129 
FXUS63 KFGF 290953
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
453 AM CDT Tue Sep 29 2026

.KEY MESSAGES...

- Rain ends from west to east during the day. Localized flooding
  impacts may be found this morning in a zone from Thief River
  Falls to just south of Grand Forks to north of Valley City.
  

&&

.UPDATE...
Issued at 449 AM CDT Tue Sep 29 2026

Flood watch for parts of southeast ND including Fargo-Moorhead
will expire on schedule. The heaviest rainfall overnight fell
more north of the watch area, with the exception of Barnes
county. Overnight the heaviest rainfall with amounts of 1.50 to
2.50 inches 06z-09z fell from near Valley City northeast to 
just south of Grand Forks to near Thief River Falls. Since 08z 
the rates of rainfall have diminished greatly with 1 hour 
rainfall rates from radar showing 0.10 to 0.20 inch. Will 
continue current areal flood warning and flood advisory for 
parts of the Sheyenne River basin where total rainfall of 4-6 
inches has fallen in the last 24 hours. Rainfall will end from 
west to east gradually today...taking the longest to exit 
Bemidji-Fergus Falls which wont be til later afternoon. But also
this area has received much lighter amounts of rainfall so far.



&&

.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 /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1153 PM CDT Mon Sep 28 2026

Highly variable flight conditions as a frontal zone lingers 
over the region and clusters of showers and embedded 
thunderstorms track southwest to northeast. Many locations are 
reporting MVFR and IFR conditions. Stratus should fill in 
through the overnight hours and IFR ceilings will become 
predominant with the potential for LIFR (mainly KDVL). Fog may 
also develop in areas outside of showers tonight/Tuesday 
morning. Drier air does eventually arrives Tuesday and VFR 
should return to ND by early afternoon, with a slower west to 
east period of improvement in the afternoon/evening across 
northwest MN. MVFR ceilings may linger over north central MN
including KBJI through Tuesday evening.

&&

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

&&

$$

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