969
FXUS63 KFGF 071744
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
1244 PM CDT Tue May 7 2024

.KEY MESSAGES...

- A few weak tornadoes, small hail, and gusty winds over 50 mph
  are possible with scattered thunderstorms this afternoon.

&&

.UPDATE...
Issued at 1244 PM CDT Tue May 7 2024

A line of storms has begun to develop along the occluded front
with SRH of 50-100 m^2/s^2 and 3km CAPE of greater than 100 J/kg
leading to an increasing landspout/weak tornado threat with any
cell that can efficiently stretch the ambient vorticity along
the front. Could also see some small hail and gusty winds to 50+
mph as these storms move north/northeast at 45 mph.

UPDATE
Issued at 932 AM CDT Tue May 7 2024

Forecast remains on track with rain through the early afternoon
in the north before the dry slot moves in from the south. A few
shallow top thunderstorms will likely form along a differential
heating boundary propagating north through the dry slot along
the backside of the cloud cover. Would expect main hazards to be
lightning and gusty to winds to 40mph. Timing of these
thunderstorms would be roughly 2pm to 8pm Along and north of
I-94.

UPDATE
Issued at 714 AM CDT Tue May 7 2024

Rain band filled in the past 2 hours with light rain now from NE
ND southeast into central MN, moving NW. This aligns pretty good
with pops and will see the higher precip chances gradually lift
north this morning...with high pops remaining NE ND and parts of
NW MN thru the day. Showers will come to an end in SE ND and WC
MN as the band shifts north.

&&

.DISCUSSION...
Issued at 317 AM CDT Tue May 7 2024

500 mb low at 08z as over northwest South Dakota. Moisture feed
around this system is from northern Arkansas to central
Minnesota then back west-northwest across parts of North Dakota
and into southern Saskatchewan and Alberta. What has been
noticed is that moisture from the south as been weakening the
past 6 hours, perhaps due to convection from Iowa to northern
Arkansas. The trends in radar with showers moving NNW from
central MN is for diminishing returns as they move toward the
RRV. Thunderstorm chances have dropped greatly since 06z and
likely to remain thru 16z based off of SPC HREF Calibrated
Thunder fcst and HREF lightning prog via DESI. So through 16z
shower activity looks to be on the light side moving NNW thru MN
into eastern ND.

This afternoon will see upper low move a tad east to west of
Bismarck with sfc low drifting a bit NNE into southwest ND near
Hettinger. A trough rotating around this upper low/sfc low will
move into NE SD midday and then into SE ND mid to late aftn
with a subtle wind shift from southeast to south. Also drier
airmass moves in. Clearing chances appear limited and in this
area of SE ND/far WC MN (Valley city-Fargo-Fergus Falls-Wadena)
chances for afternoon showers or t-storms is quite low.

Farther north, north of the boundary 0-6 km shear is quite
strong near 40 kts due to stronger 850 mb winds but by 20z 850
mb winds are in the 35-40 kt range vs 50-55 kt currently. So
some shear exists but instability looks very weak...barely
100-250 j/kg and no sfc heating is anticipated with aftn temps
in the low 60s. With upper low sufficiently far enough west and
colder 500 mb temps wrapping around the system and more into
Nebraska thinking is that some t-storms will form in a narrow
axis from near DVL-GFK-BJI area mid aftn and move north, but
lack of instability, lack of cold air aloft, will prevent much
development. Bufkit soundings for GFK show a nearly vertical
temperature column from sfc to 500 mb with very limited CAPE
(50-100 j/kg). This is from both NAM and GFS models. So net
result is thinking any chance of a stronger storm is very low
(5 pct).


Chance for showers Wednesday as upper system drops south but
drier air also moves back in from the north. Instability is
focused in southern MN, so covearge of showers look scattered.
Clearing Wed night into Thursday.

GFS/ECMWF ensembles show 500 mb ridging into Alberta and
Saskatchewan Thu-Fri period and enough to height falls over the
Great Lakes for an upper level wave to drop south-southeast into
Minnesota Friday. This will give chances for showers, and with
some colder air aloft with wave several hundred CAPE and a
chance for a few t-storms mainly in northern or central MN.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1244 PM CDT Tue May 7 2024

CIGS lifting to VFR across most sites this afternoon with clearing
area moving in, however CU/SHRA development may keep some MVFR CIGS
through the afternoon before drier air moves in with the upper low
in place and CIGS become VFR overnight. Winds to be more
southeasterly to southerly through the period with gustiness
continuing this afternoon, and should start to see diminishment in
the gustiness overnight. May still see some lower CIGS in the far
north/east build back in late tonight toward sunrise as the main
upper level system wobbles around just to the west of the area.

&&

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

&&

$$

UPDATE...TT
DISCUSSION...Riddle
AVIATION...MJB