Special Weather Statement, NWS Twin Cities, MN

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
631 AM CDT Wed May 11 2022

.DISCUSSION...(Today through Tuesday)
Issued at 236 AM CDT Wed May 11 2022

* KEY MESSAGES:

- Conditions favor severe storms/supercells with large hail and
  possible tornadoes this afternoon. Tornado threat maximized near a
  warm front.

- Heavy rain/flash flooding is an increasing threat tonight especially
  if storms end up tracking over the same locations.

- More severe storms expected Thursday, highest threat across western
  Minnesota.

An active two days are in store with an unseasonably warm and humid
airmass over the Central/Northern Plains setting the stage for
several rounds of strong storms as a large trough approaches from the
west. Currently a well-defined surface warm front stretches west-
to-east near I-80 in Iowa with the 850-hPa boundary further north
over southern Minnesota. This elevated boundary is already sparking a
few showers/weak storms near I-90 which is a signal of things to
come later today as the front quickly lifts northward. Currently a
lack of defined upper-level ascent and very dry air above 850 hPa
are keeping these cells limited in coverage and strength, and this
should continue to be the case through early/mid afternoon as upper-
level heights rise and the warm front surges north into central MN.

By late this afternoon storms are expected to rapidly grow across
southwest Minnesota as an upper wave approaches from the west and
feeds an increasing low-level jet toward the northward-advancing warm
front. A surge of warm and humid air from the south will bring
temperatures in the mid/upper 80s into southern MN with dewpoints
rapidly rising into the lower 70s. The resulting strong instability
combined with deep-layer shear of 50-60 kts will be more than
favorable for strong supercells capable of very large hail,
especially those that can develop near and just south of the warm
front where storm-relative helicity will be maximized. This helicity
could also favor tornadoes near the warm front, although this threat
is much more conditional on LCL heights and potential for strong/cold
downdrafts to lessen a prolonged tornado threat...as well as storm
motion which may cause storms to cross north of the warm front and
become more elevated in nature. These factors will need to be
watched closely this afternoon to see if and where a more localized
enhanced tornado threat can develop if these factors can become
overcome.

Storms should increase in coverage this evening as they push into
central/eastern Minnesota and eventually western Wisconsin. Large
hail, wind and isolated tornadoes will remain a threat through this
time, however the main focus through this period will be an
increasing threat for very heavy rain and flash flooding. This will
especially become true toward sunset as storm motion vectors veer to
become more parallel to the warm front, and an increasing LLJ feeds
copious moisture into the boundary. Widespread 1" to 2" rainfall
amounts seem probable from southern MN into areas near/just north of
the Twin Cities and into northwest Wisconsin. If storms end up
training repeatedly over a few locations then isolated amounts of 3"
or 4" would not be out of the question.

Once storms clear out late tonight, attention will turn to
unseasonable heat and humidity on Thursday followed by another round
of strong to severe storms. With 850 hPa temperatures rising to as
high as 22C, full mixing would favor surface temperatures as high as
the lower 90s. Combined with dewpoints in the upper 60s/near 70 this
would push heat index values in the lower or even mid 90s. This could
approach heat advisory criteria especially for the Twin Cities, but
will need to watch a couple of factors before pulling the trigger on
this, namely 1) potential for cloud cover to cut back on full heating
and 2) lower dewpoints mixing down and keeping heat index values
limited.

Regardless of how high Thursday's temperatures get, the airmass will
once again be very unstable setting the stage for another round of
strong to severe storms Thursday afternoon and evening as the main
upper trough to the west pushes through. Shear profiles will once
again favor supercells with large hail and a few tornadoes,
especially early in the event over western MN and also closer to the
warm front over central/northern MN, but given the extent of the
upper forcing a more linear storm mode appears favorable with
damaging winds a higher threat. How widespread these winds can become
will depend on shear/cold pool interactions which will need to wait
until closer to the event to be better assessed. Higher moisture
could prevent outflow from surging ahead of the storms too quickly,
which would favor a more long-lived wind event as the storms push
toward the Twin Cities and western Wisconsin. Heavy rain will again
be possible, but not as high as Wednesday's threat given a quicker
west-to-east progression of the overall system.

