213
FXUS63 KBIS 190540
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1240 AM CDT Sun May 19 2024

.KEY MESSAGES...

- Low rain shower chances (20 to 30 percent) return late
  tonight into Sunday morning.

- There is a Marginal Risk of severe weather (level 1 out of 5)
  late Sunday afternoon into the evening hours south central.

- High temperatures remain cool through the next work week,
  mainly in the 60s. Expect daily low to medium (20 to 40
  percent) chances for showers and thunderstorms through the
  week.

&&

.UPDATE...
Issued at 1225 AM CDT Sun May 19 2024

Weak high pressure remains situated from eastern Montana
eastward across western and central ND. Skies were mostly clear
with light and variable winds. Clouds are beginning to increase
over southwest North Dakota. These clouds will continue to lift
north and east through the night in moderate warm advection.
Models are depicting some light precipitation as warm advection
clouds spread northward. In general, think this may be overdone.
Will leave some low pops in the forecast but with very dry low
levels, think that any qpf reaching the ground will be minimal.
Otherwise, we made some minor adjustments to sky cover
overnight. Updated text products will be transmitted shortly.

UPDATE
Issued at 949 PM CDT Sat May 18 2024

Clear skies and calm winds as the daytime heating driven clouds
have died. It will be a calm night before clouds and some light
showers move in early morning.

UPDATE
Issued at 643 PM CDT Sat May 18 2024

The diurnal cumulus continue to slowly die across most of the
area and will be clear skies be sunset. Winds are also relaxing
and will go calm after sunset as well. The Wind Advisory will be
allowed to expire as winds are calming now.

&&

.DISCUSSION...
Issued at 231 PM CDT Sat May 18 2024

An upper low continues to spin off to the east just north of the
Canadian border over eastern Manitoba. Associated light rain
showers continue over Bottineau and Rolette counties, but should
move out in the next hour or two.

Western and central North Dakota generally sits under the
influence of near zonal flow aloft but we will see some subtle
ridging move across the state through the rest of the day. While
visible satellite imagery shows a decent amount of fair weather
cumulus, this progressive ridging should lead to some
subsidence across the west, leading to some clearing.

The strongest cold air advection and pressure rises have mainly
moved off to the east, so while it will remain windy though the
rest of the afternoon (winds out of the west northwest), it
should very gradually diminish as we move towards sunset. Given
the tight pressure gradient, we are still expecting sustained
winds up to 30 mph and gusts to 45 mph for a few more hours.
Thus, the Wind Advisory still looks to be in good shape.

Late tonight and into Sunday morning, we will gradually
transition to southwest flow aloft as a Pacific Northwest trough
starts to approach. Warm air advection may lead to some low to
medium (20 to 40 percent) chances for hit and miss showers late
tonight into Sunday morning, mainly across the south central
and James River Valley. This activity should move north through
the morning and into the early afternoon but uncertainty remains
about how long it will be able to sustain itself.

A better chance for showers and thunderstorms (40 to 70 percent)
should start to develop over the south central and James River
Valley by late Sunday afternoon and into the evening hours. A
surface low will start to deepen over South Dakota with an
inverted surface trough extending to it`s north northeast. This
boundary should be the focus for thunderstorm development by the
late afternoon hours. Across the far south, RAP soundings
suggest the potential for up to 2000 J/kg of MUCAPE. However,
looking at MLCAPE, we generally max out in the 500 to 1000 J/kg
range. Still, with forecast deep layer shear will range from 45
to 55 knots over the same area. On paper, these parameters
should be more than enough for a strong to severe storm or two.
However, there are concerns with moisture quality and depth. It
is also worth noting that the RAP is a bit more bullish on
higher instability than most of the other short term models (but
the RAP still shows fairly "skinny" CAPE which may mean
relatively narrow updrafts). That being said, deep layer shear
vectors will mainly be orthogonal to the surface trough so
storms that do form could be discrete or semi- discrete. The
Storm Prediction Center has placed Emmons, Logan, McIntosh,
LaMoure, and Dickey counties in a Marginal Risk (level 1 of 5)
for severe weather. After analyzing soundings and the latest
CAMS, we have decided to message the marginal severe weather
potential up to Kidder, Stutsman, and Foster counties as well.
For now, we will message wind gusts up to 60 mph and hail to the
size of quarters. The one caveat is that if the RAP were to
verify, these thresholds would possibly be too low. However,
the RAP appears to be an outlier right now, maybe not mixing
out dewpoints enough.

Regarding temperatures, Sunday will be the warmest day of the
week with highs ranging from the lower 60s to the lower 70s. By
Monday we will only see lower 70s in our far southeast with
highs in the 60s elsewhere. Highs will mainly be in the 60s
through midweek. The coolest days will then be possible towards
the end of week (Thursday and Friday) when we could see some
highs in the upper 50s to lower 60s.

The active progressive flow will also continue through the week,
leading to daily low to medium (20 to 40 percent) chances of
precipitation at various locations across western and central
North Dakota. Thunderstorm potential will be limited given the
cooler temperatures but a slight chance seems warranted towards
the end of the week across the south as most models have a
potent trough moving into the region (Thursday-Friday). The
eventual track of this trough and associated upper low is still
a bit up in the air. Most models/ensemble members have this
feature but substantial uncertainty remains regarding the track
and strength. It may be worth nothing that CIPs extended analogs
suggest some severe potential across our south by the end of the
week, but CSU Machine Learning guidance is not showing the
potential at this point.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1225 AM CDT Sun May 19 2024

VFR conditions to begin the 06Z TAF period. Expect increasing
mid level cloudiness from south to north through the night and
into Sunday morning. Sunday afternoon into Sunday evening, there
will be lowering clouds north with a hit and miss shower. Added
a VCSH at KXWA and KMOT later in the TAF period. In the south,
especially from KBIS to KJMS, there will be the potential for
showers and thunderstorms late afternoon through the evening.
The favored area looks to be south of KBIS so added a VCSH
around 2300 UTC. AT KJMS we added a VCTS beginning around 01
UTC. Increasing low level clouds will also lift into the area
with the potential for MVFR-IFR around KBIS-KJMS and south
after 00Z Monday. Will add a scattered layer MVFR at this time
and monitor. Light winds to begin the TAF period. Winds will
become south to southeast Sunday morning and then shift east to
northeast later in the day. Western and northern Taf sites will
shift to northerly aft 00Z Monday. winds generally 10 to 20
knots aft 12Z Sunday but southeast flow will be on the higher
side of this range Sunday afternoon.

&&

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

&&

$$

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