283 
FXUS63 KBIS 210305
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1005 PM CDT Fri Aug 20 2021

.UPDATE...
Issued at 1005 PM CDT Fri Aug 20 2021

The main area of rain extends through the north central late this
evening, with some scattered showers extending as far south as
Linton. Things are progressing about as expected, with rain slowly
tapering off in the west and parts of the south as the surface low
moves off to the northeast. Did go ahead and add in patchy fog for
almost the entire area through the night, with low ceilings and
plentiful low level moisture from all the rain today already
leading to some reduced visibilities across central North Dakota.
Skies should be clearing from west to east through the night, 
with rain ending by morning.

UPDATE Issued at 639 PM CDT Fri Aug 20 2021

Widespread showers and a few thunderstorms continue across western
and central North Dakota under the deformation zone, located west
and north of the surface low that is currently in northeast North
Dakota. Thunderstorm activity should be decreasing through the
evening, with the SPC mesoanalysis page showing instability behind
the cold front that moved through is quite low. Expecting these 
to slowly move off to the northeast through the night, with a 
broad expanse of low clouds along with the showers. No major 
changes needed with this update. 

UPDATE Issued at 504 PM CDT Fri Aug 20 2021

Quick update to cancel the Severe Thunderstorm Watch for our 3
counties. 

UPDATE Issued at 232 PM CDT Fri Aug 20 2021

The Storm Prediction Center has issued Severe Thunderstorm Watch
451, which includes only Foster, Stutsman, and LaMoure counties
in our area. The watch is in effect until, 10 PM CDT but we
anticipate that the window for severe weather will be much shorter
in our area after the front moves out, maybe just for the next 2 
to 3 hours.

&&

.SHORT TERM...(This afternoon through Saturday)
Issued at 205 PM CDT Fri Aug 20 2021

Widespread showers and thunderstorms continue through the short
term forecast period. 

For the rest of this afternoon and evening, expect two main areas
or precipitation. The first will be along and east of a surface
low and cold front. This activity will be in the form of scattered
to widespread thunderstorms that could become strong to severe
this afternoon and evening, mainly across the south central and
into the James River Valley. The other area will be to the north
and west of the low in the deformation zone. While there may be
handful of lightning strikes in this deformation area before the
day is done, precipitation will mainly be steady light to 
moderate rain in this area as it lifts north and east. The areas 
under the heaviest part of this deformation band could end up 
seeing 1 to 2 inches of rain before the upper low departs to the 
northeast tonight. The highest amounts are likely to be found 
across the north central, including Minot and the Turtle 
Mountains. 

Not much has changed regarding the severe threat in our southeastern
zones. Modest instability and moderate to strong deep layer shear
will be present with weak lapse rates. Along with the lapse 
rates, messy storm mode and strong forcing could also limit the 
severe threat. Still, a parameter space will be in place that 
could support a few line segments with embedded mesocyclones that 
could mix down some damaging wind gusts or produce large hail. 
Enhanced vorticity along the triple point could provide a brief 
window for a weak tornado in the James River Valley (if storms can
remain discrete) but low level shear is forecast to be fairly 
weak and the better tornado environment will likely be east of our
area. The long story short is that there will be some potential 
for severe weather, but it seems like there are more factors 
working against the potential than for it.

The upper low will move off to the northeast tonight, leaving some
lingering wrap around showers in place through Saturday morning, 
mainly across the northeast. Lows tonight will be chilly for this 
time of year, getting down into the low to mid 40s across the west
to the upper 40s and lower 50s elsewhere. Transient ridging then 
moves in aloft on Saturday and brings a break in the precipitation
chances with slightly warmer highs in the upper 60s to mid 70s. 

.LONG TERM...(Saturday night through Friday)
Issued at 205 PM CDT Fri Aug 20 2021

Active weather and cooler temperatures continue through the long
term forecast period.

The next trough begins to approach the west Saturday night with
height falls forecast over the far west after 00z Sunday.
Precipitation chances then increase, spreading central and east
through Sunday night. More widespread rainfall totals look 
possible in the 0.25" to 0.60" range with another chance for 
severe storms east of the Missouri River. The Storm Prediction 
Center has placed this area in a Marginal Risk for severe weather 
which seems reasonable, but there are still quite a few details 
that need to be worked out in model land before specifics can be 
discussed. 

Guidance continues the active trend with several progressive 
waves moving through mid to late week, bringing more precipitation
chances.

Monday will be the warmest day of the extended with highs back in
the lower 70s northeast to upper 80s southwest. For the rest of 
the period, temperatures will mainly be normal to below normal.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 639 PM CDT Fri Aug 20 2021

Widespread showers and a few thunderstorms will continue across
much of western and North Dakota through the evening, with the
majority of the precipitation moving out late this evening. Periods
of MVFR/IFR/LIFR visibilities will be possible under the heaviest
shower and storms as well as erratic gusty winds. Widespread MVFR
ceilings are also extending across most of the forecast area.
Conditions will gradually improve from west to east overnight and
into the early morning, with VFR conditions expected at all
terminals by 12Z. 


&&

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

$$

UPDATE...MJ
SHORT TERM...ZH
LONG TERM...ZH
AVIATION...MJ