Nimrod, Minnesota Weather Forecast Discussion

351
FXUS63 KFGF 122058
AFDFGF
Area Forecast Discussion
National Weather Service Grand Forks ND
358 PM CDT Fri Sep 12 2025
.KEY MESSAGES...
- There is a level 1 out of 5 risk for severe thunderstorms
  Sunday into Monday. The main hazards will be hail to the size
  of quarters and gusty winds to 70 mph.
- Well above average temperatures continue into next week.
  Active pattern continues through early next week, including
  periodic chances for strong to severe thunderstorms.
&&
.DISCUSSION...
Issued at 321 PM CDT Fri Sep 12 2025
...Synopsis...
Highly amplified and blocked pattern aloft is revealing itself
on water vapor imagery today, with a high amplitude upper trough
in the West detached from the polar jet, with high amplitude
upper ridging just downstream centered over the Great Plains,
and another high amplitude upper trough over the East. This
omega block-type pattern will continue through the weekend
before breaking down into next week. With the Northern Plains
and Upper Midwest largely under the influence of upper ridging
and exit region of the western upper trough, above average
temperatures and periodic chances for thunderstorms will
continue in these regions through the weekend into next week.
Closer to our area of eastern ND and northwest MN, suppressive
influence of the upper ridging will attempt to limit
thunderstorm development over majority of the area through
Saturday night. The only exception to this would be
mesoscale/storm- scale influences to overcome this, allowing
thunderstorms within central Dakotas to eek further eastward
into brushing through areas west of the Red River Valley.
Getting into Saturday overnight and Sunday, shortwave trough
rounding the base of the western upper trough will allow its
axis to pivot into the Northern Plains, gradually increasing
synoptic forcing for ascent. Most guidance continues to pinpoint
late Sunday into Monday holding more notable chances for severe
weather due to this shortwave trough`s passage through our area.
The overall large scale pattern doesn`t chance too much into
early next week, with repositioning of the upper ridging
extending into the Great Lakes region, and broad western upper
trough extending out of central Canada into the Intermountain
West. This places our region under southwesterly flow aloft,
serving to continuing above average temperatures and additional
bouts of thunderstorms, some of which may be strong to severe.
More details on severe chances through early next week can be
found below.
It isn`t until around midweek/Wednesday do ensemble guidance
sweep the western upper trough axis through our area,
introducing drier continental air mass and trend toward more
average temperatures and perhaps less storminess. However, there
is a cluster of guidance that weakens this upper trough in lieu
of redevelopment of upper troughing over the West, yet again
reintroducing our region into a warming trend and perhaps more
active pattern. The other subset of ensemble guidance keeps flow
aloft more zonal and weak, maintaining the trend of average
temperatures and less active pattern.
A quick comment on fog potential tonight - easterly surface flow
and very unseasonably moist air mass will promote upslope and
development of low stratus. This is expected to allow low
stratus to "scrape" against the surface in the form of fog. This
type of set up typically favors fog at locations along and west
of the Red River Valley, lakes country of west-central
Minnesota, and far southern Red River Valley. Other locations
like those near Lake of the Woods and Red Lakes also hold chance
for fog. Fog will likely be dense at some locations, although
hard to say exactly which ones. Messaging of this potential
hazard will be handled as confidence increases in more precise
locations of dense fog.
...Severe storm potential this weekend into next week...
While latest guidance has kept severe storm potential most
likely to remain confined in central and western Dakotas through
Saturday, periodic chances of thunderstorms still exist almost
daily today Sunday through Tuesday.
Machine learning severe weather guidance continue to highlight
Sunday through Tuesday with low severe probabilities,
coinciding with the first shortwave trough rounding the eastern
flanks of the upper low, followed by southwesterly flow aloft
and eventually upper trough axis moving through the region. NBM
CWASP guidance also highlights two particular days with greater
than 80% chance of values of 70 (aka notable severe weather
parameter spacing) - one on late Sunday into early Monday, and
then the other around Tuesday. CAMs are just peeking into
Sunday`s potential, with increased low level flow and
instability along with expected orientation/progression of
forcing favoring gusty winds up to 70 mph as the main hazard.
Couldn`t rule out hail as well, especially if storms can remain
more clustered.
It remains unclear to the expected hazards beyond Sunday,
although there continue to be a lack of signals for significant
severe potential at this time, keeping strong to severe storm
potential more on the lower end of severity spectrum.
With persistent intervals of thunderstorms, and ample overall
moisture content as well as sufficient instability into our area
for an extended period of time, localized flash flooding still
remains a potential hazard this weekend through early next
week. Confidence is not high in coverage or location of this
potential hazard, and will likely hinge upon mesoscale/storm-
scale processes to drive this potential - something that
wouldn`t likely be known until very near the event (less than 24
hours).
&&
.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1252 PM CDT Fri Sep 12 2025
Aviation impacts from lowered ceilings are forecast in some TAFs
through 18Z Saturday.
Portions of eastern North Dakota into west-central and northwest
Minnesota are forecast to have ceilings develop after 03Z
into the LIFR to MVFR range. There is a 70% chance for LIFR
conditions for areas along and west of the Red River Valley,
including KDVL, starting around 10Z and potentially lasting
beyond 15Z. MVFR ceilings are forecast at KBJI starting around
10Z, with a 50% chance of dipping into the IFR/LIFR category,
also potentially lasting beyond 15Z. Dense fog will also be
possible with these lowest ceilings starting around 10Z,
however, confidence is not high enough in its occurrence at
these sites and have been left out of the TAF for now. While a
gradual lifting of impactful ceilings is forecast to occur
between 15-18Z, it is possible (30%) they last beyond 18Z.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
DISCUSSION...CJ
AVIATION...CJ

NWS FGF Office Area Forecast Discussion