Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 270845

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
345 AM CDT Tue Jul 27 2021

.SHORT TERM...(Today through Wednesday)
Issued at 345 AM CDT Tue Jul 27 2021

Another morning with a few areas of our CWA seeing a nice soaking
round of showers and thunderstorms, this time in western WI and
sliding through the northern part of Mille Lacs and Kanabec counties.
A few sub severe wind gusts have been seen but generally it has just
been a nice steady rainfall for a few hours, with over an inch
falling in parts of Rusk county around Ladysmith already. These
showers and storms are expected to dissipate slowly this morning,
with redevelopment possible this afternoon. This morning round is
associated with a stationary front stretching from west-northwest to
east-southeast across central MN and into WI, with just enough of a
shortwave to reinforce the front. The expectation for this afternoon
is a complete hit or miss scenario, with forecast soundings showing
an impressive amount of instability and upper level shear, however
our low level shear is mediocre and we lack a strong forcing
mechanism to kick things off. It isn`t until another potential
shortwave arrives by the evening in far southern MN that we see the
second round developing, and with the front sagging south this could
end up missing us entirely as activity follows the front. Both the
HRRR and NAMNEST like to kick things off at around 23-00Z and quickly
drag it south, keeping our area mostly dry, and this scenario was
already the expected outcome in our internal office discussions. We
also have heat considerings today, with a heat advisory beginning at
1pm this afternoon and lingering through 9pm this evening for the 7
county metro through southern MN and west along the MN river.
Apparent temperatures are expected to range from upper 90s in the
metro to low 100s in southern and western MN with dew points
increasing to the low 70s this afternoon.

Wednesday is the far more volatile day as far as both heat and
thunderstorms are concerned, with the excessive heat watch still in
place beginning at 9pm Tuesday night through 9pm Wednesday. We are
going to have at least a heat advisory across the area again on
Wednesday, with potential for an excessive heat warning as
temperatures reach near 100 in western MN and upper 90s in the metro.
Apparent temperatures reach the mid 100s in western MN to low 100s in
the metro with dew points in the low to mid 70s once again. The
difference maker between advisory and warning will likely be the
convective potential for the day, with some models pushing earlier
convection beginning by the late morning across parts of southern.
This could keeps things just cool enough to prevent an excessive heat
warning from being needed, as we will be right on the border where a
degree or two of either cooling or warming will make the difference.
This uncertainty, as well as collaboration with neighboring offices,
led to the decision to forego issuing any heat headlines for
Wednesday just yet. Wednesday severe weather parameters look
incredibly impressive within model forecast soundings showing
upwards of 3000 J/KG MLCAPE with impressive veering winds and
effective shear of 50kts. The big question is the cap that still
exists due to the incredibly warm 850mb temperatures and if our
forcing will be strong enough to overcome it, which at least right
now looks more likely east of the Mississippi river and would put our
WI counties at a greater likelihood of seeing storms.

.LONG TERM...(Wednesday night through Monday)
Issued at 345 AM CDT Tue Jul 27 2021

Compared to the short term period, the long term will be quiet and
absent of significant weather to talk about. The only real chance for
any precipitation will be on Saturday with a passing shortwave
through central MN, however lack of significant moisture and forcing
will keep things tame and likely not amounting to all that much.
Temperatures will be much cooler than the short term, with upper 80s
on Thursday falling back even further with some low to mid 80s highs
through the rest of the forecast and into the first few days of
August. Broad high pressure moves in over the Great Lakes and remains
entrenched through the weekend and into early next week, giving us
light winds, clear skies, and no active weather to talk about. Dew
points will also fall back down into the 50s and low 60s through the
period, which could end up giving us some slight fire weather
concerns, however the lack of any significant winds should keep this
contained as well.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1042 PM CDT Mon Jul 26 2021

Have kept all TAFs as VFR and devoid of precip mention as there is
high uncertainty as to the timing/placement of any convection
overnight into Tuesday morning. CAMs are still highly variable on
the placement with diminishing returns on any potential convection at
the two WI TAF sites. Cannot rule out any convection for sites along
and north of the I-94 corridor but chances are too low for inclusion
at this point. So with such uncertainty and lowering PoPs, have gone
an optimistic route with dry TAFs and will adjust if/as necessary.
Southwesterly winds early on will swing around to easterly during
the day Tuesday, speeds under 10kt. Have maintained mention of LLWS
for 35 kts at 230 degrees at RWF overnight.

KMSP...VFR conditions expected throughout this duration with much
greater chances for a dry TAF than seeing convection. Chances are
non-zero for SHRA/TSRA but any convection is expected to remain to
the N and E of MSP. Will monitor radar trends and amend as needed.

Wed...VFR. Chc MVFR/SHRA/TSRA. Wind SW 10-15kts bcmg NW late.
Thu...VFR. Winds N/NW 5-10kts.
Fri...VFR. Winds SE 5kts.


MN...Heat Advisory from 1 PM this afternoon to 9 PM CDT this evening for
     Anoka-Blue Earth-Brown-Carver-Chippewa-Dakota-Faribault-
     Hennepin-Kandiyohi-Lac Qui Parle-Le Sueur-Martin-McLeod-Meeker-
     Waseca-Washington-Watonwan-Wright-Yellow Medicine.

     Excessive Heat Watch from this evening through Wednesday evening
     for Anoka-Blue Earth-Brown-Carver-Chippewa-Dakota-Faribault-
     Freeborn-Hennepin-Kandiyohi-Lac Qui Parle-Le Sueur-Martin-
     Washington-Watonwan-Wright-Yellow Medicine.



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