755
FXUS63 KFGF 121459
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
959 AM CDT Wed Jun 12 2024

.KEY MESSAGES...

- Scattered severe thunderstorms this afternoon in northwest
  Minnesota. All hazards possible with up to 2" hail, wind to
  70mph, and isolated tornadoes.

&&

.UPDATE...
Issued at 958 AM CDT Wed Jun 12 2024

A few lingering elevated showers and isolated thunderstorms
near Lake of the Woods, but looks like the main show will still
be later on this afternoon as the boundary later destabilizes
and the weak surface low currently over eastern ND pushes east.
Adjusted POPs for current radar trends and latest CAMs. Highest
probabilities severe have shifted slightly east and are more
over DLH`s area, but still a 2 out of 5 risk for severe storms
later this afternoon in western MN.

UPDATE
Issued at 627 AM CDT Wed Jun 12 2024

Thunderstorms forced by elevated instabilty on the nose of a LLJ
will continue to work east through the morning clearing the area
by 9 to 10am. Thunderstorm forecast remains on track for the
afternoon with a notable outflow boundary laid down along HWY 2
from northern convection overnight and will be key to see how
this evolves through the day or if it remains by initiation
this afternoon.

&&

.DISCUSSION...
Issued at 324 AM CDT Wed Jun 12 2024

...Synopsis...

Currently noting two clusters of storms with one straddling the
Canadian border in our north and another along the ND/SD border in
central SD. Northern area will continue to translate east with the
850-700 mb flow and isolated thunder. Southern cluster
approaching Aberdeen being aided by strengthening low level jet
with very steep mid level lapse rates atop a sfc inversion.
Elevated convection may pose a wind risk through the AM as any
stronger updrafts collapse with negative buoyancy translating
these stronger LLJ winds through the inversion to the sfc. Max
wind speed above the inversion looks to be around 40 mph so
compressional heating could push gusts into sps territory
though low confidence in this scenario. Main thing to watch with
any of this overnight convection will be if any outflow
boundaries are produced which would heavily dictate the
mesoscale environment for initiation later in the day with the
regards to the afternoon severe threat.

Lastly while not meeting any heat criteria, today will likely
be the warmest day of the year thus far with 925 mb temps in the
low to mid 20s C translating to highs well into the 80s for
most except the far north where max temps will only reach 80 as
the effective warm front remains just south of the intl border.

...Severe Today...

Current picture is messy to say the least with a ceiling of hail
near 2", winds to 70 mph and a few tornadoes. Floor of isolated
hail as boundary parallel shear leads to a messier convective
mode with less discrete convection and upscale growth. A 500mb
jet streak of 50-60 kt will overspread the area ahead of a weak
shortwave in southern Manitoba this afternoon. In combination
with an incoming EML and steep mid level lapse rates over 8 C/km
the environment will be primed for strong to severe convection
this afternoon. A sfc trough will continue to shift east into
northern MN this aftn with an effective warm front extending
east along the MN/Canada border. Tds in the warm sector in the
low 60s and temps in the mid 80s will contribute to MLCAPE of
2500-3000 J/kg near the sfc low in NW MN. All this and the
ingredients for scattered to numerous severe storms across
northern MN exist today.

Any tornado threat will likely be tied closely to storms along
boundaries toady (cold front, warm front, residual outflow from
morning convection) as low level shear is not particularly
favorable for tornadoes and thus remains a conditional threat.
Low level stretching will however be maximized with 0-3 km CAPE
at least locally exceeding 100 J/kg near the low. When looking
at the hail threat best chance for sig hail (> 2") would be from
storms forming off the cold front and racing E/ESE as minimized
CAPE below the 0C would maximize time for hail embryos in the
HGZ. Eventual upscale growth is still possible this evening with
wind becoming the main threat though this aspect remains
slightly more uncertain.

... Thursday and Beyond...

Upper flow towards late week shifts northwesterly as an intensifying
ridge sets in keeping us quiet at least through Friday until
southwesterly flow becomes prominent and gives us increased
chances for widespread rainfall. How much rain falls is
dependent on intensity and track of the wave. At this point in
time, NAEFS percentiles do have an enhanced corridor of PW in
the 97.5th percentile across the northern plains from South
Dakota into North Dakota and west central Minnesota. This gives
us solid confidence in a more widespread rain event but also
the potential for more focused moisture advection across the
northern plains.

After this system, ensemble guidance diverges and
predictability for impacts next week is low. There is a strong
signal for another wave to move through early next week,
although the potential range of outcomes is very wide and
predictability needs to increase to ascertain potential impacts.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 627 AM CDT Wed Jun 12 2024

Showers and isolated thunder working east this morning affecting
TVF and BJI through 15Z. VFR ceilings through the day with winds
turning south to west through the day. Thunderstorms will form
this afternoon along and east of the valley with main impacts
between 20z and 00z today. Ceilings during t-storms down to 050
otherwise SCT080 for the afternoon.

&&

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

&&

$$

UPDATE...JR/TT
DISCUSSION...TT
AVIATION...TT