-- Discussion containing changed information from previous version are highlighted. --
285
FXUS63 KFGF 231742
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
1242 PM 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.

&&

.UPDATE...
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Issued at 1242 PM CDT Thu May 23 2024

Main band of showers has mostly lifted to around Highway 2, but
there is some storms starting to develop in northeastern SD.
This is a bit ahead of schedule according to CAMs so will have
to keep a close eye to see if it is the main show or just some
preliminary convection that could have an impact on how things
develop later.

UPDATE
Issued at 1005 AM CDT Thu May 23 2024

Tweaked POPs a bit for current radar trends, as there continues
to be two bands of rain across the CWA, one just north of the
Highway 2 corridor and another near the I-94 area. These bands
should continue to lift northeastward through the rest of the
morning. Still thinking that the more intense convection will be
moving into southeastern ND around 21Z or so, so will continue
to monitor the instability trends as the afternoon goes on.

UPDATE
Issued at 704 AM CDT Thu May 23 2024

Model data and CAMs since 08z have shown little overall change
to the anticipated conditions later this afternoon. Main
question will remain where surface boundary sets up and
initiation of convection, which still looks to be in between
Aberdeen and Bismarck on the North Dakota side of the border.

Did though expand likely pops for showers and they remain pretty
numerous in the area near or just north of Highway 2 this
morning. There is a break farther west, west of Minot and
Bismarck so do think there is a break coming later this morning.
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&&

.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
reflectivity 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 /18Z TAFS THROUGH 18Z FRIDAY/...
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Issued at 1242 PM CDT Thu May 23 2024

A mix of VFR and IFR as there continues to be showers and low
stratus across portions of our northern forecast area, but
starting to clear out across the south. Additional showers and
thunderstorms will develop and move in later this afternoon and
evening, with convective activity possible at all TAF sites,
confidence highest in strong to severe convection at KFAR during
the 21 to 03Z time frame. The thunderstorms will diminish
overnight and give way to showers, and ceilings that improved to
VFR will lower back down to MVFR or IFR with some lower
visibility down into the 2 to 5SM range with rain and some BR.
The showers will linger into the morning hours on Friday. Winds
will be all over the place as low pressure and several frontal
boundaries cross the area during the TAF period. East to
northeast will shift to the northwest in northern portions of
the forecast area, with southwest winds in the south in the warm
sector for a period tomorrow morning.
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&&

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

&&

$$

UPDATE...Riddle/JR
DISCUSSION...Riddle
AVIATION...JR