updated the cloud coverage to account for these. Otherwise, some fog
has begun to develop near the Turtle Mountains, with some reduced
visibilities reported in Bottineau. We`ve added in some patchy fog
to that area for the next 4 hours, as it will likely dissipate
relatively soon. Otherwise, the forecast remains on track.

&&

.DISCUSSION...
Issued at 332 AM CDT Wed Jul 3 2024

Presently, mostly clear skies and light winds are being observed
across western and central North Dakota. A small patch of mid-level
clouds may move into west-central North Dakota over the next few
hours, but isn`t expected to linger for long. Lows this morning are
forecast to be largely in the 50s across the area.

Aloft, broad cyclonic flow is present across the Northern Plains,
positioning North Dakota under generally westerly flow. A large
upper level trough sits across northern Ontario, forecast to move
east through the day today while a secondary trough across southern
Alberta and northern Montana is forecast to move east through the
northern High Plains at the same time. Ahead of this secondary
trough, surface low pressure is expected to deepen across Colorado
and Nebraska. As a result, we will continue to see the usual chances
for showers and thunderstorms this afternoon and evening while we
remain under the active flow aloft. Currently, we see some chances
(mostly 20 to 40%) for showers and thunderstorms across the west and
south this afternoon and evening. Given the lack of sufficient
instability, and only a small corridor of deep layer shear near 40
kts, we are not expecting severe weather to be a concern today. The
most recent model runs have pushed the surface low further to the
south, and in turn, have pushed much of the necessary ingredients a
bit further south as well. Thus, the SPC has moved the Marginal Risk
(level 1 of 5) out of our area, which is in line with what we`ve
been thinking as well. The most recent CAMs have also kept nearly
all of the robust convection to our south in South Dakota, with
mostly popcorn showers and thunderstorms in our area. A stray strong
thunderstorm cannot be ruled out however, as we do still have that
corridor of ample deep layer shear in our far southwest. If
something does strengthen down in that area, it won`t last for a
long time, but it could bring about some stronger winds and small
hail. All in all, the severe risk remains minimal for the day today.
Otherwise, high temperatures will remain just below seasonable, with
highs in the mid 70s to lower 80s.

As this trough continues to move east overnight into Independence
Day, additional moisture is expected to be transported north, while
the surface low begins to slide northeast into South Dakota. As
a result, chances for precipitation will linger around
overnight in the south, before expanding north and increasing
during the day. NBM PoPs continue to advertise 60 to 75% chances
for showers and thunderstorms across all of western and central
North Dakota. Given the slightly cooler temperatures, ample
moisture, and complete lack of shear, we are expecting the
makeup of this precipitation to largely be non-severe spotty
showers and thunderstorms. It is worth noting that while chances
for rain are rather high across the entire area for the entire
day, it is highly unlikely that any given area will see rain for
the entire day. Rather, the more likely outcome will be that
many locations will see brief, occasional showers, with breaks
in between them. Current CAMs do suggest potentially a small
area in the south central and southern James River Valley that
could see rain for most of the day, but we still are not
confident this would be the case. NBM probabilities for
exceeding 0.25" of rain have remained rather steady, with the
highest chances (40 to 50%) centered across the south central
and southern James River Valley. It is also worth noting that
while the daytime hours may be showery for much of the area, the
chances for rain decrease rather quickly heading into the
evening hours and towards sunset. At the moment, chances for
rain at 7 PM CDT are somewhere around 15 to 30%, with these
chances decreasing further afterwards. There could be some time
near the end of the day to enjoy the holiday, but given the
spotty nature of the showers, it is still a bit difficult to
tell exactly when we can expect the rain to end. Luckily, winds
will not be a concern for Independence Day, with sustained
northerly winds around 10 to 15 mph expected for much of the
area. The overnight hours heading into Friday are expected to be
drier, with skies gradually clearing, winds becoming light, and
lows in the 50s.

We will remain in this active pattern through at least the weekend,
with continued daily chances for showers and thunderstorms from
Friday through Sunday. Northwesterly cyclonic flow aloft will
persist, with embedded shortwaves passing through North Dakota each
day. The highest chances appear to be on Saturday, with the
shortwave being a bit more pronounced, however this wave is expected
to be fairly transient in nature. Most days see chances in the
afternoon and evening, before they decrease heading into the
overnight hours. The severe threat for these days appear to be low
at the moment, with the continued lack of necessary shear and
instability combined with relatively weak forcing at the
surface persisting through the period. It appears that the
extent of what we`ll be seeing is just some pop-up showers and
thunderstorms.

Beyond the weekend, we appear to be gaining confidence in a
breakdown of the active pattern, and the arrival of a warming and
drying trend. Long range guidance has begun to come more into
agreement with regards to the synoptic pattern on Monday, which is
suggesting that the broad ridge across the western CONUS will build
east and into the Northern Plains through the first half of next
week. WPC cluster analysis suggests a 70% chance of this ridge
beginning to influence North Dakota by Monday night, while the 30%
solution has it delayed by about a day. The NBM is also starting to
advertise this shift in pattern as well, with blended PoPs
decreasing and high temperatures increasing through this period. The
NBM spreads in high temperatures, while somewhat large heading into
the middle of next week, do continue to point at a gradual warming
trend through essentially the entire week. We`ll continue to monitor
how this pattern breakdown evolves, but at the moment, we are
thinking that next week we`ll see drier and warmer weather.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1241 PM CDT Wed Jul 3 2024

VFR with daytime cumulus clouds. In the northwest, there are a
few showers and thunderstorms, and a band of showers moving into
the southwest. VCSH or VCTS was used almost the whole period as
popcorn type showers are possible through the period. Winds
could gust to 25kts from the northwest, then calming and turning
north.


&&

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

&&

$$

UPDATE...Smith
DISCUSSION...Besson
AVIATION...Smith