Behind Thursday's strong storm system, a transition to more zonal
upper flow will bring somewhat cooler and much drier air into the
area for Friday and into the weekend. With temperatures in the
lower/mid 70s and dewpoints in the 40s and 50s, we should get to
enjoy quite a nice spring weekend across the area...a seeming rarity
this spring so far.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 624 AM CDT Wed May 11 2022

Strong storms currently south of KMSP should eventually weaken but
may get close to MSP if current trends continue. Otherwise VFR today
with gradually veering winds to SE. Complex of strong storms expected
to develop over southwest and western MN late this afternoon and
spread into MSP area and points north late evening into the early
morning. Damaging wind gusts possible when these storms come through.

KMSP...
Strong storm to the south should begin weakening as it approaches
MSP, but may hold together long enough to impact the terminal. Will
monitor storm trends and add thunder to TAF shortly if current trends
continue. Otherwise more widespread storms expected near or shortly
after sunset and could be strong/severe with high wind.

/OUTLOOK FOR KMSP/
Thu...VFR/MVFR, chc SHRA/TSRA. Wind S 10-15G25 kts.
Fri...Mainly VFR. Wind SW 10 kts.
Sat...VFR, chc pm MVFR with -SHRA. Wind WNW 10-15g25kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
&&

DISCUSSION...DPH
AVIATION...DPH

Hazardous Weather Outlook
National Weather Service Twin Cities/Chanhassen MN
1252 PM CDT Wed May 11 2022

MNZ041>045-047>070-073>078-082>085-091>093-WIZ014>016-023>028-
121500-
Douglas-Todd-Morrison-Mille Lacs-Kanabec-Stevens-Pope-Stearns-
Benton-Sherburne-Isanti-Chisago-Lac Qui Parle-Swift-Chippewa-
Kandiyohi-Meeker-Wright-Hennepin-Anoka-Ramsey-Washington-
Yellow Medicine-Renville-McLeod-Sibley-Carver-Scott-Dakota-
Redwood-Brown-Nicollet-Le Sueur-Rice-Goodhue-Watonwan-Blue Earth-
Waseca-Steele-Martin-Faribault-Freeborn-Polk-Barron-Rusk-
St. Croix-Pierce-Dunn-Pepin-Eau Claire-
1252 PM CDT Wed May 11 2022

This Hazardous Weather Outlook is for portions of central and
southern Minnesota, and west central Wisconsin.

.DAY ONE...This Afternoon and Tonight.

Strong to severe storms are expected across much of the area
today and tonight. Very large hail, damaging winds and a few
tornadoes are possible. In addition, very heavy rain and localized
flash flooding are possible, especially near and after sunset.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Another round of widespread strong to severe storms is expected
Thursday afternoon and evening, with large hail and damaging
winds the primary threats. Isolated tornadoes are also possible,
especially across western Minnesota.

Temperatures could reach the lower 90s Thursday afternoon with
heat index values as high as 95 degrees.

.SPOTTER INFORMATION STATEMENT...

SKYWARN spotter activation will likely be needed later this
afternoon through tonight and again on Thursday.

Special Weather Statement
National Weather Service Twin Cities/Chanhassen MN
1145 AM CDT Wed May 11 2022

MNZ041-042-111715-
Douglas MN-Todd MN-
1145 AM CDT Wed May 11 2022

...A strong thunderstorm will impact portions of northeastern Douglas
and northwestern Todd Counties through 1215 PM CDT...

At 1145 AM CDT, Doppler radar was tracking a strong thunderstorm near
Carlos, or 9 miles north of Alexandria, moving north at 35 mph.

HAZARD...Winds in excess of 30 mph and nickel size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

This storm will remain over mainly rural areas of northeastern
Douglas and northwestern Todd Counties, including the following
locations... Belle River, Miltona and Rose City.

This includes U.S. Highway 71 between mile markers 212 and 218.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4635 9503 4593 9518 4595 9544 4611 9543
      4611 9515 4636 9516
TIME...MOT...LOC 1645Z 187DEG 31KT 4602 9530

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...30 MPH

NDC

Special Weather Statement
National Weather Service Twin Cities/Chanhassen MN
1210 PM CDT Wed May 11 2022

MNZ049-051-058-059-111800-
Sherburne MN-Stearns MN-Meeker MN-Wright MN-
1210 PM CDT Wed May 11 2022

...A strong thunderstorm will impact portions of northern Wright,
east central Meeker, western Sherburne and southeastern Stearns
Counties through 100 PM CDT...

