802
FXUS63 KFGF 281748
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
1248 PM CDT Fri Jun 28 2024

.KEY MESSAGES...

- There is a level 1 out of 5 risk for severe thunderstorms
  across the region today in the late afternoon and evening.

- There is a low chance for severe thunderstorms again Monday
  across the region.

&&

.UPDATE...
Issued at 1248 PM CDT Fri Jun 28 2024

Clouds beginning to clear with SFC heating kicking across
eastern North Dakota ahead of the severe threat later on. Two
main scenarios have become favored with a discrete mode or a more
clustered mode. For discrete convection the thought is that
weak funnels and hail as large as ping pongs would be possible
with transient supercell structures following along the
inverted trough across eastern North Dakota. Should we get more
of a cluster mode wind would be predominant as straight
hodographs and storm motions parallel to the inverted trough
seem to conceptually favor this outcome. The problem is CAMs
seem to favor the discrete mode more leading to a spilt in
confidence. Either way a low end threat with a 5% threat for
severe storms this evening.

UPDATE
Issued at 947 AM CDT Fri Jun 28 2024

No change in thoughts for today`s severe risk with rain mostly
clear of the forecast area now aside from a few showers in the
Lake of the Woods area. Has been a persistent area of sub 2 mi
visibility in Pembina and Kittson though seems to be more mist
related than fog based on webcams currently so no SPS needed.
Mist will continue across much of the area through noon as
clouds lift.

UPDATE
Issued at 641 AM CDT Fri Jun 28 2024

Patchy fog has started forming this morning thanks to last
nights moisture. There are lingering showers slowly working
their way out of northwest Minnesota. Expecting by this
afternoon this fog to lift or dissipate as we are mixing out.
The severe risk still seems very conditional and heavy rain
showers or strong thunderstorms may still be the more likely
scenario.

&&

.DISCUSSION...
Issued at 404 AM CDT Fri Jun 28 2024

...Synopsis...

The wave responsible for last nights showers is moving off to the
east into the great lakes region. The upper level low is currently
on the border of Alberta,Canada and Montana. Convective guidance
shows the low moving directly over the Northern Plains and then
exiting the region via the arrowhead before moving back into Canada
over the great lakes. Starting this afternoon this low is depicted
as entering North dakota from the West and having this narrow band
of instability off the frontal boundary that extends into the
valley. However, the moisture and theta-e axis is being pulled
across the arrowhead potential leaving our area with very little to
lift. Looking at model soundings our mixed layer Cape is around 500
joules which could lead to showers and some pretty lightning bolts
but not really severe. However, the catch is the shear profile ahead
of the low is about 30-40kts which is sufficient to sustain storms
if convection were to initiate. With this upper low passing directly
conceptually we can obtain more forcing and instability ahead of the
low but I`m not quite to sure if we have a long enough
destabilization period to help the dynamics produce more than heavy
showers. The model soundings better support heavy rain but SPC did
keep the marginal risk over the majority of that CWA because of the
low passing through. Because of this going to message severe
potential of quarter sized hail and 60 mph just because if we do
reach a long enough destabilization period then we might hit severe
but another round of heavy rain with lightning is probably more
likely.

...Severe threat Monday....

Another mid/upper wave follows a very similar track and evolution as
the system Friday, with a period of widespread showers or embedded
thunderstorms. There is a signal for a deeper warm sector building
into our region within most clusters, and higher probs for SB CAPE
to exceed 1000 J/KG during the peak heating/diurnally favored period
of the afternoon/evening. CSU GEFS based machine learning (15-30%
severe probs) are supported by 100% chance for greater than 55 NBM
CWASP and 50-60% probability for NBM CWASP values exceeding 65. That
aligns with a threat for isolated to scattered severe convection.
This is still farther out, so details/impacts are still inherently
uncertain.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1248 PM CDT Fri Jun 28 2024

As clouds clear this afternoon in eastern North Dakota ceilings
briefly become solidly MVFR everywhere with a few sprinkles
remaining until 20Z in BJI. Gusty NW winds at all sites until
03Z with gusts near DVL already topping 25kts at times. Could
see a few thunderstorms form near DVL around 00Z tracking
southeast towards GFK and FAR by 03Z end ending 06Z accordingly
have added VCTS to the TAFS though further adjustment may be
needed later on for timing. Post storm overnight cigs drop
between 005 and 015 leading to widespread IFR to MVFR with LIFR
still a 20% chance.

&&

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

&&

$$

UPDATE...TT
DISCUSSION...MM
AVIATION...TT