167
FXUS63 KFGF 182336
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
636 PM CDT Fri Jul 18 2025

.KEY MESSAGES...

- Low chance for isolated strong to severe storms possible in
  far southeast North Dakota into west-central Minnesota late
  this afternoon.

- There is a level 1 out of 5 risk for severe storms for
  portions of eastern North Dakota late Sunday. Additional
  potential for strong to severe storms Monday and Tuesday.

- Smoke from Canadian wildfires will degrade air quality
  Saturday into Monday.

&&

.UPDATE...
Issued at 636 PM CDT Fri Jul 18 2025

Current radar has a stronger storm over NE SD this hour that
should remain south of our CWA. Looking at mesoanalysis we
continue to have sufficient shear, sfc vorticity, and
instability across Richland county through Wadena county points
south. However, lapse rates continue to hinder development of
storms in our far south. We will continue to monitor conditions
through the evening to see if we can get any initiation or
cumulus development in our far south. Otherwise, we are
expecting fog to develop overnight across the area thanks to the
wetting rain today, high pressure moving in, and light and
variable winds.

&&

.DISCUSSION...
Issued at 257 PM CDT Fri Jul 18 2025

...Synopsis...

Water vapor imagery today shows zonal flow pattern over the
northern tier of the CONUS, with a low amplitude mid layer
impulse moving east out of North Dakota into northern Minnesota.
This forcing and sufficient moisture is resulting in an area of
mostly light rainfall that will continue pushing east. In its
wake, between 1.0 - 3.5 inches of rainfall fell between the US
Highway 2 and 200 corridors. There is a small window of
opportunity for instability to overlap forcing near the tri-
state area, bringing the possibility for isolated strong to
severe storms in far southeast North Dakota into west-central
Minnesota. More details on this found below.

As the mid level wave departs, surface high pressure will build
into the area. With today`s wetting/soaking rainfall saturating
the ground and high pressure allowing surface inversion to
build, there is high confidence in fog to develop across the
region. Areas of dense fog are also possible (40% chance)
tonight into Saturday mid morning.

Shortwave ridging propagates through the Northern Plains
Saturday into Sunday, keeping conditions generally dry. Brief
period of northern low level flow will reintroduce wildfire
smoke back into the region starting Saturday, lasting through at
least Sunday. There is potential for smoke to linger even
further into early next week, although confidence is low.
Degraded air quality is expected during this period, including a
period where smoke concentrations will be high enough to
increase risk for adverse health effects to all population
groups.

As ridge axis traverses east, it is replaced with shallow
southwest flow aloft. This will help return richer moisture back
into the Dakotas and Minnesota by late Sunday into early next
week. The pattern remains this way through at least Tuesday.
Embedded impulses within this upper pattern will mean increased
chance for a more active precipitation pattern, with multiple
waves of showers and thunderstorms starting late Sunday through
at least Tuesday. This includes the chance for strong to severe
storms. More details on this below.

... Isolated severe storm potential this afternoon ...

There is a small window of opportunity to see isolated strong
to potentially severe storms late this afternoon in far southern
Red River Valley into lakes country of west-central MN as
forcing from the wave lingers in this area possibly utilizing
weak to moderate instability nosing into the area, juxtaposed
with strong effective shear. Main severe hazards would be hail
and gusty winds, although couldn`t rule out the possibility of a
brief tornado due to relatively strong low level instability
and surface boundary aiding in ambient vorticity to stretch,
should a storm develop and follow along the boundary. Current
satellite still indicates stratus in this area which would favor
more elevated storms favoring hail, although there is still a
low chance (10%) for surface base parcels which would increase
potential for brief tornado. This window closes around 7 PM.

... Severe storm potential late Sunday into early next week ...

With the synoptic pattern conducive for increased convective
activity, AI guidance like Pangu and FengWu are also
highlighting severe probabilities into our area Monday and
Tuesday. Uncertainties are plenty in details like storm mode or
frontal/boundary orientation and location, limiting confidence
in hazards. GEFS probabilities of supercell composite greater
than 1 are 70% or higher in portions of southeast ND into west-
central MN on both Monday and Tuesday.

Additionally, other machine learning guidance from CSU also
indicate potential for flash flooding Monday and Tuesday (namely
UVFS-based). This is supported by conceptual model of low
amplitude flow pattern, multiple waves, and PWATs into the 90th
percentile for our region.

While signal for significant severe is rather minimal at this
time, this is largely in part due to low predictability, but
conceptually the pattern may allow for this opportunity.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 636 PM CDT Fri Jul 18 2025

Isolated showers continue to move near GFK, TVF, and BJI this
hour, but chances will diminish as we get further into the
evening. Dense Fog is expected to develop this evening and
overnight through tomorrow morning for each of the TAF
locations. GFK, DVL, and TVF will see the highest likelihood of
reaching down to 1/2SM or even 1/4SM overnight and into the
morning. Around 13-14z fog will start to dissipated and
visibilities improve. Light and variable through the TAF
period, with ceilings improving for all locations post 17-18z.

&&

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

&&

$$

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