Special Weather Statement, NWS Bismarck, ND

Area Forecast Discussion
National Weather Service Bismarck ND
902 PM CDT Sat Jun 5 2021

.MESOSCALE DISCUSSION...
Issued at 820 PM CDT Sat Jun 5 2021

(905 PM Update discussion directly below the mesoscale
discussion)

Convection over eastern Montana has not been overly impressive
early this evening, despite a few recent observations of wind
gusts around 60 mph in the Miles City area. The majority of this
convection is currently moving through an environment with much
lower instability compare to surrounding areas. However, recent
satellite imagery is suggesting more upscale growth on the
southern flank of the broader line of showers and storms in
southeast Montana, with some evidence this may be supported by
mountain wave interactions. There also appears to be some weak
surface cyclogenesis occurring in this area.

The 00Z Bismarck sounding shows a weak capping inversion just above
700 mb, which has likely suppressed the convective initiation
potential over western and central North Dakota early this evening.
However, falling mid level heights and an increasing low level jet
should work to reduce MLCIN over the next few hours ahead of the
approaching convection from Montana, which should arrive in western
North Dakota around 930 PM CDT. Sufficient forcing and deep layer
shear should be present to maintain this convection across western
and central North Dakota through the late evening and early
overnight hours. Observed trends and recent CAM guidance suggest the
greatest potential for severe storms is more favored from southwest
into central North Dakota due to the presence of greater low level
moisture (dewpoints as high as the lower 60s) and the increasing low
level jet. The main expected threat continues to be damaging wind,
which is supported by 1576 J/kg of DCAPE observed on the 00Z
Bismarck sounding.

&&

.UPDATE...
Issued at 902 PM CDT Sat Jun 5 2021

Updated pops based on latest radar trends and observational data
(see mesoscale discussion above). Blended hourly pops through 12z
more heavily toward shorter term (CONSShort) guidance which
appeared to capture best the current thinking of convective
activity being more widespread slightly farther south into central
ND.

UPDATE Issued at 646 PM CDT Sat Jun 5 2021

Main update was to sky cover this evening and overnight, blending
heavily toward NBM guidance. Otherwise, forecast remains on track.
Hot temps continue, still 102 at the NWS in Bismarck. Skies are
mostly clear with some cumulus that has developed during the
afternoon and early evening, but other than some brief rain at
Minot, convective inhibition has kept things in check. SPC meso
page continues to show generally 500-1500 J/kg MLCAPE over much of
the state with shear continuing to be on the low side still.
Incoming upper air data from KBIS shows deep mixed layer to around
680mb with weak cap in place.

Otherwise, continuing to monitor ongoing convection in Montana
that is approaching ND, expected at the border around 02Z.

&&

.SHORT TERM...(This evening through Sunday)
Issued at 241 PM CDT Sat Jun 5 2021

Severe weather remains possible through tonight, with critical
fire weather conditions possible on Sunday. Rest of this afternoon
will remain warm, with areas again seeing upper 90s to low 100s
temperatures. This will likely be another record breaking heat
day. A weak boundary is currently pushing northeast across the
CWA. A few isolated showers are possible along this boundary
through the evening. Surface cape remains quite high, although
MLcape is not as high and is fairly capped. Thus the threat for
severe storms this afternoon is low.

This evening through tonight will be the better severe weather
threat. The mentioned cold front starting to show up nicely across
central MT where storms are already firing. As this front enters
into ND this evening, abundant cape should be meet increasing
shear from a strong jet stream. The result could be severe weather
across much of the region, especially the central and north. DCAPE
is quite high with this feature, so winds to 70 mph will be the
main threat. With the higher cape areas, some hail is possible
although expected size to just be near that severe criteria of
around an inch. Of note is some higher PWAT values given some
higher dewpoints. Some brief moderate to heavy rain is possible,
although flooding is not expected given recent dry conditions.

Showers could then linger across the north before diminishing
Sunday morning. The remainder of Sunday looks breezy, cooler with
seasonal high temperatures, and drying conditions. The combination
of winds gusting to 40 MPH and RH dropping into the low 20s has
prompted a Fire Weather Watch for Sunday afternoon into the
evening across much of the CWA. The exception comes across
southern portions where uncertainty remains in winds, min RH
values, and overall fuel status. Overall most the CWA will see
unfavorable fire weather conditions during the day despite any
rain that may fall tonight.

.LONG TERM...(Sunday night through Saturday)
Issued at 241 PM CDT Sat Jun 5 2021

Continued warm conditions with periods of active weather look to
be found in the long term.

Monday sees a developing warm front set up across the Dakotas
returning warm temperatures to the region. This front opens up the
Gulf of Mexico to bring increased dewpoints to the area. This
could bring copious amounts of cape, with some increasing shear.
The set up itself could be quite conducive for severe weather.
The uncertainty lies in how far north this front gets and any
capping along it. Regardless at least the southern half of the
state will see a severe weather potential on Monday, with wind and
hail the main threats.

A few thunderstorms could linger for Tuesday and Wednesday as the
front lifts north and stalls. Weak ridging then brings limited
storm potential the remainder of the week, although a passing
front may bring and uptick to activity later in the week. Warm
temperatures look to remain through next week. Dewpoints will
increased at times, although may be low enough for some fire
concerns throughout the week. Winds may also be breezy at times
for the upcoming week, further complicating fire weather concerns.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 646 PM CDT Sat Jun 5 2021

Main issues are area of thunderstorms currently in Montana
expected to reach ND around 02Z. Expect mainly VFR conditions
through the forecast cycle, however could see brief MVFR
associated with any thunderstorms. For now mainly covered
thunderstorm chances with VCTS at all locations except KJMS,
where there is lower confidence for thunderstorm chances.

Also continued to carry LLWS at KJMS between 05Z and 13Z.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Sunday afternoon through Sunday evening
for NDZ001>005-009>013-017>023-025-034>037.

&&

MESOSCALE...Hollan
UPDATE...JNS
SHORT TERM...Anglin
LONG TERM...Anglin
AVIATION...JNS

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Special Weather Statement
National Weather Service Bismarck ND
925 PM CDT Sat Jun 5 2021

NDZ009-017-031-032-040-043-060315-
McKenzie ND-Golden Valley ND-Williams ND-Billings ND-Slope ND-
Bowman ND-
925 PM CDT Sat Jun 5 2021

...SIGNIFICANT WEATHER ADVISORY FOR GOLDEN VALLEY...BOWMAN...
BILLINGS...MCKENZIE...SLOPE AND WILLIAMS COUNTIES UNTIL 1015 PM
CDT/915 PM MDT/...

At 924 PM CDT/824 PM MDT/, strong thunderstorms were located along a
line extending from near Plentywood to 5 miles east of Sidney to 13
miles northeast of Ekalaka. Movement was northeast at 40 mph.

Wind gusts to 55 mph will be possible with these storms.

Locations impacted include...
Williston, Watford City, Bowman, Beach, Amidon, Fairview, Grenora,
Alexander, Rhame, Marmarth, Arnegard, Medora, Epping, Golva, Alamo,
Sentinel Butte, and Grassy Butte.

These storms 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 4863 10405 4863 10340 4769 10310 4734 10310
      4698 10323 4595 10324 4594 10404
TIME...MOT...LOC 0224Z 243DEG 35KT 4872 10458 4770 10404 4600 10433

HOLLAN