Severe Thunderstorm Warning 8, NWS Bismarck, ND

Area Forecast Discussion
National Weather Service Bismarck ND
406 PM CDT Sun Jun 2 2019

.SHORT TERM...(This evening through Monday)
Issued at 406 PM CDT Sun Jun 2 2019

Thunderstorm chances southwest through this evening, and over all
of western and central ND Monday afternoon and evening, highlight
the short term forecast period.

Through mid afternoon, satellite imagery shows a steady eastward
trend of the smoke aloft in tandem with mean winds aloft, with the
back edge of the thicker smoke along a line from Minot to Bismarck
as of 20 UTC. The smoke layer appears to be more transparent than
it was at this time yesterday when it was centered on southwestern
ND, which is in line with HRRR-Smoke simulations which have long
expected vertically integrated smoke particulates to diminish in
time. This is likely why temperatures have been less-impacted by
the smoke layer than this time yesterday. HRRR-Smoke guidance is
consistent in suggesting the smoke layer will continue moving out
of the area tonight, leaving us smoke-free on Monday.

Meanwhile, cumulus fields are deepening from southeastern MT north
toward the Beach and Wibaux areas as of 20 UTC. Moisture advection
is ongoing with 20 UTC dewpoints in the lower to middle 50s F in
southwestern ND, in line with guidance expectations and supportive
of late afternoon and early evening MLCAPE around 1000 J/kg amid
steepening midlevel lapse rates. Background ascent is weak given
weak height rises aloft, and surface observations suggest the main
convergence feature is the north end of a lee trough and/or Black
Hills convergence zone that extends into southeastern MT. Storms
that develop near that feature could propagate into southwest ND
in the very late afternoon or evening. Otherwise, cumulus has been
most notably developing along higher ridgetops across the region
and thus topographic influences may play a role in this convective
initiation scenario. Some CAMs, such as the 12 UTC 3 km NAM and
NSSL WRF-ARW, support convective initiation over west central ND,
and indeed visible satellite imagery suggests that is possible in
the next few hours. Finding a focus for ascent in that area within
the model simulations that focus convective initiation there is
difficult, but the 12 UTC 3 km NAM does so immediately following
formation of weak boundary layer confluence in wind fields where a
more south-southwest wind direction meets a more southeast wind
field in the model. Such a meso-gamma-scale feature may be ongoing
due to topographic effects or the development of a weak differential
mixing boundary near the edge of the northward-returning higher-
dewpoint air, but uncertainty exists in whether or not either of
these features will be sufficient to sustain parcel ascent long
enough to yield thunderstorm development given the background
weak-ascent regime. Indeed, ESRL HRRR cycles have been consistent
in generating no deep convection in western ND, supporting the
opposite end of the potential envelope of scenarios. If storms do
occur though, the instability combined with 25 to 30 kt of deep-
layer shear supports a marginal risk of severe hail or wind. The
12 UTC HREF calibrated severe probabilistic guidance suggests the
wind threat may be the slightly more prominent of the two threats,
which is reasonable given the high-based and potentially outflow-
dominant nature of convection.

Regardless of what occurs through this evening, convection will be
diurnally-driven as shortwave ridging crosses the region overnight
and the terminus of a modest low-level jet gets focused north into
southern Canada. Thus, the opportunity for convective-generating
forcing for ascent will be minimal, though with broad and ongoing
low-level theta-e advection surmounted by continually-steepening
midlevel lapse rates as elevated mixed layer air continues moving
to the east, MUCAPE of 1000-1500 J/kg will exist and is expected
to be relatively uncapped for parcels originating around 875 mb.
Again, though, forcing for ascent is negligible and so while the
chance of elevated convection overnight is non-zero, it is far too
low to include in the forecast. Note that even if any storms did
form overnight deep-layer shear would be weak, minimizing their
organization.

