697
FXUS63 KFGF 061929
AFDFGF

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

.KEY MESSAGES...

- There is a level 2 out of 5 risk for severe storms this
  afternoon and evening in portions of the Devils Lake and
  Sheyenne Basins, mainly for hail to ping pong ball sized. A
  level 1 out of 5 risk for the rest of eastern ND and western
  MN.

- 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 /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1243 PM CDT Sun Sep 6 2026

MVFR to IFR ceilings at many of the TAF sites, but the MN side
is starting to mix out and the other airports could see at least
the lower stratus decreasing in coverage in the next few hours.
Convection will come in from the west later this afternoon and
evening, so kept prob30 groups going as there is still a lot of
uncertainty as to exactly when and where. Some MVFR or even IFR
ceilings possible behind the storms later tonight and into
tomorrow. Winds will remain southeasterly except near
thunderstorms, and some gusts up to 20 kts will be possible late
in the period.

&&

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

&&

$$

DISCUSSION...JR
AVIATION...JR