332
FXUS63 KFGF 120959
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
459 AM CDT Sat Jul 12 2025

.KEY MESSAGES...

- Wildfire smoke will degrade air quality today, with an
  additional round Sunday.

- There is a level 1 out of 5 risk for severe thunderstorms
  Monday. The main hazards are hail, gusty winds, and flash
  flooding.

&&

.DISCUSSION...
Issued at 417 AM CDT Sat Jul 12 2025

...Synopsis...

Upper level shortwave trough axis resides over the Northern
Plains, with post-frontal air mass filled with wildfire smoke
over the region. The shortwave trough will continue to migrate
eastward into the Upper Midwest and western Great Lakes region
today followed by generally northwest flow aloft. This will
continue to advect continental air mass originating within
Canada, bringing additional wildfire smoke Sunday. Additional
details on wildfire smoke and associated impacts found below.

Flow then turns more zonal as large upper low over the Hudson
Bay develops early next week. This will promote entrance region
upper jet dynamics to overspread the High Plains, promoting lee
troughing at the surface. This also will promote moisture
return from the south into the Northern Plains and Upper Midwest
along with increasing instability and frontal development. With
forcing for ascent increasing within the region via
aforementioned dynamics and frontal development, chance for
showers and thunderstorms increases Monday and Tuesday.
Increased instability and flow aloft will introduce the
potential for strong to severe storms during this timeframe over
the Dakotas into Minnesota. More details on this found below.

As the Hudson Bay low develops further, there will be a tendency
for cooler, continental air mass to intrude over the region.
Ensemble guidance like ENS EFI is noting on higher probabilities
of below average temperatures between Wednesday and Friday.
Lows are currently forecast into the 40s at some locations
already. Drier conditions will also accompany this set up, as
well as additional chance for more wildfire smoke to infiltrate
the region.

... Wildfire smoke today and Sunday ...

Current visibilities and AQIs indicate very dense smoke still
over the region. VIIRS Day Night Band overnight pass also shows
smoke over the Dakotas into Minnesota. This will continue to be
the case today with gradual migration of smoke from west to
east. Smoke guidance hints at a brief reprieve in near surface
smoke tonight into early Sunday before another bout of smoke
behind a secondary cold front moves back into the region. Areas
like northern Red River Valley into Minnesota are relatively
more favored to see smoke impacts than other locations as
suggested by available smoke guidance.

Smoke is forecast to continue to be thick enough to increase
risk of adverse health effects to all populations today and
Sunday.

Smoke may mix with fog early this morning to further decrease
visibilities, perhaps becoming dense at times less than half a
mile. It is unclear just how reduced visibilities will become.
While low in confidence, cannot rule out smoke mixing with fog
to create locally severe reductions in visibilities, with
visibility near zero. Should this occur, this would pose
significant potential impact to travel conditions.


... Potential severe storms Monday ...

There is an emerging confidence in potential for severe storms
Monday. AI guidance like NCAR`s Pangu and Fengu Convective
Hazard Forecasts both highlight increased probabilities above
15% within portions of North Dakota into Minnesota Monday. While
the Storm Prediction Center highlights central ND into Devils
Lake basin with a level 1 out of 5 risk for severe storms,
confidence is low in location of severe storms due to important
synoptic and mesoscale details remaining uncertain. Moderate to
strong instability appears likely to build south of a
developing frontal boundary somewhere within North Dakota into
northern or central Minnesota. This coupled with sufficient
shear and increased lower level flow will allow for main hazards
to currently favor hail and gusty winds (although to what
degree remains uncertain).

Additionally, heavy rainfall leading to flash flooding is
possible as well. Current modeled guidance presents large swath
of 1-2 inches of rainfall over the Dakotas into Minnesota
Monday and Tuesday, with low probabilities of 3-5 inches already
showing up. Coverage of showers and thunderstorms may be
widespread given the slow moving and generally diffuse nature of
forcing for ascent in this type of synoptic pattern, but will
hinge upon other mesoscale factors like instability, boundary
orientation/location, and cloud- bearing flow. This lowers
confidence in coverage, location, and amount of rainfall. The
Weather Prediction Center currently has a level 1 out of 4 risk
for excessive rainfall leading to flash flooding over our region
for Monday and Tuesday.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1008 PM CDT Fri Jul 11 2025

Smoke will continue to be the primary aviation impact for the
TAF period. There will be a brief improvement overnight but
smoke will once again cover the region tomorrow, bringing
visibilities down to MVFR and IFR. Other than that, winds will
remain sustained around 12 knots by tomorrow afternoon with
periodic gusts to 20 knots at times until the sun sets late.

&&

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

&&

$$

DISCUSSION...CJ
AVIATION...Perroux