628
FXUS63 KFGF 220433
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
1133 PM CDT Mon Jul 21 2025

.KEY MESSAGES...

- A Severe Thunderstorm Watch is in effect for southeastern
  North Dakota and west-central Minnesota from now through 5
  AM. Scattered showers and thunderstorms will develop and pose
  a risk for damaging wind gusts to 70 mph.

- There is a 2 of 5 risk for severe thunderstorms on Tuesday.
  Hazards could include large hail up to 2 inches, damaging wind
  gusts of 70 mph, and tornadoes.

- A few isolated storms could reach severe criteria on Wednesday
  before pushing out of the forecast area.

&&

.UPDATE...
Issued at 1121 PM CDT Mon Jul 21 2025

A very strong MCS has developed across northern South Dakota and
is progressing east-northeastward on the periphery of a 1000
J/kg DCAPE gradient. Tracking this line brings it a few hours
earlier than initially forecast thanks to likely intensification
of rear inflow jets forcing stronger forward propagation. The
main question right now is where that DCAPE gradient sets up for
our area as it will drive impacts with this line. Guidance
features a wide range of potential scenarios from as far north
as I-94 to as far south as northeastern South Dakota.
Additionally, low-level jet displacement complicates matters in
questioning how long this complex will hold together.

Additional showers and thunderstorms are likely to develop
overnight, impacting much of the CWA. Severe potential is much
less outside of the current severe thunderstorm watch thanks to
DCAPE limitations, but strong 0-3km shear may be enough for some
isolated wind gusts to arise. The bulk of this round of
lightning and severe thunderstorm activity should exit the area
by 18z, but another round remains on tap for tomorrow afternoon
with additional development along a cold front.

UPDATE
Issued at 949 PM CDT Mon Jul 21 2025

The complex in northwestern South Dakota and western North
Dakota is likely to become the main complex that impacts us
after 3 AM. While the degree of severe potential is uncertain as
DCAPE looks to stay mostly limited to the far south, but strong
low level flow should facilitate some organized UDCZs and
stronger wind gusts. Most guidance fizzles it out as it
approaches the Red River Valley, however the current background
environment, severe convection lasting into northwest Minnesota
cannot be ruled out, hence the marginal risk continuing that far
east.

UPDATE
Issued at 641 PM CDT Mon Jul 21 2025

Some light cumulus has attempted to form in the southern Red
River Valley, but depth has been hard to come by, so
thunderstorms aren`t necessarily imminent but may still arise in
the next 1-2 hours. These should be fairly short-lived as the
low level jet will remain west of the region.

Further north, supercells have formed in the vicinity of
Winnipeg with a right moving storm pushing southeastward. If
these storms hold together long enough, it would be feasible to
see severe storms impact Roseau/Lake of the Woods area, but
there is high uncertainty in how long these storms last. These
should have the same issues as the aforementioned potential
storms in the south given the same reasons.

Showers and storms are likely to push eastward from the western
Dakotas tomorrow morning, although severity remains a big
question mark with the same uncertainties as earlier.

&&

.DISCUSSION...
Issued at 310 PM CDT Mon Jul 21 2025

...Synopsis...

Water vapor loops shows near zonal flow over the Northern
Plains, with the shortwave that brought overnight convection
near the MN/WI border. Another shortwave will come out in the
Red River Valley tonight from the Northern Rockies, and another
is indicated by the models for late Tuesday/Tuesday night. A
surface trough axis/frontal boundary will drop into our central
forecast area tomorrow, then sag southeastward into west central
MN for Wednesday. A bit of a break on Thursday with weak surface
high pressure, then the pattern becomes active again for Friday
and into the weekend with additional weak ridge riding
shortwaves. Upper heights will be on the rise towards the end of
the period, bringing above average temperatures for next weekend
into early next week.

...Severe chances overnight...

Mesoanalysis page shows some fairly strong mixed layer CAPE,
around 2000 J/kg extending into our southern counties this
afternoon. This is in addition to some 40 to 45 kts of deep
layer bulk shear. On the other hand, there is not a lot of
forcing currently over our CWA and quite a bit of warm air aloft
keeping us capped. A few of the CAMs still break out some cells
just before 00Z around Grant county, but even the more bullish
solutions have this activity fizzling quickly. The better
shortwave trough is still out over the Northern Rockies and will
not move into the Plains until later tonight. Plenty of
elevated instability will be remaining over our southern
counties, over 3000 J/kg, and there will still be good effective
shear. A convective complex with some potential for isolated
large hail and damaging winds seems reasonable.

...Slight risk on Tuesday...

Much will depend on how the early morning convection plays out
but it does look like there will be enough of a break to
destabilize before another shortwave and frontal boundary arrive
in our forecast area. Convection should develop along the front
during the afternoon, initially discrete but then rapidly
becoming linear as we head into Tuesday evening, with hail and
winds the main threat along with heavy rain. Even with the
storms becoming more linear, there will be such strong
instability and 0-3km winds are such that can`t rule out a brief
spin up within the line. PWATs are very high but at this point
think there will be enough forward propagation to limit
training and flash flood potential.

...Marginal risk in west central MN on Wednesday...

The front will have pushed through much of the forecast area by
Wednesday morning, although again much will depend on how
convection plays out in the previous 36 hours. With NBM
probabilities for over 1500 J/kg around 50 percent and deep
layer shear expected to be at least 30 kts, could still get some
isolated severe reports as storms develop along the boundary
before they move off into DLH or MPX`s area.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1121 PM CDT Mon Jul 21 2025

MVFR ceilings should overspread northwest Minnesota and
southeast North Dakota this evening. Most guidance clears this
out by around 15-21z for all TAF sites. Showers and
thunderstorms will develop and progress from west to east this
morning, likely impacting most, if not all, TAF sites sometime
between 08z and 15z. Gusty winds with these storms are most
likely to arise at FAR, however certainty in wind gust maximums
is low. Right now, routine TAF issuance features 40 knots given
the low certainty in severe potential that far north, but the
reasonable worst case scenario is an organized squall of
thunderstorms that produces 50-60 knots of gusts.

Regardless of the gust potential, most TAF sites will be under
the threat of lightning through at least 23z tomorrow, as
additional thunderstorms along a cold front are likely to
develop. These storms, in addition to wind, will carry a greater
potential for large hail.

After 23z, expect winds to become light and variable and skies
to become VFR with minimal aviation impacts as thunderstorms
exit the region.

&&

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

&&

$$

UPDATE...Perroux
DISCUSSION...JR
AVIATION...Perroux