860
FXUS63 KFGF 092335
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
635 PM CDT Sat May 9 2026

.KEY MESSAGES...

- Near critical fire weather conditions are expected over parts
  of eastern North Dakota and west central Minnesota through
  early evening. Near critical to critical fire weather
  conditions are expected again over parts of the region as
  temperatures increase next week.

- Cold overnight and early morning temperatures are expected
  through Monday, with frost and freeze conditions over parts of
  the region.

&&

.DISCUSSION...
Issued at 340 PM CDT Sat May 9 2026

...Synopsis...

Large scale pattern features a Hudson Bay low and a long fetch
of north-northwest flow from northern Canada into the Northern
Plains/over our CWA. Below average temperatures are in place,
and until this pattern begins to break down early next week will
support periodic frost/freeze conditions the next several
nights/morning. The Hudson Bay low begins to break down early
next week with a transition to a more westerly/progressive flow
through the week, with ensemble trends towards a more
southwesterly shift towards the 7-10 day period (late next
weekend into next week). For the current forecast period, this
pattern shift will support increasing temperatures region-wide,
with the arrival of above average temperatures by the end of
next week. Increasing low level southerly flow will also help
bring increasing precipitation chances late in the weekend
towards next week, with much more spread on details at that
point.

There is a quick moving shortwave Monday evening-Monday night
that is shown to pass north of our region, and there may be
enough elevated instability to support isolated thunderstorms
embedded within areas of showers that pass through. Chances are
high for light precipitation (0.1-0.2") in our far north and
northeast, but chances are low for greater than 0.25" in the
same areas (20% or less). Timing for this is mainly after sunset
Monday, but if any thunderstorms arrived before low levels
decouple/we loose favorable low level lapse rates there could be
a few stronger gusts (50mph+). During the late afternoon/early
evening models show high mixed layers in interved-V profiles,
with DCAPE 700-1100 J/KG. This threat is much less likely based
on the current timing, and is just something to monitor if the
system speeds up.

...Fire weather potential through the end of the week...

Deep mixing ahead of the increasing mid level CU has supported
frequent gusts across the region 25-35 mph, however as clouds are
increasing temperatures have leveled off keeping RH values
generally above 25%. Tds are in the 25-28F range, so where
temperatures approaching 60F RH values may still drop to 25% or
lower. In the end, the chance for Red Flag Warning conditions is
low, but near critical fire weather conditions should continue
through sunset.

Almost every day of the week Sunday through the end of the week may
feature the potential for RH values to fall under 30% over parts
of the region, with surface pattern and exact mixing heights
ultimately determining the potential for near critical winds/RH
each afternoon. Some days may feature a better chance for RH
values near 25%, but winds may not line up to support RFW
conditions. Eventually increasing southerly flow should bring
increasing Tds through the mixed layer in the later periods
limiting the potential for lower RH values despite temperatures
reaching the 80s over many areas into the weekend. During the
pattern transition, one day that my carry a better chance for
RH/wind overlap and RFW conditions would be Thursday. There is
a good signal for at least higher winds (even potential wind
advisory gusts 45mph+). Deeper westerly flow does tend to
support deep mixing as shown by a consensus of ensembles, so if
southerly return flow isn`t as strong we may see a window for
both low RH and windy conditions. Certainly a day to monitor,
with the standard uncertainty that comes with a forecast
regarding RH/wind beyond day 4 in this type of pattern.

...Frost/freeze impacts Sunday and Monday mornings...

Frost/freeze headlines issued for later tonight through Sunday
Morning. Freeze headlines issued where ensemble probabilities for
32F or less temperatures were 80% or greater and frost advisories
were 32-36F range is more likely. Urban heat island may result in
marginal (32-34F) conditions in the immediate Grand Forks metro,
however where this influence is less, temperatures are likely to
drop below 32F during the early morning hours Saturday in Grand
Forks and western Polk Counties.

There is still uncertainty in how much winds drop off (may hold
around 10kt) in the Red River Valley (particularly in the south)
due to the northerly component of the pressure gradient winds.
There is also a signal for lingering pockets of mid level
clouds, and the exact locations/coverage/timing in this type of
pattern are often not well resolved. Current consensus favors
southern part of our forecast area for these clouds, with more
likely clearing in the north and northeast. These factors could
complicate where widespread freeze conditions (32F or less)
occur, and this factored into the decision on where headlines
were drawn up. Even with clouds and winds around 10kt, low
temperatures would be 36F or lower considering the cold nature
of the air mass in place tonight. Where clearing/lighter winds
occur within the frost advisory, impacts to sensitive vegetation
would still be anticipated.

Sunday night/Monday AM frost/freeze potential: The pattern shift
(building low pressure to the west/southwest) will result in
moderating temperatures west to east and shifting low level flow to
the southeast. The colder air mass will still remain in place across
our eastern CWA and this is the type of set up where stronger
gradient remains west allowing lighter winds to remain in place
within the Red River Valley. There is a much better signal for clear
skies Sunday night as well, so with better radiational conditions,
it appears likely (greater than 60% probability) that freeze
conditions will develop in northwest MN with a chance for
frost/freeze within the Red River Valley. Chances for sub 36F
temperatures are much lower due to this pattern shift west of the
Red River Valley in ND Monday morning. We will ultimately need to
consider additional frost/freeze headlines.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 635 PM CDT Sat May 9 2026

VFR will prevail throughout the TAF period. Ceilings will rise a
bit this evening into early tonight as cumulus decreases and
coverage and pockets of mid level clouds pass through. On
Sunday, cloud bases may come down again a bit, but remain above
6,000 ft AGL. Winds are on the decrease this evening, already
losing their gusts at most terminals. Winds will fall to about 5
to 10 knots overnight, then pick back up to about 12 knots or a
little higher by the mid hours of Sunday morning, continuing
through the end of the TAF period.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...Freeze Warning from 1 AM to 9 AM CDT Sunday for NDZ006>008-
     014>016-024-026>030-038-054.
     Frost Advisory from 3 AM to 9 AM CDT Sunday for NDZ039-049-052-
     053.
MN...Freeze Warning from 1 AM to 9 AM CDT Sunday for MNZ001-002-
     004>009-013>017-022>024-027-028.
     Frost Advisory from 3 AM to 9 AM CDT Sunday for MNZ003-029>032-
     040.

&&

$$

DISCUSSION...DJR
AVIATION...Rafferty