518
FXUS63 KFGF 171131
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
631 AM CDT Mon Aug 17 2026

.KEY MESSAGES...

- Isolated severe thunderstorms may develop over parts of
  southeast North Dakota and west central Minnesota this
  afternoon and early evening. Hail to 1 inch and wind gusts to
  70 mph would be the main threats.

&&

.UPDATE...
Issued at 532 AM CDT Mon Aug 17 2026

As been the case in recent weeks, short term CAM guidance hasnt
been doing too well. It earlier indicated some risk of showers
and t-storms developing in south central MN and moving east
along SD border and thus pops from NBM and in most models were
in the 30 pct range 12z-15z in SE ND. This doesnt appear to be
occurring so tried to trim them back. Cold front will work
southeast across the area. Limited moisture and instability this
morning but instability will increase later on this afternoon by
21z as front is near a Bemidji-Fargo line. Depending on dew pts,
MU CAPE values of 1000-1500 j/kg may be present near the
ND/SD/MN border area. Some hi-res models indicate dew pts 65-70
which would put instability considerably higher, while high res
model ensemble mean has dew pts lower 60s to give the 1000-1500
MU CAPE values. Soundings would support wind gusts 60-70 mph if
any supercell could develop due to dry sub cloud layer.

&&

.DISCUSSION...
Issued at 259 PM CDT Sun Aug 16 2026

...Synopsis...

Westerly flow is currently in place across the Northern Plains,
with the next mid/upper trough upstream over Alberta and
Saskatchewan. This feature tracks east tonight through Monday
night north of our region, and deepens into a larger upper low
over the Hudson Bay region Tuesday into Wednesday. This places
our region in northwest flow through the middle and later part
of the week before ridging begins to reamplify over the next
weekend. Outside of the Monday period when scattered
showers/thunderstorms may develop with the frontal passage, the
general pattern will not support organized precipitation
chances. Temperatures will tend to be below average once we
enter NW flow, with above average temperatures returning as the
ridge amplifies and builds back into the region during the later
periods.

...Severe Thunderstorm Risk Monday...

The severe risk Monday in our CWA will be dependent on the
timing of  the cold front and position of the the warm sector
ahead of this during the afternoon/peak heating period.
Initially elevated morning showers/storms may be progressing
through the region ahead of the front and this could result in
more cloud cover limiting initiation in our area as well. A lot
of guidance places the front near west central MN by time
afternoon destabilization occurs, narrowing the window and the
region where stronger/severe storm could initiate, while some
12Z guidance is just slow enough for the window to include
southeast ND. Shear profiles are top heavy, but there is enough
mid/upper level winds with the wave passing to the north to
support effective shear values 30kt+ as the front passes. Mid
level lapse rates are marginally steep (generally 7-7.4 C/km)
and the result in modest CAPE values in the warm sector. If
severe storms were to develop lower end severe impacts appear to
be favored (quarter size hail/60 mph winds).

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 629 AM CDT Mon Aug 17 2026

Timing of the cold front and related wind shift will be the main
issue today. Thunderstorm timing and coverage as well. For now
I used the prob30 for thunderstorm at each site in the time
period when t-storm chances are highest. This timing of t-storm
changes and related wind shift and speeds will be the reasons
for amendments thru the day. Cloud bases will run in the VFR
range, mostly 6000 ft agl and higher. Wind gusts may reach 20-25
kts for a time in E ND/RRV from the southwest or west midday or
afternoon.


&&

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

&&

$$

UPDATE...Riddle
DISCUSSION...DJR
AVIATION...Riddle