069 
FXUS63 KBIS 211740
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1240 PM CDT Sat Aug 21 2021

.UPDATE...
Issued at 1240 AM CDT Sat Aug 21 2021

Some scattered cu developing across the forecast area but still
mostly sunny most areas. Breezy north central into the JRV, but
expect these winds to diminish shortly north central and by mid
afternoon JRV. Current forecast temperatures look reasonable so no
significant updates.

UPDATE Issued at 844 AM CDT Sat Aug 21 2021

Low pressure was exiting the region with surface high pressure
situated over the western Dakotas. Precipitation has exited the 
forecast area. For the most part skies were clear across western 
and central ND. A few areas of low stratus/fog were indicated over
southwest ND, with some low to mid clouds around the Turtle 
Mountains. Expect a quiet day today with upper level ridging over
the area, ahead of the next wave approaching tonight. We will see
increasing high level clouds today in western ND with any 
precipitation holding off until mid-late this evening.

UPDATE Issued at 634 AM CDT Sat Aug 21 2021

Deformation zone precipitation continues to exit to the northeast. 
Radar shows majority of reflectivities completely north into
southern Manitoba, while Rolla stopped reporting precipitation at
09Z. With this update precipitation chances were lowered based on
observed trends. Patches of stratus were observed on Nighttime RGB
satellite imagery over the west and central, with this coverage
likely to decrease through the morning as the boundary layer
begins to mix out.

&&

.SHORT TERM...(Today through Sunday) 
Issued at 401 AM CDT Sat Aug 21 2021

Skies becoming mostly sunny today with highs mostly in the 70s.
Chances for precipitation return late tonight, with the 
conditional potential for a few severe thunderstorms in the south 
central through southeast Sunday afternoon and evening.

Aloft, the mean flow pattern over the CONUS features ridging over
the south, with two troughs evident on water vapor imagery within
the stronger flow across the north. The first trough was exiting
the Northern Plains to the east, having delivered widespread
precipitation to the region on Friday. A shortwave ridge will move
from the Northern Rockies to the Northern Plains today, ahead of
the upstream trough currently located over Washington and Oregon. 

With the brief ridging pattern expected today, mostly sunny skies
will be expected after the comma head cloud region of the
previous low exits eastward. Highs today will be mostly in the
70s, with some upper 60s scattered across the north.

The next shortwave trough is expected to impact the region late
tonight, with showers moving from west to east through Sunday. By
Sunday afternoon the associated surface trough should be into
central to eastern North Dakota, where a potential for stronger
convection in the James River Valley is possible depending on how
instability develops. Given the progressive nature of the wave
which should push the stronger instability eastward through the 
afternoon, as well as the lingering cloud cover and showers 
impacting possible instability, the window for stronger convection
Sunday afternoon and evening remains uncertain. HREF/SREF severe 
guidance does highlight a modest severe potential in this region 
with 35-40 kts of effective shear providing the kinematics 
necessary for discrete rotating storms. With uncertain 
instability but adequate shear and vectors oriented orthogonally
to the initiating boundary for a discrete cell potential, we will
advertise half- dollar size hail and 60 mph wind gusts possible 
in the HWO. Though locally heavy rainfall with any storm will be 
possible, it should remain brief with the progressive nature of 
the upper level wave. More widespread precipitation during the day
Sunday will be favored on the nose of the 850mb jet, which should 
be near or north of the International Border. 

.LONG TERM...(Sunday night through Friday)
Issued at 401 AM CDT Sat Aug 21 2021

The upper level pattern over the northern CONUS remains active
with another shortwave set to impact the region Monday night and
Tuesday. Shortwave riding ahead of this wave again keeps Monday
sunny and mild before precipitation chances increase Monday night.
Moderate upper level flow with an injection of steep mid-level
lapse rates may create a potential for stronger convection, though
the various deterministic solutions have major differences on 
location and timing with this potential.

The end of the week features good agreement in another trough
impacting the region, this one more broad with precipitation
chances becoming widespread Thursday and Friday. WPC cluster
analysis shows some differences in wave amplitude and QPF, but 
with all clusters showing some sort of precipitation at the end of
the period. NBM's blend of guidance produces chance to likely 
PoPs which lines up with deterministic/ensemble signals.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1240 AM CDT Sat Aug 21 2021

VFR conditions are expected today and this evening. An area of
showers and possible thunderstorms will lift northeast through the
forecast area late tonight through Sunday morning. Expect VFR
ceilings at this time, but there could be a period of MVFR vsbys 
in rain showers at each site with any heavier showers. For now 
kept vsbys to 6SM in showers. Also for the time being, kept only 
VCTS through 18Z as any embedded thunder looks to be pretty 
isolated through 18Z Sunday. Breezy northwest winds at KMOT and 
KJMS to begin the forecast period will diminish by mid afternoon. 
Winds become southeast to east tonight with very strong winds 
aloft at KDIK and KBIS late tonight into Sunday morning, added 
LLWS for these sites. 

&&

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

$$

UPDATE...TWH
SHORT TERM...AE 
LONG TERM...AE 
AVIATION...TWH