508
FXUS63 KBIS 021128
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
628 AM CDT Tue Jul 2 2024

.KEY MESSAGES...

- There is a chance (20 to 40%) for showers and thunderstorms
  today.

- Breezy northwesterly winds are expected during the day today,
  diminishing near sunset.

- There is a chance (30 to 50%) for showers and thunderstorms
  Wednesday. An isolated strong storm is possible, mainly in
  the southwest.

- The chance for showers and thunderstorms on Independence Day
  is 60 to 80 percent across all of western and central North
  Dakota.

&&

.UPDATE...
Issued at 628 AM CDT Tue Jul 2 2024

Minimal changes were made to the forecast for this update. Some
radar returns have shown up across the far northwest, with a few
instances of drizzle being recorded. We`ve kept the PoPs as is, as
there may be some additional showers moving into the north over the
next hour or so. Otherwise, just blended the current observations
into the forecast along with some minor cloud coverage updates to
account for latest satellite observations.

&&

.DISCUSSION...
Issued at 402 AM CDT Tue Jul 2 2024

Showers have since exited the area this morning, with generally
clear skies and light westerly winds present across much of western
and central North Dakota this morning. However, wraparound moisture
associated with the low pressure system to our northeast has begun
to push some additional low clouds and spotty showers into our
northwest from southern Saskatchewan. As the low pressure system
moves off to the east, these showers may continue across the
northern tier of the area through the day today, with occasional
rumbles of thunder associated with them. Severe weather is unlikely
given the lack of forcing, but instability is just enough to allow
for the development of some isolated thunderstorms. With the surface
pressure gradient tightening on the back side of the aforementioned
low, some breezy northwesterly winds are expected through the day
today, with sustained winds generally around 20 mph, and gusts up to
30 mph. High temperatures will remain slightly below normal for this
time of year, ranging from the lower to upper 70s. The overnight
period is forecast to be rather uneventful, with precipitation
chances and wind speeds gradually diminishing. Lows will mostly be
in the 50s.

Aloft, the northwesterly flow associated with the generally cyclonic
pattern is expected to remain across the area through at least the
work week. A shortwave embedded within the flow is expected to pass
through southern Montana and northern Wyoming on Wednesday, helping
initiate some more showers and thunderstorms across the region.
Surface forcing and instability as a whole remain rather weak, with
the most robust values staying to our south across Nebraska and
South Dakota, thus keeping much of the severe threat to our south.
However, 0-6km deep layer shear values of roughly 40 kts do encroach
into our far southwest for a few hours, which may support a very
isolated strong to severe storm threat near the South Dakota border
Wednesday evening. Most of the CAMs keep convection well to our
south, with a few solutions suggesting a few thunderstorms across
our southwest in the evening hours. The severe threat, while
remaining rather low, is non zero for that area. The SPC did
maintain a Marginal Risk (level 1 of 5) area across our far
southwest, but given the uncertainty in the exact location of
convective initiation and the marginal makeup of the ingredients
needed for strong to severe storms, the areal extent of this risk
remains rather small. The CSU machine learning guidance has also
removed the low risk of severe hail from our southwest, pushing it
further south and out of our area.

As the trough deepens and moves through the Great Plains through the
middle of the week, we continue to see indications of Independence
Day being cooler and wetter than usual. WPC cluster analysis has
really begun to come into agreement with regards to where this upper
level trough will set up across the Plains, which owes to the
continued confidence in NBM PoPs ranging from 70 to 80% across the
entire area during the day. Showers and thunderstorms are likely
across nearly all of western and central North Dakota during the
day, with mostly cloudy skies expected. Along with the deepening
trough aloft, cooler midlevel temperatures are expected to filter in
from the northwest, helping reduce highs on Independence Day to the
lower to mid 70s. Winds, however, are expected to be rather light
for much of the area. Even though the chances for precipitation
overall has remained the same, the actual amount of precipitation
that can be expected has decreased somewhat. NBM probabilities of
exceeding 0.25" of rain on Independence Day has decreased to around
30 to 50%, with the highest chances in the south central and
southern James River Valley. The chances for severe weather during
the day is very low, given the cooler temperatures and cloud
coverage helping stabilize the atmosphere. CSU machine learning
guidance keeps severe probabilities entirely out of our area. While
occasional rumbles of thunder can be expected, severe weather is not
anticipated. Model precipitable water values range from around 1.00"
to 1.10", which places it between 75th and 90th percentiles for this
time of year, which helps support the widespread chances for
precipitation and the chances for exceeding a quarter inch of rain.
All in all, we can expect Independence Day to be rainy and cloudy,
with chances for rain and cloud coverage decreasing overnight into
Friday.

The active cyclonic flow aloft will continue into the weekend, with
daily chances for showers and thunderstorms continuing as a result.
Long range guidance is indicating multiple shortwave troughs to pass
through the Northern Plains during this period, with chances for
rain returning to the area Friday into Saturday morning, Saturday
into early Sunday morning, and Sunday afternoon into the overnight
hours. Day to day high temperatures will remain in the mid 70s to
lower 80s. Given the moisture return and instability each day, we
can expect to see some rumbles of thunder with these waves, though
its a bit too far out to really tell what the severe potential will
be with them.

This active pattern may finally break down next week, as the very
prominent trough across the western CONUS may slowly build its way
east into the Plains. WPC cluster analysis indicates that there is a
65% chance for this ridge to be influencing North Dakota by
Wednesday, while the remaining 35% chance keeps the ridge to our
west, building into the Northern Plains a day later. Generally, with
a ridge pattern like this, we can expect to see a gradual warming in
temperatures, clearer skies, and drier conditions, reducing the
chances for the near-daily showers and thunderstorms we`ve been
seeing for much of this summer. The NBM spreads in high temperatures
do widen out heading into next week, but the overall trend does
suggest a warming pattern, lasting through at least next Wednesday.
Beyond this point, its hard to say whether or not the ridge pattern
will continue. Needless to say, confidence continues to increase in
the active pattern breaking down some time early next week, with a
warmer and drier pattern taking its place.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 628 AM CDT Tue Jul 2 2024

Generally VFR conditions are present across the area, with higher
pressure building into the area from the west. Chances for showers
and thunderstorms return across the north and west during the day
today, with the greatest chances near KMOT and KXWA. Gusty
northwesterly winds are also expected during the day today, with
sustained speeds near 20 kts and gusts up to 30 kts. Winds will
decrease after 00z, along with chances for precipitation. Generally
light winds and clear skies can be expected by late tonight.

&&

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

&&

$$

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