364
FXUS63 KFGF 071257
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
757 AM CDT Sun Sep 7 2025

.KEY MESSAGES...

- Frost is expected this morning across much of the region.

&&

.UPDATE...
Issued at 757 AM CDT Sun Sep 7 2025

Temperatures are rapidly recovering with diurnal heating
underway, so I allowed the Frost Advisory to expire as
scheduled.

UPDATE
Issued at 630 AM CDT Sun Sep 7 2025

Temperatures continue to generally range from 33-36 at many
locations where the Frost Advisory is in place, with a few
colder spots 30-32F (very localized). Frost Advisory remains on
track, and with improvement expected after 8am due to increasing
daytime heating, will allow the product to run its course.

Radiational fog had developed with a few locations reporting
1/4sm at times (Fosston, MN and Cooperstown, ND). Webcams show
fog is very shallow where it has developed, further limiting
impacts. I adjusted wx grids to reflect locations where patchy
fog is occurring, but unless these dense pockets increase in
coverage/depth I will hold off on hazard products for now.

&&

.DISCUSSION...
Issued at 339 AM CDT Sun Sep 7 2025

...Synopsis...

A large scale rough remains in place from Hudson Bay and south
towards the Ohio River Valley with much drier/northerly flow in
place over the Northern Plains. The breakdown of this trough
tonight into Monday will result in a shift to a westerly split-
flow and a baroclinic zone near our southern CWA may act as a
focus for diurnal showers/thunderstorms as weaker mid level
waves pass to the south. Guidance continues to show some
instability pooling near this feature, but with limited lift,
marginal mid level lapse rates, and weak shear at most a few
stronger storms may develop just near our southeast (small
hail/lightning). Ridging then builds into our region mid week,
followed by some form of weak southwest flow between the ridge
and a cutoff mid level low to the west late week into the
weekend. This does allow for increasing moisture advection in
the mid-upper levels, and daily shower/thunderstorm chances.
However, instability/shear remain marginal, and any there
remains higher spread in smaller scale features/details lowering
confidence in evolution/coverage/impacts through the weekend.
Each day may support a few diurnal strong thunderstorms, but as
has been the case the probability for severe thunderstorms
remains low as ECMWF EFI and machine learning system do not
highlight any period for potential severe risk.

...Frost this morning...

Temperatures have varied, but colder 2m Temps in the 32-36F
range have been reported within the areas of the Frost Advisory,
and clear skies/calm winds support frost formation on surfaces.
By sunrise a few locations could drop below 32 under good
radiational cooling conditions (clear skies calm winds). BL Tds
for most areas are generally in the 33-39 range, so the
potential for a widespread freeze is low this morning. Forecast
is on track and the Frost Advisory remains in place through 8 AM
CDT. Lower temperatures may linger a bit beyond 8 AM before
daytime heating kicks in, but the trend should be there (temps
recovering), so I opted not to extend the advisory in time.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 630 AM CDT Sun Sep 7 2025

Radiational fog has developed over parts of southeast ND and
northwest/west central MN with localized visibility reductions
below 1 mile in shallower/ground fog. IFR to MVFR has occurred
at KTVF and may impact KFAR/KBJI before the fog clears after
sunrise. VFR should then prevail through the TAF period with
southerly winds generally under 12kt through the TAF period due
to surface high pressure shifting east and weak southerly
gradient building from the west.

&&

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

&&

$$

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