Special Weather Statement, NWS Bismarck, ND

Area Forecast Discussion
National Weather Service Bismarck ND
248 PM CDT Sat Aug 12 2017

.SHORT TERM...(This evening through Sunday)
Issued at 248 PM CDT Sat Aug 12 2017

Latest GOES16 water vapor imagery loop shows a mid level upper
low circulating over northwestern ND, soon to transition south as
a stronger shortwave rotates and into southwest/south central ND
this evening. The mid/upper low slowly meanders into the southern
James River Valley after midnight. Areas of fog 05z-15z Sunday for
southwest and south central ND has been added to the gridded
forecast per HRRR/RAP13 Surface Visibility Forecast.

For this afternoon and evening, per water vapor imagery, our
attention is directed toward a pair of 700mb-500mb shortwaves
noted over Dawson and Custer Counties in eastern Montana. The
GFS/RAP13 have both initialized this very well with the current
location, and begins pushing these shortwaves into southwestern
ND 21z-00z, then into far south central 03z-06z, and exiting the
southern James River Valley 12z-15z Sunday. Large scale ascent
increases this afternoon southwest and far south central in
response to the shortwave aloft and the left exit region of a 60kt
300mb jet streak scooting through southeastern MT/southwestern
ND. A cold pocket of -16C also aiding in destabilization. Air
parcels will encounter moderate instability with mixed layer CAPE
between 1000-2000 J/kg, Effective Bulk Shear values of 40kt, and
mid level lapse rates around 7.5C/km. With that said, will
continue with previous forecasts and maintain a mention of severe
thunderstorms in far southwest and into far south central ND
through early this evening. This is also in line with the Marginal
Severe Thunderstorm Risk per SPC. Main threats of large hail and
damaging winds continue. Localized heavy rainfall (1 to 2 inches)
per WPC in a short amount of time with any thunderstorm remains
valid as well.

The Simulated High Resolution Composite Reflectivities in decent
agreement with developing pockets of showers/thunderstorms from
Williston south to Bowman, which is in line with the current
Regional Radar. The Non-Supercell Composite Index is between 1
and 2 over northwest ND. Will need to monitor the low level lapse
rates and surface vorticity for any potential landspouts that
could develop within this area.

Scattered showers and thunderstorms continue through the evening,
then shift away from southwest ND towards midnight. As mentioned
above, concur with fog southwest and south central given the
moisture, and crossover temperatures being met later tonight per
BUFKIT soundings.

.LONG TERM...(Sunday night through Saturday)
Issued at 248 PM CDT Sat Aug 12 2017

A mid level transitory shortwave ridge shifts into eastern MT and
western ND Sunday, behind the departing upper low. Increasing
sunshine west Sunday morning, with clouds decreasing in the
afternoon in the central. Lingering precipitation over the James
River Valley Sunday morning, diminishes through 18z Sunday before
ending. Highs in the 70s.

The next in a series of shortwaves moves into eastern MT and
western ND Monday with a chance for showers and thunderstorms.
Additional shortwaves traverse through a southwest flow aloft
Monday night through Tuesday night affecting western and central
ND with showers and thunderstorms. A break on Wednesday with
another shortwave slated for Thursday/Thursday night. Highs in the
upper 70s to lower 80s Monday through Saturday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 248 PM CDT Sat Aug 12 2017

Mid and upper level circulation will keep the threat of showers
and thunderstorms through the forecast period. Currently band of
showers and thunderstorms approaching KJMS and extending north
northwest to around KMOT. Will have a mention of showers and
thunderstorms for these areas as TAF period begins. Better risk of
stronger storms will be this afternoon into early this evening
for KDIK to KBIS and points south. MVFR cigs/vsbys will be
possible with any thunderstorms. East to southeast flow continues
through the period with indications of MVFR to IFR ceilings
Sunday morning, especially across the southern TAF sites. Will
bring MVFR ceilings and start off with a SCT layer of IFR and MVFR
Vsbys. Later shifts may need to trend lower with ceilings and
vsbys.

&&

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

SHORT TERM...KS
LONG TERM...KS
AVIATION...TWH

Hazardous Weather Outlook
National Weather Service Bismarck ND
1154 AM CDT Sat Aug 12 2017

NDZ001>005-009>013-017>023-025-031>037-047-048-050-051-131700-
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-Logan-La Moure-McIntosh-Dickey-
1154 AM CDT Sat Aug 12 2017 /1054 AM MDT Sat Aug 12 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...This Afternoon and Tonight

Thunderstorms are possible, more prevalent the farther south you
go. A few storms could be strong along Interstate 94 with small
hail and wind gusts as high as 40 mph. Lightning is a hazard.

