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000
FXUS63 KBIS 231129
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
629 AM CDT Sun Jul 23 2017

.UPDATE...
Issued at 629 AM CDT Sun Jul 23 2017

Forecast is on track. No changes other than to blend in the latest
observations.

&&

.SHORT TERM...(Today and tonight)
Issued at 309 AM CDT Sun Jul 23 2017

With sunny conditions and light winds today, the main highlights
in the short term period arrive tonight, with increasing high
level smoke in western North Dakota, as well as a chance for
non-severe elevated thunderstorms in the southwest.

The latest suite of satellite imagery shows broad ridging over the
northern Rockies resulting in a mostly clear sky. With the
approach of an amplifying 700mb-500mb ridge today, height rises
commence and warming through the column results, especially in
the west. Expect afternoon highs in the lower 90s west and mid
80s elsewhere. The exception is in/around the Turtle Mountains
where mid/upper 70s will reside. Surface high pressure will slide
from southeast Saskatchewan early this morning, into central ND
this afternoon, then sink through South Dakota this evening. In
the process, winds will be light, but veer from northerly to
southeast, then southerly tonight.

First for tonight, the latest HRRR-Vertically Integrated Smoke
Forecast depicts an increasing thicker layer of smoke aloft moving
into western ND by 06z Monday. This seems to follow the passage
of the 700mb ridge axis into central ND, with the 500mb ridge axis
aligned with our western border. Essentially a southwest flow
aloft will push the high level smoke into the west, with the
northwest expected to have the thickest layer aloft. At the
surface, indications from the HRRR is that with an increase in the
southeasterly to southerly low level flow will push any surface
smoke potential back to the northwest - through Montana and away
from western ND.

Secondly, the increase in sfc-850mb southerly winds results from
the development of a surface low and cold front near Glasgow,
Montana tonight, which is supported by a mid/upper level closed
low/shortwave trough in south central Alberta. BUFKIT soundings at
Bowman/Dickinson/Lemmon all indicate increased chances for
elevated thunderstorms. Appears parcels that can be launched from
around 5kft will be able to make it to the LFC/level of Free
Convection. Elevated Cape should remain in the 500 to 750 J/kg
range with Effective Shear less than 20kt. Thus, not expecting
severe weather at this time. The CAM`s have some consistency with
signaling an area of showers/thunderstorms approaching Billings,
MT by 00z Monday. It will be this area of lift associated a lead
700mb shortwave and a strong low level jet coming together to
produce some chances for elevated thunderstorms in southwest ND
after 06z Monday.

.LONG TERM...(Monday through Saturday)
Issued at 309 AM CDT Sun Jul 23 2017

The long term looks to be active early on - from Monday late
afternoon through Monday night. This is in response to an
approaching cold front mentioned in the short term and the forcing
associated with the closed low sliding through southern Canada.

For Monday, SPC continues with a Marginal Risk for thunderstorms
across all but far western ND. Soundings indicate that north
central ND would be in line for the greatest threat of isolated
severe thunderstorms, mostly due to greater instability and
stronger forcing. The atmosphere is forecast to be uncapped by
5pm CDT at Minot, while weak capping continues at KDIK/KBIS, which
is farther away from the strongest forcing. The brunt of the
strongest forcing resides north of the border, ahead of where the
closed mid/upper level is tracking. Nonetheless, ample instability
with temperatures in the mid/upper 90s and low level forcing
being enhanced by an approaching surface cold front late in the
afternoon, essentially from Minot to Dickinson, suggests the
potential for isolated severe thunderstorms. Soundings suggest
large hail and damaging winds continue as the main threats. Mixed
Layer Cape 00z-06z Tuesday in central ND ranges between 1500 J/Kg
and 2500 J/kg, with Effective Shear 30kt to 35kt. Downdraft Cape
on the order of around 1800 J/kg. Will continue to monitor for any
indications of an uptick in the severe risk potential.

Temperatures Monday will highly depend upon how much smoke aloft
resides across western ND, and how far east this smoke travels
during the day. Potentially, it may very well be a hot day with
highs in the mid/upper 90s - but smoke may also complicate things
as it may shade the sun and result in cooler temperatures. Will
continue to monitor and refine the temperature forecast as we get
closer. Otherwise, the cold front from late Monday afternoon sluggishly
marches into the southern James River Valley by 12z Tuesday, but
doesn`t exit it until 18z. Thinking is that thunderstorms will
likely percolate most of Monday night across central ND.
Showers/thunderstorm chances continue to reside in southern ND
Tuesday, favoring the southern James River Valley.

Tranquil weather then returns Tuesday night through Wednesday
night, with high temperatures in the 80s Wednesday. Additional
shortwaves begin to traverse across western and central ND
Thursday through Saturday. Weak/spotty chances for showers/thunderstorms
at this time. Most of western and central ND will remain dry.
High temperatures warming back up to around 90 degrees Friday/Saturday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 629 AM CDT Sun Jul 23 2017

Expect VFR through the period. High level smoke is forecast to
move into KISN/KDIK between 00z and 06z Monday. Otherwise, light
winds/at or below 10kt through 06z Monday. After 06z, expect
southerly winds to increase at KDIK. A strengthening low level
jet is also expected tonight, resulting in low level wind shear
being included in the KISN and KMOT TAFs after 06z.

&&

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

$$

UPDATE...JNS
SHORT TERM...KS
LONG TERM...KS
AVIATION...JNS