Marine Hail in Lake Superior, April 5, 2021

Area Forecast Discussion
National Weather Service Duluth MN
1015 PM CDT Mon Apr 5 2021

.DISCUSSION...(This evening through Sunday)
Issued at 253 PM CDT Mon Apr 5 2021

Near critical fire weather conditions across northeast Minnesota
this afternoon, a threat for thunderstorms possibly severe this
evening, all followed by very much needed rainfall mid to late
this week highlight the forecast.

High temperatures in the 70s with relative humidity between 10 and
20 percent will continue this afternoon into the early evening
across much of northeast Minnesota away from the influence of Lake
Superior. When combined with dry fuels and southeast wind gusts to
20 mph, near critical fire weather conditions are possible.

Most of northeast Minnesota and northwest Wisconsin are in a
Marginal Risk from SPC for severe thunderstorms for this evening,
with a Slight Risk from the Brainerd Lakes area through the I-35
corridor. The threat is greatly dependent on moisture return south
of a warm front that has made its way from the Brainerd Lakes
through Hayward and Phillips as of 20 UTC. Even still dewpoints
to the south of the warm front that will continue to advect into
the Northland look even more marginal than before with values in
the lower 40s to the lower 50s. Thus, the best chance for severe
convection, and perhaps just thunderstorms themselves is from the
Brainerd Lakes area towards the I-35 corridor and into northwest
Wisconsin where moisture will be greatest. Dewpoints as low as the
teens and 20s across much of the Arrowhead of Minnesota as well
as a far inland reaching lake breeze will limit the threat for
these areas.

Regarding forcing, a cold front across northwest Minnesota will
propagate east to an International Fall to Brainerd line around 00
UTC, arriving across western Lake Superior around 06 UTC. MLCAPE
around 1000-1500 j/kg with steep mid level lapse rates and around
30-35 kts of deep layer shear largely orthogonal to the cold front
supports the conditional severe threat for scattered
thunderstorms possibly severe this evening. Again this is
dependent on moisture return from the south. The 12 UTC CAM suite
shows a large spread of solutions from very little organized
convection, to the more relatively intense HRRR and FV3-SAR. Large
hail to around half dollar size and damaging wind gusts to 60 mph
with remain the primary threats with high based discrete storms
along the cold front, with convection eventually growing upscale
as the warm front continues to propagate north, intersecting with
the cold front.

Looking ahead to Tuesday night through at least Friday, a very
slow moving and closed system will impact the Upper Midwest with a
very broad precipitation shield. This is favored to bring very
much needed widespread rainfall to the region, possibly 1 to 2
inches by Saturday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 649 PM CDT Mon Apr 5 2021

A warm front has moved north into far northern Wisconsin and
extended west toward a cold front that was into north central
Minnesota. Showers and thunderstorms were occurring ahead of the
cold front as far east as northern Wisconsin and the Arrowhead. We
expect these to continue and others to form along and just ahead
of the cold front this evening. Some strong to possibly severe
storms will be possible with the main threats strong wind and hail
around to just over an inch in diameter. Conditions for most areas
will remain VFR but with the stronger storms/showers, brief
periods of MVFR or even IFR will be possible. The front will
continue east overnight and clear the Arrowhead and northern
Wisconsin late tonight into early Tuesday morning. Winds will
switch to northerly behind the cold front.

Some low level wind shear will occur this evening, mainly
affecting KHYR but possibly KDLH briefly.

&&

.MARINE...
Issued at 1015 PM CDT Mon Apr 5 2021

Winds have diminished some from what they were earlier today.
However, showers and thunderstorms will continue to move across
western Lake Superior for the next several hours and locally
higher winds and waves will occur near them. Gusts to 40 knots
will be possible with the strongest storms and hail to nickel size
will also be possible. These storms will occur ahead of a cold
front which will move across the lake tonight switching the wind
to northerly for a time. There may also be brief gusts to 25 knots
with frontal passage.

