909
FXUS63 KFGF 010904
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
404 AM 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.

&&

.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 /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1150 PM CDT Sun Jun 30 2024

Gusty winds from the south during the day on Monday. Ceilings
will lower into MVFR and eventually IFR in some locations on
Monday, but not until afternoon or even the evening. Scattered
storms on Monday, but confidence in location not high enough
yet to include, although trends are that most sites will
experience at least brief periods of thunder, mainly later
afternoon into the evening hours.

&&

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

&&

$$

DISCUSSION...DJR
AVIATION...AH