.DAYS TWO THROUGH SEVEN...Sunday through Friday

Thunderstorms are possible for most areas Sunday through Tuesday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will likely not be needed.

NDZ040>046-131700-
Slope-Hettinger-Grant-Bowman-Adams-Sioux-Emmons-
1154 AM CDT Sat Aug 12 2017 /1054 AM MDT Sat Aug 12 2017/

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

.DAY ONE...This Afternoon and Tonight

Thunderstorms are forecast and they could be severe into early
Saturday evening. Widespread severe weather is not expected, but
a few storms could reach severe limits in the heating of the day.

.DAYS TWO THROUGH SEVEN...Sunday through Friday

Thunderstorms are possible for most areas Sunday through Tuesday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed today. The main threats will be
large hail, as large as half-dollar size, and wind gusts as high
as 60 mph. Report any hail at all and any wind gust of 40 mph or
higher to the National Weather Service. If you have a rain gauge
let us know how much is in it. We have on-line reporting at
weather.gov/bis, are on social media, and are proud to say a human
being answers 701-223-4582 whenever it rings at NWS.

KS/JP MARTIN

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BISMARCK ND
1027 AM CDT SAT AUG 12 2017

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

1025 AM     HEAVY RAIN       1 NNE BISMARCK          46.82N 100.78W
08/12/2017  M1.10 INCH       BURLEIGH           ND   PUBLIC

            STORM TOTAL. ATMOSPHERIC RESOURCE CENTER.

&&

RK

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BISMARCK ND
1030 AM CDT SAT AUG 12 2017

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

1029 AM     HEAVY RAIN       3 SSE BISMARCK          46.77N 100.76W
08/12/2017  M1.96 INCH       BURLEIGH           ND   PUBLIC

            STORM TOTAL. NWS OFFICE.

&&

RK

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BISMARCK ND
1130 AM CDT SAT AUG 12 2017

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

1100 PM     HAIL             MEDORA                  46.92N 103.53W
08/11/2017  M1.00 INCH       BILLINGS           ND   PUBLIC

&&

RK

Special Weather Statement
National Weather Service Bismarck ND
203 PM CDT SAT AUG 12 2017

NDZ050-121945-
McIntosh ND-
203 PM CDT SAT AUG 12 2017

...A STRONG THUNDERSTORM WILL AFFECT EASTERN MCINTOSH COUNTY UNTIL
245 PM CDT...

At 203 PM CDT, a strong thunderstorm was located 7 miles north of
Ashley, moving east at 10 mph.

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

Locations impacted include...
Ashley, Danzig and Green Lake.

Very heavy rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 4609 9956 4625 9944 4624 9900 4595 9901
      4595 9924
TIME...MOT...LOC 1903Z 290DEG 11KT 4614 9939

HAMILTON

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BISMARCK ND
306 PM CDT SAT AUG 12 2017

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

0304 PM     HEAVY RAIN       3 WSW LINCOLN           46.75N 100.76W
08/12/2017  M2.66 INCH       BURLEIGH           ND   NWS EMPLOYEE

            RAINFALL RECEIVED IN ROUGHLY 7 HOURS.

&&

Special Weather Statement
National Weather Service Bismarck ND
215 PM MDT SAT AUG 12 2017

NDZ033-122100-
Stark ND-
215 PM MDT SAT AUG 12 2017

...A STRONG THUNDERSTORM WILL AFFECT NORTHWESTERN STARK COUNTY UNTIL
300 PM MDT...

At 213 PM MDT, a strong thunderstorm was located 5 miles north
of Dickinson, moving east at 10 mph.

Nickel size hail and wind gusts to 40 mph will be possible with this
storm. Another strong storm was developing over South Heart, also
moving east around 10 mph and may impact Dickinson in the next 30
minutes.

Locations impacted include...
Dickinson, South Heart and Gladstone.

Very heavy rainfall is also occurring with these storms, and may
lead to localized flooding. Do not drive your vehicle through
flooded roadways.

&&

LAT...LON 4685 10302 4698 10282 4698 10247 4676 10250
TIME...MOT...LOC 2013Z 284DEG 9KT 4693 10274

HAMILTON