196
FXUS63 KFGF 152333
AFDFGF

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

.KEY MESSAGES...

- Frost is forecast early Wednesday morning in northwest
  Minnesota near Lake of the Woods to Red Lakes area.

- There is a medium chance for showers and weak thunderstorms
  Wednesday. Additional chances for rain come Friday into the
  weekend.

&&

.DISCUSSION...
Issued at 338 PM CDT Tue Sep 15 2026

...Synopsis...

Post-cold frontal, continental air mass continues to spread
throughout our region behind yesterday`s cold front/system.
Breezy winds will taper tonight as surface high pressure settles
into the region, centered near northwest MN by Wednesday
morning. This will promote calm and clear conditions, allowing
frost to develop within northwest MN, in addition to the
potential for fog in northwest and west-central MN. Confidence
is not high in fog formation, but there is a 40% chance it
develops within our area. If it does develop, fog could be dense
at times.

Upper pattern mid to late week can be characterized as zonal
to weak southwesterly flow aloft. This will offer opportunities
for periods of rain starting Wednesday, lasting into the
weekend. This will also keep temperatures trended near to
slightly above average.

...Frost potential in northwest MN...

Center of high pressure settles into northwest MN tonight/early
Wed amid relatively dry continental air mass. This will
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 County.

...Rain chances ahead...

Zonal flow aloft with entrance region of an upper jet will
linger over our region through Wednesday, allowing a weak and
progressive shortwave trough/upper ascent to migrate west to
east across our area. While synoptic forcing is expected to be
weak and moisture return meager, an uptick in instability is
forecast to accompany this forcing/moisture. This will offer
opportunity for thunderstorms of the weaker variety. Very little
rainfall amounts are expected with this, despite the convective
behavior.

On Friday, a rather robust banded-rain event is expected with
strong forcing from frontogenesis fed by rich moisture and
instability. Current guidance keeps majority of this rainfall
(in excess of 3 inches) south of our area out of eastern SD into
southern/central MN. However, given the majority of this forcing
driven by mesoscale processes, confidence in location is not
great. Thus, there is potential for this banded heavy rainfall
to eek into locations near the SD border into west-central MN.

Into this weekend, a more consolidated shortwave trough is
progged to translate across the Dakotas into Minnesota west to
east. This will bring widespread rainfall chances. However,
confidence is low in evolution of this particular wave given its
time into the future nearing the predictability horizon. At
this time, there is very little evidence to suggest amounts more
than 1 inch from this particular wave.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 633 PM CDT Tue Sep 15 2026

VFR conditions for now and the next 6 hours as cumulus above
5000 ft will dissipate after sunset. northwest winds 10 to 15
kts will become light and variable around the same time. There
is the possibility of some patchy fog formation later tonight,
but probabilities are only around 20 percent at KBJI and a few
spots in the Red River Valley. Will leave out of the TAFs for
now, but will continue to monitor. Light and variable winds will
pick up out of the southeast less than 12 kts tomorrow morning,
with increasing high and mid clouds keeping conditions VFR.

&&

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

&&

$$

DISCUSSION...CJ
AVIATION...JR