271
FXUS63 KFGF 111137
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
637 AM CDT Fri Apr 11 2025

.KEY MESSAGES...

- Dense fog this morning will reduce visibility to 1/4 mile or
  less at times.

- Near critical fire weather conditions will develop in the
  Devils Lake Basin with relative humidity between 20-30% and
  sustained winds between 15 and 20 mph. There is a 40% chance
  for winds to become high enough for critical conditions to
  develop.

- Rain and snow is expected this weekend with a 20% chance of
  minor impacts due to falling snow Sunday night into Monday
  morning in far northern Minnesota.

&&

.UPDATE...
Issued at 634 AM CDT Fri Apr 11 2025

The fog area has remained within the dense fog advisory area.
Conditions via webcams, observations and satellite show the
typical variations in fog thickness, visibility as one expects
from radiational fog. Forecast is on track and no changes
needed.


&&

.DISCUSSION...
Issued at 247 AM CDT Fri Apr 11 2025

...Synopsis...

A broad surface high over much of the Central Plains has created
weak winds this morning, thus providing for fog development
across the region. This will continue to move and spread this
morning before diminishing after sunrise as mixing increases.
Dry conditions will develop today with warmer temperatures,
allowing for near critical fire conditions in the Devils Lake
Basin and a lower chance for critical conditions.

Weather impacts outside of fire will remain fairly benign
through the early weekend, but a system will push through Sunday
into early next week. Generally you should expect to see rain
and snow, with a low chance for advisory conditions to develop
in northwest Minnesota due to falling/accumulating snow. After
that, there is no strong signal for other impacts thereafter so
the probability for hazardous weather after Monday is low.

...FOG THIS MORNING...

Fog has developed mainly near water sources this morning and has
expanded due to radiational impacts. Based on webcams, dense fog
has not been consistent but it is widespread enough to warrant a
Dense Fog Advisory. The expectation is for continued expansion
through the morning before improvements start to arise after
sunrise. There is high confidence that we will be able to end
the advisory by 9 AM as drier air will allow for deep mixing
later this morning and through the day. Additionally, sustained
winds will increase, adding to confidence in fog ending shortly
after sunrise.

...FIRE CONDITIONS TODAY...

Low-level thermal ridging will settle in over western North
Dakota today, with the eastern end of ridging scraping into the
Devils Lake Basin. This will allow for deep vertical mixing and
dry air to develop over there. Relative humidity values should
fall between 25-30% with a lower chance for 20%. As you progress
eastward away from thermal ridging, RH values generally will be
above 30%.

With the thermal ridge, there also will be a pressure gradient
that develops across eastern North Dakota. This will increase
winds this afternoon from the south between 15 and 20 mph. Winds
aloft are very weak, with wind maxes generally 20-30 mph. This
means it will be very difficult to get winds high enough to
create critical fire weather conditions in the Devils Lake
Basin. If winds are stronger, which would have to be by a
tighter pressure gradient rather than from mixing, then critical
conditions will develop. Right now, there is a 40% chance for a
warning being necessary in that area.

...RAIN/SNOW AND WIND SUNDAY THROUGH MONDAY...

Precipitation is expected to sweep through Sunday into Monday.
Surface temperatures are very warm and in the leadup to the
system, warm temperatures should keep the precipitation type as
primarily rain. The column will cool, however, as we head into
Sunday evening into Monday morning. The main question right now
is saturation near the surface and what temperatures will look
like. Right now, the bulk of ensemble guidance keeps
temperatures above freezing in the lowest 100mb, however there
remains a scenario for cooler lower level temperatures. This
would facilitate a faster changeover to snow and improve the
probability for accumulating snow. EFI doesn`t really shade much
over our area, however some shift of tails are scraping the Lake
of the Woods area, so there is still a few ensemble members
spitting out heavier snowfall totals, but this is becoming less
likely.

Of higher confidence is wind potential with this system, as EFI
shades 0.6-0.7 across our area for winds and wind gusts, and
even adds a nice shift of tails to the mix. This means there is
high confidence we will see wind impacts Monday as this system
moves through. If we see this occur with falling snow, then
perhaps we could see some blowing snow from it, however surface
temperatures should limit the potential for more significant
impacts. Right now, base NBM sustained winds are between 30 and
35 knots, so we are probably looking at at least a Wind Advisory
type of day, but we`ll see what the degree of impacts are as we
get closer. Right now, the region for greatest winter impact
potential is primarily along the Lake of the Woods area where
temperatures will have the best chance to get below freezing.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 634 AM CDT Fri Apr 11 2025

Once we can get to 14 or 15z then the fog areas will dissipate.
Until them variable visibilities at many sites, including GFK,
FAR, TVF especially. But after fog burns off, cirrus moves in
and south winds develop 5 to 10 kts, then 12-18kts in the
afternoon over E ND. Gusts this evening over 20 kts within the
RRV and eastern ND. Clouds to remain high based and VFR thru 12z
Sat.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...Dense Fog Advisory until 9 AM CDT this morning for NDZ008-016-
     027>030-038-039-049-052-053.
MN...Dense Fog Advisory until 9 AM CDT this morning for MNZ001>005-
     007-008-013>015-022-027-029>031-040.

&&

$$

UPDATE...Riddle
DISCUSSION...Perroux
AVIATION...Riddle