Special Weather Statement, NWS Twin Cities, MN

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
222 PM CDT Sun Aug 22 2021

.SHORT TERM...(This evening through Monday night)
Issued at 222 PM CDT Sun Aug 22 2021

Mostly sunny skies were evident on satellite imagery this afternoon,
with some increase in high clouds across the west. Upstream
convection was occurring along the leading edge of the 850 mb theta-e
gradient (MUCAPE axis) over the eastern Dakotas. This activity will
push east through the evening, although we may continue to see
leading edge activity fall apart as it outruns the instability (and
wait on subsequent convection to develop and advance eastward).
Severe weather potential looks limited, without a good overlap of
shear and instability, although a few elevated hailers can't be
discounted (with wind also a possibility given the large dewpoint
depressions and potential for evaporative cooling with downdrafts).
Expect things to transition eastward through the evening, but at this
point coverage looks to remain fairly scattered, so many locations
will get through tonight without seeing much if any rainfall. Any
lingering SHRA/TSRA over the south/east portion of the area early
Monday morning should quickly move away, leaving mostly sunny
conditions for the balance of the day. The warm frontal boundary will
start to lift northward Monday night, and as warm advection and
elevated instability increase we should see some SHRA/TSRA develop
over the southern portion of the area Tuesday evening and lift
north/east overnight. Will have to see how instability and effective
shear values pan out, but there is at least some chance for a few
stronger elevated storms (with some hail potential) over the southern
portion of the area Monday night into early Tuesday morning.

.LONG TERM...(Tuesday through Sunday)
Issued at 222 PM CDT Sun Aug 22 2021

The key message in the long term is increasing confidence in several
chances for showers and thunderstorms, with the potential for some
widespread beneficial rain late in the week.

The chances for showers and thunderstorms will be on the increase
Tuesday with a shortwave moving through the Dakotas into Central
Canada in the southwest flow. Thunderstorm coverage looks to
increase into the afternoon, especially north of I-94, where the
best potential for heavier rains exist. Tuesday afternoon dewpoints
will rise into the upper 60s and lower 70s and the atmosphere will
become more unstable with CAPE values rising to 2000-3000 J/kg
Tuesday afternoon/evening. Bulk shear will be sufficient for storms
to organize and the SPC has a Marginal Risk in place for most of the
Forecast area, but the forcing looks rather weak. We will continue
to monitor for the possibility of severe storms Tuesday
afternoon/evening. Tuesday night the associated cold front will
clear the forecast area and cooler drier air will filter into the
forecast area from the northwest with high temperatures on Wednesday
in the upper 70s to lower 80s with dewpoints falling into the 50s
during the day under mostly sunny skies.

Confidence is increasing in widespread beneficial rains late in the
week. We will continue under southwest flow aloft with broad ridging
over the southern and southeastern CONUS. As short wave energy moves
through the flow we will have several chances for showers and
thunderstorms. Moisture transport into the north central US looks to
become pretty strong as well with a good fetch of Gulf moisture
advecting north towards the CWA, with PWATs progged to increase to
around 2 inches, the potential for heavy rains is there. The NBM has
likely PoPs for parts of the forecast area from late Thursday into
Saturday. Future model runs should provide better clarity on this
system. The Climate Prediction Center has the forecast area favored
for above average precipitation for both the 6-10 day outlook and
the 8-14 day outlook which is not something we have seen much of
lately. Stay tuned...

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1208 PM CDT Sun Aug 22 2021

Made minimal changes to the going forecasts for this period. We
should still see scattered convection work across the area tonight,
but instability looks fairly limited as does moisture, so many
locations may not see anything. The going TEMPO and PROB groups seem
sufficient at this point, allowing for increased confidence in
subsequent forecasts as things get closer to the area (current
convection to the west has been outrunning the instability and
weakening, so may see that occur a few more times through tonight).
Ceilings should remain mostly VFR and there isn't enough confidence
to go lower than that with any potential SHRA/TSRA at this point. We
should see quick improvement behind the surface trough as the upper
wave shears out and moves east of the area later tonight and Monday.

KMSP...Primary concern is chance for a window of SHRA/TSRA tonight.
Confidence isn't sufficient to go with more than a PROB group at this
point, but guessing subsequent forecasts will need a TEMPO depending
on the evolution of upstream activity.

/OUTLOOK FOR KMSP/
Monday night...VFR. East wind less than 10 kt.
Tuesday and Tuesday night...MVFR possible with a chance of showers
and thunderstorms. Southeast wind 10 to 15 kt becoming east.
Wednesday...VFR. Northeast wind 5 to 15 kt.
Wednesday night...MVFR possible with a chance of showers and
thunderstorms. Northeast wind 10 to 15 kt becoming southeast.
Thursday...MVFR possible with a chance of showers and thunderstorms.
Southeast wind 10 to 20 kt.

&&

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

SHORT TERM...
LONG TERM...CEO
AVIATION...

Hazardous Weather Outlook
National Weather Service Twin Cities/Chanhassen MN
906 AM CDT Sun Aug 22 2021

MNZ041>045-047>070-073>078-082>085-091>093-WIZ014>016-023>028-
231415-
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-
906 AM CDT Sun Aug 22 2021

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

.DAY ONE...Today and Tonight.

Scattered thunderstorms are possible tonight. There is a Marginal
Risk of severe thunderstorms generally south of Interstate 94 and
west of Interstate 35 today. The primary hazards are large hail
and damaging winds.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

Multiple chances for thunderstorms this week. Severe weather is
possible but a lot of uncertainty regarding thunderstorm timing
and location currently exists.

.SPOTTER INFORMATION STATEMENT...

SKYWARN spotter activation may be needed.

Special Weather Statement
National Weather Service Twin Cities/Chanhassen MN
350 PM CDT Sun Aug 22 2021

MNZ054-064-222130-
Yellow Medicine MN-Lac Qui Parle MN-
350 PM CDT Sun Aug 22 2021

...A strong thunderstorm will impact portions of Lac qui Parle and
west central Yellow Medicine Counties through 430 PM CDT...

At 350 PM CDT, Doppler radar was tracking a strong thunderstorm near
Gary, or 12 miles east of Clear Lake, moving northeast at 40 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...
  Canby around 355 PM CDT.

Other locations in the path of this storm include Madison and Dawson.

This includes the following highways...
 U.S. Highway 212 between mile markers 0 and 30.
 U.S. Highway 75 between mile markers 95 and 115.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4495 9646 4515 9618 4498 9582 4495 9580
      4462 9632 4463 9633 4463 9645
TIME...MOT...LOC 2050Z 224DEG 36KT 4476 9641

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

CEO