Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 290517

Area Forecast Discussion
National Weather Service Bismarck ND
1217 AM CDT Thu Jun 29 2017

Issued at 1217 AM CDT Thu Jun 29 2017

Latest water vapor imagery and 00Z model suite advertise two
shortwaves overnight. The first shortwave was seen along the
Montana/Saskatchewan border moving east with time. Regional and
Canadian radars indicate showers and isolated thunderstorms
moving east, and high resolution models suggest this will remain
north of the border. Current gridded forecast has this handled
well. The second shortwave was seen over northern Wyoming with an
area of light showers in southeast Montana. Latest trends in the
both the NAM/GFS/RAP is to develop a closed mid level low in
southeast Montana overnight, then push it along the southern
border Thursday morning. The NAM/GFS indicate increasing large
scale ascent and low level frontogenesis shifting across southern
ND Thursday morning. This looks to result in a swath of light
rainshowers from southwest through south central ND from mid
Thursday morning into the afternoon. Will evaluate this further
in the next forecast discussion. Current gridded forecast remains
on track.

UPDATE Issued at 945 PM CDT Wed Jun 28 2017

Have confined shower chance to extreme southwest North Dakota and
dropped pops to less than 20. Really, sprinkles at best.

There is a batch of showers and storms crossing the south-central
part of Saskatchewan, moving east. Will expect these to weaken as
they move into drier low level air with no CAPE and no surface
support for convergence to keep them going. Have opted NOT to add
pops to the Canadian Border counties.

Final issue is the possibility of fog in the James River Valley.
Patchy fog is possible, but not likely. More likely formation is
east of Jamestown where more rain fell last night and this
morning. Will NOT add patchy fog at this point.

UPDATE Issued at 715 PM CDT Wed Jun 28 2017

Will be updating the weather forecast grids to completely remove
the risk of thunder for this evening. Storms in eastern Montana
continue to weaken as they move into dry low level air and an area
where there is no CAPE or surface convergence to sustain them.

Will keep the increased chances southwest for the very late
night / toward daybreak.


.SHORT TERM...(This evening through Thursday)
Issued at 145 PM CDT Wed Jun 28 2017

The regional weather for the rest of the work week will focus on
an upper level low over western Canada forecast to move into the
Northern Plains. This will set the stage for increasing chances
for scattered showers and isolated thunderstorms. However limited
available moisture will keep rainfall to scattered light amounts.

A weak h500 shortwave trough moving through Montana with an
associated surface low is currently supporting scattered showers
and isolated thunderstorms across eastern Montana. These may
diminish somewhat after peak heating and as they move into western
North Dakota as depicted by the HRRR this evening.

A better scenario for showers and scattered thunderstorms will
form Thursday as a lobe of vorticity moves into the region. The
Superblend guidance gives 30 to 50 POPs across the region
although once again precipitation amounts will be hit and miss and
generally light.

.LONG TERM...(Thursday night through Wednesday)
Issued at 145 PM CDT Wed Jun 28 2017

The extended forecast will initially be impacted by the cool h500
upper low over the Northern Plains Friday. However Global models
are trending toward a broad warm and dry ridging pattern which
will herald warm and dry weather for the start of July. Scattered
showers and isolated thunderstorms associated with the upper low
will exit the region on Friday, and will be followed by a long
and steady warming trend. Highs Friday will be in the 60s and
lower 70s. By early next week and the Fourth of July highs will be
well into the 80s to lower and even mid 90s. No significant
precipitation is expected.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1217 AM CDT Thu Jun 29 2017

Although vfr cigs/vsbys expected this Taf period, high probability
that -shra will develop from KDIK/KBIS/KJMS between 13z Thursday
and 17z Thursday, and continue through mid afternoon. -Shra also
expected at KISN by 21z Thursday, while KMOT remains on the
fringes of showers, thus will add a vcsh at 18z Thursday. Showers
will wane and end by 00z Friday.




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