059
FXUS63 KFGF 171529
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
1029 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.

&&

.UPDATE...
Issued at 1029 AM CDT Fri May 17 2024

Still trying to time out the potential for severe storms today.
The cap may break around 2100z allowing for convection to
develop. Looking at the available CAPE and low level shear
today`s main threat still looks to be hail and wind. With our
scattered to clear skies this morning we shouldn`t have an
issue with daytime heating. Currently thinking the convection
may start around 23-00z but some of the CAMS had convection
starting as early as 20z but that conditional upon our CAP to
erode become weaker to allow storm development.

UPDATE
Issued at 707 AM CDT Fri May 17 2024

There are still some lingering showers early this morning as a
warm from list northeast, but there is already a clearing/drying
trend behind this. Other than lingering shower mention during
the morning hours, precip timing is still on track.

&&

.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 /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 707 AM CDT Fri May 17 2024

VFR conditions should prevail, with some potential for brief
MVFR conditions if a stronger shower or thunderstorm moves over
a TAF site late afternoon/evening (better chances in eastern ND
but coverage still uncertain for severe in vicinity of TAFs).
There are a few light showers this morning, but more widespread
shower and thunderstorm activity by the evening period. Winds
will tend to shift from the southeast to south and eventually to
the west as a cold front arrives later tonight.

&&

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

&&

$$

UPDATE...MM
DISCUSSION...DJR
AVIATION...DJR