081
FXUS63 KBIS 171814
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
114 PM CDT Fri May 17 2024

.KEY MESSAGES...

- Scattered severe thunderstorms are possible this afternoon
  and evening. The expected hazards will be damaging winds up to
  70 mph and hail up to quarter size.

- Warmer today with highs from the mid 70s northwest to the mid
  80s south central. Windy and cooler on Saturday with highs
  mostly in the 60s.

- Daily chances (40%) for showers and thunderstorms continue
  through the weekend and into early next week.

&&

.UPDATE...
Issued at 105 PM CDT Fri May 17 2024

The upper level wave has started to move into the state, as seen
in satellite with agitated mid level clouds. Near the
Montana/North Dakota border near Glendive, MT cumulus has
started. We should be warmer than our convective temperature
now, so more cumulus should start to pop in the next hour,
especially with the diffluence over head from the upper level
wave. The latest SPC update at 1630z expanded the slight risk
through the whole CWA. The storm mode still looks the same being
a strong line along the cold front, with the potential to
produce 70mph winds. Some storms may form ahead of the line.

UPDATE
Issued at 1000 AM CDT Fri May 17 2024

Skies have cleared across the area, allowing for max heating
this morning. The severe threat remains the same, our morning
sounding had a strong warm nose (capping), however the
convective temperature is 79 degrees with our forecast high of
83 degrees. It is still unknown if storms will go up this
afternoon before the cold front or not with this capping layer.

UPDATE
Issued at 631 AM CDT Fri May 17 2024

Except for maybe a stray sprinkle, shower activity has either
dissipated or moved east of the forecast area. Mostly sunny
conditions should prevail this morning. We made some minor
adjustments to sky cover based on latest satellite imagery.
Otherwise no changes to the forecast early this morning.

Just looking at the more recent runs of the RAP, there is more
instability in the north and potentially a greater hail threat
north, but this is quite a switch from earlier and will wait for
additional 12Z guidance for any significant changes to threats.
Will continue with 1 inch hail and 70 mph winds.

&&

.DISCUSSION...
Issued at 332 AM CDT Fri May 17 2024

Isolated to scattered showers were moving across western and
central ND early this morning. Low pressure continues to spin
over southwest Saskatchewan, with surface pressures also
developing over central and eastern Montana, ahead of a strong
shortwave tracking across central/eastern Washington and Oregon.
As shower activity dissipates and or exits to the east, we
should see a quiet and mostly dry morning with temperatures
climbing well into the 70s most areas by midday.

This afternoon as temperatures climb into the lower and mid 80s
over southwest and central ND, we see steepening low and mid
level lapse rates and increasing instability over the forecast
area. Strong bulk shear will be present across the entire
forecast area today. The aforementioned shortwave and attendant
surface low pressure will catch up with the lingering frontal
boundary from the Saskatchewan low pressure system and push
quickly across the forecast area late this afternoon and this
evening. This will bring a chance of strong to severe storms to
most of the forecast area.

When looking at the potential for sever weather, just compared
to yesterday, the areal extent and the window of opportunity
looks a bit smaller (far southwest and south central then
lifting a little more north, east of the Missouri, into the JRV
from around 21Z-04Z). However, with the strength of the
shortwave, strong to possibly severe storms can`t be ruled out
pretty much anywhere across western and central ND (perhaps not
the far northwest which is currently in the general TSTM
risk).

As far as hazards, it seems like winds will be the main threat.
After coordination with FGF/ABR we bumped up the wind threat to
70 mph. There is an area of strong DCAPE over south central ND
this afternoon. However, it does begin to dissipate as
convective potential increases. Also, just with the strength of
the shortwave and the strong jet dynamics, a strong wind gust
seems possible. Bufkit soundings show the potential for 40-50
knot winds mixing down to near the surface just behind the cold
front. Any convection with the front would help to push this
cold air to the surface, and the Inverted V type soundings are
favorable for stronger winds mixing to the surface.

The hail threat seems lower with 1 inch hail a good upper limit
at this time. There is some instability ahead of the front this
afternoon and if there is convection there would be enough
instability for some marginally severe hail. This will be a
conditional threat given the capping that will exist ahead of
the cold front. If we do see convection develop ahead of the
front this afternoon we could see some hail to 1 inch. One
additional thought...Latest RAP guidance and NAM guidance is
showing some larger hail potential along the Canadian border.
This wasn`t the case earlier, so will continue to monitor.

Based on the storm mode, which would favor a linear or mixed
mode as the shear is mostly parallel to the cold front. Ahead of
the front, a better hail threat would exist with the potential
for a discrete cell if the cap can be overcome, as mentioned
earlier, but with that condition remaining, seems reasonable to
limit hail to 1 inch.

Also as mentioned earlier, environmental winds alone will be
strong behind the cold front tonight and added convection could
make for a windy overnight. There is another shortwave following
late tonight into Saturday morning. Shower/thunderstorm
activity with that wave could also mix down some stronger winds
aloft. Saturday looks to be windy across the forecast area and a
wind advisory may be needed for at least portions of the area
on Saturday. Saturday will also be much cooler, with scattered
showers mainly in the north.

Sunday will bring a modest warm-up with highs climbing back into
the 70s across most of the forecast area. A broad southwest
flow with an approaching shortwave could bring some shower and
thunderstorm activity once again. At this time it looks the
southeast CWA would be favored for thunderstorms. Monday and
through the remainder of the forecast period temperature look to
remain seasonable with near daily chances for showers and
thunderstorms.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 105 PM CDT Fri May 17 2024

VFR this afternoon until strong thunderstorms move west to east
between 21 and 03z. Overnight light rain may continue until the
early morning. Winds will gust around 20kts today from the
southwest increasing to 35kts from the west by Saturday
morning. Skies will clear out by late morning Saturday except
near KMOT where 3kft ceilings could linger, left it as SCT for
now until we get more confidence.


&&

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

&&

$$

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