979
FXUS63 KFGF 140010
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
710 PM CDT Thu Jun 13 2024

.KEY MESSAGES...

- Multiple rounds of showers and thunderstorms are forecast
  Saturday into early next week. This brings the potential for
  multiple rounds of strong to severe thunderstorms, in
  addition to potentially excessive rainfall.

&&

.UPDATE...
Issued at 710 PM CDT Thu Jun 13 2024

Satellite continues to show mid level clouds across eastern
North Dakota and northwestern Minnesota this evening. We
increased the sky coverage through the evening hours to account
for the cloud coverage. Highest concentration of clouds are
along Highway 2 points north. Guidance has the clouds staying
around this evening, but slowly eroding as we head into the
overnight period. Watching for the potential for fog tomorrow
morning. Light winds, cooler temperatures, and recent saturated
soils may bring the chance for patchy fog.

&&

.DISCUSSION...
Issued at 333 PM CDT Thu Jun 13 2024

...Synopsis...

Current water vapor imagery reveals broad upper troughing over
central Canada extending into the Upper Midwest and Great Lakes
regions, with ridging in the western CONUS ahead of seasonably
strong and broad upper troughing over the northeast Pacific.
Within the base of upper troughing smaller mid level wave is
noted moving into north- central Minnesota, and away from our
area. This wave will focus shower and thunderstorm chances
within it, thus pulling chances for scattered showers and
thunderstorms away from our area for the remainder of the
afternoon.

Ensemble guidance is in good agreement of building upper ridging
into the Northern Plains from the western CONUS on Friday,
keeping conditions mostly dry at least through the afternoon.
This is short lived, however, as the Pacific upper troughing
also propagates east toward the northwestern CONUS and southwest
CAN. Upper ridging also builds over the Ohio Valley into Great
Lakes regions. This sets the stage for several rounds of showers
and thunderstorms starting Saturday into next week as the upper
pattern stalls allowing zonal to southwesterly flow aloft over
the Northern Plains.

Ensemble guidance starts to deviate in timing and strength of
shortwave impulses ejecting out of the broader western troughing
into the Northern Plains and Upper Midwest next week. Regardless
of these synoptic uncertainties, these will provide the upper
support for forcing for ascent to drive precipitation chances.
Additional uncertainties exist in location and orientation of
surface boundaries/air masses which would also dictate location
of precipitation chances, as well as focus for thunderstorm
chances with attendant strong to severe storms.

...Multiple rounds of showers and storms, with attendant strong
to severe storm potential...

With an extended period of overall zonal to southwest flow
aloft, deeper moisture and more unstable air mass will likely
near or extend through our area of eastern ND into MN.
Additionally, with the likelihood of several shortwave troughs
ejecting into/near our region within the broader flow aloft,
higher winds nested around each wave will bring increased
chances for better kinematics for storm organization.

Timing, location, and magnitude of instability and kinematics is
still quite uncertain that would drive strong to severe storm
chances. Additionally, orientation of surface boundaries that
would have implications on storm mode (and as such most likely
severe hazards) are also low in confidence.

Still, ensemble and machine learning guidance like CSU ML Severe
forecasts and NBM CWASP both indicate the potential for several
days of potentially strong to severe storms from Saturday
through Tuesday. SPC also has highlighted our area with 15%
chance for severe storms Monday as there is relatively higher
confidence in a stronger shortwaves contributing to organized,
severe storms, but does not mean other days between Saturday and
Tuesday would not hold severe chances as well.

Not to be discounted is the potential for flooding impacts from
excessive rainfall as well. With several shortwave troughs
passages, richer moisture content feeding into these shortwaves,
and potential for stalled frontal boundaries, excessive
rainfall leading to flooding is possible. Relatively moist
soils from higher than average rainfall May into early June, as
well as higher river levels from said rainfall also provides
antecedent conditions for such impacts.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 630 PM CDT Thu Jun 13 2024

VFR conditions are expected to remain throughout the TAF period
for all sites. Winds are expected to start to become light and
variable starting around 03z. Starting around 10z some model
sounding showed the possibility of patchy fog across the TAF
sites. However, there is uncertainty with how much moisture will
be trapped under the early morning inversion. If the air is
saturated near the surface then fog may develop under these
conditions. I left the mention of fog out of the TAFS due to the
uncertainty in formation and location.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.

&&

$$

UPDATE...Spender
DISCUSSION...CJ
AVIATION...MM