Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 140525

Area Forecast Discussion
National Weather Service Bismarck ND
1225 AM CDT Mon Aug 14 2017

Issued at 1223 AM CDT Mon Aug 14 2017

No major changes required for this update. Latest HRRR runs
continue to develop fog across the James Valley.

Issued at 1002 PM CDT Sun Aug 13 2017

T/Td spreads nearing or at zero southeast. HRRR also continues to
advertise widespread fog development across the James River
Valley, patchy areas elsewhere overnight. Thus maintained fog in
the grids and will monitor overnight for possible statements.

Issued at 705 PM CDT Sun Aug 13 2017

Forecast is in good shape for this evening and the overnight.
Expect clouds to clear most areas with the removal of daytime
heating. Lingering showers over the James River Valley will
diminish now through mid evening. Fog remains a possible impact
for the James Valley tonight.


.SHORT TERM...(This evening through Monday)
Issued at 250 PM CDT Sun Aug 13 2017

Latest suite of satellite imagery shows a mid/upper level low
circulating over southeast ND, with one last 500mb-300mb vorticity
lobe swinging into the James River Valley this afternoon. With
this vort passage, the mid/upper low will shift east this
evening, as a brief mid level shortwave ridge migrates into
western ND by 12z Monday. Will continue to mention isolated
showers far southern James River Valley through the afternoon.
With mixed layer cape between only between 250 and 500 J/Kg, weak
lapse rates and no shear, feel the threat for thunder will be too
minimal to mention at this time.

For tonight, dry weather will commence as a mid/upper level ridge
transitory ridge shifts from eastern MT into western ND by 12z Monday.
Despite light northerly to northeasterly winds/drier air in the
boundary layer tonight across the southern James River Valley,
enough low level moisture remains per BUFKIT soundings for some
fog formation. This trend continues in the HRRR/RAP13 surface
visibility forecast. Have utilized these models which produce an
area of fog based on expected visibility reductions from 06z-15z
Monday. Future shifts can monitor/adjust as we get closer and fog

Otherwise, the mid level transitory ridge quickly loses its
identity as southwest flow begins to impinge into western ND
Monday morning, with the approach of our next mid level shortwave
trough. NAM/GFS show the strongest synoptic scale ascent shifting
from Alberta into Saskatchewan Monday, with weaker lift extending
into western/central ND. Have collaborated with SPC on the
Marginal Risk for Severe Thunderstorms Monday through Monday night
across southwest ND. A lack of strong forcing, mixed layer/most
unstable CAPE close to zero, along with weak/marginal mid level
lapse rates of 6C to 6.5C/Km, will hinder and limit severe
thunderstorms. This despite decent 0-6km Bulk Shear of 25kt to
40kt. Thus, have gone with the gridded solution which just barely
nudges a mention of thunderstorms in Bowman County Monday
afternoon and evening. This thunderstorm mention is highly
dependent on the SREF model, which also keeps the threat for
thunderstorms/and severe thunderstorms south of our border
Monday/Monday night - per 15Z SREF Calibrated Thunderstorms.

.LONG TERM...(Monday night through Sunday)
Issued at 250 PM CDT Sun Aug 13 2017

Scattered showers expected Monday night with the initial shortwave
mentioned from the short term period. The next shortwave arriving
from the Great Basin will have stronger synoptic scale ascent,
which overspreads western/central ND Tuesday. It also appears to
have a stronger mid level low associated with it, but placement
varies between the NAM/GFS/ECMWF. Overall though, Tuesday represents
a more widespread shower/thunderstorm day then Monday/Monday night.
The SREF 3hr Calibrated Severe Thunderstorm indicates that on
Tuesday, there is some potential for severe thunderstorms in far
south central ND, closest to the ND/SD border. The SPC Day
3/Tuesday Convective Outlook portrays a Marginal Risk for Severe
Thunderstorms mainly in the James River Valley. Showers exit the
James River Valley Wednesday morning, with dry/clearing weather
elsewhere . A quasi zonal flow then ensues through the weekend
with periodic fast moving shortwaves and chances for showers/thunderstorms.
At this time, it appears that Thursday and Friday would support
some chances of showers/thunderstorms while the weekend looks dry.
Given the fast flow and timing of shortwaves, expect changes
throughout the upcoming week.


.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1223 AM CDT Mon Aug 14 2017

VFR conditions expected at all sites with the exception of KJMS
where IFR in fog is possible overnight. Showers and an occasional
thunderstorm appear likely to develop across western North Dakota
late this afternoon and spread eastward overnight.




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