479
FXUS63 KBIS 201950
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
250 PM CDT Thu Jun 20 2024

.KEY MESSAGES...

- Chances for showers and thunderstorms will increase through
  this afternoon and evening. A stronger storm with small hail
  and gusty winds will be possible across the northwest this
  evening.

- Widespread showers and scattered thunderstorms are expected on
  Friday, with a Marginal Risk (level 1 of 5) for isolated
  severe storms over portions of the far southwest and far south
  central.

- Showers and thunderstorms will diminish through Saturday
  morning, with continued daily chances for showers and
  thunderstorms into the middle of next week.

- Temperatures will continue warming through the weekend, with
  expected highs on Monday in the mid 80s to lower 90s.

&&

.DISCUSSION...
Issued at 247 PM CDT Thu Jun 20 2024

Precipitation has been slow to arrive today, with very few radar
returns in the northwest and southwest. There may be a few drops of
rain reaching the ground in these areas, but it seems rather
unlikely at this point. Surface high pressure dominates north of the
International Border, with a weak pressure gradient across most of
the state. Southwesterly flow aloft continues, with a weak embedded
impulse moving through the flow to our south, across South Dakota.
Convection is ongoing in that area, with the expectation that this
convection won`t move north into North Dakota. The SPC has
introduced a Marginal Risk (level 1 of 5) to eastern Montana, but
this risk stops short of the North Dakotan border. As such, we can
really just expect to see some showers and an occasional
thunderstorm in the northwest and south today and tonight, with the
greatest chances for thunder being in the northwest, aligned with a
narrow corridor of MUCAPE near 1500 J/kg and 0-6 km bulk shear of
around 40 to 50 kts. Severe weather is not anticipated at this time,
though some storms that perfectly ride the CAPE boundary may see
some small hail.

After a brief break in precipitation overnight, chances begin to
move back into the area from the south on Friday. An upper level
trough positioned across Alberta is expected to dive south through
Friday, helping drive some more embedded shortwaves across the
Northern Plains. A surface low across eastern Wyoming and western
South Dakota is expected to deepen and track northeastward through
Friday, helping push that precipitation northward. At the moment,
chances for precipitation range from 40 to 70 percent, with the
highest chances expected during the late evening and early overnight
period. Similar to today, we are anticipating most of this to be
showery, with some isolated thunderstorms. However, this time the
SPC has outlined a Marginal Risk (level 1 of 5) for the very far
southwestern corner of the state, as well as right along much of the
border with South Dakota. There`s a very narrow corridor of MUCAPE
near 1500 J/kg in this area, combined with 0-6 km bulk shear values
nearing 50 kts. The setup just outside of our area is a bit more
potent, which may result in greater chances of storms forming
outside of our area, riding the CAPE boundary and intensifying as it
approaches our border, and briefly being able to sustain itself and
potentially strengthen once they enter North Dakota. However, given
how borderline the event is to begin with, the chances for anything
being severe within our area is still rather low, but also still non-
zero. Given the quick reduction in instability and shear as you move
east, any thunderstorm that forms across much of the rest of our
area is not expected to become severe.

As the aforementioned upper level trough continues moving east, we
are expected to enter a slightly drier and warmer pattern, with a
fairly pronounced ridge building into our west. While temperatures
today and Friday are expected to be slightly below normal, we can
expect to see a quick warmup into the mid 80s and lower 90s by
Monday, which is also expected to be the warmest day of the forecast
period. Chances for precipitation will be on and off, with 15 to 30
percent chances for showers and thunderstorms on Monday, and 10 to
15 percent chances for showers each subsequent day. Due to how warm
it will be, and with the continued southerly flow bringing in decent
moisture over the next few days, instability values will support at
least isolated thunderstorms associated with these showers each day.
The shortwaves embedded within the upper level flow that will bring
these chances each day are not very strong, given the more west-
northwesterly flow aloft, so the exact positioning and timing of
these waves of precipitation are not well resolved from Monday
onward. Tuesday will see a slight reduction in temperatures,
dropping into the upper 70s to lower 80s, and with the upper level
pattern remaining largely the same, these high temperatures are
expected to remain consistently within this range through at least
the end of next week. NBM spreads are somewhat high, owing to the
confidence in this pattern holding true, so we can expect to see
similar conditions from Tuesday onward to at least next Friday.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1232 PM CDT Thu Jun 20 2024

Some rather dense cumulus have begun to develop across the
south, bringing MVFR ceilings to KBIS and KDIK, with some
forming just to the south of KJMS. Across the north, mostly
clear skies are present, with some additional, less expansive
cumulus across the north central. Generally southwesterly winds
will prevail through the day, before shifting overnight to
become more southeasterly. Some showers and potentially a
thunderstorm may develop across the northwest near KXWA
tonight, though confidence is rather low. Clouds will recede
south through the late evening, before a more widespread
MVFR/IFR deck builds in from the south early Friday morning.
More rain is expected with this, bringing about showers and
reduced visibilities to KBIS, KDIK, and KJMS by 09z.

&&

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

&&

$$

DISCUSSION...Besson
AVIATION...Besson