809
FXUS63 KFGF 151928
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
228 PM CDT Tue Sep 15 2026

.KEY MESSAGES...

- Scattered Shower chances Wednesday with more widespread rain
  Friday into the weekend.

&&

.UPDATE...
Issued at 215 PM CDT Tue Sep 15 2026

Main focus this update has been on the inclusion of frost in
northwest MN. Center of high pressure settles into this region
tonight/early Wed amid relatively dry continental air mass. This
will effectively radiatively cool temperatures into the mid to
upper 30s, perhaps locally lower 30s if conditions remain
optimal. While mid/upper cloud cover is not anticipated to be a
failure- mode for frost development, the possibility of fog in
this area is. General thinking is for areas that received more
than half an inch of recent rainfall (generally south of the Red
Lakes) will promote more of a chance for fog development
compared to areas north. With this in mind, confidence has grown
enough in frost development in northwest MN near Lake of the
Woods, and not including Bemidji/Southern Beltrami.

Speaking of fog, there is a 40% chance for fog to develop within
forested portions of northwest/west-central MN. Fog may become
dense at times should it form. Main window for fog will be
4a - 9a.

&&

.DISCUSSION...
Issued at 333 PM CDT Mon Sep 14 2026

...Synopsis...

Strong mid/upper low centered near northeast Montana/northwest
North Dakota and southern Saskatchewan will continue to slide
northeast through tonight. This system is responsible for the
ongoing rain and expected period of windy conditions tonight.
The evolution of the larger scale pattern over the next 7 days
will initially be complicated across the Northern Plains as
stalled troughing to the west and weaker ridging in the central
CONUS places us in a split- flow type set-up before the upstream
trough breaks loose. Trend should be for warmer temperatures
than the last 3 days, however due to the flatter nature of the
ridging, we should be mild rather than hot. As climate averages
are in the lower 70s and dropping towards the upper 60s by the
end of this month, this pattern with some locations in the mid
to upper 70s is above average but not that unseasonable.

Regarding precipitation chances beyond today; there is a low
chance for a light shower/sprinkle Tuesday afternoon with
cyclonic flow and CAA aloft lingering in our north (wetting rain
not expected). There is a weaker/progressive mid level
shortwave Tuesday (main wave in the northern stream in Canada)
otherwise better chances for wetting rain do not arrive until
Friday-Sunday as the upstream trough breaks loose and tracks
over the Northern Plains. Evolution/details remain variable and
at this time this should be a much weaker trough passage than
what we are seeing today lowering the chance for widespread
wetting rain.

...Rain Showers Today...

The main area of rain is continuing to transition east over
northwest MN with scattered showers and some areas of drizzle
due to lingering deeper BL saturation in southeast BL flow. The
main dry slot featuring well defined subsidence is already
moving across western ND towards eastern ND and organized shower
activity should exit our region west to east. Drizzle/lower
level rain processes will be harder to pin down and may linger
along with light fog into the evening before clearing as winds
start to shift more to the southwest in the BL. In any case, dry
conditions are favored by late evening.

...Winds Tonight...

A cold front already starting to push east over wester ND will
arrive later this evening and increased CAA 925MB will result
in dry adiabatic mixed layer off the surface. While there may be
a shallow nocturnal inversion, pressure rises and strong CAA at
925MB should help create at least a period of stronger winds
from the west then northwest as the front passes. Winds near the
top of the mixed layer may be near 50kt over parts of the
Devils Lake Basin, and this raises the potential for a few
localized gusts 58mph+, though more frequent gusts with the
period of stronger winds would be 45-50mph. Due to the direction
of the winds and orientation of unidirectional flow through the
mixed layer being westerly it is less favorable for stronger
gusts east of the Red River Valley escarpment, which matches
higher resolution guidance in placement of advisory conditions
mainly west of the valley in the 10pm-7am period. There is still
potential for a few gusts 45-50 mph farther east or south than
the current advisory, however location/duration/coverage are
much less certain due to the previously mentioned flow/wind
direction. It will be something to monitor in the event we have
to expand the advisory based on trends this evening.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 215 PM CDT Tue Sep 15 2026

VFR conditions are forecast, although a BKN ceiling around 3.5-5
kft will be widespread across the region before 23Z. After 23Z,
this ceiling gives way to mostly clear skies.

Winds will be west-northwest 10-15kt, gusting near 20kt before
23Z, tapering less than 6kt by 05Z.

Fog Potential Tonight:

There is a 40% chance fog in portions of northwest/west-
central MN 09Z-15Z tonight into Wednesday. This fog may be dense
in some locations. While fog is expected to develop somewhere
within MN (more likely central/north-central MN), it remains
unclear whether or not this develops over a TAF site like KBJI.
With chance for fog at 40%, chose to omit from TAF for now;
however, subsequent TAFs/AMDs may include a 3SM BR to start - or
if confidence really increases, it will include FG.

While not expected, there is a 10% fog develops within the Red
River Valley during the timeframe as well.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...Frost Advisory from 4 AM to 8 AM CDT Wednesday for MNZ005-006-
     008-009-016.

&&

$$

UPDATE...CJ
DISCUSSION...DJR
AVIATION...CJ