Area Forecast Discussion
Issued by NWS Bismarck, ND

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000
FXUS63 KBIS 171645
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1145 AM CDT Sat Jun 17 2017

.UPDATE...
Issued at 1144 AM CDT Sat Jun 17 2017

Latest local/regional radar continues to show showers streaming
from west to east within a broad large scale cyclonic flow aloft.
Showers are stretched mainly along Interstate 94 from Dickinson
to Steele at this time. Pockets of showers and scattered thunderstorms
also noted in northwest and northern ND, which have been trending
upward in regards to stronger reflectivity`s. This will continue
this afternoon.

Current/previous forecast thinking remains in good standing.
Stalled surface boundary is aligned from near Williston to
Coleharbor and into Jamestown. Low level lapse rates beginning to
increase with 7.5C/km amidst weak deep layer shear and increasing
surface vorticity along the boundary. The result is the Non-
Supercell Tornado Parameter/NSTP value has increased, with values
of 2 across northwest ND. As the next surge of large scale ascent
slides southeast from Saskatchewan over the boundary this
afternoon, expectations of higher NSTP values remain on track
along and near the stalled boundary. An upward trend in
convection/thunderstorms and possible funnel clouds and/or a weak
landspout tornado this afternoon advertised in previous
discussions remains on track. As large scale ascent associated
with a mid/upper level shortwave slides southeast from
Saskatchewan and into the James River Valley this afternoon, deep
layer shear to 30kt in the southern James River Valley per SPC
mesoanalysis will align with the stronger ascent. Thus, the
Marginal Risk for Severe thunderstorms across the James River
Valley also is in good standing.


UPDATE Issued at 845 AM CDT Sat Jun 17 2017

Made a quick update to blend in current conditions. Will continue
to evaluate the potential for a few strong storms this afternoon,
especially towards the southern James River Valley where SPC now
has a marginal risk for today.

UPDATE Issued at 547 AM CDT Sat Jun 17 2017

Quick update for observed trends through 10 UTC and CAM trends
through the 09 UTC HRRR. Elevated convection continues to slowly
increase across the west ahead of the deepening shortwave.

&&

.SHORT TERM...(Today and tonight)
Issued at 233 AM CDT Sat Jun 17 2017

Numerous showers and thunderstorms today highlight the short term
forecast.

Relied heavily on CAM trends through the 06 UTC HRRR for shower
and thunderstorm coverage and mode for today. Expect
precipitation coverage to increase across southwest and into south
central North Dakota between 08-11 UTC as forcing increases as
the shortwave across Alberta as of 06 UTC propagates southeast and
deepens. Thereafter with diurnal destabilization, coverage of
showers and thunderstorms will increase. The focus will be along a
surface trough across the northwest, through the south central
and the James River Valley. While scattered showers and a few
thunderstorms are expected north central, trends within the CAMs
are for chances to be lowest for this portion of the area. Severe
thunderstorms are not expected today with weak instability and
shear. However, the non-supercell tornado (NST) parameter is
locally elevated along the surface trough. Thus, would not be
surprised to see funnel clouds or even a weak landspout today.

Regarding winds, no changes to the Wind Advisory were made for the
southwest for today. Gusts of 35-40kts are possible following the
highest edge of the forecast guidance with strong gradient winds,
steep low level lapse rates and a modest pressure rise bubble
around 3mb/3hr. It should be noted that given the strong
 winds, locally strong gusts with any showers and thunderstorms
are possible with convective downdrafts southwest.

.LONG TERM...(Sunday through Friday)
Issued at 233 AM CDT Sat Jun 17 2017

Rather normal mid June conditions highlight the extended
forecast.

The 00 UTC global suites are in agreement on transition to zonal
upper level flow through the upcoming week. This would support
near normal temperatures in the mid 70s into the 80s with
periodic chances for showers and thunderstorms associated with low
predictability waves embedded in the fast flow.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1144 AM CDT Sat Jun 17 2017

Showers and thunderstorms will be on the increase this afternoon
across western and central North Dakota.  Coverage is expected to
increase enough to justify the current brief tempo groups in the
forecasts for this afternoon. MVFR/IFR conditions are possible in
any of the thunderstorms. Winds have been a little slow to increase
today, but still think the potential is there for them to increase
this afternoon, especially in the west.   Stratus could linger
tonight in some locations, especially across central and eastern
aerodromes.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 7 PM MDT this evening for NDZ040-041-043-044.

&&

$$

UPDATE...KS
SHORT TERM...PA
LONG TERM...PA
AVIATION...CK



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