681
FXUS63 KBIS 151141
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
641 AM CDT Sat Jun 15 2024

.KEY MESSAGES...

- There is a Slight Risk (level 2 out of 5) for severe
  thunderstorms late this afternoon through the early overnight
  hours tonight, covering most of western and central North
  Dakota.

- There is a Marginal Risk (level 1 out of 5) for severe
  thunderstorms Sunday across far southcentral and southeastern
  portions of the state.

- There is a Marginal Risk to Slight Risk (level 1 to 2 out of
  5) for severe thunderstorms Monday across far central and
  eastern portions of the state.

- Breezy to windy west winds may return across much of western
  and central North Dakota on Sunday.

- After above normal temperatures today, below normal
  temperatures are forecast Sunday through at least mid next
  week.

&&

.UPDATE...
Issued at 640 AM CDT Sat Jun 15 2024

Limited updates needed this morning. The first of two upper
level waves may bring an isolated to scattered shower across
the northwest and north central this morning. Some lightning has
been observed in Montana with these showers, and may also do so
as they traverse North Dakota. A secondary wave combined with a
surface low could then bring strong to severe storms tonight.
Overall made only minor updates this morning and the forecast
remains on track.

&&

.DISCUSSION...
Issued at 430 AM CDT Sat Jun 15 2024

Isolated to scattered severe thunderstorms still expected today
into tonight across portions of western and central North
Dakota. This morning, a low level just could bring a few
isolated thunderstorms to eastern areas, while a developing
surface low and weak wave in southwest flow aloft brings some
showers to the west. Surface low then looks to develop through
the day today, setting up a warm front across much of the state.
High temperatures will rise slightly today as a result, with
some southwestern sites seeing highs in the lower 90s. Southerly
flow at the surface will advect higher dewpoints in today. NBM
forecast afternoon dewpoints in the mid 60s. Perhaps this is a
touch high as dewpoints of this magnitude are as far south as
Nebraska at this time. However, even dewpoints in the upper 50s
to lower 60s combined with strong heating today will bring
abundant amounts of instability with MUCAPE over 2000 J/KG, and
some areas even seeing up to 3000 J/KG. Shear will also be
robust today, with 0 to 6 KM shear up to 50 knots. The limiting
factor during the day will be capping. This breaks down later
this afternoon through this evening when another more potent
shortwave aloft moves through. An isolated severe storm is
possible ahead of this wave, although the highest confidence in
timing for today`s severe weather will be when this mid level
shortwave moves through. Given this the highest confidence in
timing for today`s severe weather is roughly 5 PM to 1 AM CDT.
Storm mode will greatly determine today`s hazards. The shear
vector is generally west to east today, until it becomes more
along the cold front tonight. Thus if storms linger into the
late evening or overnight hours, a linear storm mode can be
expected. However, storms that can go earlier in the evening
have the potential to be discrete or at the very least
multicluster. These storms will be the ones to watch for all
hazards. High CAPE and high shear aside, hodographs showing good
veering this evening, giving fair amount of 0 to 1 KM and 0 to
3 KM SRH. STP values over 1 are also found during this time.
LCLs are about 1000 m, which would be adequate for tornado
development. Thus any discrete cell that forms early in the
severe window will have the possibility of creating a tornado or
two. Large hail will also be of concern today given mentioned
parameters. Historical data showing a lot of cases with similar
parameters bringing baseball size or larger hail. Would like to
see perhaps a touch higher shear to have higher confidence in
this larger sized hail. The tornado threat also may tone down
hail slightly. Still decided to raise the max hail size today to
tennis ball size. The wind threat also remains high today. Kept
in 70 mph winds with some isolated 80 mph gusts. This again
goes along with what will the storm mode be. The higher wind
gusts would likely be if severe weather goes later and closer to
the cold front. This timing brings high DCAPE over 1000 J/KG
and 0 to 3 KM shear 25 to 30 knots. MUCAPE could be little
higher for these stronger winds, although will be adequate. Thus
kept wind values messaged as is. Of note too are higher Pwat
values and average storm motions. Thus heavy rain could also be
possible today. Cold front should progress quickly tonight
across the CWA, moving or diminishing severe weather during the
early to mid overnight hours. A switch to westerly winds may
also be found, and they could become breezy at times. Lows
tonight behind this front will be in the lower 50s in the west,
while near 60 degrees can be expected in the east.

A generally post frontal day is then expected for Sunday. Look
for cooler temperatures and breezy to windy westerly winds.
Some areas in the north and west should still be monitored for
potential advisory level winds. SPC maintained a Marginal Risk
for severe weather in southcentral and southeastern portions.
Shear will remain high, although instability looks limited.
Perhaps as the front stalls an isolated severe storm is still
possible in these areas later in the day through the night.
Highs on Sunday look to be in the mid 60s to mid 70s, with some
lower 80s in the far southeast. Lows Sunday night look to be mid
40s to mid 50s. Of note too for Sunday will be lowering RH
values in the afternoon into the 20s. Fuels may still be too
green for fire weather concerns, although breezy to windy winds
and lowering RH could bring at least some increased concerns.
The front remains stalled for Monday, then is reinforced by
another cold front through Monday night. This could bring the
next round of showers and thunderstorms. SPC now has a Marginal
to Slight Risk across central and eastern North Dakota. Shear
will again be high on Monday, although CAPE is somewhat modest
though increased over Sunday. Large hail and damaging winds
right now look to be the main threats. Another post frontal day
could then be found on Tuesday, with further cooling of
temperatures into the 60s. Lingering showers and thunderstorms
may also be found. Tuesday night into Wednesday morning could
then be quite cool for some areas. NBM forecast temperatures are
currently in the 40s for most areas. ECMWF EFI values for Min T
during this time period though are around -0.8. Looking at the
NBM 25th percentile gives some lows in the upper 30s across the
west Wednesday morning. Something to monitor perhaps. A gradual
warmup could then be in store for mid to late next week in a
zonal to perhaps slightly southwesterly flow. Another broad
trough could approach the area mid to later in the week,
returning near daily chances for showers and thunderstorms.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 640 AM CDT Sat Jun 15 2024

A few showers may be found across the northwest this morning,
and perhaps an isolated thunderstorm. Otherwise, mainly VFR
conditions will be found this morning into the afternoon. Light
winds will become southerly, and perhaps breezy for some eastern
sites. There could be some lower to perhaps MVFR clouds that
develop in the James River Valley today and linger. This may
impact the KJMS area. This afternoon through this evening could
then see isolated to scattered showers and thunderstorms. A few
may be severe at times. Confidence in timing of these storms has
increased some, and was able to add prevailing groups of TSRA
to most sites with this TAF set. Stronger storms could also
bring some brief MVFR conditions. Storms look to diminish
overnight tonight. Some sites could see lingering MVFR clouds
through the night. A cold front will turn winds to the west
tonight, and possibly become breezy.

&&

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

&&

$$

UPDATE...Anglin
DISCUSSION...Anglin
AVIATION...Anglin