171
FXUS63 KMPX 281806
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
106 PM CDT Sat Jun 28 2025

.KEY MESSAGES...

- A line of strong to maybe severe storms is tracking across
  Minnesota this morning with chances for hail and wind.

- Hot and humid today with heat index values in the 90s.

- Another chance for severe storms this afternoon into evening.
  All modes of severe are possible: tornado, wind, and hail.

&&

.UPDATE...
Issued at 1009 AM CDT Sat Jun 28 2025

Today is one of those classic summer days where you feel like
you have a good conceptual model in mind for how things will go
when you walk in the door to start your shift in the morning,
only to see a cluster of storms develop over eastern South
Dakota that throws that picture in your head into the fan...

There`s literally no guidance that produced the ongoing cluster
of showers and storms over southwest MN, which makes predicting
how this cluster of storms will impact the expected round of
convection later today difficult. The general consensus from the
HREF is that we would see storms rapidly fire between 22z and
00z up in the vicinity of Little Falls, Alexandria, and Morris.
However, none of these models had this mornings round of showers
and storms. Looking at surface observations, there is an outflow
boundary over northwest Iowa, but surface winds near the MN/SD
border are already returning to their non-convection disrupted
state, so it is possible this cluster of storms will have
minimal impacts on the atmosphere. On satellite, there`s also a
band of accas with a few storms trying to develop along eastern
portions of the ND/SD border. This all makes what happens later
today about as clear as mud. That band of accas across the SD/ND
border will likely be the forcing that gets things going over
central MN, but will those storms be able to tap into 4000+ j/kg
of CAPE that was supposed to stream north out of Iowa today? We`re
still in and a wait and see stance, even 8ish hours out from
storms firing. The going theory though this morning is that the
accas in the eastern Dakotas is the feature to key on, with
storms still most likely to fire over central MN, though the
ongoing activity over southern MN may delay that initiation.
Once storms initiate, we`re still anticipating a high
CAPE/low (but not no) shear environment. So an environment that
favors multi-cell clusters with transient supercell structures,
with at least an attempt at an organized forward propagating
MCS. However, these weakly forced, weaker flow, high instability
environments are really driven by mesoscale or smaller features
that are hard to predict, so get ready for some atmospheric
surprises the rest of the weekend.

&&

.DISCUSSION...
Issued at 231 AM CDT Sat Jun 28 2025

This weekend... A line of thunderstorms has developed across
western Minnesota early this morning. This line is in an area of
higher instability which has allowed for the rapid development
of convection as the low level jet has picked up. However as
these storms continue to the east the instability falls off
significantly. So long lived storms will require more upscale
growth into a full MCS. CAMs have not had a good show so far
this morning with almost every HRRR run being wrong. The RRFS
has shown some skill in determining the convective modes and
overall picture even if the CI timing has been off. Overall
going to have to depend more on conceptual models and
observations with this poor CAM showing. Based on the trends in
current observations the line continues to build itself and grow
upscale. It just comes down to if it can grow enough before it
outruns the best instability. How far east theses storms can get
will have in influence on the environment later today. A large
MCS moving across the whole state will make it hard for the
environment to regenerate into a more convectively favorable
one. However we still have the warm and moist air continuing to
advect into the Upper Midwest. This will bring heat index values
into the 90s across southern Minnesota and parts of western
Wisconsin. It will not get as warm in central Minnesota, more
upper 80s. Thinking back to the ingredients for thunderstorms
we will have lift from the warm front moving across Minnesota,
ample instability, tons of moisture with precipitable water
values over 1.5", and the one parameter with some doubt is
shear. This could be explosive amounts of instability like we
had a week ago, the difference this time is much less CIN. This
could lead to quick development of storms this afternoon. There
should be an initial discrete mode with supercells possible, but
it could quickly become more multicell in nature. The greatest
risk will be during this chance for supercells when all severe
modes will be in play. The tornado risk will be lesser in the
more multicell mode. Much of the rain chances today will be
convective in nature. So the temporal amount of the day
impacted by rain will not be as great as the forecast makes it
look. It is more a factor of uncertainty in when the rain will
occur. When it does occur it will be heavier thunderstorm rain
rather than what we had a few days ago with more widespread rain
that laster for longer periods. Moving into Sunday a cold front
will move in and bring some relief. However in the
afternoon/evening time frame storms will fire along the front.
Positioning of the front by this point will give most of us a
chance for more rain showers or weak thunderstorms. The area
that will be far enough ahead of the front for a chance a
stronger storms will be parts of western Wisconsin like Eau
Claire.

Next week... Great summer days to start the week Monday and
Tuesday with highs in the upper 70s to lower 80s and a break
from the rain and storm chances. By Wednesday a frontal passage
will provide the next chance for some more active weather.
Still quite the spread in global ensembles so PoPs remain low. A
generally more unsettled period continues into the later part
of the week, but with continued spread in the ensembles. So the
forecast shows low PoPs throughout this period. As we get closer
the forecast envelope will shrink and these PoPs will be fine
tuned to be higher for smaller periods of time. What is more
certain though is no huge temperature swings expected with
seasonable temperatures continuing into the mid to late week.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1254 PM CDT Sat Jun 28 2025

Although morning convection has added a bit of uncertainty to
this forecast, it looks like it`s impact on destabilizing the
atmo is going to be pretty minimal today. The main change to the
going TAFs was to delay the TS mention by a couple of hours at
terminals. Current expectations are that storms will rapidly
develop out by AXN between 23z and 01z, quickly building into
the STC area. After that, confidence diminishes as to how the
storms will evolve. A line of storms is certainly plausible, as
most CAMs show, but how quickly that forms, how fast it goes and
so on has little confidence at the moment, so outside of AXN &
STC, kept TS mention to PROB30s. One thing to watch is we do
have a band of accas right now where 700mb temp advection is
maximized in western MN and we may see some isolated TS develop
within this band of WAA before the main show gets going. Late
tonight into Sunday morning, we could also have a complex coming
out of SoDak and heading for southern MN, though confidence on
this potential shra/ts area is even lower than what we have for
this evening. Bottom line, look for amendments and continued
changes with 00z TAF update.

KMSP...Main impact from -RA moving over MSP at the start of the
period is it looks to delay the main TS threat for later this
evening, which should push the potential for strong to severe
storms out beyond the evening push for tonight. Dewpoints will
remain in the upper 60s through Sunday, with a weak boundary
coming through Sunday afternoon, this boundary will have the
potential to spark more shra/tsra Sunday afternoon, which is why
we added the second prob30 for TS to the 18z TAF.

/OUTLOOK FOR KMSP/
MON...VFR. Wind NW 10-15G25 kts.
TUE...VFR. Wind NW 10-15 kts.
WED...VFR. Chc TSRA. Wind SW 5-10 kts.

&&

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

&&

$$

UPDATE...MPG
DISCUSSION...NDC
AVIATION...MPG