Special Weather Statement, NWS Twin Cities, MN

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
620 AM CDT Tue Jun 2 2020

.UPDATE...For 12Z Aviation discussion below

&&

.SHORT TERM...(Today through Wednesday)
Issued at 342 AM CDT Tue Jun 2 2020

Expect another hot day for much of the area, along with a
heightened risk for severe storms this afternoon and evening,
particularly across southern Minnesota.

The surface trough of interest is stretched from south central
South Dakota northeast across central Minnesota to Lake Superior
early this morning. The two main associated forecast challenges
today continue to revolve around how hot we'll get in the warm
sector ahead of this feature, and how impactful the associated
thunderstorm activity will be.

By 18Z, the boundary looks to have shifted to around a Mankato,
to Red Wing, to Eau Claire line. Along and south/east of this
line, we expect plenty of sunshine to allow temperatures to warm
into the low/mid 90s. Moisture pooling ahead of the boundary
should support dewpoints in the mid/upper 60s as well. While it
will indeed feel hot and sticky, particularly with relatively
light winds and plenty of sunshine, heat indices (mid/upper 90s)
and WBGT values (83F-84F) look to fall just short of warranting a
Heat Advisory. This is even with our current forecast
highs/dewpoints being around the 90th percentile of model guidance.
Therefore we will not issue any heat headlines, but will continue
to message the threat in the HWO and graphics.

Now onto the severe thunderstorm potential today. There will be
two things in play. The first will be that we expect elevated
showers and thunderstorms to move in from the Dakotas across west
central MN during the late morning...spreading toward central MN
during the early afternoon with support of weak shortwave forcing.
Given the elevated nature of this activity, the primary threat
will be large hail. By late afternoon (21-22Zish)...attention
shifts to the other area of concern...farther south where surface-
based convective development is expected. Exactly where this
occurs is somewhat uncertain, but at this point the most probable
spot looks to be near the Interstate 90 corridor. These storms
could be quite feisty given the amount of instability they'll have
to work with. The anticipated multi-cell/supercell nature of this
activity in southern MN is supported by Hi-res progs,
particularly the HRRR and NamNest, which to put it frankly, look
daunting by 23Z. Of course this is all conditional on the CAP
eroding, but most models support that occurring around/after 22Z.
In addition to the large hail potential with these storms,
damaging winds would be quite possible, both from supercell storms
and later on with potential linear evolution. Given Precipitable
water values nearing 2 inches, torrential rainfall could cause
some brief hydro issues in isolated locations, but nothing
extensive given the transient nature of the storms.

The active weather should shift out of the area during the late
evening, with clearing skies overnight. Wednesday looks to be a
pretty decent summer day, with highs in the low/mid 80s, dewpoints
in the 40s/50s, light northwest winds, and mostly sunny skies.

.LONG TERM...(Wednesday night through Monday)
Issued at 342 AM CDT Tue Jun 2 2020

The start of the extended period will be characterized as a fast
west to east flow aloft with a strong storm system moving across
southern Canada. A weak frontal boundary Wednesday night will be
across the Dakotas with southerly flow ahead of it. By Thursday
morning, this front becomes disorganized and instability remains
weak for any type of organized convection. Confidence is very low
for Thursday and Thursday night forecast as the disorganized front
lies somewhere across the Upper Midwest. Not until the southern
Canada storm moves east of Minnesota does any type of influx of
northwest flow in the boundary layer develop. Therefore, higher
percentages of rainfall will likely fluctuate until we have a
handle on when this front becomes more organized. Although bulk
wind shear values are quite high as the strong west to east flow
aloft continues, the amount of instability remains in question.
So, severe thunderstorm threat will be conditional with daytime
heating.

Friday with be the transition to another upper ridge building across
the Rockies and into the Northern Plains/Upper Midwest. The EC is
much stronger with this ridge compared to the GFS and much more
amplified. This stronger amplitude of the EC also plays an important
role on precipitation chances over the weekend, especially
considering the strength vs. the GFS. Current NBM has likely
percentages across central Minnesota Saturday night as the GFS has a
large area of precipitation developing. The EC solution keeps the
bulk of the precipitation mainly north of MPX CWA. What is more
confident is the above normal temperatures which could easily
surpass Monday's highs in the low to mid 90s.

