445
FXUS63 KBIS 161458
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
958 AM CDT Thu May 16 2024

.KEY MESSAGES...

- Isolated to scattered showers and thunderstorms today. A few
  stronger storms are possible with small hail and locally gusty
  winds this afternoon and evening.

- Isolated severe storms are possible Friday afternoon/evening.
  The main threat will be damaging winds up to 65 mph.

- Warming trend through Friday, then a cooldown with breezy to
  windy conditions Saturday.

- Daily chances for precipitation continue through the weekend
  and into early next week.

&&

.UPDATE...
Issued at 955 AM CDT Thu May 16 2024

Most of the fog has burned off, and just low stratus remains in
the central. After these clouds move off to the east the rest of
the day should be mostly sunny. We have adjusted sky cover
multiple times to account for the clouds decreasing over the
last few hours.

UPDATE
Issued at 635 AM CDT Thu May 16 2024

Shower activity approaching the northwest ND border from eastern
MT continues to dissipate as it moves east. Will keep the
mention of showers out of the forecast for now. A sprinkle or
two could sneak across the border though. Shortly after the last
forecast we added some patchy frost south central with
temperatures dropping into the mid 30s. That will end in the
next hour or so. Currently fog goes through 14 UTC. Will leave
it alone for now. We did also issue a SPS for patchy dense for
over portions of central ND. Lowest visibilities were around
linton and North of Rugby. Made some adjustments to sky cover
based on latest satellite imagery. One other thing to monitor
today will be winds/gusts with a good mixing day indicated. Did
utilize some HRRR winds which bumped the winds up a little in
the west.

&&

.DISCUSSION...
Issued at 153 AM CDT Thu May 16 2024

Currently, a weak pressure pattern was situated over western and
central North Dakota, behind an exiting low pressure system
over Minnesota. Skies were clear to partly cloudy across a good
portion of central ND, with mostly cloudy skies in the west.
Under the clear skies some areas of fog have developed, mainly
over the south central with some patchy dense fog along and east
of the Missouri River south of Bismarck and into north central
SD. Aloft, a broad northwest upper flow was situated from
British Columbia Canada and the Pacific northwest across the
Rockies and into the Northern Plains. Numerous shortwaves were
propagating through the mean northwest flow pattern.

For today we expect a warmer day than Wednesday, possibly around
20 degrees warmer in some areas of the south central into the
James River Valley. Winds should also be on the light side
generally varying from west to south around 12 mph or less.
Expect a mix of sun and clouds today with hit and miss showers
and isolated thunderstorms.

As for the risk of storms, there is currently a weak shortwave
over central ND producing some mid-level clouds and little if
any precipitation. Another was was situated along the ND/MT
border and is forecast to drop southeast this morning and could
produce an isolated to scattered shower west into south central.
A cluster of showers and isolated thunder was also dropping
southeast from southwest Saskatchewan toward northeast Montana.
Currently most of the latest CAMS have this activity breaking up
as it moves into northeast MT and towards ND. Will have to see
how it trends the next few hours and may have to include some
morning shower activity northwest. A shortwave approaching
Montana will approach the local area later today. Between the
morning shortwaves and this trailing shortwave will be a period
of shortwave ridging. Under this ridging we will become slightly
unstable this afternoon/early evening with ML CAPE on the order
of 500-1000 J/KG with decent bulk shear of 25 to 35 knots. Some
limiting factors will be the aforementioned upper level ridging
and limited low level moisture, especially west of the Highway
83 corridor. However, there could be a few stronger storms with
small hail and locally gusty winds. Overall though the potential
for severe storms looks pretty low and SPC has continued with a
general thunderstorm risk. Later in the evening as another wave
tracks along the International border, more general showers and
thunderstorms with a greater areal coverage may track along and
north of the Highway 2 corridor.

A digging upper level trough from southwest Canada into the
Pacific northwest will transition our northwest upper flow
Today, to a southwest upper flow on Friday as and upper level
low develops over the Canadian Prairie Provinces and a strong
shortwave tracks around the base of this low from the Northern
Rockies into the Northern Plains. This will set the stage for
another round of thunderstorms Friday. A surface frontal
boundary dropping south from the aforementioned Canada low,
looks to be situated over central ND around 00 UTC Saturday.
Along and behind this boundary we have strong bulk shear of
40-60 knots. Ahead of the front we once again become slightly to
moderately unstable with ML CAPE of 500-1500 J/KG. There is
stronger capping the farther east you go ahead of the front and
earlier in the afternoon, but capping becomes weaker just ahead
of the front late afternoon/early evening. Point sounding in
the vicinity of the front late Friday afternoon show long
straight line hodographs with nearly 1500 J/KG of CAPE and
inverted V shaped high based soundings with strong DCAPE. The
bulk shear looks to be nearly parallel to the frontal boundary
which would yield quick upscale growth with fast storm motions.
Therefore damaging winds look to be the greatest threat, with
possibly some marginally severe hail early within any storm
development. The severe threat quickly diminishes behind the
frontal boundary as low level flow becomes unfavorable.

Another shortwave moving through the mean flow tracks through
the forecast area late Friday night into Saturday morning
bringing some scattered shower activity, followed by stronger
winds behind the wave that continue through Saturday.
Saturday will also be cooler with highs mainly in the 60s.

The Canadian upper low hangs around through the weekend and into
early next week, keeping an active weather pattern over our
area. After the cool shot Saturday we rebound slightly Sunday
but through the middle of next week temperatures remain near mid
May normals with highs in the 60s and lows in the 40s.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 955 AM CDT Thu May 16 2024

Scattered thunderstorms later this afternoon and tonight, more
numerous across the north. Added a VCTS at KXWA and KMOT to
account for the greater areal coverage there tonight. A stray
shower or thunderstorm can`t be ruled out across the southern
TAF sites but uncertainty to high for a VCTS mention at this
time. Winds generally variable between west and south at 12
knots or less. Mentioned above that it looks like a good mixing
day this afternoon, but was hard to get stronger winds from
current guidance. Will monitor. Other than the patchy fog early
and possible MVFR vsbys in any TSTM activity, VFR conditions
will prevail.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

UPDATE...Smith
DISCUSSION...TWH
AVIATION...TWH