235
FXUS63 KFGF 210003
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
703 PM CDT Sat Jul 20 2024

.KEY MESSAGES...

- There are daily chances for showers and thunderstorms today
  through Monday. While the chance for severe weather is less
  than 10%, a few strong storms capable of small hail and gusty
  winds to 50 mph may occur.

- Smoke from Canadian wildfires will linger across the region
  through at least Monday, potentially longer. This may impact
  air quality.

&&

.UPDATE...
Issued at 700 PM CDT Sat Jul 20 2024

Pulse type convection continues, but has shown a general
weakening trend as inspected, with the decrease in solar angle.
Shear is less than 20kt lowering confidence in any
sustained/organized cores. So far most thunderstorms have had
narrower cores (even the tallest) and have been short lived.
There has been enough storm scale vorticity that under the
right conditions, it could support a brief funnel along the
escarpment where surface convergence is a little higher. Low
level lapse rates in those areas are questionable and most
convection is now outflow dominant, resulting in very low
chances for brief/weak tornadoes (near zero as we approach
sunset). There was one funnel report earlier 6-7 miles east of
Finley, ND. This specific report seemed to coincide with an
updraft along the intersections of outflow with some of the
pulse convection, but it was short lived as the parent updraft
weakened and outflow moved on.

&&

.DISCUSSION...
Issued at 318 PM CDT Sat Jul 20 2024

...Synopsis...

Water vapor satellite imagery reveals an expansive, well defined
upper low over western QB into ON, with high amplitude upper
ridging through the western CONUS into western CAN. This is
placing the Northern Plains and portions of the Upper Midwest
under weak northerly flow aloft, with weak flow is greatly
limiting wind shear. At the surface, a backdoor cold front is
pushing through western ON into northern MN pushed by the
aforementioned QB/ON upper low. Sufficient instability and
moisture is present for convection.

Thick and widespread smoke is also noted on visible satellite
imagery over the majority of central and western CAN into the
northern tier of the CONUS.

Ensemble guidance indicates the upper synoptic pattern will be
rather stagnant over the next several days. Because of this, the
backdoor cold front stalls and washes out/retreats back east
tonight into tomorrow. Because of this stagnant pattern, the
buoyant air mass lingers around the area. Additionally, weak
northerly flow aloft will help funnel smoke from Canada into our
area through at least Tuesday.

...Daily chances for showers and storms...

The resident air mass over the region is composed of rich
boundary layer moisture, seen by sfc dew points in the upper 60s
to low 70s. There is likely some enhancement from
evapotransportation that typically peaks around this time of
year as most CAMs this morning did not show 70 dew points. This
is aiding moderate instability. While wind shear is weak, there
is enough instability to generate tall enough storms to deposit
small hail, as well as downdrafts resulting in gusty winds up to
50 mph.

With a lack of changing air masses, and stagnant synoptic
pattern, the potential for small hail and gusty winds to 50 mph
will be present in relatively stronger storms today through
Monday.

Due to wind shear less than 25kt and lack of better forcing for
lift, the chance for organized thunderstorms leading to severe
hazards is very low, less than 10%.

...Wildfire smoke...

Most smoke is from wildfire activity in northern BC, AB, and
into the Yukon and Northwest Territories of Canada. Persistent
flow from this source region into our area is forecast by
ensemble guidance through mid week, keeping smoke confidently
over the area through Monday, potentially lasting as long as
Thursday/Friday even. There will also be opportunity for smoke
to reside at the surface during this timeframe, which would
reduce air quality. Low confidence in how when and how thick
smoke will be at the surface, thus lowering confidence in
impacts from reduced in air quality. But ultimately there will
be potential for impacts from reduced air quality through much
of the week.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 700 PM CDT Sat Jul 20 2024

Isolated to widely scattered thunderstorms are still lingering
over parts of the region, mainly in northeast ND and parts of
northwest MN with vcts mainly at KDVL and KBJI. This activity
should quickly dissipate with sunset this evening. High level
smoke should linger through the TAF period, with a low chance
for visibility reductions during the overnight/early morning
periods if pockets of smoke were to get trapped near the
surface (confidence too low at this time to go lower than 6sm).
Otherwise, light/variable winds continue with weak surface
gradient and weak winds aloft.

&&

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

&&

$$

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