923
FXUS63 KFGF 230859
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
359 AM CDT Thu May 23 2024

.KEY MESSAGES...

- Isolated to scattered severe thunderstorms are expected today
  between 4 pm and 10 pm south of Highway 2. Potential hazards
  include hail up to two inches and 70 mph winds, with a tornado
  possible.

- Heavy rain tonight into Friday over portions of the Red River
  basin may contribute to additional rises on area rivers.

- Patchy frost is possible Saturday early morning in the Devils
  Lake basin. Temperatures depend on cloud cover and wind.


&&

.DISCUSSION...
Issued at 328 AM CDT Thu May 23 2024

To start today, there is a weak short wave moving east-northeast
into central ND. There is a broad area of mid level moisture and
light rain showers with this wave in central and northern North
Dakota back into northeast Montana and into southwest Manitoba.
This entire area of showers will move east-northeast thru much
of the area this morning, but linger most of the day northeast
ND into far northwest MN. In this thicker cloud and shower area
temps today will remain cool with highs in the 50s. Mainly
talking about areas from Devils Lake to Roseau.

Farther south early morning mid level showers will exit SE ND
and the south valley by 16z. Some breaks in the mid clouds
should occur midday into early aftn in SE ND.

Our main player for thunderstorm development late afternoon and
rain tonight into Friday will be a potent upper low that is
moving thru central Idaho at 08z. This upper low will be in far
NW South Dakota and SW North Dakota at 06z Fri. Models are in
good agreement with this. Surface low will develop this
afternoon and at 00z Fri be located in northwest South Dakota
just east of the upper level low which at that time will be in
NE Wyoming. Sfc low will deepen and winds in the sfc-850 mb
layer will turn southerly and increase in speed this aftn. A
weak sfc boundary at 08z was located from central MN near St
cloud west thru far northern SD. This boundary will strengthen
this afternoon and move north as a surface warm front. 850 mb
warm front as well will develop. The location of both of these
fronts will play a key role in thunderstorm evolution by 21/22z.
Using HREF and other CAMs surface warm front looks to set up
from low pressure near Lemmon SD east-northeast toward Linton ND
to Wahpeton ND into central MN. 850 mb front will be a bit north
of this surface boundary closer to a Bismarck-Jamestown-Fargo-
Park Rapids line. Looking over CAM forecast for t-storm
development it looks like t-storms will form in between the
surface warm front and 850 mb warm front...with storms SE of
Bismarck 21/22z and then developing eastward toward Fargo area
by 00z. Narrow zone of best low level wind shear and significant
tornado parameters in the 1-2 range are in a very narrow zone in
between the surface front and 850 mb front. Various CAMS,
including the 00z NSSl indicated a narrow zone of 1-2 STP in
that area form near Linton to Lisbon to near Fargo-Moorhead.
This zone of where best environment where supercells will form
will I`m sure shift a bit during the day in terms of model
forecasts. Storms forming near the sfc boundary and just south
of the 850 mb boundary are where the best conditions exist for
supercells. You go much farther north of Fargo into the mid RRV
the instability diminishing significantly and becomes highly
elevated above 850 mb. South of the surface boundary as we head
into NE SD low level shear is weaker as winds surface to 850 mb
are south-southeast.

As we go thru the day, the location of supercell potential
development will continue to be monitored. The window for severe
is roughly 22z-02z. Thereafter the 850 mb low level jet takes
over to our south in parts of southern SD into Nebraska with
focus for severe storms shifting south.

Meanwhile though tonight into Friday 500 mb low moves northeast
thru south central into northeast ND with rain on west side
deformation zone Bismarck up thru Devils Lake-Langdon and more
showers/t-storms east of the track. Temps profiles suggest some
potential for a snow/rain mix Friday morning/midday in heaviest
rain in deformation zone over the NW fcst area. Much depends on
precipitation rate and actual dew point depressions and wet
bulb. Turtle mountains being just a bit higher would be the more
likely area to see at least a mix.

Friday will see upper low go just west of Grand Forks with sfc
low near Grand Forks. Location of these features and some CAM
reflecttivity progs indicate potential for low topped supercells
just east of the sfc low in a part of NW MN. Also anytime you
have upper low around some strange things can happen, i.e.
funnels. Will not message this but something to keep in mind.

Memorial Day weekend will see some chance for showers each
day, though not a wash out weekend. Lingering 500 mb troughing
and numerous embedded short waves moving thru will bring shower
chances.

Also Friday night, some frost potential exists in Devils Lake
basin, Langdon areas. How low temps will go highly depends on
cloud cover, and wind. If more clouds, wind then 36 more likely
if clearing occurs then some locations in Towner, Cavalier
counties may drop to near 32F.



&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1140 PM CDT Wed May 22 2024

Look for VFR conditions during the early overnight period with
possible MVFR CIGs working into primarily KBJI by sunrise.
There is a low chance for patchy fog early Thursday morning;
however, location remains uncertain. A period of mainly light
isolated showers prevails from around sunrise through Thursday
mid morning as a weak disturbance traverses the area.

For the period covering midday Thursday through late Thursday
evening, look for a chance for potentially strong thunderstorms
along a cold front and upper low. Impacts are possible during
this time at most TAF sites, with the highest chances at KFAR
and KGFK, and slightly lower chances elsewhere.

&&

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

&&

$$

DISCUSSION...Riddle
AVIATION...Lynch