273
FXUS63 KMPX 131730
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
Issued by National Weather Service La Crosse WI
1230 PM CDT Thu Jun 13 2024

.KEY MESSAGES...

- Showers across southern Minnesota this morning, then drying
  out until early Saturday.

- More widespread showers and thunderstorms likely Saturday with
  locally heavy rainfall possible.

- An intense heat wave will build across the eastern third of
  the country next week with the Upper Midwest on its western
  periphery. This will mean periods of hot and humid conditions
  and multiple rounds of thunderstorms with heavy rainfall.

&&

.DISCUSSION...
Issued at 335 AM CDT Thu Jun 13 2024

Storms have finally exited to the southeast early this morning.
A front is trying to make its way eastward across central and
southwestern MN, but surface winds have become light or calm and
for now it has stalled. West of the front dew points have
dropped into the upper 40s to mid 50s while remaining in the 60s
east. Areas of fog are developing along the front and some
locally dense fog is possible, especially where heavy rain fell
last evening. Mid level clouds across SD will spread east early
this morning and a band of showers will likely develop across
western and southern MN just after sunrise. The development of
these showers is almost certain, but CAMs are inconsistent with
the spatial details so for now kept 50-60 PoPs for this area.
Once development occurs, PoPs will likely need to be increased
further for some areas. Showers will exit to the southeast early
this afternoon and clearing will follow for the rest of the day.
Despite early day rain, highs in the low 80s are expected area
wide.

Dry conditions will prevail through most of Friday night, but a
shortwave will eject northeast from the Four Corners region and
could begin spreading showers to southern MN by early Saturday.
A 40 kt LLJ and pwats as high as 1.75 inches are likely to
accompany the shortwave across the area Saturday/Saturday night.
While lapse rates will remain poor and instability limited,
relatively strong moisture flux should allow for a moderate to
heavy round of showers and isolated storms to bring more healthy
rainfall totals. The track of the center of the disturbance
across IA will place southern/eastern MN and WI in the heaviest
swath of rain, where 1-2 inches may fall. There is a Slight Risk
of excessive rainfall for those areas.

The disturbance will exit early Sunday and upper ridging will
quickly follow. A surface cold front will approach from the
northwest Sunday afternoon. Thermal ridging will work up the
front and 925 mb temps of +25 to +27C suggest highs in the lower
90s. Dew points around 70 will send heat indices into the mid to
upper 90s, leading to the first elevated heat concern of the
season. The front should reach at least central MN by Sunday
evening. An EML with mid level lapse rates greater than 8 C/km
should cap the atmosphere and prevent convective development,
but if forcing along the front can overcome the cap, there will
be a conditional risk of severe weather through Sunday evening.

How far south the front sags Monday before returning northward
will depend on the strength of the synoptic system well to the
north in Canada and the building ridge across the east. By late
Monday or Tuesday, a trough over the Rockies should lift it back
north and allow it to become a southwest-northeast oriented
quasi-stationary boundary through at least midweek. Intense
heat and humidity will overspread the Great Lakes and Ohio
Valley throughout this time, and depending on the surface
frontal position and related convective activity, may
occasionally make an appearance this far west. The ensemble
spread for temperature is quite large next week due to spatial
differences with the front. One thing is near certain, there
will be a tremendous amount of moisture over the Gulf, marked by
pwats greater than 2.75 inches. The strength of the ridge
across the east and a 50 kt LLJ across the Plains will funnel
some of this moisture up the front and into the Upper Midwest.
Rounds of thunderstorms, potentially severe, and very heavy
rainfall are possible throughout next week. Flooding may become
an increasing concern over the next several days.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1230 PM CDT Thu Jun 13 2024

VFR conditions are expected for the TAF period with elevated
showers over south-central Minnesota departing by 21Z today.
Northwest winds of 10-15G20kts this afternoon--strongest in
central/western MN--decrease after sunset to around 5kts or
less. Winds will be light and variable for Friday with a SCT CU
deck for the afternoon.

KMSP...VFR conditions expected for the TAF period with northwest
winds around 10kts this afternoon decreasing to 5kts or less
overnight. CU develop by midday tomorrow with VFR bases.

/OUTLOOK FOR KMSP/
FRI...VFR. Wind N at 5 kts.
SAT...RA/TSRA/MVFR likely, IFR possible. Wind SE 10-15G25kts.
SUN...Mainly VFR. Slight chc TSRA/MVFR. Wind S 10-15 kts.

&&

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

&&

$$

DISCUSSION...Borghoff
AVIATION...Skow/ARX