806
FXUS63 KFGF 181929
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
229 PM CDT Mon Aug 18 2025

.KEY MESSAGES...

- Scattered thunderstorms this afternoon evening in southeast
  North Dakota and then patchy fog tonight for all areas.

- Strong to severe thunderstorms are possible Thursday with
  strong winds and large hail as the primary threats.

&&

.DISCUSSION...
Issued at 229 PM CDT Mon Aug 18 2025

...Synopsis...

As can be seen in current regional satellite imagery lead shortwave
activity across the upper great lakes continues to bring heavy rain
to areas of IA/MN/WI this morning with the SW monsoon ongoing in
areas of AZ/NM beneath building western ridging. In between closer
to home we have present southwest flow aloft with a transition to
more zonal flow today. Hurricane Erin can also be noted to the east
of the Bahamas. As this is influenced by the subtropical Bermuda high
the current midwest shortwave activity will aid digging eastern
troughing in pulling the storm north while upper diffluence stalls
mid level flow leading to slowing in the CONUS wide flow with riding
in the central and western US dominating Tuesday and Wednesday
before giving way to progressive troughing in the northern plains
Thursday and Friday with northwest flow across the upper Great Lakes
then prevailing through the weekend leading to overall cooler
temperatures in the 60s and 70s for highs Friday and beyond.

Today/tonight...

Lingering drizzle from this morning has subsided with the stratus
making a good effort to clear once it hit 11am. Overnight
thunderstorms to the east of Bismarck have dissipated but and
evident circulation in visible imagery with 2000 MUCAPE and maybe 20-
25kts of eff shear could serve as the focus point for afternoon
initiation. As the low tracks east though the afternoon along the
leading edge of an evident shortwave some strong but likely still
sub severe storms are possible in far southeast North Dakota between
5 and 8pm. MLCAPE around 2000-2500j/kg and up to 25kts of eff shear
will support a primary convective threat of lightning in addition to
some small hail and wind gusts up to 45 mph. Beyond possible storms
tonight fog once again appears likely though coverage will depend on
just how much low level saturation can be achieved though based on
water vapor across western and central North Dakota there appears to
be no lack of moisture to work with. Capped coverage at patchy
wording but would be entirely unsurprised to see a dense fog
advisory issued both tonight and Tuesday night given a once again
similar setup.

Aside from fog chances each relatively  weather Now through the
mid week. With ridging dominating through this time we will see
seasonable temperatures of highs in the low to mid 80s through
Thursday though dewpoints in the upper 60s to low 70s likely
aided by late August evapotranspiration will make for a humid
few days.

Severe Weather Thursday?...

By Thursday afternoon progressive troughing will swing through the
Canadian Prairies with an attendant cold front draped south
across the Dakotas and Minnesota by the evening/overnight. Will
the true degree of any severe threat would be contingent upon
the timing of the this front for the primary source of forcing
as it moves through an untapped warm sector already in place
with ensembles and even longer range CAMS such as the NAM
showing 2000-3000j/kg of MLCAPE ahead of the cold front with
enough shear to support organized convection. Would currently
anticipate a more linear mode given the forcing but would still
think to maintain at least some hail risk initially should
there be a window for more discrete convection. Beyond this main
window for potentially severe storms on Thursday General
thunderstorm activity remains possible both Tuesday and
Wednesday with more quiet northwest flow behind Thursday front
through the weekend as temps drop into the 60s for highs (almost
fall like).

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1223 PM CDT Mon Aug 18 2025

LIFR/IFR stratus in BJI and DVL will lift (faster in DVL) by 00z
with fog expected to form overnight between Tuesday 06z and 12z
lasting through ~15z for most. Cigs to MVFR and maybe IFR for
BJI tonight but westward cloud coverage is uncertain with
ceiling possibly remaining sct but still around the 500 to
1500ft mark through the night for any clouds that do form.
Overall another night of low clouds and potential fog for most.

&&

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

&&

$$

DISCUSSION...TT
AVIATION...TT