469
FXUS63 KFGF 170902
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
402 AM CDT Fri May 17 2024

.KEY MESSAGES...

- Isolated to scattered severe thunderstorms are possible this
  afternoon and evening. Damaging wind gusts to 70 mph and hail
  up to 1 inch in diameter are the main concern.

- There is a 70 percent chance for wind gusts greater than 40
  mph Saturday afternoon and early evening.

&&

.DISCUSSION...
Issued at 402 AM CDT Fri May 17 2024

Zonal flow is favored through the next 7 days, with a trend towards
broader troughing in Canada eventually resulting in "cooler" but
still seasonably mild temperatures. The general zonal/progressive
flow will allow for a series of mid level trough passages and
periodic shower/thunderstorm chances through next week. The focus of
the period is in the shorter range periods where predictability in
impacts is higher.

Severe thunderstorm potential today: Strong WAA develops as BL flow
increases from the south, while westerly flow brings deeper dry air
aloft. Deep mixed layers are advertised and initially forcing is
less organized before the main mid level trough moves east. Surface
convergence during peak heating near several subtle surface troughs
could support discrete initiation (as CINh decreases) and within that
environment a brief/elevated supercell with severe hail main be
possible. These high bases, dry mid level air, and marginal shear do
lower confidence initially in earlier impacts. Main period of focus
will be upstream activity expected to develop near the main wave in
eastern Montana/western ND which CAMs show evolving into a cluster
or linear MCS. Considering the high inverted-V profiles, very steep
low level lapse rates, dry mid levels (resulting in likely dry air
entrainment) and initial 0-3 and effective shear values 30-35kt this
cluster or linear MCS would support severe wind as a primary threat.
Elevated instability may remain high enough as low levels decouple
while a stronger LLJ increases effective and 0-3kt shear (35-43kt)
during the late evening severe wind potential main continue through
midnight as this activity transitions east (threat ending as mid
level lapse rates decrease and elevated instability drops off).

Saturday winds: The main cold front associated with the negatively
tilted mid level trough will have exited the region by Saturday
morning, but in its wake strong unidirectional westerly flow
develops with mixed layer winds 35 to 40kt shown by model soundings
during the daytime/early evening period Saturday. NBM probs highlight
the potential for advisory wind gusts (45mph) with the probs for
gusts over 40 mph 30-70% along and west of the Red River Valley
(higher probs west of the valley).

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 1032 PM CDT Thu May 16 2024

A band of broken precipitation is moving through Griggs, Barnes,
and Ransom counties towards the east affecting FAR within the
6z-10z timeframe. Some embedded lightning and thunder will be
possible at times. There is also an outflow boundary that
extends from Nelson through Sargent county that may bring
isolated gusts up to 30kts as it passes through the Red River
Valley over the next several hours. Isolated chances for showers
for GFK, TVF, and DVL overnight. Conditions dry out after this
main band moves east around sunrise. FEW to SCT clouds post 15z
for all sites, with a BKN cloud deck and precipitation chances
increasing from west to east 21-23z. -TSRA near the end of the
TAF period for all sites as another round of precipitation moves
in.

&&

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

&&

$$

DISCUSSION...DJR
AVIATION...Spender