847
FXUS63 KMPX 222320
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
620 PM CDT Sun Jun 22 2025

.KEY MESSAGES...

- Extreme Heat Warning continues through this evening for heat
  indices of 105-110 degrees.

- Conditional threat for severe thunderstorms tonight. Slight Risk
  (Level 2/5) in place across central and western Minnesota.

- Active weather pattern resumes Tuesday. Multiple rounds of
  showers and thunderstorms will produce heavy rain this week.

&&

.DISCUSSION...
Issued at 306 PM CDT Sun Jun 22 2025

The ongoing round of record setting heat and humidity continues
across the Upper Midwest this afternoon. Afternoon highs are on
track to reach the mid-90s for most locations, with even warmer
temperatures near 100 degrees across western Minnesota. Combine the
heat with dew points in the low to mid 70s and you get another
afternoon of triple digit heat indices. An Extreme Heat Warning
continues through this evening, before heat indices fall below
headline criteria. At this point, we are not planning on
extending the Warning past 9 PM, however, the duration of
fatigue from heat and humidity may persist across far eastern
MN/western WI tonight as minimum temperatures aim to stay above
75 degrees prior to a cold frontal passage early Monday.

The forecast focus will shift from dangerous heat to the potential
for strong to severe thunderstorms tonight. The setup for strong
convection is tied to the large scale relationship between the heat
dome over the Great Lakes (characterized by a 594dm ridge) and a
longwave trough over the Pacific Northwest. Afternoon surface
analysis depicts ~998mb surface low over eastern SD, located in the
exit region of the aforementioned upper trough. The low is forecast
to slide northeast over the coming hours, which will drag a cold
front from west to east across the area tonight into tomorrow
morning. The prefrontal environment is volatile, owing the ongoing
moisture advection of lower 70s Td`s. This is illustrated by RAP
mesoanalysis capturing 2500+ J/kg of CAPE, steep lapse rates
between 8-9 deg C/km, and 30-40kts of effective shear. That
being said, we continue to refer to this setup as conditional,
given the presence of anomalously warm mid-level temperatures
(700mb T`s ~16C/850mb T`s ~22C) acting as a stout cap aloft.
With this in mind, we feel fairly confident that the coverage
area will remain storm free through at least ~1-2z, prior to
what will be more successful attempts at convective initiation
as the front draws near. As previously stated, the best chance
for severe thunderstorms will be across western MN, which is in
closest proximity to the front while also working in tandem
with the eroding cap/pool of strong instability. Large hail and
damaging winds are the greatest concern, however an isolated
tornado or two cannot be ruled out across west-central MN closer
to the surface low. SPC recently issued a Tornado Watch across
eastern ND/northwest MN to reflect this potential.

HREF tends to show the low to mid level wind fields displaced
well to the east of the surface front tonight, which may limit
the overall forcing available for a more widespread threat
(especially when factoring in the thermo scenario). CAMs show an
uptick in scattered shower/storms as the upper level forcing
shifts east over the region heading into Monday morning, which
is reflected by 20-40% PoPs. Given the conditional nature of
this setup, SPC has maintained a Day 1 Slight Risk (2/5) for
central/western MN. A Marginal Risk (1/5) is in place across SE
MN/western WI.

The front will continue to move to the east/southeast Monday. This
feature will serve as the focus for renewed shower and thunderstorm
activity as early as late Monday morning, though more likely into
the early afternoon. Slight differences in the frontal position by
mid to late morning across the guidance suite have prompted a
Marginal Risk (1/5) to be extended across eastern/southern MN,
however the greater chance for stronger convection is SE of a
line from Rochester to Eau Claire where a Slight Risk (2/5) is
in place. Once again looking at damaging winds and hail as the
primary threats, though a brief spin-up cannot be ruled out in
the expected prefrontal environment. The eastward movement of
renewed convection will signal the end of active weather for
tomorrow. Northwesterly winds will bring a "cooler" day with
highs in the 70s across western MN and the lower 80s along and
east of I-35.

The aforementioned front will sag south of the MN/IA border heading
into Tuesday and is forecast to stall in this general area through
midweek. Guidance displays a zonal pattern aloft taking shape this
week, which will result in multiple waves sliding east across
the flow/the surface boundary. We anticipate several rounds of
showers and thunderstorms driven by moisture transport into the
boundary in combination with the passing waves aloft. With PWATs
forecast to be near/in excess of 2", each round of convection
will likely produce heavy rain and training of thunderstorms
will become a concern from a hydro perspective. WPC`s latest QPF
forecast features 2-3" of QPF across southern MN/western WI
from Tuesday morning through Friday morning. Given the frontal
position, lower amounts between 1-2" are forecast across central
MN. Training of thunderstorms and enhanced rainfall rates tied
to stronger convection may produce more substantial localized
amounts, though will lean on CAM solutions in the coming days to
better define the corridors of highest rainfall. WPC continues
to display Slight Risk ERO`s across the southern half of the
area Tuesday-Thursday. On the flip side, the active wet pattern
will keep temperatures in check, so look for a more comfortable
stretch of air with highs in the 70s midweek. Guidance teases
height rises within the zonal flow heading into next weekend,
which supports highs climbing back into the 80s.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 620 PM CDT Sun Jun 22 2025

VFR to start the period with gusty southerly winds this evening.
Winds will continue into tonight with VFR holding until our
boundary approaches overnight. As this boundary approaches a drop
into MVFR is likely and storms will be possible. Still a conditional
environment as mentioned in the main discussion above. So have
kept with PROB30 for TSRA for now. Behind the boundary a shift
to the west for winds and less gusty. Ceilings should also lift
behind the boundary with a return to VFR from west to east.
Later in the day the wind shift will continue to the northwest.

KMSP...Gusty southerly winds sustained above 20 knots will
continue this evening. Winds will calm some overnight to below
this threshold. There will also be a shift to the west by 12Z
before the morning rush. However this is also the most likely
time for storms to pass through if they can maintain themselves
all the way to the terminal area. It should only last an hour or
two if they occur. Behind this the winds will shift farther to
the northwest by the afternoon.

/OUTLOOK FOR KMSP/
TUE...VFR. Chc MVFR/-SHRA.Wind E 5-10kts.
WED...SHRA/MVFR. Chc TSRA. Wind E 5-15kts.
THU...SHRA/MVFR. Chc TSRA. Wind E 5-15kts.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...Extreme Heat Warning until 9 PM CDT this evening for Anoka-
     Benton-Blue Earth-Brown-Carver-Chippewa-Chisago-Dakota-
     Douglas-Faribault-Freeborn-Goodhue-Hennepin-Isanti-
     Kanabec-Kandiyohi-Lac Qui Parle-Le Sueur-Martin-McLeod-
     Meeker-Mille Lacs-Morrison-Nicollet-Pope-Ramsey-Redwood-
     Renville-Rice-Scott-Sherburne-Sibley-Stearns-Steele-
     Stevens-Swift-Todd-Waseca-Washington-Watonwan-Wright-
     Yellow Medicine.
WI...Extreme Heat Warning until 9 PM CDT this evening for Barron-
     Chippewa-Dunn-Eau Claire-Pepin-Pierce-Polk-Rusk-St. Croix.

&&

$$

DISCUSSION...Strus
AVIATION...NDC