590
FXUS63 KFGF 282043
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
343 PM CDT Mon Sep 28 2026

.KEY MESSAGES...

- Widespread soaking rainfall with embedded thunderstorms will
  continue this afternoon through tonight. Localized flooding
  impacts may occur in portions of southeast North Dakota into
  central and southern Red River Valley from rainfall amounts 3
  to 6 inches.

&&

.DISCUSSION...
Issued at 301 PM CDT Mon Sep 28 2026

...Synopsis...

Broad southwest flow aloft currently resides over the Northern
Plains and Upper Midwest as a result of longwave upper troughing
in the West. This is helping draw northward increasing moisture
content, while also allowing several shortwave troughs embedded
within the flow aloft to provide forcing for ascent to drive
widespread rainfall into the eastern Dakotas and northern
Minnesota this afternoon through tonight. Weak but sufficient
instability accompanying the surge in moisture will also allow
embedded thunderstorms to be present, especially tonight. Two or
more "waves" of rainfall with embedded thunderstorms will drive
potential for training higher rain rates - bringing potential
for localized flooding impacts. More details on this potential
found below.

Tuesday morning, rainfall should end west to east, with most/all
of the area becoming dry by the afternoon. This will usher in a
relatively dry period through the remainder of the week, with
the exception of some transient showers potentially late
week/weekend, but ultimately resulting in little rainfall
amounts, if any. This is a result of generally zonal to
northwest flow aloft amid upper ridging building over the High
Plains/Intermountain West. Near to above average temperatures
are forecast through Wednesday, turning average to below average
temperatures late this week.


...Potential flooding impacts this afternoon & tonight...

There remains potential for an additional 3 to 6 inches of
rainfall this afternoon through tonight in portions of southeast
ND, central/southern Red River Valley, into northwest MN. The
majority of CAMs continue to paint this scenario somewhere
within the aforementioned areas, but each with their own variety
of exactly where this will occur. Locations that experience
these amounts are liable to see flooding impacts.

Confidence is relatively high in this output based on the
presence of a stationary boundary extending southwest to
northeast generally from the southern James River Valley in
southeast ND into the central Red River Valley into northwest
MN. This sets the stage for additional upper forcing to act
upon, which is well advertised to resurge tonight in the form of
a shortwave trough propagating out of the High Plains of WY/SD,
through the Dakotas, and into northwestern ON by Tuesday
morning. This will help reinvigorate the low level jet within
the "warm sector" of the aforementioned stationary front -
suggested to generally remain in this orientation/position
through the event, with some eventual movement eastward Tuesday
morning.

Abnormally high moisture content (~1.5 inches of PWATs)
coupled with weak but sufficient instability (MUCAPE ~800 J/kg),
and storm motion generally parallel to frontal orientation will
drive high rain rates. Rain rates like 0.5-1" per hour and/or
2-4" per 6 hours will result in areas that see repeated
thunderstorms move over any particular location for at least 2
hours.

Pre-conditioned areas that have recently experienced soaking
rainfall is also important to consider when identifying
potential areas for subsequent flooding impacts. While these
advertised highest rain rates may occur in northwest MN, higher
rain amounts from this morning have generally missed this area.
Conversely within southeast ND, rainfall from this morning in
the 1-2 inch range have already occurred, with continued
convective rates from thunderstorms still ongoing in southeast
ND at the time of this Forecast Discussion issuance. Despite
this area in drought, higher rain rates coupled with
previously/currently received rainfall still allow for excessive
runoff.

Of course, urban areas are relatively more susceptible to these
higher rain rates; this includes cities like Fargo-Moorhead
and/or Valley City.

While the overall area of concern holds generally medium to high
confidence, more precise location of highest rainfall amounts
remain in question. Because of this, have opted to not issue a
Flood Watch; however, a Flood Watch may be issued should
confidence increase in more precise location of potential area
of concern later this afternoon/early evening.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 1152 AM CDT Mon Sep 28 2026

Showers and general thunderstorms will continue to move north
and east today bringing moderate to heavy rain to much of
Eastern North Dakota and Northwest Minnesota. This is expected
to bring widespread MVFR and IFR conditions. Ceiling reductions
will be more widespread with reductions to visibility occurring
during times of precipitation. Tonight into Tuesday morning
brings the potential for fog and LIFR conditions. The best
chance for fog is from the Devils Lake Basin into far Northwest
Minnesota. Starting Tuesday morning conditions will begin to
clear from west to east as rain moves out of the region.

&&

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

&&

$$

DISCUSSION...CJ
AVIATION...LT