On Monday, a surface low will move into central Canada, placing
western and central ND in the cyclone's warm sector ahead of a
surface trough that is expected to move into western ND by late
afternoon. That trough and its related convergence field should
serve as the focus for scattered thunderstorm development in an
environment characterized by steep low and midlevel lapse rates,
and MLCAPE over western ND in the 1000-1500 J/kg range. Guidance
suggests the surface moist axis will be displaced east of the
surface trough such that dewpoints in central ND will be around 60
F with MLCAPE increasing into the 2000-2500 J/kg range. Where wind
fields are concerned, effective-layer shear will be weak, in the
20-25 kt range, supporting multicellular convective modes, though
the orientation of cloud-layer mean winds and deep-layer shear
vectors orthogonal to the north-south pressure trough suggests
discrete cells will be favored after convective initiation. A
marginal risk of large hail and wind -- minimized by the magnitude
of deep-layer shear -- will exist in western ND along the surface
trough, though the potential for a somewhat greater severe-storm
threat, albeit still marginal, may exist with any cells that can
propagate into the higher-CAPE axis in central ND by Monday
evening. Once more the convection may be diurnally driven per the
12 UTC CAMs, and thus could diminish by late Monday evening.
Otherwise, highs Monday in the warm sector will be well into the
80s F, with lower 90s possible in the northwest and north central
where soil moisture content is lower due to a lack of springtime
rainfall.

.LONG TERM...(Monday night through Sunday)
Issued at 406 PM CDT Sun Jun 2 2019

A summer-like pattern will persist this week with highs mainly in
the 80s F and slight chances of storms, before a cooling trend
arrives by next weekend along with a greater chance of storms.

On the synoptic scale, broad westerly flow aloft will be in place
Tuesday through Thursday, with low-amplitude impulses embedded in
the flow potentially generating convection as mass fields respond
to their passage with return-flow moisture advection then taking
place beneath steep midlevel lapse rates occurring thanks to the
eastward advection of elevated mixed layer air aloft. Low-grade
PoPs dominate the forecast in this time period owing to the low
predictability of these impulses, and while instability could be
sufficient for a severe-storm risk, deep-layer shear is forecast
to be weak, with all of the 12 UTC GEFS members calling for 0-6-km
bulk wind shear less than 30 kt persisting through Thursday across
most of the area.

The 12 UTC global model suites remained consistent in advertising
a deepening trough moving into the Pacific Northwest by Friday and
turning flow aloft southwesterly across the Northern Plains. This
will yield a background environment more favorable for organized
convection, particularly as the trough passage occurs, though the
GFS and ECMWF and their ensembles differ in its timing. Deep-layer
shear will likely increase with the approach of this trough, too.
Finally, warm air advection could yield a period of temperatures
which are even warmer than advertised, before a following cold
frontal passage results in cooler weather in its wake. The 12 UTC
multi-model consensus supported the beginning of that cooldown on
Saturday, though several GEFS members and the 12 UTC ECMWF were
less progressive with the trough passage and suggested Saturday
could remain warm with a greater thunderstorm probability.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 406 PM CDT Sun Jun 2 2019

VFR conditions are forecast to prevail across western and central
ND through the 18 UTC TAF cycle. There's a chance of thunderstorms
in southwestern ND through early evening, potentially impacting
KDIK. Confidence in impacts at KDIK is modest at best, but later
trends could support amendments to their TAF. Otherwise, south to
southeast flow will prevail through the period, bringing higher-
dewpoint air into the region. That will yield a non-zero chance of
low stratus formation late tonight and Monday morning, but
there's no evidence of its occurrence in model simulations at this
point, so no mention of it was made in the 18 UTC TAFs.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

SHORT TERM...CJS
LONG TERM...CJS
AVIATION...CJS

Hazardous Weather Outlook
National Weather Service Bismarck ND
350 PM CDT Sun Jun 2 2019

NDZ001>005-009>013-017>023-025-034>037-042-045>048-050-051-032100-
Divide-Burke-Renville-Bottineau-Rolette-Williams-Mountrail-Ward-
McHenry-Pierce-McKenzie-Dunn-Mercer-Oliver-McLean-Sheridan-Wells-
Foster-Morton-Burleigh-Kidder-Stutsman-Grant-Sioux-Emmons-Logan-
La Moure-McIntosh-Dickey-
350 PM CDT Sun Jun 2 2019 /250 PM MDT Sun Jun 2 2019/

This Hazardous Weather Outlook is for portions of north central
North Dakota, northwest North Dakota, south central North Dakota,
southeast North Dakota, and southwest North Dakota.

.DAY ONE...This Afternoon and Tonight

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

Scattered thunderstorms may develop in western North Dakota Monday
afternoon and then move eastward into central North Dakota Monday
evening. A few of these storms could become severe with the main
threats being large hail up to quarter size and damaging winds up
to 60 mph. The risk of a few severe thunderstorms is greatest from
about 3 PM to 9 PM CDT, or 2 PM to 8 PM MDT Monday.

