Hail and Damaging Winds in North Dakota, July 5 to 6, 2017

Area Forecast Discussion
National Weather Service Bismarck ND
358 PM CDT Wed Jul 5 2017

.SHORT TERM...(This evening through Thursday)
Issued at 358 PM CDT Wed Jul 5 2017

Potential severe thunderstorms late this afternoon through this
evening are our focus with this forecast release.

As of 20 UTC, high-based convection is developing in southwestern
ND where intense boundary layer heating has allowed the convective
temperature to be met along and ahead of a surface wind shift. We
believe this initial activity will have a wind threat given very
steep low- and mid-level lapse rates, surface temperature-dewpoint
spreads around 50 F, and seasonably-strong mid-level flow aloft.
This convection will propagate eastward into south central ND, and
could further intensify as it reaches greater instability, but we
are not particularly confident as to whether or not that will take
place. CAMs have offered up quite dispersive scenarios with regard
to convective longevity and intensity in south central ND owing to
the dry boundary layer air mass from which it emanates, but if any
updrafts can survive dry air entrainment eastward into the Highway
83 corridor they could be supercellular with an attendant risk of
large hail along with damaging winds. This is the lower, but non-
zero risk of severe weather that exists for places such as Elgin,
Beulah, Bismarck/Mandan, and Linton.

Meanwhile, a corridor of greater low-level moisture characterized
by lower 60s F dewpoints is being maintained over central ND ahead
of a subtle warm front that is lifting northeast. This is yielding
MLCAPE of 2500 to 3000 J/kg along and east of a line from roughly
Minot to Jamestown late this afternoon and evening. Model derived
soundings and recent RAP objectively-analyzed mesoscale analysis
data suggests this reservoir of significant instability is capped
to boundary layer parcels, and there remains some uncertainty as
to whether or not MLCIN will indeed be minimized sufficiently for
surface-based convective initiation by evening. However, moisture
channel imagery has suggested a weak mid-level impulse rounding
the top of the ridge aloft in southern Canada which may serve as
the impetus for storm development into north central ND by 00 UTC.
CAMs through the 19 UTC HRRR and 18 UTC 3 km NAM, including the 12
UTC NCEP-run WRF-ARW and WRF-NMM, have been extremely consistent
in advertising intense storms impacting north central ND into the
upper James River valley this evening. Maximum updraft helicity
values from those CAMs have also consistently been in the 100 to
150 m2/s2 range with simulated storms in those areas, indicative
of potentially higher-end severe thunderstorm risk. Moreover, the
projected near-storm environment is a match to many high-end hail
events with peak sizes over two inches in diameter, and the NSSL
WRF-ARW ensemble from 00 UTC and more recent HRRR iterations have
all supported peak wind gusts of 55 to 65 kt, which is a rather
noteworthy signal. Suffice to say that this could be a formidable
event. MLLCL heights are forecast to be around 2000 m AGL, which
should limit tornado risk, but the potential does exist given the
expected intense mesocyclones driven by the CAPE and shear setup,
the latter of which is driven by effective bulk wind differences
around 50 kt. Upscale growth from initial supercells into a bowing
complex is possible from north central ND into the James River
valley given the largely unidirectional flow aloft.

A cold front will then move southward across the area tonight and
lead to a dry and relatively cooler day on Thursday.

.LONG TERM...(Thursday night through Wednesday)
Issued at 358 PM CDT Wed Jul 5 2017

The primary synoptic-scale feature of interest in the long term
forecast period will remain the stout middle- and upper-level
ridge centered across the western United States. The 12 UTC GFS
and ECMWF stayed the course in advertising a period of northwest
flow aloft across the local area through the upcoming weekend as
the axis of the ridge remains near the spine of the Rockies. This
will allow the air mass to be somewhat cooler - highs in the 80s
and 90s F as opposed to 90s and 100s F - Friday through Monday. A
seasonably strong shortwave trough may cut across the top of that
ridge axis next week, which would in turn allow for another surge
of hotter mid-level temperatures to push eastward into western and
central ND Monday or Tuesday. A low-end thunderstorm risk may also
be centered on that period given the glancing influence of that
shortwave rolling across the top of the mean ridge.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 358 PM CDT Wed Jul 5 2017

A cold front will slide across western and central ND this TAF
period. Aside from a windshift to the west and northwest behind the
front, the threat for thunderstorms exists, especially from KMOT to
KJMS. At this time, due to the isolated nature and narrow timeframe,
we have decided to include a VCTS at KMOT/KJMS between 00z and 06z
Thu. If a thunderstorm does develop over or in the vicinity of the
terminal, large hail and damaging winds will be the primary threats.
Elsewhere, more isolated storms are possible. Sub-VFR conditions
are possible in any storms through this evening.

