478
FXUS63 KFGF 041758
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
1258 PM CDT Fri Jul 4 2025

.KEY MESSAGES...

- There is a level 2 out of 5 risk for severe storms in the
  afternoon and evening today. Main hazards will be flash
  flooding, wind gusts to 60 mph, and hail to the size of
  quarters, along with frequent lightning.

- Heat related impacts today due to high temperatures and high
  dew points.

&&

.UPDATE...
Issued at 1130 AM CDT Fri Jul 4 2025

As 12Z CAMs/HREF continue to show the signal for the
horizontally orientated/back-building linear complex where
5-15kt corfidi vectors support backbuilding along the northern
theta-e gradient/frontal zone. The upper end of guidance
supports PWATs exceeding the 95-99th percentile and considering
the reservoir of high instability/deep warm soundings would
increase the potential for thunderstorms to produce greater than
1"/hr rates. Antecedent soil conditions are more hit or miss in
rural parts of the region due to the dry nature of the summer
and soils in many areas, so it will likely take 3-6" rainfall
over a short enough duration to increase the chance for impacts
outside of poor drainage areas.

Highest probs for 1"+/hr rates from Valley City to Baudette and
to the southeast of that axis. Confidence has increased enough
to issue the Flood Watch for excessive runoff/flash flood
potential focused on the locations that have the best potential
to see higher durations of heavier rates from 4PM through 1AM
tonight.

UPDATE
Issued at 1014 AM CDT Fri Jul 4 2025

We are currently in a "lull" regarding organized convection
within our CWA with light showers lingering from the overnight
activity transitioning to the northeast and a strong cap in
place. Deep BL moisture is pooling across our CWA this morning
with Tds in the low 70s approaching 75 in the south.
temperatures area already in the middle 80s at 10am and
ML CAPE already exceeds 2000 J/KG. The focus for convection
will be the baroclinic zone/theta-E axis near the Highway 2
corridor and we are monitoring the latest 12Z data as it comes
in for any adjustments to timing/coverage. Trends continue to
favor initiation shortly after peak mixing at 21Z (4pm). The
signal for back-building/training along that zone within the
Hwy 2 corridor is a concern considering the anomalous PWATs
(1.5" or greater), so if the signal within that zone remains a
Flood Watch for excessive rainfall/flash flooding may be
considered early this afternoon.

UPDATE
Issued at 724 AM CDT Fri Jul 4 2025

The last of the showers and t-storms with the t-storm complex is
exiting Lake of the Woods while a small area of showers are
moving northeast to the north of Devils Lake. I would suspect by
14z or so no precipitation will be in the fcst area. Enough sun
as the clouds clear out to warm everyone up as forecast. 06z NAM
and latest HRRR indicate continued good agreement in having a
boundary and t-storm development around 21z Warroad to Grand
Forks to Cooperstown.

&&

.DISCUSSION...
Issued at 308 AM CDT Fri Jul 4 2025

...Synopsis...

Outflow boundary with north-northeast winds has been dropping
south and and passed Devils Lake and will likely go through
Grand Forks, Thief River Falls with main rainfall activity and
t-storms holding farther north closer to the border.

This wind shift should wash out this early morning with winds at
12z likely turning back southeast or be light/variable in
northeast ND and far NW MN, with a south wind 10-25 kts in SE ND
and WC MN. Frontal boundary at 12z likely will still be well
northwest of the area from near Estevan into northeast Montana.
This frontal boundary moves east. It seems that short term
models want to develop t-storms early to mid aftn in the zone of
more variable wind right ahead of the front where it bumps up
with a steadier south wind. That boundary looks to be from about
Roseau to Grand Forks to Cooperstown at 00z.

Cooler and less humid airmass follows for the weekend.

...Severe risk and heavy rain potential for this afternoon and
tonight...

Models in general agreement in developing an axis of
thunderstorms by 21z along a boundary from near Roseau/Warroad
to Grand Forks to Cooperstown to Jamestown/Bismarck. Sfc CAPE
from NBM 3km shows over 4000 j/kg just ahead of boundary at 21z
where temps likely in the mid 90s Bemidji to Fargo. potential
Sfc CIN values at that time becomes negligible, or forecast to
be. Thus a rapid increase in storms anticipated around 21z along
the boundary and the area of storms will grow and slide
gradually east/southeast in time thru the evening. PWATs around
2.3 inches would certainly favor heavy rainfall potential with
high rainfall rates leading to potential for urban flooding.
Most of the area in June saw rainfall deficits of 1.50 to 3
inches in the area where storms will form and where highest
rainfall amounts are forecast. Thus feel outside of rapid
rainfall rate flooding in areas of poor drainage, streets, the
ground will be able to absorb most of it where it falls on
grassy surfaces, fields. No flood watch issued at this time due
to this and usual uncertainty in exactly where heaviest rainfall
will be.

Severe weather is more uncertain. Early on in the development of
the line, large hail and wind gusts 60 mph or higher is possible
before it turns into more of a heavy rain threat. SPC has area
in 2 pct tornado threat and think that would be short lived and
in the early stages of development.

Shower and t-storm chances linger in SE ND into MN into much of
Sunday before pushing east.

...Heat today...

Heat indices will reach the upper 90s to low 100s in most areas,
except DVL basin. So will maintain the heat advisory. Wet bulb
globe temp is in the high and extreme values (mid 80s).

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1258 PM CDT Fri Jul 4 2025

Thunderstorm activity which is expected to increase in coverage
after 21Z is going to the be primary aviation impact through the
first 12hr of the TAF period. Many storms will be capable of very
heavy rain and LIFR visibilities, while a few severe
thunderstorms may develop (lower coverage) with large hail and
brief gusts around 60 mph the main threats. We will be
monitoring the severe development and amend as needed. As a cold
from pushes east and rain begins to transition across MN an axis
of MVFR (pockets of IFR) stratus may develop late in the TAF
period.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...Heat Advisory until 7 PM CDT this evening for NDZ027-029-030-
     038-039-049-052-053.
     Flood Watch from 4 PM CDT this afternoon through late tonight
     for NDZ027-029-030-038-039.
MN...Heat Advisory until 7 PM CDT this evening for MNZ001>003-
     005>009-013>017-022>024-027>032-040.
     Flood Watch from 4 PM CDT this afternoon through late tonight
     for MNZ001>003-006-008-009-013>017-022>024-027-028.

&&

$$

UPDATE...Riddle/DJR
DISCUSSION...Riddle
AVIATION...DJR