Additional chances of thunderstorms exist from Tuesday through
Saturday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed.

NDZ031>033-040-041-043-044-032100-
Golden Valley-Billings-Stark-Slope-Hettinger-Bowman-Adams-
250 PM MDT Sun Jun 2 2019

This Hazardous Weather Outlook is for portions of southwest North
Dakota.

.DAY ONE...This Afternoon and Tonight

There is a chance of late afternoon and evening thunderstorms in
southwestern North Dakota. There is a marginal risk of a severe
storm with hail up to the size of quarters or wind gusts to 60
mph.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

Scattered thunderstorms may develop in western North Dakota Monday
afternoon and then move eastward into central North Dakota Monday
evening. A few of these storms could become severe with the main
threats being large hail up to quarter size and damaging winds up
to 60 mph. The risk of a few severe thunderstorms is greatest from
about 3 PM to 9 PM CDT, or 2 PM to 8 PM MDT Monday.

Additional chances of thunderstorms exist from Tuesday through
Saturday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is unlikely this afternoon and evening due to
the marginal nature of the severe storm risk.

CJS

Special Weather Statement
National Weather Service Bismarck ND
338 PM MDT Sun Jun 2 2019

NDZ031-032-022230-
Golden Valley ND-Billings ND-
338 PM MDT Sun Jun 2 2019

...A STRONG THUNDERSTORM WILL AFFECT EAST CENTRAL GOLDEN VALLEY AND
SOUTHWESTERN BILLINGS COUNTIES UNTIL 430 PM MDT...

At 337 PM MDT, a strong thunderstorm was located 5 miles southwest of
Medora, or 18 miles east of Beach, moving east at 15 mph.

Penny size hail and wind gusts to 40 mph will be possible with this
storm.

This storm will remain over mainly rural areas of east central Golden
Valley and southwestern Billings Counties.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek shelter
inside a building or vehicle.

Campers should move to a sturdy shelter until this storm passes.

&&

LAT...LON 4682 10376 4691 10372 4689 10333 4668 10344
TIME...MOT...LOC 2137Z 290DEG 13KT 4687 10363

KRANZ

Special Weather Statement
National Weather Service Bismarck ND
437 PM MDT Sun Jun 2 2019

NDZ032-040-022330-
Billings ND-Slope ND-
437 PM MDT Sun Jun 2 2019

...A STRONG THUNDERSTORM WILL AFFECT SOUTHWESTERN BILLINGS AND NORTH
CENTRAL SLOPE COUNTIES UNTIL 530 PM MDT...

At 437 PM MDT, a strong thunderstorm was located 11 miles south of
Medora, or 20 miles northwest of Amidon, moving southeast at 15 mph.

Nickel size hail and wind gusts to 40 mph will be possible with this
storm.

This storm will remain over mainly rural areas of southwestern
Billings and north central Slope Counties.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek shelter
inside a building or vehicle.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

Campers should move to a sturdy shelter until this storm passes.

&&

LAT...LON 4678 10361 4682 10351 4667 10327 4656 10352
TIME...MOT...LOC 2237Z 323DEG 12KT 4675 10353

KRANZ

Special Weather Statement
National Weather Service Bismarck ND
453 PM MDT Sun Jun 2 2019

NDZ031-040-022315-
Golden Valley ND-Slope ND-
453 PM MDT Sun Jun 2 2019

...A STRONG THUNDERSTORM WILL AFFECT
SOUTHEASTERN GOLDEN VALLEY AND NORTHWESTERN SLOPE COUNTIES UNTIL 515
PM MDT...

At 452 PM MDT, a strong thunderstorm was located 9 miles east of
Carlyle, or 22 miles south of Beach, moving east at 15 mph.

Nickel size hail and wind gusts to 50 mph will be possible with this
storm.

Locations impacted include...
Alpha and Three V Crossing.

Very heavy rainfall and frequent cloud to ground lightning is
occurring with this storm. Lightning can strike 10 miles away from a
thunderstorm. Seek shelter inside a building or vehicle.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 4668 10395 4667 10361 4663 10361 4663 10348
      4636 10369 4657 10399
TIME...MOT...LOC 2252Z 285DEG 13KT 4661 10388

HAMILTON