879
FXUS63 KFGF 162039
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
339 PM CDT Fri Aug 16 2024

.KEY MESSAGES...

- Wildfire smoke may impact sensitive groups within northwest
  Minnesota and eastern North Dakota this afternoon into the
  weekend.

&&

.DISCUSSION...
Issued at 252 PM CDT Fri Aug 16 2024

...Synopsis...

Current satellite reveals broad upper troughing within the Upper
Midwest and western Great Lakes with embedded lobes of
vorticity, one of which resides over our area on the backside of
the upper trough. Lingering low level moisture and associated
broad scale lift within the trough is continuing areas of light
rain/drizzle in the southern Valley into Minnesota. Guidance
generally migrates the upper trough to the east as upper ridging
currently in the Canadian Prairie Provinces into the
Intermountain West. Low stratus is scouring out in some
locations allowing heating to generate isolated showers, of
which may generate weak lightning activity (20% chance of
occurring).

Surface high pressure behind the exiting upper trough/attendant
surface low is contributing to gusty northerly winds to 30 mph
within the Red River Valley into eastern ND. This northerly flow
will also help pull smoke from Manitoba into our area. More on
this potential impact below. Lingering northerly wind and
scattered clouds tonight should help mitigate widespread fog
development, although local areas that can clear out and calm
may see morning fog.

Another opportunity for isolated to scattered showers and
perhaps weak thunderstorms comes Saturday afternoon. These
chances (30%) currently reside within northwest Minnesota as
most high resolution guidance indicates enough surface
convergence between an incoming wedge of high pressure and the
exiting surface low pressure gradient to generate enough lift
for convection after convective temperatures in the mid 70s are
reached.

Ensemble guidance favors upper ridging to build into the
Northern Plains and Upper Midwest from the west, helping re-
introduce summer-like temperatures, with medium-high chances of
seeing temperatures in the 80-90 degree range next week. This
ridging will also allow increased moisture content and potential
for more unstable air mass to develop into our area. This may
help set the stage for additional strong to perhaps severe
convection, although confidence in strength of storms is quite
low given uncertainties into the degree of unstable air mass as
well as details revolving around potential forcing and moisture.

One potential forcing mechanism for eventual thunderstorms comes
from a potential shortwave trough rounding the crest of the
upper ridge through the Dakotas into Minnesota around the
Tuesday. This brings our next appreciable chance for
precipitation to our area, but again, confidence is low on
potential for strong to severe storms during this episode.

...Potential Smoke Impacts...

Visible satellite and air quality sensors reveal surface
wildfire smoke from Canadian wildfires over portions of western
ND and southern MB. Overall northerly flow lends credence into
most available smoke guidance bringing this smoke into eastern
North Dakota and the Red River Valley this afternoon and
evening. Nocturnal inversion tonight will likely trap surface
smoke near the surface at least through early morning hours.

Confidence decreases in smoke residing in our area
through the weekend as the surface high pressure builds into our
region, and guidance depicts different levels of smoke
concentration meandering within the anticyclonic flow (likely
owing to differences in handling smoke mixing within the
boundary layer during the diurnal cycle).

Despite this lowered confidence into the weekend, we will
maintain messaging of potential impacts from smoke this weekend,
with sensitive individuals holding the risk of being impacted,
especially if exposed to smoke for relatively long periods of
time.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 100 PM CDT Fri Aug 16 2024


Ceiling Impacts:

Lingering aviation impacts from lowered CIGs into MVFR and IFR
categories will continue through at least 21Z for KFAR and KBJI.

Overall, low CIGs behind an exiting low pressure system will
start to scattered out as cloud layer moisture retreats with the
system. There will still be scattered cumulus and shallow
cumulus congestus before 01Z for areas that do lose CIGs.

There is uncertainty in whether or not CIGs return across the
region after 06Z tonight into Saturday morning, although
guidance indicates relatively better chance (60%) for this to
occur within MN, namely at KBJI. For this reason, decided to
maintain MVFR/IFR CIGs at KBJI throughout the TAF period.

Potential Smoke Impacts:

Smoke will spread into eastern North Dakota into the Red River
Valley out of Canada this afternoon into tonight, potentially
impacting KDVL, KFAR, and KGFK. Confidence in vsby reductions
being low enough to present impacts (ie less than 3SM) remains
low, but does remain as a potential outcome after 00Z. For now,
kept vsby reductions at 6SM for now with the anticipation of
updating/amending as needed.

&&

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

&&

$$

DISCUSSION...CJ
AVIATION...CJ