289
FXUS63 KFGF 171137
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
637 AM CDT Sat Aug 17 2024

.KEY MESSAGES...

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

&&

.UPDATE...
Issued at 637 AM CDT Sat Aug 17 2024

Patchy fog is still developing along the valley, parts of
Devils Lake Basin, and across West Central Minnesota. With the
sun rising, the fog should be dissipated by 15z. Visibilities
are currently dropping between 1/2 SM and 3 SM across the
forecast area.


&&

.DISCUSSION...
Issued at 344 AM CDT Sat Aug 17 2024

...Synopsis...

Areas of smoke, haze, fog cover the area. Pockets of dense fog
are forming in central ND in area of clear sky and light winds.
For today, expect likely some residual smoke/haze but just how
thick it is is highly uncertain as RAP/HRRR surface smoke
numbers fall below 10 ug/m3 today. Extensive collaboration was
done with BIS/ABR to come up with a unified approach and net
result was to stick to 7-10 ug/m3 concentrations for our smoke
grids and then blend as needed to avoid small patches of smoke
which wouldn`t make sense. Overall with lower concentrations
once you get past 15z there is little to no smoke in the grids
today and beyond.

Did keep the 20 pop for shra/tsra in NW MN this aftn per prev
fcst. MUCAPE does reach around 1000 j/kg in the area and
convective temps in mid 70s, which will be reached. CAMs are not
producing much in the way of precip but certainly think that
keeping a chance is warranted based on CAPE values and any
potential short wave or weak convergence on backside of upper
low and east side of upper ridge/sfc high building in.

Dry tonight into Sunday. A little warmer Sunday with mostly low
80s.

Theme of having highs in the low-mid 80s continue next week as
500 mb ridge builds into the northern high plains and spreads
east. 500 mb flow becomes more zonal mid to late week as 500 mb
high shifts back from 4 corners region into the mid Mississippi
valley. Couple short waves will move along the US/Canadian
border, one Tuesday/Tuesday night which has been well
advertised. This one is associated with MUCAPE potential values
in the 1500-2000 j/kg range. In fact Tues-Thu afternoons will
see high CAPE values with probability of sfc CAPEs above 2000
j/kg in the 50 pct range in central ND. Thus Tues-Fri period
has chances for thunder in the fcst (except for Thu). 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.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 637 AM CDT Sat Aug 17 2024

A mixed bag of MVFR and IFR as a mixture of fog and smoke reduce
visibilities this morning. By 15z the fog should dissipate to
increase visibilities. By 20z the smoke should have mixed out to
bring no visibility reductions. Winds are going to be from the
North through the TAF period bouncing between 340 and 010. By
02z winds are expected to drop to VRB 05kts until 12z tomorrow.
Theres is a slight chance of some afternoon showers for KBJI
starting around 20z and ending by 02z. Uncertain the
temperatures and forcing will be there to create afternoon
convection with the high pressure setting in.

&&

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

&&

$$

UPDATE...MM
DISCUSSION...Riddle
AVIATION...MM