361
FXUS63 KFGF 070839
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
339 AM CDT Tue May 7 2024

.KEY MESSAGES...

- Isolated thunderstorms mainly this afternoon over northeast
  North Dakota and northwestern Minnesota.



&&

.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 convfection 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 nothern or central MN.




&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1142 PM CDT Mon May 6 2024

Kept with the same ideas from the 00z set of TAFs. Still trying
not to chase the showers/storms with too many TEMPO groups.
Showery activity tends to have on and off periods, but think
for at least most of the first 6 hours of the TAF period there
will be more "on" periods. Therefore, will just mention -SHRA
in the predominant group and leave the TEMPO`s off. There has
been some lightning, but overall think that will stay isolated
enough that will leave that mention out too. Put the LLWS in the
TAFs with the 00z issuance, and will keep that through most of
the night as well. Wind speeds have been very challenging, as
some stations are still seeing breezy winds, while others have
lost their gusts. Think those that have lost gusts will get them
back again, and that is really not worth chasing too much
either. Beyond that, have gone with VFR conditions arriving
again by mid to late Tuesday morning, but don`t have much
confidence that it will scatter out. If it does scatter out,
some instability could form again south of the highway 2
corridor, leading to isolated shower/storm development again.
The breezy conditions will return by mid Tuesday morning,
before they decrease again by late afternoon and early evening
(although much less than today).

&&

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

&&

$$

DISCUSSION...Riddle
AVIATION...Godon