873
FXUS63 KFGF 190433
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
1133 PM CDT Fri Jul 18 2025

.KEY MESSAGES...

- 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 1010 PM CDT Fri Jul 18 2025

Isolated showers continue across parts of Becker and Otter Tail
counties this evening. This will slowly dissipate and shift
eastward over the next couple of hours. Otherwise, the cloud
deck is moving east and skies are clearing from the west. Fog
has already developed in parts of the area most notable just
west of Grand Forks and in Walsh and Pembina counties.
Visibilities have already dropped to as low as a quarter of a
mile. We will continue to monitor the fog and the potential for
it to become widespread.

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 /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1133 PM CDT Fri Jul 18 2025

Showers have moved away from TAF locations this evening, with
clouds shifting through the Highway 200 corridor bringing lower
ceilings to MVFR at times. Otherwise, where there is clearing we
are starting to get fog developing. This is noted at GFK with
visibilities already down to 1/4SM. This will continue through
the overnight and spread through the TAF locations. Widespread
nature of fog is possible, with dense locations down to 1/4SM.
Fog begins to lift near the 13-14z timeframe when temps start to
warm. Skies will be clear from the end of tomorrow morning into
the afternoon and evening.

&&

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

&&

$$

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