822
FXUS63 KBIS 021755
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1255 PM CDT Tue Jul 2 2024

.KEY MESSAGES...

- There is a chance (30%) for showers and thunderstorms today.

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

- There is a chance (40%) 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 80 percent across all of western and central North Dakota.

&&

.UPDATE...
Issued at 1251 PM CDT Tue Jul 2 2024

More showers have developed in the cyclonic flow and are slowly
moving south as they rotate around the low in Canada. Slight
chance of thunder with these, the chance will increase some as
more diurnal heating occurs. PoPs have been adjusted.

UPDATE
Issued at 940 AM CDT Tue Jul 2 2024

The very light isolated showers in the north continue, have not
seen any observations of the rain making it to the ground. These
showers chances will continue in the cyclonic flow. PoPs were
reduced to slight chance through the late morning.

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 /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1251 PM CDT Tue Jul 2 2024

Mainly VFR with scattered to broken cumulus clouds at 4000ft.
Scattered showers around most terminals this afternoon then
skies clear around sunset. Winds will gust near 30kts from the
west until sunset.

&&

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

&&

$$

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