454
FXUS63 KMPX 111759
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1259 PM CDT Tue Jun 11 2024

.KEY MESSAGES...

- Rain showers across MN this morning will continue to move
  east. Redevelopment of one or two strong thunderstorms
  possible in eastern MN/WI this afternoon.

- Warm and muggy Wednesday with strong to severe thunderstorms possible
  in the afternoon and evening.

- Seasonable temperatures to end the week with precip chances
  returning next weekend.

&&

.DISCUSSION...
Issued at 311 AM CDT Tue Jun 11 2024

Scattered rain showers have made their way into central MN early
this morning. This activity will continue to move east, reaching the
Twin Cities by around 6 AM, EAU around 9 AM, before exiting our CWA.
Rainfall amounts for most of our area should be just enough to wet
the pavement, except in our north-central MN counties where perhaps
a 0.1-0.25" may occur. Clouds should clear out behind the precip,
allowing for most of MN to see quite a bit of sun in the afternoon.
Highs will warm into the mid 70s to lower 80s as a result. There
still is also a chance for an isolated thunderstorm or two to
develop in eastern MN/western WI this afternoon. However, latest
CAMs are even less optimistic than yesterday morning`s. Still, can`t
rule out a stronger thunderstorm capable of producing a strong wind
gust or large hail within the pool of 500-1000 J/kg CAPE.

Our attention now turns to Wednesday, as it is currently the most
interesting day of the period. Southwesterly flow will increase
throughout the day as an upper-level jetstreak along the
US/Canadian border approaches from the west. This surface flow
will cause warm air and moisture advection into the MN and
western WI into Wednesday afternoon. Large-scale forecast models
have continued to produce light to moderate QPF across MN
during the morning hours, likely in response to the moisture
advection and convergence at the nose of a LLJ. CAMs are now
also showing this possibility, with some scattered convection
developing in western MN and pushing east through late morning.
This will need to be monitored as greater coverage of elevated
morning convection than anticipated could influence the severe
weather risk later in the afternoon. Where precip does manage to
hold off, highs will be really warm in the mid to upper 80s. A
few 90s are even possible in southwest MN. It will also feel
really muggy as dewpoints will climb into the 60s, with some
upper 60s in western MN. These combined with modest mid-level
lapse rates should allow for MLCAPE values between 1500-2500
J/kg by late afternoon. Thunderstorm initiation will eventually
occur, though timing and placement remains uncertain as
evidenced by CAMs. Some solutions want to intensify the morning
convection (making it the main show) and move it southeast into
IA. Others suggest a second round developing somewhere between
central and southern MN in the late afternoon. Where initiation
occurs will likely depend where the least capping is located,
considering there is not an overly strong lifting mechanism with
this system. Once storms do form, they will be within 40-50
knots of bulk shear. This will be sufficient for supercells;
some of which could remain discrete for the first 1-2 hours.
During this time, large hail (potentially +2") will be the main
threat but damaging winds and a few tornadoes may also occur.
The latter being more likely as we get closer Wednesday evening
in southern MN with the increasing low-level helicity. As storms
travel southeast, it seems like upscale growth into small
clusters is most probable. This would then transition the main
severe threat to damaging winds. Heavy rain is also expected
with any storms, given the 1.5-1.8" PWATs. Flash flooding still
doesn`t seem very likely but could occur if rounds of storms
travel over the same area. The convection should exit to our
southeast during Wednesday night.

After Wednesday, temperatures return to more seasonable levels to
end the week. The forecast looks mostly dry Thursday and Friday as
high pressure from the Canadian Prairies moves into the Northern
Plains. However, guidance favors this surface high moving east of
the region by Saturday. Following in its wake will be a compact
trough moving northeast into the Upper Midwest from the desert
Southwest. In fact, the GFS, ECMWF, and GEM all show this trough
originating from the closed off low currently near Baja California!
With a "tropical" wave forecast to affect our region, NBM PoPs make
a big return on Saturday with values of 50% to over 70% for the
entire CWA. (And still 5 days in advance.) Sunday may have a chance
to be slightly drier, though model solutions start to diverge after
Saturday. General model consensus after Saturday hints that we will
be favored with warmer than normal temperatures and above normal
precipitation for most of the next 2 weeks.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1219 PM CDT Tue Jun 11 2024

VFR at initialization for all TAF sites. Visible satellite
imagery shows the cloud shield continuing to erode to the east
with the progression of the cold front. Still a small chance of
a few showers in western WI, mainly near KEAU, that could pop
up but any development will be isolated so just used a 3hr
window of VCSH to account for it at this point. Clearing skies
expected overnight with diminishing winds (breezy W to NW winds
post-fropa this afternoon) then winds increase from the SSW
after sunrise Wednesday. Mid-level clouds will increase late
morning into early afternoon Wednesday ahead of likely RA/TSRA
development. Precip could impact TAF sites as early as 16z for
most locations but chances ramp up more significantly beyond
18z, so have included PROB30 mentions for locations with the
best potential of late morning/early afternoon convection. Later
TAFs will be able to fine tune the convective potential,
including "upping" the wording to TEMPO or prevailing.

KMSP...Fairly benign conditions expected through Wednesday
morning. Winds will continue to quickly shift from SW to WNW
during the first few hours of the 11/18z TAF, with speeds around
12G18kts. Could be a little gustier than that at times early
this afternoon before winds settle down closer to 10kts late
this afternoon. Winds to drop into the 5-8kt range overnight
while backing to SSW, then increase back to near 12G20kts by
midday. Chances increase mid-to-late afternoon for convection to
impact MSP, especially in that 21z-00z timeframe. Have
introduced the broad timeframe of 18z-00z with a PROB30 at this
point to get the prep time across that TSRA will be developing
Wednesday afternoon. Later TAFs will be able to fine tune the
thinking but opted to get the mention of CB/TS going now.

/OUTLOOK FOR KMSP/
THU...VFR. Wind NW 10-15 kts.
FRI...VFR. Wind N 5-10 kts.
SAT...RA/TSRA/MVFR likely, IFR possible. Wind SE 10-15 kts.

&&

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

&&

$$

DISCUSSION...CTG
AVIATION...JPC