The center of this ridge begins to move east of Minnesota next week.
A very strong and anomalous long wave trough over the western 1/4 of
the CONUS will lead to strong southwest flow aloft developing across
the plains next week. Another factor that needs to be monitored is
the tropical disturbance that is forecast by both the EC/GFS to move
into the Gulf of Mexico next weekend, and into the southern plains
next week. This will have major impacts for the Upper Midwest in
terms of heavy rainfall potential especially considering the
orientation of the trough, and if the tropical system becomes
entrenched with the long wave trough in the west.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 620 AM CDT Tue Jun 2 2020

VFR conditions with mostly clear skies are expected this morning,
and then widespread thunderstorms are expected across central and
southern MN this afternoon and early evening. A southwest to
northeast oriented line of activity looks to push in from the
eastern Dakotas, possibly reaching northern/western sites between
16z and 19Z (KAXN/KSTC), and central/southern sites
(KRWF/KMSP/KMKT) between 20Z and 22Z. The eastward extent of the
thunderstorms is a bit uncertain, but any activity that holds
together would reach WI sites (KRNH/KEAU) after 22Z. Given more
warm and humid air in place over southern MN, the storms look to
have the potential to be stronger at KRWF and KMKT. Large hail and
strong winds are the greatest risks. Additional (supercell)
storms may develop late this afternoon ahead of the main line, but
those still look to occur south of the TAF sites. MVFR ceilings
and MVFR/IFR look the most probable with the storms.

KMSP...There's been fairly decent consistency pointing toward the
22Z-02Z time frame as having the highest chance of thunderstorm
activity. Large hail cannot be ruled out with this activity, along
with strong wind gusts.

/OUTLOOK FOR KMSP/
Wed...VFR. Wind NW at 5-10 kts.
Thu...VFR. Evening MVFR/TSRA possible. Wind SW at 10 kts bcmg NW
at 10-20 kts.
FRI...VFR with chance of MVFR/TSRA. Wind NW 10G20 kts.

&&

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

SHORT TERM...LS
LONG TERM...JLT
AVIATION...LS

Hazardous Weather Outlook
National Weather Service Twin Cities/Chanhassen MN
432 AM CDT Tue Jun 2 2020

MNZ041>045-047>070-073>078-082>085-091>093-WIZ014>016-023>028-
030945-
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-
432 AM CDT Tue Jun 2 2020

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

.DAY ONE...Today and Tonight.

Severe thunderstorms are possible this afternoon and evening,
generally along and south of an Olivia, to Twin Cities metro, to
Bloomer Wisconsin line. Large hail and damaging winds are the
primary threats. In addition, some storms may produce torrential
rain which could lead to isolated flooding issues. The greatest
threat for severe storms is from southern Minnesota to west
central Wisconsin, or along and south of a New Ulm, to Red Wing,
to Eau Claire line, where there is an Enhanced Risk of severe
storms. There is also a risk for tornadoes in this area, but it
is low.

Heat and humidity will remain in place today, with heat indices
in the low to mid 90s expected in east central and south central
Minnesota and west central Wisconsin. Once the afternoon showers
and thunderstorms move in, heat indices will reduce.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Additional thunderstorms are possible Thursday, and from Saturday
night into Monday. There is a marginal risk of severe storms in
southern Minnesota on Thursday.

Stay tuned to future outlooks for information about the severe
weather potential with the weekend thunderstorm activity.

.SPOTTER INFORMATION STATEMENT...

SKYWARN spotter activation will likely be needed this afternoon
and evening.

Special Weather Statement
National Weather Service Twin Cities/Chanhassen MN
1207 PM CDT Tue Jun 2 2020

MNZ041-021730-
Douglas-
1207 PM CDT Tue Jun 2 2020

...AN AREA OF STRONG THUNDERSTORMS WILL AFFECT DOUGLAS COUNTY...

At 1206 PM CDT, strong thunderstorms were clustered near Hoffman, or
16 miles west of Alexandria, moving east at 55 mph.

Wind gusts up to 50 mph and half inch hail are possible with this
storm.

Locations impacted include...
Alexandria, Evansville, Carlos, Brandon, Kensington, Holmes City,
Leaf Valley, Miltona, Garfield, Belle River, Nelson and Alexandria
Airport.

This includes Interstate 94 in Minnesota between mile markers 83 and
115.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

LAT...LON 4611 9515 4582 9514 4577 9576 4587 9575
      4600 9577 4609 9535
TIME...MOT...LOC 1706Z 251DEG 49KT 4590 9572

CEO