Special Weather Statement, NWS Grand Forks, ND

Area Forecast Discussion
National Weather Service Grand Forks ND
703 PM CDT Sat Aug 5 2023

.UPDATE...
Issued at 659 PM CDT Sat Aug 5 2023

Upper low continues to move east-southeast this evening. Showers
and embedded thunderstorms are forming, generally in waves, in
areas to the east of the Red River, with more stratiform activity
to the west. Some of the updrafts have been strong enough to
produce funnel clouds as low-level vorticity is rather high. This
threat will diminish through the evening.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 341 PM CDT Sat Aug 5 2023

-Rain showers with embedded (scattered) thunderstorms are on track
to overspread southeast ND and west central MN through the evening
hours/overnight transitioning southeast through Sunday. Lightning
will be the main threat, and severe thunderstorms are not
anticipated. A few stronger storms capable of small hail and gusts
to 40 mph will still be possible.

-Localized heavy rain may lead to excessive runoff if rates are high
enough (3"+/hr), particularly in locations near the SD border where
earlier thunderstorm activity occurs. The probability for higher
rates is low in all by our far south (south of I-94), with
probabilities shifting towards SD/southern MN for 2"+ totals.

The main mid level circulation is deepening over central SD in line
with the southerly track that had been favored on ensemble/forecast
trends in the last 24hr. As a result the strongest signal for broad
heavier rain has shifted south. We are seeing broad areas of
moderate rainfall with embedded thunderstorms filling in the
northern side of this circulation along the warm conveyor belt and
eventually this should move into the I-94/US10 corridor early this
evening. Elevated instability in the RAP is 1000+ J/KG but
skinnier profiles are favored and cloud cover would limit surface
based convection. As a result even the strongest updrafts will
mainly favor heavy rain/smaller hail and max gusts to 40 mph.
Still, with at least some potential for training within these
heavier rain pockets there is potential for 1-3"/hr rates. Over
dry soils we would likely need 4-5"/hr rates for flash flooding,
but preconditioned locations could support excessive runoff if 3"+
rainfall fell over 6hr (mainly near the SD border).

Additional storms are forming near the cold front as an inverted
trough is beginning to form ahead of the norther wave/mid level jet
in Canada. The interaction of these features is still highlighted by
CAMs to resulting in organized deformation in our east-southeast late
this evening into the overnight/early morning hours with broad light
to moderate rainfall. HREF probs show 90%+ probs for 0.01" per hour
during those periods while blended ensemble 12hr probs for 0.1"+ are
60-80%. The probability for 0.5" and 1.0"+ 6hr probs drops off
quickly (main to the south of I-94) and for those values
thunderstorm activity would likely need to occur farther north).
THe entire deformation area of rain should decrease in intensity
and transition southeast through Sunday morning, with dry
conditions arriving by midday based on current timing/consensus.

.LONG TERM...(Monday through Saturday)
Issued at 341 PM CDT Sat Aug 5 2023

-The pattern will support low probabilities for showers or
thunderstorms, with the probability for hazardous weather low through
the long term periods.

-Temperatures will tend to remain near seasonal normals early in the
week, with below average temperatures (by 5-10F) favored late next
week into next weekend.

Large scale mid/upper level pattern will tend to be dominated by
relatively flat NW zonal flow in our region as a result of broad
ridging in the southwest US and a more elongated Hudson Bay low in
Canada. There is variance in the strength and exact position of those
upper level features, but the main impact on the pattern locally
between the various clusters is on the timing/track of progressive
weak mid level shortwaves. Due to the flow and limited southerly
return before each cold front (and tendency for moisture return to
be from drier parts of Canada) the potential for wetting
precipitation (0.1") and instability will be low with each of these
waves and associated fropas. As a result there isn't a signal for
severe potential in NBM CWASP or GEFS based machine learning from
CSU.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 634 PM CDT Sat Aug 5 2023

MVFR conditions are possible tonight as showers and embedded
thunderstorms move across the area. An upper low will pass to our
south overnight and into Sunday morning, which will gradually
shift the winds more out of the north. As this happens, showers
will be winding down in coverage, with slow improvements in
ceilings. Visibility is expected to remain 5SM or higher,
especially outside of heavier shower activity. VFR conditions
develop by mid-morning Sunday.

&&

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

UPDATE...Lynch
SHORT TERM...DJR
LONG TERM...DJR
AVIATION...Lynch

Preliminary Local Storm Report
National Weather Service Grand Forks ND
726 PM CDT Sat Aug 5 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0700 PM     Rain             2 WSW Brampton          45.98N 97.82W
08/05/2023  M4.04 inch       Sargent            ND   Mesonet

            NDAWN report.

&&

TT

Special Weather Statement
National Weather Service Grand Forks ND
732 PM CDT Sat Aug 5 2023

MNZ027-028-060115-
West Becker MN-East Becker MN-
732 PM CDT Sat Aug 5 2023

...A strong thunderstorm will impact portions of central Becker
County through 815 PM CDT...

At 732 PM CDT, Doppler radar was tracking a strong thunderstorm near
Rochert, or 10 miles east of Detroit Lakes, moving northwest at 10
mph.

HAZARD...Penny size hail.

SOURCE...Radar indicated.

IMPACT...Minor damage to outdoor objects is possible.

Locations impacted include...
Height Of Land Lake and Rochert.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4683 9553 4677 9563 4690 9583 4701 9562
TIME...MOT...LOC 0032Z 139DEG 9KT 4684 9563

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...<30 MPH

Lynch

Special Weather Statement
National Weather Service Grand Forks ND
807 PM CDT Sat Aug 5 2023

MNZ027-060130-
West Becker MN-
807 PM CDT Sat Aug 5 2023

...A strong thunderstorm will impact portions of southwestern Becker
County through 830 PM CDT...

At 807 PM CDT, Doppler radar was tracking a strong thunderstorm over
Detroit Lakes, moving northwest at 15 mph.

HAZARD...Penny size hail.

SOURCE...Radar indicated.

IMPACT...Minor damage to outdoor objects is possible.

Locations impacted include...
Detroit Lakes.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4680 9578 4675 9584 4684 9600 4691 9591
TIME...MOT...LOC 0107Z 136DEG 13KT 4680 9585

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...<30 MPH

Lynch