Special Weather Statement, NWS Twin Cities, MN

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
100 PM CDT Tue Apr 12 2022

.UPDATE...
Issued at 1249 PM CDT Tue Apr 12 2022

Updated to include 18z aviation discussion below.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 427 AM CDT Tue Apr 12 2022

KEY MESSAGES:

- Severe thunderstorms are possible late this afternoon into the
  evening from south central into east central MN and western WI.
  All modes of severe weather will be possible.

- Weather for Wednesday has continued to trend toward being dry.

Water vapor imagery this morning shows an upper low over southern
Idaho, with a shortwave on its southern periphery approaching Las
Vegas. By Wednesday afternoon, the upper low will have deepened as
it moves to eastern NoDak, with the southern shortwave moving into
the lower MO Valley. At the surface, we have cyclogenesis ongoing
this morning over NE CO. This low will advance across Neb today,
moving from roughly Albert Lea to Eau Claire between 3z and 9z this
evening. On Wednesday, this low will broaden out over Lake Michigan,
with a new surface circulation taking shape over eastern NoDak as
the upper low arrives/deepens.

Precipitation chances for today are bit tricky when looking at
forecast soundings. Southeast winds will keep the low levels bone
dry, but by the afternoon we start to see the mid/upper levels dry
out as the low levels moisten and stratus moves in. This disjunction
in moisture is why we are seeing varying degrees of success in
generating precip today. For the grids though, we did follow a blend
of the HRRR and other CAMs that develop a NW to SE oriented band of
light rain developing late morning roughly along the MN River that
will track northeast through the afternoon within a zone of strong
isentropic lift associated with strengthening of the h7 winds into
the 50-60 kt range. We may get a rumble of thunder or two out of this
activity, but the thunder threat really shows up with round 2 of
precip.

Round 2 of precip is the one that contains our severe threat. The
biggest area of uncertainty now is just how far north with the warm
sector and its associated lower 60 dewpoints make it. This airmass
is currently locked up to the south of a stationary front across
central OK and northern Arkansas. So it has about 600 miles to
travel today to get up to just the I-90 corridor. Within the HREF,
we a see a spread in the northern extent of this warm sector from
being as far north as the far southern Twin Cities metro, to making
it only as far north as far northern IA. We'll have to watch closely
where this low/triple point ends up through the evening, as this
region will have the greatest risk of seeing a more significant
severe weather risk (including the risk of a strong tornado or two)
given the highly sheared environment that will be in place. To the
north of the surface low, a secondary severe environment will exist
within the MUCAPE gradient. Here, we could see elevated supercells
develop with the attendant risk of large hail. The greatest window
for a severe threat looks to fall within 23z (6 pm) and 05z (12 am)
this evening. The Day 1 SPC convective outlook does a good job at
this time of capturing where that more significant surface based
severe threat exists (Enhanced risk with a 10% hatched tornado) and
the northern extent of the elevated hail risk.

For Wednesday, we've seen everything come around to the front being
well east of us, with a pronounced and deep layer of dry air over
the MPX area. In fact, not only does it looks like the MPX area will
be dry much of the day, but there may even be a fair amount of
sunshine as well. However, even if we see sunshine, it will come
with a healthy does of CAA, which will hold temperatures back in the
upper 30s to mid 40s on west winds gusting upwards of 35 mph.

.LONG TERM...(Wednesday night through Monday)
Issued at 427 AM CDT Tue Apr 12 2022

KEY MESSAGES

- Temperatures will be well below normal through the entirety of the
  long term period.

- Another chance for snow exists Sunday night into Monday

Rain along the arching cold front in western WI will push northeast
Wednesday night as the deep surface low in northeastern ND occludes.
Meanwhile, a potent mid-level dry slot will wrap into the low from
the south causing precip to subside across the region Wednesday
night. Strong low-level CAA will also begin as very cold air from
Canada is wrapped counter-clockwise around the backside of the low.
As the low to mid-levels cool, the boundary layer should become
well-mixed as lapse rates steepen. With a strong "stinger" LLJ
overspreading the region from west to east Thursday and appreciable
low-level lift, this momentum should reach the surface. Forecast
soundings across the CWA show as much as 50 knots at the top of the
channel. With surface winds already 25-30 knots sustained and the
potential for much stronger gusts, a future Wind Advisory seems
necessary for the entire CWA Thursday. In fact, a High Wind
Watch may even be needed as the 50th percentile of the NBM4.1 has
sustained winds exceeding 35 knots for much of southwest MN.
Additional increases to winds from the current forecast may be
necessary if the upper-percentile of the models are correct.

