150
FXUS63 KBIS 171926
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
226 PM CDT Mon Jun 17 2024

.KEY MESSAGES...

- Widespread showers with isolated to scattered thunderstorms
  later this afternoon through Tuesday.

- Isolated to scattered severe storms possible this evening
  through tonight, with expected hazards of hail up to golf ball
  size and winds up to 60 mph. Very heavy rainfall is also
  possible with any storm, possibly resulting in localized
  flooding.

- Below normal temperatures expected Tuesday and Tuesday night,
  followed by temperatures trending warmer and another active
  period developing for later this week.

&&

.DISCUSSION...
Issued at 215 PM CDT Mon Jun 17 2024

Currently, strong southwest flow aloft with a 90-100kt upper
level jet aloft. Mid level low/S/WV trough moving into the
Montana Rockies, with multiple lead embedded waves moving across
the Dakotas today, resulting in scattered showers and extensive
cloudiness. Still only seeing trace amounts of moisture reported
across the north underneath showers there, so don`t see the need
to increase POPs much for the next few hours.

Looking at two rounds of showers/storms over the next 12-18
hours, the first will be convection firing up to our southwest
as increasing ascent develops east into the high plains
(currently clear and becoming unstable), with this activity
then quickly moving/developing to the northeast into western ND
this evening. The overall severe threat will be limited with
minimal instability projected, though with 60-80 knots of 0-6km
shear, a few organized updrafts can`t be ruled out, hence the
Marginal Outlook being maintained. Northwest ND looks to see the
heavier rainfall amounts, upwards to an inch and half. Given
the limited strength expected and fast progression of storms,
these amounts will likely fall over a few hours vs. several
minutes, so do not anticipate any hydro issues northwest.

Second round of convection looks to originate across South
Dakota (possibly far southern ND) mid to late evening, as the
aforementioned forcing continues east and interacts with
increasing MUCAPE developing from south to north across SD and
into parts of south central and southeastern ND. 0-6km shear not
as robust, but still in the 40-50 kt range so can`t rule out a
few large hail producers. It does appear that the threat for
heavy rain and localized flooding is becoming an elevated
concern, with PWATs nearing max climatology values of 1.5". Thus
will continue to mention this in our messaging (HWO and social
media).

Much cooler air is pulled south across the Northern Plains in
the above S/WV`s wake, with highs Tuesday ranging from the 50s
northwest to around 70 in the far southeast. Overnight lows
Tuesday night/Wed morning continue to be a closely looked at,
with NBM continuing its cooling trend with now widespread
mid/upper 30s across the west. For now, will not mention frost
but will def need to keep an eye on this period over the next
24-36 hours.

We never really get out of the active west/southwest flow
pattern, but precipitation chances looks more isolated through
Thursday, until we trend more active later this week as models
bring in more defined waves into our local region. Temperatures
will also trend slightly warmer Wed-Fri, then more-so later this
weekend into early next week.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1231 PM CDT Mon Jun 17 2024

VFR ceilings and visibility at all terminals early this
afternoon. A few scattered showers north, though cloud bases
remain elevated so little reaching the ground.

Ceilings will begin to drop later this afternoon into this
evening along with chances for showers and thunderstorms
increasing through the evening and early overnight hours. A few
strong to severe storms will be possible across south central
and southeastern North Dakota, with more shower activity and
VCTS elsewhere. Widespread MVFR to LIFR visibilities and
ceilings are forecast, along with some terminals occasionally
observing LIFR ceilings. Winds will remain moderate from the
east at 10 to 15 knots and gusts up to 25 knots at all terminals
through early Tuesday morning, before diminishing and turning
northerly through the end of the TAF period. Where thunderstorms
to develop, gusty and erratic winds are anticipated.

&&

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

&&

$$

DISCUSSION...NH
AVIATION...NH