632
FXUS63 KBIS 142023
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
323 PM CDT Sun Jul 14 2024

.KEY MESSAGES...

- Isolated to scattered severe storms possible this afternoon
  and evening, but timing of the storms remains tricky.

- Hail to the size of tennis balls and damaging wind gusts to 70
  mph remain the main hazards.

- Cooler weather returns to start the work week, with a modest
  warmup for the second part of the upcoming week.

&&

.DISCUSSION...
Issued at 216 PM CDT Sun Jul 14 2024

Current surface analysis places low over northeast Wyoming with
inverted trough stretching up to the north into eastern Montana.
Upper level analysis places broad high over the Four Corners
region with low over far northern Manitoba. West-northwesterly
flow remains over our area, which remains active with a series
of short waves passing through. Initial wave now passing
through northwestern North Dakota, with the secondary one over
southwest Saskatchewan/northern Montana. Yet another wave noted
upstream from there. Over our area, temperatures over most
locations have climbed into the 80s knocking on the lower 90s.

For this afternoon into tonight, the threat of severe weather
remains in place but as has been going on for quite a while,
the timing remains our fly in the ointment. A diverse group of
solutions are being shown by latest CAMs, with some initiating
convection with the initial wave moving through the area, while
others are holding off until later. Some of the CAMs indicate
convection developing with the initial wave in the not to
distant future, but a quick look at our 19Z special sounding has
a pretty pronounced cap over us, thus confidence in this
occurring is diminishing, so now the best bet looks to be more
towards the evening hours.

Once convection does finally initiate, the potential is there
for it to become quite robust. Deep layer shear is notably
stronger than what we have had here the past few days, forecast
to be about 50 kts across the area by early evening. This will
combine with plenty of instability with MLCAPE values still
anticipated to be in the 1500 to 2500 J/Kg range, plenty ample
for severe convection. With the strong shear and ample
instability, will maintain the threats previously forecast of
tennis ball size hail and wind gusts to 70 mph. As for the
tornadic threat, with the inverted trough sliding east, possibly
closing off, enough lower level shear may be provided if a
storm passes over the right area, though this setup is not ideal
we cannot rule out a tornado or two if a discrete supercell
were to develop early in the event. Convection will slide to the
east/southeast through the evening/overnight hours.

By Monday morning short waves will be pushing off to the east,
but some showers/thunderstorms may linger over parts of
northwest North Dakota into the James River Valley primarily
during the morning hours. Upper flow does become a bit cyclonic
in the afternoon as upper low with various waves swinging around
it drops southward along the Manitoba/Ontario border, so can
not rule out an increase in cloud cover in the afternoon, along
with a few stray very light showers in the afternoon/early
evening with additional activity overnight. Temperatures will
be notably cooler as the north/northwesterly flow pulls in a
cooler airmass, resulting in highs in the mid 70s to lower 80s.
Flow aloft remains modestly cyclonic on Tuesday, continuing low
chances for showers/weak storms.

Stout ridge builds to our west and remains in place for the
middle/end to the week. This will result in a modest warming trend
returning temperatures to the 80s to around around 90 by Thursday
continuing into the weekend. A few weak waves passing over the ridge
will bring some low precipitation chances to the area towards the
weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1244 PM CDT Sun Jul 14 2024

Thunderstorms are expected to develop this afternoon into this
evening, but the timing of this development remains in question.
Still, expect development to occur and affect most TAF sites.
The exception may be at KDIK including far southwest North
Dakota, where chances are low enough to not mention in the TAF
at this point. The storms are expected to clear out late tonight
from west to east, but may continue to affect parts of north
central into eastern North Dakota into early Monday morning,
which includes the KJMS terminal.

&&

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

&&

$$

DISCUSSION...JJS
AVIATION...JJS