454
FXUS63 KFGF 021750
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
1250 PM CDT Sun Jun 2 2024

.KEY MESSAGES...

- There is a level 2 out of 5 risk for severe storms this
  afternoon and evening for the entire FA. Hazards include hail
  up to golf ball size, wind gusts up to 60 mph, and a few
  tornadoes possible.

- Widespread showers and thunderstorms are expected late Monday
  night into Tuesday. Severe storms are unlikely.

&&

.UPDATE...
Issued at 1250 PM CDT Sun Jun 2 2024

Showers and thunderstorms continue to develop near the I-94
corridor, slightly stronger than earlier this morning, but still
not severe. The better surface based CAPE and effective bulk
shear are setting up over south central ND to our west, so will
have to keep an eye on that area and see if severe cells can
develop there and move into our western counties later this
afternoon. At this point do not see any reasons to make changes
to our overall messaging, but will continue to monitor.

UPDATE
Issued at 955 AM CDT Sun Jun 2 2024

Scattered areas of showers and some thunderstorms continue to
push into the forecast area with warm air advection and a weak
lead shortwave in the southwesterly flow. Some stronger cells
have developed just southwest of our counties in the James River
Valley, but seem to be elevated and do not think they will
maintain strength very far as they push eastward into
southeastern ND. Still a lot of question marks as far as how
things will develop later this afternoon. With clouds and
precipitation affecting destabilization in the Red River Valley,
the best bet for severe may be storms developing in central ND
and pushing eastward into our area, which is what some of the
CAMs show at this point. Will continue to see how things develop
as the morning progresses.

UPDATE
Issued at 627 AM CDT Sun Jun 2 2024

POP grids where tweaked to reflect the ongoing radar signatures
moving across our forecast area this morning. Weak thunderstorms
moved over the Fargo metro area this morning as well as the
Devils Lake Basin. CAMs are still in disagreement about the
initiation time but have general consensus of transitioning to a
linear mode after 21z. Otherwise the severe potential still
looks to be in the afternoon and persist during the evening.

&&

.DISCUSSION...
Issued at 304 AM CDT Sun Jun 2 2024

...Synopsis...
As the CAMs were starting to show at this time yesterday,
scattered showers have begun to show up along the Interstate 94
corridor early this morning. There haven`t been any lightning
strikes yet, but the HREF 1-hour thunder probability does show
this potential developing in the next hour or two. This is
elevated convection, tied more so to 700mb warm advection and a
developing 25-35 knot low level jet. These parameters lift
northward, so by sunrise into mid Sunday morning most of this
activity should lift into the highway 2 corridor and northward.
After seeing this consistency from yesterday, have pretty good
confidence with it. However, this will have implications on
heating and instability for later, as the clouds and any
precipitation will hold down the temperature rise along and
north of highway 2 today. The NBM has caught on to this with
cooler highs in these areas today.

...Severe potential this afternoon and evening...
After having pretty good confidence on how convection may occur
early this morning, the confidence for how things may unfold
this afternoon is much lower. So why is that? First, the surface
features look very weak today, versus what was there at this
time yesterday (a surface low near Jamestown at 00z Monday with
a trailing cold front, and a warm front extending eastward along
Interstate 94). As of now, not sure there will be much of any
surface low or boundaries, or it will just be a weak trough.
Surface winds do look pretty gusty from the south today, but
behind the so called cold front/trough they are pretty light. So
there is no strong push behind this weak boundary in the 21z
Sunday to 03z Monday period. Second, as mentioned in the
synopsis section, morning clouds and precipitation will likely
limit the convective potential across the north. CAMs yesterday
had showed a nice line of storms forming over central North
Dakota 21z Sunday-00z Monday, then moving into eastern North
Dakota and weakening during the evening.

CAMs now show an earlier and more southern track to the best
severe potential this afternoon and evening. And again, this
could change. To start, SPC kept the entire FA in a slight risk
for severe weather. Some of the main parameters remain the
same, starting with good moisture return. However, SPC did note
that surface dewpoints by afternoon in the 60s might be a
little too optimistic. The upper support is not ideal, but
enough. The HREF is indicating maybe 1500-2000J/kg of MLCAPE
across southeast North Dakota by 21-23Z Sunday, with about 35
knots of 0-6km effective shear. The better mid level lapse rates
hold along the Dakotas border down into eastern South Dakota.
Meanwhile, the low level jet cranks up pretty good from 21z
Sunday to 00z Monday (around 50 knots), so much stronger than it
is right now. However, its best focus may be into Minnesota
lifting into southern Canada in the evening. CAMs seem to be
latching on to one cluster of storms across northwest Minnesota
during the late afternoon and early evening, feeding off the low
level jet, while another cluster tries to get going from
Jamestown to Oakes. As the storms from Jamestown to Oakes push
east during the late afternoon and early evening, they turn
linear and sag southeastward toward the better CAPE. These would
be more wind producers. The HREF shows the best UH tracks
developing around Barnes County about 22z Sunday, and continuing
across southeast North Dakota and adjacent areas of west
central Minnesota until about 03z Monday. Will maintain the
inherited hazard wording for hail (although will go golfball
size to match Bismarck, wind (60 mph), and a few tornadoes
possible, although it may be trending more toward wind and maybe
hail.

...Next event Monday night into Tuesday...
The next good shortwave is still on track to move through the FA
Monday night into Tuesday. This is a little faster than what was
seen yesterday, so that most of the precipitation moves through
during non-peak heating hours. This means there is not very much
CAPE to work with. The track of the wave may favor the northern
half of the FA with slightly heavier precipitation amounts now.
Quarter inch amounts look pretty favorable for all areas,
ranging from a 90 percent probability along the Canadian border
to 60 percent along the Dakotas border. Probs for amounts
greater than 1 inch range from 40 percent along the Canadian
border to 10 percent along the Dakotas border. Uncertainty then
comes into play for the later periods, with the potential for
an upper low to linger over the Northern Plains for a few days,
or slowly shift east.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1250 PM CDT Sun Jun 2 2024

Scattered showers and a few thunderstorms will continue to
impact area airports through this afternoon and evening, and
cannot rule out some severe convection although unknown at this
point if the strongest cells will impact the TAF sites. The best
chances for convection will be during the 21Z to 03Z time frame,
ending from west to east later tonight. Mostly VFR ceilings but
could see some brief drops to MVFR vis with heavier rain. More
widespread MVFR to IFR conditions later tonight into tomorrow
morning as stratus moves in behind the departing thunderstorms,
but some improvement by the end of the period. Winds will shift
from the south to southeast with gusts to around 25 kts around
to the southwest then northwest by Monday morning.

&&

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

&&

$$

UPDATE...MM/JR
DISCUSSION...Godon
AVIATION...JR