At 1210 PM CDT, Doppler radar was tracking a strong thunderstorm near
Annandale, or 16 miles west of Buffalo, moving northeast at 30 mph.

HAZARD...Winds in excess of 30 mph and nickel size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

This strong thunderstorm will be near...
  Annandale around 1220 PM CDT.
  Maple Lake around 1230 PM CDT.

Other locations in the path of this storm include Clearwater,
Monticello, Clear Lake and Becker.

This includes the following highways...
 Interstate 94 in Minnesota between mile markers 172 and 197.
 U.S. Highway 10 in Minnesota between mile markers 181 and 204.
 U.S. Highway 12 between mile markers 113 and 119.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4529 9367 4504 9421 4514 9441 4556 9409
      4556 9406
TIME...MOT...LOC 1710Z 225DEG 26KT 4520 9419

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...30 MPH

CTG

Special Weather Statement
National Weather Service Twin Cities/Chanhassen MN
1241 PM CDT Wed May 11 2022

MNZ059-060-068-111830-
Hennepin MN-Carver MN-Wright MN-
1241 PM CDT Wed May 11 2022

...A strong thunderstorm will impact portions of northwestern
Hennepin, southeastern Wright and northwestern Carver Counties
through 130 PM CDT...

At 1240 PM CDT, Doppler radar was tracking a strong thunderstorm over
Watertown, or 17 miles south of Buffalo, moving northeast at 25 mph.

HAZARD...Winds in excess of 30 mph and nickel size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

This strong thunderstorm will be near...
  Watertown and St. Bonifacius around 1245 PM CDT.
  Mound, Minnetrista and Delano around 100 PM CDT.

Other locations in the path of this storm include Orono, Maple Plain,
Rockford, Medina, Independence, Maple Grove, St. Michael and
Corcoran.

This includes U.S. Highway 12 between mile markers 133 and 140.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4483 9382 4490 9400 4523 9379 4508 9347
TIME...MOT...LOC 1740Z 213DEG 23KT 4492 9386

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...30 MPH

CTG

Special Weather Statement
National Weather Service Twin Cities/Chanhassen MN
1258 PM CDT Wed May 11 2022

MNZ073-111830-
Redwood MN-
1258 PM CDT Wed May 11 2022

...A strong thunderstorm will impact portions of southeastern Redwood
County through 130 PM CDT...

At 1258 PM CDT, Doppler radar was tracking a strong thunderstorm over
Wabasso, or 9 miles southwest of Redwood Falls, moving north at 40
mph.

HAZARD...Winds in excess of 30 mph and penny size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

This storm will remain over mainly rural areas of southeastern
Redwood County, including the following locations... Clements, Wanda
and Seaforth.

This includes U.S. Highway 71 between mile markers 58 and 74.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 4455 9501 4454 9497 4429 9491 4429 9532
      4447 9535
TIME...MOT...LOC 1758Z 201DEG 33KT 4444 9524

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

NDC

Special Weather Statement
National Weather Service Twin Cities/Chanhassen MN
116 PM CDT Wed May 11 2022

MNZ065-073-111845-
Renville MN-Redwood MN-
116 PM CDT Wed May 11 2022

...A strong thunderstorm will impact portions of north central
Redwood and northwestern Renville Counties through 145 PM CDT...

At 116 PM CDT, Doppler radar was tracking a strong thunderstorm near
Redwood Falls, moving north at 30 mph.

HAZARD...Winds in excess of 30 mph and nickel size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
  Olivia and Renville.

This includes the following highways...
 U.S. Highway 212 between mile markers 62 and 80.
 U.S. Highway 71 between mile markers 74 and 75, and between mile
markers 89 and 106.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

A Tornado Watch remains in effect until 900 PM CDT for southwestern
Minnesota.

&&

LAT...LON 4451 9507 4450 9535 4489 9528 4489 9486
TIME...MOT...LOC 1816Z 193DEG 27KT 4455 9520

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...30 MPH

NDC

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