Tuesday will be dry with winds veering to east to northeast but
remaining at or below 15 knots. An area of low pressure will bring
widespread rain into the area later Tuesday night into Wednesday.
East to northeast winds will increase and be form 15 to around 20
knots with higher gusts by Wednesday morning and they will
strengthen further Wednesday into Wednesday night. Some gales will
be possible Wednesday into Wednesday night.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  41  55  39  44 /  40  20  90  80
INL  33  56  35  51 /  10   0  10  60
BRD  41  61  42  51 /  30  20  90  80
HYR  47  60  44  60 /  50  50  90  70
ASX  43  53  39  50 /  50  20  90  70

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&

DISCUSSION...PA
AVIATION...Melde
MARINE...Melde

Hazardous Weather Outlook
National Weather Service Duluth MN
1023 PM CDT Mon Apr 5 2021

MNZ010>012-018>021-025-026-033>038-WIZ001>004-006>009-070330-
Koochiching-North St. Louis-Northern Cook/Northern Lake-
North Itasca-Central St. Louis-Southern Lake/North Shore-
Southern Cook/North Shore-North Cass-South Itasca-South Cass-
Crow Wing-Northern Aitkin-South Aitkin-Carlton/South St. Louis-
Pine-Douglas-Bayfield-Ashland-Iron-Burnett-Washburn-Sawyer-Price-
1023 PM CDT Mon Apr 5 2021

This Hazardous Weather Outlook is for portions of northeast
Minnesota and northwest Wisconsin.

.DAY ONE...Tonight

Scattered thunderstorms will continue from near Mille Lacs Lake
northeast into the Arrowhead and over all of northern Wisconsin
late this evening but will diminish from west to east after
midnight. A few storms could be strong to severe with large hail
to around half dollar size, damaging wind gusts to 60 mph and
dangerous lightning. The best chance for severe weather will be
from east central Minnesota into northern Wisconsin. Storms over
far eastern Minnesota into northern Wisconsin will continue into
the early morning hours.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

There is a slight chance of thunderstorms across northeast
Minnesota and northwest Wisconsin Tuesday night and Wednesday.
Severe weather is not expected.

.SPOTTER INFORMATION STATEMENT...

Skywarn spotters may be needed tonight.

LSZ121-140>148-150-070330-
Bayfield to Oak Point WI-Grand Portage to Grand Marais MN-
Grand Marais to Taconite Harbor MN-
Taconite Harbor to Silver Bay Harbor MN-
Silver Bay Harbor to Two Harbors MN-Two Harbors to Duluth MN-
Duluth MN to Port Wing WI-Port Wing to Sand Island WI-
Sand Island to Bayfield WI-Oak Point to Saxon Harbor WI-
Outer Apostle Islands Beyond 5 NM from Mainland-
1023 PM CDT Mon Apr 5 2021

This Hazardous Weather Outlook is for portions of Lake Superior
and the Nearshore waters of western Lake Superior.

.DAY ONE...Tonight

Scattered thunderstorms are possible across the western Lake
Superior nearshore waters tonight. A few storms could have small
hail and wind gusts to 40 kts.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

Northeast gales may be possible Wednesday and Wednesday night

Melde

More information may be obtained at the following web address:
http://www.weather.gov/duluth (all lower case)

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DULUTH MN
1218 AM CDT TUE APR 6 2021

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

1210 AM     HAIL             2 S AMNICON FALLS S.P.  46.57N 91.89W
04/06/2021  E0.25 INCH       DOUGLAS            WI   PUBLIC

&&

KL

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DULUTH MN
1219 AM CDT TUE APR 6 2021

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

1200 AM     HAIL             1 ENE DULUTH            46.78N 92.11W
04/06/2021  E0.25 INCH       ST. LOUIS          MN   TRAINED SPOTTER

            THREE-EIGHTHS INCH HAIL.

&&

KLH