307
FXUS63 KFGF 130941
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
441 AM CDT Sun Jul 13 2025

.KEY MESSAGES...

- Another round of wildfire smoke will degrade air quality later
  this afternoon into evening in northeast North Dakota into
  northwest and west-central Minnesota.

- There is a level 1 out of 5 risk for severe storms both late
  Monday and Tuesday. The main hazards will be gusty winds,
  hail, and flash flooding.

&&

.DISCUSSION...
Issued at 357 AM CDT Sun Jul 13 2025

...Synopsis...

Departing shortwave upper trough/low is exiting the western
Great Lakes region into ON as seen on water vapor imagery early
this morning. In its wake, northwest flow aloft will persist
continuing to advect continental air mass originating from
Canada today, with an additional cold front set to move through
the area today. This will bring another, final round of
wildfire smoke behind the cold front into the region degrading
air quality. More on details on this can be found below.

Flow aloft then turns more zonal over the Northern Plains and
Upper Midwest as large upper low over the Hudson Bay begins to
develop early next week. This will promote entrance region upper
jet dynamics to overspread the Northern Plains, promoting lee
troughing/frontal development at the surface, increasing overall
forcing for ascent within the region. This also will promote
moisture return from the south into the Northern Plains and
Upper Midwest along with increasing instability. With forcing
for ascent increasing over the region, chance for showers and
thunderstorms increases Monday and Tuesday.

Widespread medium to high chance for rainfall increases
beginning late Monday, lingering through Tuesday. Increased
instability and flow aloft will introduce the potential for
strong to severe storms during this timeframe over the Dakotas
into Minnesota. Additionally, above average moisture content
pushing into the region of ascent within the Dakotas and
Minnesota along with potential for training thunderstorms will
introduce potential for excessive rainfall leading to flash
flooding. More details on this found below.

As the Hudson Bay low develops further into Thursday and Friday,
there will be a tendency for cooler, continental air mass to
intrude over the region. Ensemble guidance like ENS EFI
continues to note on high probabilities for below average
temperatures between Wednesday and Friday. Overnight/early
morning low temperatures continue to be forecast into the mid
40s and low 50s. Should ideal radiational cooling conditions
occur, there is a low chance for low temperatures into the upper
30s, perhaps more in the typical cooler spots of northeast ND
and northwest MN. Drier conditions will also accompany this set
up, as well as additional chance for more wildfire smoke to
infiltrate the region.

... Wildfire Smoke Today ...

Before sunset Saturday, visible satellite imagery showed an area
of dense smoke emerge from wildfires within SK behind a passing
cold front. This cold front and attendant air mass will move
through the area. Smoke guidance continues to show this smoke
to move through portions of northeast ND into northwest and
west- central MN this afternoon into evening. Observing the
thick smoke lends credence to this scenario unfolding, however,
there is uncertainty how dense smoke will be behind as it
envelopes these areas given the lack of upstream surface
observations. Will continue to message increased risk of adverse
health effects to all populations today from wildfire smoke
today into this evening.

... Severe Potential Late Monday into Tuesday ...

There continues to be increased confidence in potential for at
least isolated severe thunderstorms within portions of eastern
ND into northwest and west-central MN starting late Monday,
lasting through the day Tuesday. This is supported by AI
guidance like NCAR`s Pangu and FengWu Convective Hazard
Forecasts both highlighting increased probabilities above 15% in
these areas Monday and now Tuesday.

There is still however large uncertainty in how storm evolution
will unfold. While confidence is high that window for severe
potential starts late Monday (possibly after sunset), confidence
in locations and timing through Tuesday is low. This is partly
due to the fact that there will be broad scale ascent over the
Northern Plains and Upper Midwest with potentially several mid
level shortwave impulses moving over a frontal boundary that
will gradually push southward late Monday through Tuesday.
Additionally, important mesoscale details continue to remain in
question that would dictate more precise timing and location.

Sufficient instability (potentially moderate instability around
the order of 2000 J/kg) and increasing shear (particularly in
the lower levels) will drive severe hazards. While low level
shear will be high at times, warm low level temperatures and
relatively dry lowest levels will preclude tornado potential.
High low level shear will however drive potential for wind gusts
to 70 mph (with a low chance for potentially up to 80 mph should
conditions align right), even for overnight storms Monday night.
Additionally, elevated instability aloft and sufficient shear
aloft will drive hail potential. Confidence is low on hail size
potential, however, hail up to the size of ping pong balls seems
reasonable given elevated convection pushing cloud bearing layer
closer to freezing temperatures.

Additionally, heavy rainfall leading to flash flooding is
possible as well. Latest modeled guidance continues to present
large swaths of 1-2 inches of rainfall over the Dakotas into
Minnesota late Monday and Tuesday, with low neighborhood
probabilities of 3-5 inches continuing to show up. Coverage of
showers and thunderstorms may be widespread given the generally
large scale nature of forcing for ascent with potential for
several impulses to move through 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.

In coordination with the Weather Prediction Center, there has
been an upgrade to a small area of level 2 out of 4 risk for
excessive rainfall leading to flash flooding over our region for
Tuesday.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1128 PM CDT Sat Jul 12 2025

The main aviation impact will continue to be smoke. MVFR to IFR
visibilities can be expected at times for the entire TAF period.
Brief breaks to VFR can be expected as ceilings will remain VFR,
but for the most part MVFR should be the primary visibility.
A front will push through tomorrow morning shifting winds to
more northwesterly, ending the break in smoke and bringing
another swath down. Wind gusts behind this front should max out
around 25 to 30 knots with sustained winds between 10-20 knots
depending on sheltering near TAF sites (more forested areas like
BJI should have winds lower). Wind speeds will remain elevated
above 6 knots in the evening but will diminish to mainly the
single digits to low double digits after 00z.

&&

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

&&

$$

DISCUSSION...CJ
AVIATION...Perroux