726
FXUS63 KFGF 011734
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
1234 PM CDT Mon Jul 1 2024

.KEY MESSAGES...

- There is a level 1 out of 5 risk for severe thunderstorms this
  afternoon and evening across much of the forecast area, with
  a level 2 out of 5 risk for severe thunderstorms along and
  south of Interstate 94.

- A system is expected to bring numerous showers and
  thunderstorms to parts of the Northern Plains on Independence
  Day, with a low chance for severe thunderstorms.

&&

.UPDATE...
Issued at 1234 PM CDT Mon Jul 1 2024

As expected, the main area of precipitation on radar has been
shifting into northwest Minnesota (seeing a 45 knot low level
jet focused into this area). NDAWN and several spotter reports
indicate some locations under these echoes have received over 1
inch of rain so far. The office here in Grand Forks has had a
few decent showers roll overhead and we have picked up about a
tenth of an inch. Looking out to the west (western North Dakota)
where additional convection is possible near the surface front,
it has become cloudy again. This is going to limit the
instability, making it tougher to get much organized activity
going again this afternoon.

UPDATE
Issued at 1003 AM CDT Mon Jul 1 2024

Most of the echoes on the regional radar this morning were
centered over the northern Red River Valley. Per the latest SPC
mesoanalysis page, this is driven by a piece of 700mb shortwave
energy and the low level jet (40 knots). Throughout the rest of
the day, the 700mb wave will lift into Canada, but the low
level jet will linger (and increase through the afternoon, but
it will remain east of the Red River Valley). Recent CAMs
indicate the most activity today transitioning from the northern
Red River Valley into northwest Minnesota, and mainly along the
Canadian border. Any shower/storm activity elsewhere looks to
fairly isolated. More activity may move into eastern North
Dakota this evening, as storms that fire closer to the surface
front over western North Dakota move eastward.

UPDATE
Issued at 645 AM CDT Mon Jul 1 2024

There is one cluster of showers/thunderstorms in northeast ND
(higher coverage), with isolated showers/thunderstorms near our
far eastern counties (Beltrami/Lake of the Woods). This matches
trends from CAMs and earlier HREF mean. Some adjustments to
refine coverage are necessary, the general forecast remains on
track this morning with a likely delay in new development for
some locations (namely south) until midday or early afternoon.

&&

.DISCUSSION...
Issued at 404 AM CDT Mon Jul 1 2024

...Synopsis...

Large scale flow remains progressive across the Northern Plains,
with a series of mid level shortwave troughs. This larger scale
pattern shows strong consensus in ensembles, with variances in
specific tracks and strength of some of the waves and surface
features. The strongest/most organized mid level waves are today
and another on Thursday (Independence Day Holiday), with less
organized/more diffuse forcing between these waves keeping
shower/thunderstorm chances. There is a larger spread in the
evolution of the large scale pattern late next weekend and
early next week, with a subset of clusters favoring more
amplified ridging versus a larger percentage of ensembles
favoring NW flow over our region. Overall, temperatures are
favored to trend back towards seasonal averages through the
week, with a much larger spread in highs by next week (chance
for above normal temperatures).

...Today...

Initial showers that developed early this morning have been
associated with an axis of 700MB WAA within SW flow ahead of the
main mid level trough (still located over the Northern Rockies). A
cluster of showers and embedded thunderstorms (a few stronger) are
shown by CAMs to arrive in our northwest later this morning, but
the severe threat should be delayed due to narrower limited CAPE
profiles locally. Strong low level moisture advection is
underway and additional isolated-scattered shower/thunderstorms
may develop within less organized forcing through the day
before the main wave approaches and a strengthening LLJ
organizes activity into larger areas of showers and
thunderstorms this evening (evolution well represented by all HREF
members). Widespread rain totals exceeding 0.5" should be
expected (particularly this evening/overnight) with a strong
signal in HREF PMM for one or more swaths of 1-2" rainfall
(strongest signal north). Hydrological this wouldn`t be enough
for excessive runoff/flash flooding in our area outside of urban
areas with poor drainage, though additional/eventual rises on
rivers would be possible.

As surface low pressure deepens southeast BL flow may
increase and there is a signal in some guidance for near
advisory winds across the southern RRV, though mixing heights
appear limited due to a strong elevated inversion/warm nose and
persistent stratus.

This stratus stable layer also plays a role in limiting potential
impacts from deeper convection that may develop this afternoon and
evening. Parcel traces remain very elevated and while elevated CAPE
does increase as the LLJ builds east (along with strong deep layer
shear) the potential for surface based parcels is not reflected and
DCAPE is minimal (well under 500 J/KG). This raises the possibility
that most activity will tend to be heavier rain with a few stronger
cores supporting large hail to around 1". Wet downbursts can`t be
ruled out though considering the shear profiles, especially if there
are any linear segments that become orthogonal to higher shear
vectors. This may be less prevalent due to the stable low levels,
limiting confidence/coverage for our area in a wind threat.

...Independence Day Rain and Severe Threat...

The system Thursday continues to show good agreement in timing and
broader track at 500/700MB. However, the specific strength/evolution
and exact track all shift surface features and create higher spread
in potential rain totals and any severe potential. There is still a
low chance for severe storms (5% probs on CSU GEFS based machine
learning), but little confidence in those types of details at this
range. Despite the variances, there is still a strong signal for
showers and thunderstorms during the afternoon/evening period which
even if not severe could impact Independence Day festivities.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1234 PM CDT Mon Jul 1 2024

Low clouds (MVFR to IFR) are creeping slowly to the east, and
will likely hold through most of the night. This will be the
main aviation impact outside of any thunderstorm activity. Most
of the current convective activity has shifted from KGFK into
northwest Minnesota. The visibility briefly dropped under 2SM as
the heavier rate rains moved through KGFK, otherwise
visibilities have been P6SM. This afternoon activity may clip
KTVF yet, but should mainly stay closer to the Canadian border.
CAMs still show additional thunderstorm development back along
the surface front over western North Dakota this afternoon, then
track it into this FA during the evening. If this activity does
develop, it could bring another period of about 2 hours of
showers or thunderstorms tracking through. After this passes,
clouds should slowly decrease, and it may clear or scatter out.
As far as winds, they have been all over the place this morning,
varying from light to gusting to 38 knots. It should stay on
the gusty side through the afternoon into evening, with some
decrease showing up late tonight into Tuesday morning.

&&

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

&&

$$

UPDATE...Godon
DISCUSSION...DJR
AVIATION...Godon