-- Discussion containing changed information from previous version are highlighted. --
835
FXUS63 KBIS 021801
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
101 PM CDT Thu May 2 2024

.KEY MESSAGES...

- Widespread rain showers will continue through the morning and
  much of the day, mainly east of the Highway 83 corridor.

- Expect more hit and miss showers later this afternoon and
  evening across the west and central. A few isolated
  thunderstorms are possible. Chances for showers continue
  Friday.

- Chances for rain return Sunday night, becoming likely by
  Monday (60 to 70 percent). Monday may also bring a better
  chance for some thunderstorms. Low to medium rain chances (20
  to 60 percent) continue into mid week.

- Near to slightly below normal temperatures expected through
  Saturday, becoming near to above normal Sunday and Monday.

&&

.UPDATE...
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Issued at 1223 PM CDT Thu May 2 2024

Showers continue to push eastward into the James River Valley
moving out of the Bismarck/Mandan area. Showers are beginning to
pop up across the northwest and move across northeastern
Montana. Some low level cumulus is beginning to increase across
the western half of the state as the upper low moves close to
the northwestern half of the state. This is increasing
instability giving us a shot for thunderstorms afternoon.
Adjusted PoPs to match current conditions.

UPDATE
Issued at 935 AM CDT Thu May 2 2024

Rain continues to fall across the eastern half of the state
an the eastern half of central North Dakota. Some showers over
north central South Dakota will move into south central North
Dakota today continuing rain across central North Dakota. Later
this afternoon wrap around showers and thunderstorms may form
over much of the western half of the state. Another burst of
energy from the upper low will be the driving force for
thunderstorms and energy that is currently over northeastern
Montana. The forecast remains on track at this time so no
further updates were needed.

UPDATE
Issued at 612 AM CDT Thu May 2 2024

No major changes were needed for this update. The precipitation
axis continues to trend just a bit further east than most of the
CAMs were suggesting. However, we have seen some redevelopment
across the south central and this activity may still yet push
it`s way into the Bismarck/Mandan area later this morning and
into the early afternoon.
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&&

.DISCUSSION...
Issued at 411 AM CDT Thu May 2 2024

An upper level low was located in the vicinity of the eastern
Montana/southern Saskatchewan border early this morning with a
surface low centered over southern Saskatchewan. Several
shortwaves will rotate around this low and into western and
central North Dakota, providing various chances for
precipitation through Friday night.

The initial impulse will continue to spread from south central
North Dakota and into the east. The heaviest precipitation
should remain mostly east of the Highway 83 corridor with the
exception of parts of the far south central. The latest NBM
shows continued medium to high chances (50 to 90 percent from
west to east) for a half inch or more of additional rainfall
over the aforementioned areas. While most of the rain from this
initial impulse will mainly move out of the area to the east by
the mid to late afternoon hours, the upper low is going to be
slow moving out. Another shortwave will rotate into our area
this afternoon and interact with a surface trough/frontal
boundary across portions of the west and central. The latest
CAMs suggest that we will see convective showers and isolated
thunderstorms developing in the mid to late afternoon hours
across the west, eventually spreading into the central. RAP
soundings suggest the potential for around 300 to 600 J/kg
MUCAPE so some thunder seems reasonable. There will be some
strong shear present, but mainly to the east of the instability
axis. Thus, severe weather is not expected.

On Friday, we could see a few more hit and miss wrap around
showers but this activity looks mainly focused across the
northern half of the forecast area for now. Instability will be
even weaker on Friday so thunder chances appear low at the
moment.

An upper ridge pops up to our west on Saturday with the axis
located over central Montana by the afternoon hours, placing
western and central North Dakota under northwest flow aloft.
After highs mainly in the upper 40s to the upper 50s today and
Friday, we start to clear out and warm on Saturday with forecast
highs in the lower 50s to lower 60s. The ridge then approaches
the Montana/North Dakota border late Saturday night and crosses
the state on Sunday. This will lead to even warmer temperatures
on Sunday, with highs forecast to be mainly in the upper 60s to
mid 70s.

By Sunday night, the ridge moves off to our east and we
transition into nearly meridional flow aloft as a strong
negatively tilted trough approaches. An upper low will close
off at the base of the trough and eventually swing up to the
North Dakota/South Dakota border by late Monday. Several rounds
of widespread precipitation appear to be in the cards Sunday
night through mid to late week as ensemble guidance suggests
this low will have a tough time getting kicked out of the
region. Monday may also bring a better chance for some
thunderstorms. Shear will be plenty strong, but instability is
likely to still be lacking a bit. That being said, CSU Machine-
Learning Probabilities suggest at least marginal chances for
some severe weather in the Sunday through Tuesday time frame so
it will be an interesting period to watch. Chances for showers
will linger mid to late week.

After Monday, temperatures will likely cool back to slightly
below normal categories through mid to late week with NBM highs
mainly into the lower 50s to lower 60s. It is worth noting that
ensembles continue to struggle with the pattern beyond Monday,
and this uncertainty is evident in significant high temperature
spread among NBM members. Thus, the temperature forecast next
week still includes quite a bit of uncertainty. As a final note,
periods of breezy conditions appear likely, mainly Friday and
then most of next week.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
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Issued at 1223 PM CDT Thu May 2 2024

MVFR conditions will continue in areas with rain which is
eastern half of the state. While low clouds are forming out west
which will lead to showers this afternoon and maybe a few
thunderstorms. Winds are forecast to switch out of the
southwest this afternoon to northwest by early tomorrow
afternoon. Temporary visibility reductions and lower ceilings are
possible under showers this afternoon. Thunderstorms may cause
gusty erratic winds.
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&&

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

&&

$$

UPDATE...Johnson
DISCUSSION...ZH
AVIATION...Johnson