679
FXUS63 KBIS 041745
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1245 PM CDT Thu Jul 4 2024

.KEY MESSAGES...

- Numerous showers and scattered thunderstorms are expected
  today, especially during the afternoon. However, the entire
  day will not be a washout, as much of the activity will be of
  the "hit or miss" variety.

- Slightly below normal temperatures with daily chances for
  showers and thunderstorms will continue through the holiday
  weekend. Highs will mainly be in the mid to upper 70s.

- A gradual warming and drying trend is expected to begin next
  week.

&&

.UPDATE...
Issued at 1235 PM CDT Thu Jul 4 2024

Storms are increasing in coverage with the warming of the day as
expected. As of right now, we have two main areas of relatively
dense lightning: one across the west (mainly the northwest
where we also have had reports of pea size hail), and another
along a line from just east of Harvey, down into southwest
Kidder county. Showers and storms will continue to increase in
intensity and coverage as they rotate around the upper low
currently located over South Dakota. While the severe threat is
low with this activity, there will be plenty of lightning so be
alert if outdoors for holiday activities. We are also growing at
least a little more concerned about some training convection as
the upper low will be stubborn to kick out of the region. Over
these areas, we will have keep a close eye on the rainfall
rates as these storms are very efficient rain makers and not
moving very fast. No major changes were needed for the gridded
forecast update. Just blended in the latest observations to the
forecast.

UPDATE
Issued at 917 AM CDT Thu Jul 4 2024

No major changes were needed for this update. Just adjusted
precipitation chances slightly over the next couple of hours
based on the latest radar trends and observations. Recently, the
only thunderstorm activity has been over Bottineau and Foster
counties. We expect that lightning activity will be on the
increase towards the late morning or early afternoon.

UPDATE
Issued at 626 AM CDT Thu Jul 4 2024

Minimal changes were made with this forecast update. Showers and
isolated thunderstorms are ongoing across the south central and
southern James River Valley, with coverage expected to increase and
expand across the rest of the area through the afternoon and early
evening hours. Shower development in the west has been a bit slow to
begin, but within the past few radar scans, popup showers have begun
to form in northeastern Montana and southern Saskatchewan. For the
most part, just blended the current observations into the
forecast.

&&

.DISCUSSION...
Issued at 331 AM CDT Thu Jul 4 2024

At the moment, surface low pressure is positioned across northern
North Dakota, while a trough aloft continues to deepen and pass
across the Dakotas. Showers and isolated thunderstorms have already
begun to develop across the southern half of the area this morning,
with additional showers slowly making their way south from southern
Manitoba and southern Saskatchewan. Lightning activity has been
limited due to the near complete lack of instability, but a few
isolated lightning strikes have been reported to the north of
Bismarck. Mid- to high-level clouds have expanded across nearly the
entire area, and will remain across the area through the day today.
Lows this morning will mostly be in the lower to mid 50s, with light
and variable winds.

Confidence remains fairly consistent with regards to the forecast
for Independence Day. As the aforementioned trough and attendant
surface low slowly move east through the day, wraparound moisture
will help with the formation with numerous showers and isolated to
scattered thunderstorms across all of western and central North
Dakota. These chances will be maximized from the early afternoon
through the evening, before beginning to decrease towards/after
sunset. The important thing to know with the setup for today is that
while chances for showers will be pretty high (roughly looking at 60
to 70% chances across essentially the entire area), the spotty
nature of these showers will make for a very "hit or miss" day when
it comes to storm activity. There`s a good chance that any of these
numerous storms will impact any given location, but the storm itself
will be rather short lived, allowing for breaks between rounds of
rain. Basically, the day today will not be a washout, but there`s a
pretty good chance that most locations will see a quick round of
rain at some point during the afternoon and evening hours. Luckily,
given the persistent cloud coverage, lack of instability and shear,
and the weak forcing at the surface, severe weather will not be a
concern today. Given the influence of the trough aloft, high
temperatures will be relatively cool, with most areas staying in the
low to mid 70s. Under the slack pressure gradient, winds will
generally be light, with a few areas in the far southwest
potentially seeing speeds up to 15 mph.

Beyond the holiday today, we can expect near daily chances for
showers and thunderstorms through the weekend. Cyclonic
northwesterly flow aloft will allow for a few additional shortwaves
to pass across the Dakotas, bringing about these chances for showers
and thunderstorms. These chances are maximized every afternoon and
evening, with the highest chances in the northwest on Friday, the
north-central on Saturday, and in the northeast on Sunday. While
severe weather remains unlikely with these waves of precipitation,
the CSU machine learning guidance has picked up on a narrow
corridor of low severe hail chances across the James River
Valley on Sunday. At the moment, the shortwave passing through
the area on Sunday does appear to be the most robust out of any
of the waves through the weekend, but the forcing and
instability still appear to be marginal at best. We will
continue to monitor this period for any severe potential over
the coming days. Generally, with the pattern persisting through
the weekend, we can expect highs each day to be mostly in the
70s, with overnight lows mostly in the 50s. Winds will generally
be light and out of the northwest, with sustained speeds maxing
out around 10 to 15 mph.

Heading into next week, confidence has continued to increase in a
breakdown of the cyclonic pattern aloft, resulting in a slow warming
and drying trend through the week. The large ridge currently in
place across the western CONUS is forecast to very slowly build
eastward through the coming days, with the 850 mb thermal ridge
expected to begin influencing North Dakota on Monday. Chances for
rain decrease thereafter, with clearer skies and drier conditions
expected under the ridge. NBM spreads in high temperatures have
narrowed considerably through Wednesday, with the 25th/75th spread
only reaching 5 to 6 degrees during this period. Even though the
spread increases heading into the end of next week, the general
warming trend actually continues even further. We`ll have to
continue monitoring the extended period to see the extent of this
warming trend, but as it stands right now, we may start seeing
widespread highs in the 80s by Thursday, with temperatures
increasing further beyond that point.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1235 PM CDT Thu Jul 4 2024

Hit or miss thunderstorms continue to increase in coverage and
intensity as expected early this afternoon. The isolated to
scattered nature of the convection makes the precipitation
forecast complicated for any individual point. Thus, we are
relying heavily on vicinity wording and tempo groups for the
18z TAF period. Severe storms are not expected but the strongest
storms may produce locally heavy rainfall and small hail. If a
heavier storm moves overhead, brief MVFR to IFR visibilities
will be possible. Some embedded MVFR ceilings are not out of the
question either but it seems that most will see VFR ceilings
through the period. Showers and storms will start to diminish in
the evening. Winds may become gusty and erratic in and around
any thunderstorms.

&&

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

&&

$$

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