012
FXUS63 KMPX 041901
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
201 PM CDT Thu Jul 4 2024

.KEY MESSAGES...

- Thunderstorms and locally heavy rainfall likely today and tonight.

- Numerous chances for showers and a few thunderstorms will
  linger into next week with temperatures remaining below
  normal.

&&

.DISCUSSION...
Issued at 159 PM CDT Thu Jul 4 2024

Our first round of rain today is currently located along the I-94
corridor and slowly moving northeast. Rainfall amounts from this
activity has resulted in generally 0.1-0.2" with up to 0.5" within
the very isolated heavier cells. Behind this first round is a brief
clearing, evidenced by the lack of returns on radar and thinning
clouds and small clearings on satellite over southern MN. However,
in our weakly stable environment, it won`t take much for new
convection to develop with a little daytime heating as the mid-level
jet and vorticity maximum moves in from the west. Indeed, scattered
showers and thunderstorms are in the process of developing across
southwestern MN late this morning. This activity will move
northeast, growing in coverage into scattered broken lines of cells,
reaching the Twin Cities around 2-3 PM and western WI later this
afternoon. The best chance of severe weather remains in southern to
southeastern MN along I-90 where enough heating should result in
1500-2000 J/kg of MLCAPE within 35-40 knots of bulk shear. A weak
tornado or two is possible within the surface vorticity rich
environment near the surface low, but the main threat from any
stronger storms will be large hail.

Heavy rain will be possible with any thunderstorms, as PWATs range
from 1.2-1.4" and vertical profiles are very moist. Though, the
transient non-continuous nature of the storms should limit the flash
flooding risk to a large degree. Nevertheless, rounds of storms with
rainfall rates of 1-1.5" per hour over the same area could lead to
localized flash flooding. This will be especially true as we
progress through tonight, as the precip becomes more favored from
south-central MN into northwestern WI. Precip in southeastern MN
should decay with the dissipating instability while precip within
the deformation zone north of the occluding surface low will be
favored as synoptic lift increases. Showers and thunderstorms will
wrap westward around the surface low as it travels east, meaning
that a county wide or two area could see heavier rainfall rates for
a period of 2-4 hours. This could lead to localized areas of 3-4" of
rain while elsewhere from south-central MN to western WI will see
rainfall of 1-2.5" by 12Z Friday. The low pressure system will
slowly move east-northeast out of our area by early Friday afternoon
with lingering, but decaying wraparound precip exiting with it.
However, isolated showers and a thunderstorm may occur across MN
during Friday afternoon underneath the backside of the upper-level
shortwave.

While the aforementioned shortwave will move east into the
Great Lakes Saturday, a broader longwave trough will settle in
over the Northern Plains/Upper Midwest through at least early
next week. This will result in stagnant, mild temperatures
(highs in the mid 70s to lower 80s into Monday). Additional
chances for precipitation will also be possible Saturday through
at least Tuesday as embedded impulses round through the trough.
The heavy rain and severe weather threats don`t appear to be
significant with any of the impulses, but don`t expect a
prolonged break in the wet weather just yet. However, long-range
forecast models do suggest the trough finally exits to our east
during mid-next week. At the same time, a strong upper-level
ridge will move into the western CONUS, with pieces of this
ridge potentially spilling over into the central CONUS the
latter half of next week. This signals a potential warmer,
drier summer pattern occurring eventually for our region (also
supported by the 6-10 and 8-14 Climate Prediction Center
Outlooks) sometime within the next 2 weeks. We just need to get
through a few more days of rain first.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1234 PM CDT Thu Jul 4 2024

Main aviation concern will be the ongoing showers and storms,
which will last through this evening for most. A cluster of
storms are currently developing over south-central MN, which
would bring MVFR/IFR visibilities during the heaviest rainfall
rates. A bit of a lull in precipitation is still expected late
this evening/night, before rain showers and MVFR/IFR ceilings
become more widespread overnight into tomorrow morning. Winds
will remain generally light and variable today, before shifting
out of the N/NW and increasing slightly tomorrow. The strongest
thunderstorms, which could have wind gusts up to 50 mph and
hail greater than an inch, are expected to stay further south
near and along I-90.

KMSP...The first wave of showers have passed this morning, and
the focus turns to the redevelopment of precip to the southwest.
Most of the cells over south-central MN are still elevated, so
the threat for severe weather is lower, but reduced vis and
thunder will still be likely. Storms could move in as early as
1:30-2pm, and would be off and on through the early evening.
Cigs are still on track to drop to low MVFR by this evening and
will likely become IFR late tonight through tomorrow morning.
Isolated showers/storms are possible tomorrow afternoon/evening,
but confidence is low so have kept mention out of the TAF for
now.

/OUTLOOK FOR KMSP/
SAT...Chance PM MVFR SHRA/TSRA. Wind SW 5-10 kts.
SUN...MVFR/SHRA/TSRA likely. Wind SW 10-20 kts.
MON...VFR, chance MVFR. Wind WNW 5-10 kts.

&&

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

&&

$$

DISCUSSION...CTG
AVIATION...BED