619
FXUS63 KFGF 132330
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
630 PM CDT Wed Aug 13 2025

.KEY MESSAGES...

- Scattered strong thunderstorms expected tonight across
  southeast North Dakota into Minnesota. The main hazard will
  be lightning and hail to the size of quarters.

- There is a level 2 out of 5 risk for severe thunderstorms late
  afternoon into evening Thursday. The main hazards will be
  gusty winds hail to the size of golf balls, gusts to 60 mph,
  and possibly a couple tornadoes. Uncertainty lingers on
  coverage of thunderstorms.

- There is a level 1 out of 5 risk for severe thunderstorms
  Friday afternoon within southeast North Dakota into west-central
  Minnesota.

&&

.UPDATE...
Issued at 630 PM CDT Wed Aug 13 2025

WAA and a relatively weak LLJ will be focus for potential
thunderstorm initiation later this evening/overnight, with the
main warm front/baroclinic zone southwest of our region.
Skinny CAPE profiles with effective shear 25-30kt may support a
few stronger storms, though the overall severe risk is low.
Brief heavy rain, lightning, and small hail will be the most
likely threats, with a low chance for marginally severe hail
with stronger storms tonight (1"). Will continue to monitor
trends.

&&

.DISCUSSION...
Issued at 135 PM CDT Wed Aug 13 2025

...Synopsis...

Broad upper ridging is noted on water vapor satellite imagery,
with a low amplitude wave moving through eastern SD as well as
within northern WY into southern MT. These will aid in low level
jet/warm air advection induced scattered showers and storms
tonight in southeast ND into MN. There is enough shear and
instability to suggest hail up to the size of quarters will be
possible, but more likely sub-severe hail will be more
prevalent if hail arises.

...Severe storm potential Thursday and Friday...

Upper forcing for ascent increases over the Northern Plains and
Upper Midwest as upper troughing migrates eastward out of the
Canadian Rockies into central Prairie Provinces. At the surface,
a fairly progressive and stout cold front through the region,
including the Dakotas. While this combined with increasing
instability potentially greater than 3000 J/kg and effective
shear on the order of 30-45kt is driving the severe storm
potential, there are still important details that remain
uncertain. Uncertainties are mainly tied to the relationship
between degree of forcing and convective inhibition lowers
confidence in storm evolution. CAMs suggest enough convergence
and surface heating should minimize convective inhibition very
near the front, although there may still be a complicating
factor of dry air entrainment to limit initial updrafts from
sustaining themselves under a weakly forced regime, particularly
south of US Highway 2 corridor.

This opens up a range of possible outcomes ranging from isolated
discrete supercells along the cold front capable of all hazards
(including hail up to golf ball sized, potentially greater as
well as tornadoes), or more clusters of storms eventually
turning into more linear feature placing high wind and hail in
the forefront of most likely hazards (relatively greater
potential within northwest MN).

The evolution of convection as well as frontal placement will
dictate Friday`s severe storm potential. Should the front be
slow to move through the area, it could stall near the tri-state
area of the Dakotas and Minnesota. This would allow severe storm
to develop near this stalled front and perhaps eventual surface
cyclogenesis near the same area. Should this occur, all hazards
would again be possible. This is what is driving the level 1 out
of 5 risk for severe storms Friday afternoon.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 630 PM CDT Wed Aug 13 2025

VFR conditions are favored by guidance across eastern ND and
northwest MN through the TAF period, with the main aviation
impacts through tonight from scattered thunderstorms (mainly in
southeast ND/west central MN) and a 30-40kt LLJ developing after
08Z. Best chance for thunderstorms is at KFAR where a PROB30
group was introduced, and we will monitor trends/amend if
activity actually begins to develop in the 03-09Z window as some
guidance indicates.

&&

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

&&

$$

UPDATE...DJR
DISCUSSION...CJ
AVIATION...DJR