535
FXUS63 KBIS 140541
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1241 AM CDT Sun Jul 14 2024

.KEY MESSAGES...

- Thunderstorms continue to move south and out of the area with
  only a few lightning strikes remaining along the South Dakota
  border in the vicinity of Sioux county. The severe weather
  threat has diminished for the night.

- Scattered severe storms will be possible once again late
  Sunday afternoon and into the evening. Hail to the size of
  golf balls and damaging winds up to 70 mph will be the main
  hazards.

&&

.UPDATE...
Issued at 1233 AM CDT Sun Jul 14 2024

The bulk of the storms have moved south into north central South
Dakota. After these last few lightning strikes move out of North
Dakota, we should be done with precipitation and thunderstorms
for the night. Thus, for this update, we elected to remove
precipitation chances overnight for everywhere except the far
south central over the next couple of hours. Otherwise, we just
blended in the latest observations to the going forecast.

UPDATE
Issued at 1008 PM CDT Sat Jul 13 2024

Cluster of strong to severe storms will move across far
southwest North Dakota, with mainly a wind threat as Baker MT
gusted to 79 mph and the Cannonball Creek RAWS gusted to 55.
Threat should be over here in a couple of hours.

UPDATE
Issued at 805 PM CDT Sat Jul 13 2024

Strong to severe convection continues to our east and west early
this evening. Robust storms to our east across the southern Red
River Valley of North Dakota with several severe t-storm
warnings as well as a few tornadic supercells. This activity is
moving south/southeast and will stay to the east of the James
River Valley this evening. Another area of robust storms over
eastern Montana associated with a mid level impulse and upper
level jet streak continues southeast, and it appears the
stronger reflectivity cells will just miss far southwest
ND/Bowman county. Cannot rule out other convective threats
southwest this evening, and will continue to closely monitor.

UPDATE
Issued at 643 PM CDT Sat Jul 13 2024

The forecast for tonight remains on track. Cold frontal boundary
now through the northern two thirds of western and central ND,
evident by a southward moving CU field. Robust convection has
take off to our east, where severe weather is expected to push
into Minnesota. Large custer of strong to severe storms over
eastern Montana moving to the southeast. It will be interesting
how this convection tracks, with the latest storm motion maybe
just grazing far southwest North Dakota if not missing our area
entirely. Will continue to monitor closely.

&&

.DISCUSSION...
Issued at 340 PM CDT Sat Jul 13 2024

Currently a cold front is moving southeast through the northwest
part of the state. Besides cooling temperatures, the front is
also drying dew points to the mid 50s. A thin band of cumulus
clouds is seen across the front from Roulette County down
through the big lake and over through Watford City. There is a
possibility that this front could kick some convection in the
James River Valley where the pressure is lower, however
confidence is low as only one or two CAMs have this solution. So
we will keep a close eye on it. There is also a surface low
pressure on the border of the Dakotas near Ashley. Aloft there
is a very slight shortwave over eastern Montana, creating some
diffluence over North Dakota. We still have the Heat Advisory
for Dickey and LaMoure counties for heat indexes around 103
expiring at 8pm CT.


*Severe Threat Tonight*

The new SPC outlook has an enhanced in the southwest, a slight
in the west and south central and a thin marginal followed by a
general thunder in the north central. We just released a
special timed weather balloon to measured the atmosphere here
in Bismarck. There is still a cap here, and unfortunately we
cant measure the real atmosphere where the main show will be
(southwest ND).

The upper level shortwave will move into western North Dakota,
creating more lift as time goes on. The complex of storms is
currently north of the International border in eastern Montana,
moving south. MUCAPE values after 00z (when storm will be near
ND) is around 1400 J/kg on the Montana border, to 2500 J/kg near
Bismarck. The 0-6km shear is off the chart at 60kts. The 0-3km
shear (most useful for severe wind) is around 32kts. This amount
of low level shear is very favorable for severe winds over
70mph. DCAPE is another good indicator of severe wind potential
and it is well over 1000 J/kg. The special sounding we launch
has the drier lower level "inverted V" look. So like yesterday,
when storms are alone hail will be the threat. When they form
into a line at least 70mph winds are possible. The main area for
that is western ND and southwestern ND. Basically where the
enhanced is. Timing looks to be 8 and 9pm MT for storms coming
across the Montana. The challenge is timing with CAMs all very
different, plus some have the storms missing ND to the south.


*Sunday`s Threat*

Sunday we have very high MUCAPE over most of the CWA. Shear both
0-6km and 0-3km is still very high. Currently we are in a
slight risk. CAMs have storms popping in the north central
pretty much all day and then so more scattered storms in the
west. Then into the evening, scattered supercells pop all
over. With how the CAMs have been all over the place the last
two days, not sure there is high confidence in this solution.
Aloft little waves look to move through all day kicking off
storms.

*Rest of the week*

Starting Monday the flow aloft turns northwest, bringing
slightly cooler temperatures (in the 80s) while a ridge sets up
over the Western CONUS. There are on and off chances of showers
and thunderstorms as little embedded waves move through. By
Thursday that ridge moves in. Highs will warm back to near 90 to
end the week.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1233 AM CDT Sun Jul 14 2024

VFR conditions are generally expected through the period at all
sites. However, more showers and storms will develop Sunday
afternoon, potentially lasting into the late evening. Storms
will be isolated to scattered with exact locations and tracks
uncertain. A few storms could become severe. Large hail to the
size of golf balls and damaging winds to 70 mph will be possible
with the strongest storms. If a stronger storm does move
overhead any particular site, brief MVFR to IFR visibilities
will be possible. Winds may become gusty and erratic in the
vicinity of any thunderstorms.

&&

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

&&

$$

UPDATE...ZH
DISCUSSION...Smith
AVIATION...ZH