The cooling thermal profile will also saturate the DGZ as wrap-
around moisture on the backside of the low is advected into MN.
Ongoing broad lift and steep low-level lapse rates will create an
environment for convective snow showers that will spread east from
western MN into western WI during Thursday. Many of these snow
showers could be intense as a sliver of CAPE is hinted in forecast
soundings. While above freezing surface temperatures will limit
accumulation, any intense showers will produce a coating of snow
and greatly reduced visibilities. Have increased PoPs for most of
the CWA Thursday for the potential snow showers. This activity will
lift north during Thursday night, but could linger into Friday. As
the surface low fills and lifts away to the northeast, the surface
pressure gradient will begin to relax. However, winds will still be
stronger Friday with gusts near 30 knots possible. It will also
remain cold as models show a pool of -15 to -18 C 850 mb air
settling over the Upper Midwest into Saturday. Temperatures are
forecast to be 15-20 degrees below normal Thursday thru Saturday.
Combined with the still breezy winds, Friday and Saturday mornings
could see wind chills in the low teens to single digits.

Sunday onward, temperatures are forecast to somewhat improve (but
still remain well below normal). Additionally, long-range models
show potential for another wintry system Sunday into Monday as a
series of shortwaves travel across the central CONUS. However,
differences between models are currently much too great to delve
into specifics of this next system.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1249 PM CDT Tue Apr 12 2022

Busy period ahead with surface low forecast to track across
southeast MN this evening. Expect two waves of precip this period.
The first mainly a band of showers and thunderstorms that will move
northeast across the area early this afternoon. Wave two shows up
this evening and will be strong to severe storms as the surface low
moves into southeast MN. Followed the HRRR for timing things and
added TS further north to include threat of elevated storms shown on
several CAMS. CIGS will remain VFR until the rain arrives, but will
quickly trend toward MVFR levels as the back edge of that rain
shield approaches a terminal. IFR CIGS take over this evening ahead
of the second round of thunderstorms. CIGs and Vsby will improve to
MVFR and eventually VFR late Wednesday morning.

KMSP...Initial line of TSRA will impact MSP between 19z and 20z
before a break in precipitation. Area of greatest concern comes
between roughly 1z and 5z, when MSP will have the threat for strong
to severe thunderstorms. Expect VFR conditions into the afternoon,
but expect MVFR and IFR cigs to set in between 21z and 23z as we get
into back edge of the initial rain shield.

/OUTLOOK FOR KMSP/
Thu...IFR/MVFR chc -RASN. Wind W 20-25 kts, gusts 40-45 kts.
Fri...VFR. Wind W 20-25 kts, gusts 35-40 kts.
Sat...VFR. Wind WNW 10-15 kts, gusts 25kts.

&&

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

SHORT TERM...MPG
LONG TERM...CTG
AVIATION...BPH

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

Special Weather Statement
National Weather Service Twin Cities/Chanhassen MN
1259 PM CDT Tue Apr 12 2022

MNZ076-083-084-121830-
Le Sueur MN-Waseca MN-Blue Earth MN-
1259 PM CDT Tue Apr 12 2022

...A strong thunderstorm will impact portions of southeastern Le
Sueur, east central Blue Earth and northwestern Waseca Counties
through 130 PM CDT...

At 1259 PM CDT, Doppler radar was tracking a strong thunderstorm near
Pemberton, or 13 miles southeast of Mankato, moving northeast at 60
mph.

HAZARD...Half inch hail.

SOURCE...Radar indicated.

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

This strong thunderstorm will be near...
  Janesville around 110 PM CDT.
  Elysian around 115 PM CDT.

Other locations in the path of this storm include Waterville.

This includes U.S. Highway 14 between mile markers 141 and 151.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4397 9398 4432 9370 4431 9353 4421 9352
      4393 9382
TIME...MOT...LOC 1759Z 215DEG 52KT 4399 9387

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...<30 MPH

ETA

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>