textproduct: Grand Forks

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.

..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.