934
FXUS63 KFGF 210905
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
405 AM CDT Mon Sep 21 2026

.KEY MESSAGES...

- Frost chance exists Monday night/early Tuesday for northwest
  MN and possibly northeast ND.

- Next rain chance is Wednesday night/early Thursday and
  Saturday.

&&

.UPDATE...
Issued at 359 AM CDT Mon Sep 21 2026

Broad 500 mb low moving slowly south-southeast into northern
Nebraska this morning. Clouds and leftover sprinkles, very light
rain showers perist in north central ND around Minot and does
extend east toward Rugby and near Devils Lake where sprinkles
are in grids thru 6 am. Overall though today will see this upper
low move farther away and an upper level ridge begin to build
from western Montana into Saskatchewan and Manitoba. This will
aid in pushing the upper level system farther south and
eventually allow the clouds to clear out over the area today
into tonight. Surface high will be well east of our area and we
will have no fresh supply of cool air. But sufficiently dry
airmass and winds under 5 kts should lead to at least a chance
for frost for NW Minnesota, and possibly even parts of northeast
ND. The 20-30 percent probabilities of temps below 36F exist in
areas east and west of the RRV overnight in northeast ND and
northwest MN.  The biggest signal of frost is in northeast MN.


&&

.DISCUSSION...
Issued at 220 PM CDT Sun Sep 20 2026

...Synopsis...

Upper low currently rotating over WY will push out into South
Dakota and Nebraska tonight, weakening and moving into the
Upper Midwest tomorrow. Some high clouds from this system for
our area, but all models keep most of the precipitation to our
south. At the surface, center of high pressure over Ontario
will move only very slightly east, allowing light east to
southeast surface winds over our CWA. While can`t completely
rule out some fog formation tonight, it will be hampered by
higher clouds and a little bit of mixing. Right now best chances
are up against the escarpment or Turtle mountains where the
southeasterly winds will bring some upslope. The upper low pulls
off to the east and leaves blocky ridging over the region
through Tuesday. Upper flow starts to become more southwesterly
Wednesday, with one shortwave coming out into the Northern
Plains late Wednesday and into Thursday. There is decent
consensus on southwesterly flow with various weak shortwaves
continuing into next weekend. Can`t really pin down
precipitation at this point, but temps look like they will be
above seasonal averages.

...Frost chances for Monday night into Tuesday morning...

With the upper low moving east of our area by the first part of
the work week, clouds look to be decreasing for at least some
period Monday night, and a bit drier air moving in from the
east. Probability of temperatures below 36 degrees range from
below 20 percent in most of the central and western CWA, but get
up to around 40 to 50 percent along our far eastern border.
Advisory level temperatures dropping into the mid 30s are
possible, although much will depend on exact cloud cover trends.

...Next precipitation chances Wednesday night and Thursday...

Shortwave trough moving into the western Dakotas Wednesday will
progress quickly into the Great Lakes by Thursday. Instability
is pretty weak at less than 500 J/kg, so severe is not expected
although some thunderstorm activity is not completely out of the
question. Main impacts look to be rain, with 40 to 60 percent
probabilities of over a quarter of an inch in portions of our
western and southern counties.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1148 PM CDT Sun Sep 20 2026

The main question overnight is if fog will form. There remains
uncertainty on its coverage and exact location. Model guidance
shows slightly higher probabilities for fog at KGFK and KBJI
compared to elsewhere. With BR already introduced in previous
TAF issuance`s at these two terminals, maintained its inclusion
in this set. However, predictability remains too low to
introduce BR or FG at any other terminals at this time.
Otherwise, conditions will remain VFR for Monday, with easterly
wind of up to 10 knots during the afternoon. Winds will drop off
after sunset Monday evening, becoming light and variable to end
the TAF period.

&&

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

&&

$$

UPDATE...Riddle
DISCUSSION...JR
AVIATION...Rafferty