&&

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

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

Hazardous Weather Outlook
National Weather Service Bismarck ND
414 PM CDT Wed Jul 5 2017

NDZ001>005-009>013-017>023-025-031>037-040>048-050-051-062115-
Divide-Burke-Renville-Bottineau-Rolette-Williams-Mountrail-Ward-
McHenry-Pierce-McKenzie-Dunn-Mercer-Oliver-McLean-Sheridan-Wells-
Foster-Golden Valley-Billings-Stark-Morton-Burleigh-Kidder-
Stutsman-Slope-Hettinger-Grant-Bowman-Adams-Sioux-Emmons-Logan-
La Moure-McIntosh-Dickey-
414 PM CDT Wed Jul 5 2017 /314 PM MDT Wed Jul 5 2017/

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...Tonight

Scattered thunderstorms are expected through this evening. Some
storms will be severe. The greatest risk of severe thunderstorms
remains in north central North Dakota and the upper James River
valley, including the Minot, Rolla, Rugby, Harvey, Carrington, and
Jamestown areas. Hazards include potentially very large hail up to
the size of baseballs and destructive winds up to 75 mph. A
tornado is possible.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Weather spotters will likely be needed late this afternoon and
this evening.

CJS

Special Weather Statement
National Weather Service Bismarck ND
223 PM MDT WED JUL 5 2017

NDZ033-052115-
Stark ND-
223 PM MDT WED JUL 5 2017

...A STRONG THUNDERSTORM WILL AFFECT SOUTHEASTERN STARK COUNTY UNTIL
315 PM MDT...

At 222 PM MDT, Doppler radar was tracking a strong thunderstorm 11
miles south of Dickinson, moving east at 35 mph.

Wind gusts to 55 mph will be possible with this storm.

Locations impacted include...
Richardton, Gladstone, Lefor and Dickinson Regional Airport.

LAT...LON 4663 10283 4664 10283 4679 10288 4697 10210
      4669 10210 4663 10268
TIME...MOT...LOC 2022Z 255DEG 32KT 4672 10274

SIMOSKO

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BISMARCK ND
412 PM CDT WED JUL 5 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0405 PM     HAIL             8 E LEFOR               46.69N 102.40W
07/05/2017  E0.50 INCH       STARK              ND   TRAINED SPOTTER

            LIGHT RAIN FALLING RATHER VERTICALLY, LIGHT
            WIND. SOME SMALL HAILSTONES REPORTED.

&&

KS/AR

Special Weather Statement
National Weather Service Bismarck ND
320 PM MDT WED JUL 5 2017

NDZ041-042-044-045-052215-
Grant ND-Hettinger ND-Sioux ND-Adams ND-
320 PM MDT WED JUL 5 2017

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT SOUTHWESTERN SIOUX...
SOUTHEASTERN HETTINGER...SOUTHWESTERN GRANT AND SOUTHEASTERN ADAMS
COUNTIES UNTIL 415 PM MDT...

At 320 PM MDT, Doppler radar was tracking strong thunderstorms along
a line extending from Mott to 10 miles northeast of Haynes. Movement
was east at 30 mph.

Nickel size hail and wind gusts to 50 mph will be possible with these
storms.

Strong thunderstorms will be near...
  North Lemmon around 345 PM MDT.
  Thunder Hawk around 405 PM MDT.

Other locations impacted by these storms include Burt and Bentley.

LAT...LON 4594 10217 4604 10246 4646 10237 4626 10177
      4594 10177
TIME...MOT...LOC 2120Z 287DEG 25KT 4637 10229 4609 10235

SIMOSKO