608
FXUS63 KBIS 242006
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
306 PM CDT Mon Jun 24 2024

.KEY MESSAGES...

- There is a low probability for isolated severe storms this
  evening from the Highway 83 corridor through the James River
  Valley. Potential hazards include hail up to golf ball size
  and damaging winds up to 70 mph.

- A drier and quieter middle of the work week is expected, with
  mostly clear skies and highs in the 70s and lower 80s on
  Tuesday and Wednesday.

- Medium to high chances (ranging from 60 percent south to 80
  percent north) for showers and thunderstorms Thursday
  afternoon through Thursday night.

- Friday and Saturday will cool further, with highs in the 60s
  north to lower 70s south.

&&

.DISCUSSION...
Issued at 254 PM CDT Mon Jun 24 2024

Currently, mostly clear skies are present across western and central
North Dakota, with a few high cirrus streaming into the northwest,
and some fair weather cumulus across the south central.
There were some billow clouds in the south central earlier as
well, but they have since eroded away, indicating the
possibility that the boundary layer is beginning to destabilize
across the south central, especially in the southern James
River Valley. There was a single little clump of cells
attempting to strengthen in western Stutsman County about an
hour ago, with a few attempts looking pretty decent in terms of
reflectivity. Each subsequent attempt resulted in better looking
updrafts and higher reflectivity values, but it was just a bit
too narrow for it to really sustain itself, and within the past
30 to 60 minutes it has completely fallen apart. Lightning was
also analyzed in this storm, showing up after a few attempts,
but overall, the storm kept weakening before becoming anything
strong, before it would attempt to strengthen again.

While these storms failed, it was interesting to see how quickly it
seemed to overcome the cap that had been in place. The environment
within this area is absolutely worthy of supporting some strong to
severe storms, with deterministic MUCAPE values exceeding 3000 to
4000 J/kg as a result of the very warm and moist environment. 0-6 km
bulk shear isn`t as high, with values only in the 30 to 40 kt range,
but its certainly still supportive. As a result, the SPC kept much
of our far eastern portions within a Marginal Risk (level 1 out of
5), supporting isolated strong to severe storms through this
evening. However, the main concern from previous forecasts has been
the strength of the cap across the area. Initially, we had been
anticipating the cap to be very strong, which would help subdue most
attempts of convection. If anything managed to break through later
this evening, we would anticipate quick growth into a strong to
severe storm, but CAMs have not been resolving really any convection
in the area whatsoever. The fact that there has already been a storm
strong enough to start intensifying has suggested that the cap may
not be as strong as initially thought. It is still certainly strong,
but definitely worth following closely, in case more signs begin
to point towards it weakening.

Something else we`ve noticed has been the presence of some sort
of boundary, stretching roughly west to east from southwestern
Kidder county, through central Stutsman county, and into Barnes
and Cass counties within Grand Forks` forecast area. This cell
formed on the western half of this boundary, which leads us to
believe that this may have been a residual, slow moving outflow
boundary from the convection earlier this morning. We`ll
continue to monitor how both this boundary and this storm
develop, but if this boundary can sufficiently help erode the
cap as it slowly wanders east southeast, we may see more
attempts at convection strong enough to overcome the cap and tap
into the potent instability across the southern James River
Valley this evening. Given that instability is expected to
decrease quite a bit later this evening, the threat for severe
weather isn`t expected to last long. Temperatures today continue
to climb, with many places in the south approaching the upper
80s. Some places may briefly see 90 degrees, which combined with
dew points in the mid 60s to lower 70s, may make it feel even
warmer than 90.

The middle of the work week is expected to be a bit quiet, with
temperatures on Tuesday and Wednesday forecast to largely be in the
70s, with lower 80s possible in the southwest. Aloft, zonal westerly
flow will be present through Wednesday morning, before shifting to
be more northwesterly Wednesday night. Minimal precipitation chances
are expected during this time, as well as generally clear skies, as
surface high pressure from southern Saskatchewan and Manitoba slides
southeast across North Dakota. It might be a bit breezy in the north
on Tuesday as well, as the pressure gradient deepens a bit with the
approach of the surface high. All in all, a generally quiet period
is expected from tonight through Wednesday evening.

Late Wednesday night sees the arrival of our next wave of
precipitation chances. Flow aloft becomes a bit more disturbed and
out of the southwest early Thursday morning, as a deep trough across
the Pacific Northwest deepens and moves east into the northern High
Plains. The attendant surface low is forecast to deepen and move
east through South Dakota, resulting in wraparound moisture
filtering into North Dakota and bringing about a good amount of
rain. Current long range guidance suggests PWAT values within the
90th to 95th climatological percentile for PWAT values at
Bismarck (roughly in the 1.1 to 1.3 inch range), with a few
areas potentially even higher than that, which indicates that
any showers and thunderstorms that develop will be very
efficient producers of precipitation. It`s also worth noting
that the NBM PoPs have already begun to advertise widespread 60
to 80 percent chances for showers and thunderstorms on
Thursday. This could also be our next wave of severe weather as
well, with long range deterministic guidance also indicating
favorable conditions for all hazards. CSU machine learning
guidance continues to advertise the potential for severe weather
across much of our western and central areas as well.

Temperatures on Thursday will remain warm, with temperatures ranging
from the 70s in the northeast to the lower 90s in the southwest. As
the system moves through on Friday and Saturday, highs will cool
quite a bit, with highs on Saturday only in the 60s for much of the
area. Precipitation chances decrease and temperatures increase once
more heading into the start of next week, with zonal flow aloft and
ridging arriving from the west once again.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1225 PM CDT Mon Jun 24 2024

VFR conditions are present across the area, and will prevail
through the TAF period. Some isolated low clouds are forming in
a few areas as well, but should dissipate shortly. Winds are
not being resolved well by the models due to the residual
boundaries left behind by the convection this morning, but by
later this afternoon, they will mostly be out of the northwest
around 10 to 15 kts, before decreasing to mostly light and
variable into the overnight hours.

&&

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

&&

$$

DISCUSSION...Besson
AVIATION...Besson