997
FXUS63 KFGF 220648
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
148 AM CDT Sat Jun 22 2024

.KEY MESSAGES...

- Isolated strong to severe storms are possible in the northern
  Red River Valley and Devils Lake region late Saturday
  afternoon into the evening.

- Potentially strong to severe storms again Monday afternoon and
  evening.

&&

.UPDATE...
Issued at 144 AM CDT Sat Jun 22 2024

Not much change since last update. Diffuse and broad forcing
from approaching troughing and subtle height falls aloft
continues to utilize available moisture producing pockets of
light rain. This is expected to continue through the remainder
of the night into Saturday morning. Main impact from this
activity is to aviation (details of which can be found in the
Aviation section below within this discussion).

UPDATE
Issued at 1018 PM CDT Fri Jun 21 2024

The more organized area of moderate to locally heavy rain has
since fallen apart, but pockets of light rain continue to move
across eastern ND/northwest MN (much lighter rates though).
Besides some minor adjustments the forecast is on track and
additional amounts should generally be less than 0.25" through
the night (more likely a few hundredths of an inch).

UPDATE
Issued at 701 PM CDT Fri Jun 21 2024

Rain associated with a less organized mid level impulse has held
together as it spread into eastern ND/southern RRV and while
guidance shows this weakening/falling apart trends support at
least a 1-3hr period of widespread rain where it tracks. I made
short term adjustments to better reflect current coverage
timing and blended to guidance in the overnight period. Based on
upstream obs anywhere from 0.25 to 0.5" will occur where the
main area of moderate/locally heavy rain tracks, though with
lightning activity/thunderstorm coverage diminished rates may
be trending down already.

&&

.DISCUSSION...
Issued at 243 PM CDT Fri Jun 21 2024

...Synopsis...
The southwest flow at 500mb over the Northern Plains finally
turns more zonal tonight into Saturday. After a low point
yesterday, surface dewpoints have risen into the mid to upper
50s over most of the FA, with even some greater than 60F values
across the far south. Precipitable water values have nosed back
above 1 inch over most of the FA, although the values closer to
1.8 inches are still down across southeast South Dakota into
far southern Minnesota. Extensive cloud cover today has helped
to moderate the temperature rise somewhat. There is another
shortwave west of the Bismarck that has been pushing another
batch of precipitation slowly east-northeast today.

Not expecting much low level jet support for the above
mentioned shortwave tonight, so the activity to the west may
decay or slowly die as it progresses into this FA. Dewpoints and
precipitable water values will continue to rise on Saturday.
The next 700mb wave will drop into north central North Dakota by
00z Sunday, then slowly into Minnesota Saturday night into
Sunday morning. A brief period of ridging follows, before a
ridge rider scenario develops late Monday afternoon into Monday
evening. After that the pattern shifts to northwest flow aloft
and less confidence on the timing of any potential waves.

...Late Saturday afternoon and evening...
The HREF shows building CAPE across the FA on Saturday, with
values possibly reaching 1000-1500 J/kg over central and
possibly southeast North Dakota by late afternoon. Overall, the
surface flow is very weak, so don`t expect much forcing there.
Another caveat is how much cloud cover may linger across the FA
during the day, limiting instability. The NBM keeps it pretty
cloudy through the morning, but shows the clouds thinning by
afternoon, especially across central North Dakota. The arrival
of the shortwave should help initiate some convection, although
there is not a good consistent signal on that either. The
strongest portion of the wave may stay north of the border (in
Canada) or it could be a little slower reaching this FA. So
the exact timing is still uncertain as well. UH tracks on the
HREF show a better potential north of the border, although a few
CAMs have some weaker UH tracks potentially reaching the Langdon
to Cooperstown corridor. There is no low level jet support
Saturday night, so would expect any strong to severe storms to
weaken after dark.

...Monday afternoon and evening...
Monday still looks like the warmest day of the 7 day period, as
brief ridging moves in. Similar to yesterday at this time, 700mb
temperatures appear to hit about +10C as far north as Winnipeg,
with near +15C across the southern FA. Surface dewpoints should
rise into the 60s with precipitable water values reaching about
1.5 inches, so again there will be plenty of CAPE. The main
uncertainties with this event are how much of a surface boundary
there may be and how strong it is. Same story for the wave, its
timing and strength (the stronger portion may again lift into
southern Canada). How much capping holds. So although strong to
severe storms are again possible, there are a lot of question
marks yet, so stay tuned.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1155 PM CDT Fri Jun 21 2024

Scattered light showers/sprinkles continue across parts of
eastern ND and northwest MN, as several waves split around the
region. MVFR (and a few pockets of IFR) stratus are beginning
to develop in southern ND and guidance is starting to better
reflect timing expanding north and northeast through the early
TAF period. Eventually all sites should drop below VFR but
confidence in widespread/prevailing IFR is still low (except at
KBJI) based on trends. Eventually guidance supports all
locations in ND improving to VFR by Saturday evening. Weak
surface gradient is keeping light winds in place (less than 10
mph, with a tendency fro easterly or southeasterly directions
(though prevailing calm or variable conditions are just as
likely).

&&

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

&&

$$

UPDATE...CJ/DJR
DISCUSSION...Godon
AVIATION...DJR