Flash Flood Warning 5, NWS Grand Forks, ND

Area Forecast Discussion
National Weather Service Grand Forks ND
622 PM CDT Sun Sep 6 2026

.KEY MESSAGES...

- There is a level 1 out of 5 risk for severe storms this
  evening, mainly for hail to ping pong ball sized.

- Another round of thunderstorms expected Monday, with a level 1
  out of 5 risk for the entire forecast area. The main impacts
  for any storms that become severe will be ping pong ball sized
  hail and winds to 60 mph.

&&

.DISCUSSION...
Issued at 229 PM CDT Sun Sep 6 2026

...Synopsis...

Several weak shortwaves under the main upper ridge currently
bringing some thunderstorms to central ND and eastern SD.
The main surface low and inverted trough is still over the
western Dakotas, and should begin to move eastward tomorrow as
the flow turns southwesterly and a lead shortwave moves out. The
main upper trough starts to move into Saskatchewan and Manitoba
Monday night, pushing the surface trough and associated cold
front east into the Red River Valley by early Tuesday. West to
northwest surface winds will pick up Tuesday and Wednesday
behind the surface front with decent cold air advection and
pressure gradient, possibly meeting advisory criteria. Near
zonal flow sets up late week and into next weekend, although a
cluster of 34 percent of ensemble members tries to dig a trough
into the Northern Plains. There is a signal in the ECMWF EFI for
a break in the above normal temperatures by next weekend.

...Severe chances this afternoon and evening...

Water vapor loop has the main shortwaves to our south or west,
but there is a small vort currently moving through central ND
that could provide support for more convection as it moves into
our forecast area. ML CAPE is around 3000 J/kg, and while deep
layer shear is not super strong it is around 30 to 35 kts which
should be enough to keep some updrafts going. The low level
lapse rates are not too impressive given the stratus we have
seen much of the day, but there is a decent amount of
instability thanks to dew points in the 70s and temps in the
80s. CAMs continue to be very unreliable and enough ensemble
members of the HREF were showing good probability of updraft
helicity tracks over the southern Red River Valley this morning,
which have not developed. Some of the machine learning runs show
some low to moderate chances for severe impacts, while other
runs do not. Can't completely rule out more convection
developing as the central ND vort moves east, but uncertainty is
high as to what actually develops. If severe storms do develop,
the main threat will be large hail.

...Marginal risk for severe Monday...

The ridge axis shifts east tomorrow and the flow aloft becomes
southwesterly. Deep layer shear will be increasing up into the
40 to 50 kt range by tomorrow afternoon. But the instability
becomes more uncertain. Some of the ensemble members don't have
any surface based CAPE at all, but enough do that the mean CAPE
into eastern ND is around 1500 J/kg. Much will depend on what
exactly happens this evening and into the overnight. HREF and
REFS updraft helicity probabilities have some chance, but not
super impressive. At this point with all the unknowns the level
1 risk seems reasonable.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 622 PM CDT Sun Sep 6 2026

Widespread disorganized thunderstorms will continue this
evening but confidence in the evolution and placement is
negligible and thus have chose to prevail thunderstorms at all
sites for the next few hours to give some breathing room and too
let people know to plan for thunderstorms in the area even if
not at the taf site. MVFR overnight as cigs lower and winds
picking up as cigs improve late tomorrow morning. Overall an
unpleasant next 24 hours for aviation.

&&

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

&&

DISCUSSION...JR
AVIATION...TT

Hazardous Weather Outlook
National Weather Service Grand Forks ND
447 AM CDT Sun Sep 6 2026

MNZ001>005-007-008-013>016-022-023-027>031-040-NDZ006>008-014>016-
024-026>030-038-039-049-052>054-071000-
West Polk-Norman-Clay-Kittson-Roseau-West Marshall-East Marshall-
Pennington-Red Lake-East Polk-North Clearwater-Mahnomen-
South Clearwater-West Becker-East Becker-Wilkin-West Otter Tail-
East Otter Tail-Grant-Towner-Cavalier-Pembina-Benson-Ramsey-
Eastern Walsh-Eddy-Nelson-Grand Forks-Griggs-Steele-Traill-Barnes-
Cass-Ransom-Sargent-Richland-Western Walsh-
447 AM CDT Sun Sep 6 2026

This hazardous weather outlook is for portions of eastern North
Dakota, west central and northwest Minnesota.

.DAY ONE...Today and Tonight

There is a level 1 out of 5 risk for severe thunderstorms this
afternoon and evening across much of eastern North Dakota,
northwest, Minnesota, and west central Minnesota. Hazards could
include large hail and damaging wind gusts. A tornado cannot be
ruled out in southeast North Dakota, west central Minnesota, and
the southern Red River Valley.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

There is a level 1 out of 5 risk for severe thunderstorms Monday
afternoon and evening. Hazards could include large hail, damaging
wind gusts, and possibly an isolated tornado.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be required today.

MNZ006-009-017-024-032-071000-
Lake Of The Woods-North Beltrami-South Beltrami-Hubbard-Wadena-
447 AM CDT Sun Sep 6 2026

This hazardous weather outlook is for portions of west central
and northwest Minnesota.

.DAY ONE...Today and Tonight

Isolated strong storms are possible this afternoon and evening,
with hail and gusty winds being the primary hazards.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

There is a level 1 out of 5 risk for severe thunderstorms Monday
afternoon and evening. Hazards could include large hail, damaging
wind gusts, and possibly an isolated tornado.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be required today.

Preliminary Local Storm Report
National Weather Service Grand Forks ND
538 PM CDT Sun Sep 6 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0526 PM     Tstm Wnd Gst     1 NE Northwood          47.74N 97.56W
09/06/2026  M62 MPH          Grand Forks        ND   Trained Spotter

            62 mph gust reading on handheld kestrel east
            of Northwood. 35-40mph sustained.

&&

TT

Preliminary Local Storm Report
National Weather Service Grand Forks ND
539 PM CDT Sun Sep 6 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0512 PM     Tstm Wnd Gst     7 W Northwood           47.72N 97.72W
09/06/2026  M53 MPH          Grand Forks        ND   Public

            Davis personal weather station.

&&

TT

Preliminary Local Storm Report
National Weather Service Grand Forks ND
553 PM CDT Sun Sep 6 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0535 PM     Flash Flood      1 SW Perham             46.59N 95.59W
09/06/2026                   Otter Tail         MN   Law Enforcement

            Law enforcement relayed water standing in
            poor draining areas with over a foot of
            water standing on 8th St SW in Perham and
            over 3.5 so far since 3pm (2.5 hours).

&&

TT

Preliminary Local Storm Report
National Weather Service Grand Forks ND
743 PM CDT Sun Sep 6 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0730 PM     Tstm Wnd Gst     8 NE Karlstad           48.65N 96.38W
09/06/2026  M60 MPH          Roseau             MN   Mesonet

            MN DOT sensor.

&&

JK