479
FXUS63 KMPX 040006
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
706 PM CDT Mon Jun 3 2024

.KEY MESSAGES...

- Scattered showers and thunderstorms across western Wisconsin
  this afternoon.

- A line of thunderstorms will move through the area tomorrow
  afternoon & evening. Isolated damaging winds & a tornado or
  two are possible, primarily across eastern Minnesota & western
  Wisconsin. Widespread rainfall amounts of 0.5-1" could
  exacerbate ongoing flooding, especially where locally higher
  amounts occur.

- Trending drier towards the end of the week & through next
  week.

&&

.DISCUSSION...
Issued at 232 PM CDT Mon Jun 3 2024

Showers and thunderstorms have developed across western
Wisconsin along a lingering frontal boundary left over from last
night`s precipitation. Deep shear values on the order of 20-25
kts mean storms will relatively short-lived & pop-up in nature,
but CAPE values of 1500-2000 J/kg mean a few stronger updrafts
capable of small hail & gusty winds are possible. This activity
will wane towards sunset, with a relatively clear & calm night
expected. Slight warm advection will help to limit fog
development overnight, but patchy dense fog still looks possible
across low-lying areas of eastern Minnesota & western Wisconsin.

A cold front will move through the region during the on Tuesday,
with an elongated pressure trough stretching back to a fairly
deep parent surface low over the southern Canadian prairies.
This front is forecast to move through our area during the peak
heating of the afternoon, and forecast CAPE shows ample
instability of around 2000 J/kg ahead of the front across
eastern minnesota & western Wisconsin. However, the best forcing
& deep shear will remain behind the frontal boundary and any
showers & thunderstorms, and any shear along that storms will
be able to utilize will be fairly weak & nearly unidirectional
along the front. This would suggest that storms that initially
develop during the early afternoon across eastern SD/western MN
would quickly merge & become linear, with the line of showers
and thunderstorms progressing eastwards across Minnesota through
the afternoon & during the evening across western Wisconsin.
Various high-resolution models show pockets of updraft helicity
tracks & stronger reflectivity cores within the line, meaning
isolated damaging wind gusts and a tornado or two are possible
if a few stronger cells are able to modify their local
environment & increase shear values via mergers & remnant
boundaries. Heavy rain is expected with the thunderstorms
during the afternoon & evening, but the progressive nature of
the front should limit how long it rains over any given area.
Widespread precipitation amounts generally around 0.5-0.75" are
expected, but localized amounts near 2" can`t be ruled out if
additional thunderstorms ahead of the line are able to develop.
The chances for this look highest over east-central Minnesota &
northwest Wisconsin, & flood watches may be needed by tomorrow
morning if a signal for heavier rain over these areas continues
to develop.

The line of storms will be through eastern Minnesota by early
evening & out of our area into central Wisconsin by midnight,
with clearing skies and cooler temperatures by sunrise.
Strong northwest flow & cooler temperatures aloft develop behind
the front, which will likely allow for another round of
scattered diurnally- driven showers and thunderstorms across
central Minnesota and western Wisconsin. Daytime temperatures
will be quote cooler behind the front with highs in the mid-60s
to low-70s.

The upper air pattern remains fairly consistent through the
weekend which will lead to generally cooler and drier
conditions. A few diurnally-driven showers are possible daily
with the cooler temperatures aloft, but the support for these
wanes by later in the week. saturday could see a bit more
widespread precipitation as models depict a weak shortwave
embedded within the northwest flow passing over the Upper
Midwest. daytime temperatures will generally be in the low to
mid 70s into early next week.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 630 PM CDT Mon Jun 3 2024

Aside from a stray shower at KEAU over the next hour or so, dry
conditions are expected at all TAF sites through the Tuesday
morning. Areas of fog, especially near bodies of water, look
likely from eastern MN through western WI, so this would impact
the WI TAF sites. As such, have added MVFR-IFR fog mention
there. Then attention turns to organized convection sweeping
eastward over MN/WI during the day Tuesday. Have transitioned
the PROB30 mention to TEMPO mention for CB/TS. Held it at MVFR
at this point but IFR-or-lower conditions are certainly viable
in heavy rainfall. The timing will be 18z-22z in western MN to
20z-24z in eastern MN into western WI, potentially even a bit
later (as in, beyond this TAF period).

KMSP...No issues through midday Wednesday as winds remain under
10kts but near 5kts, so just enough to avoid fog concerns.
Convection looks to impact MSP starting early afternoon, with
best timing in the 21z-02z timeframe, with conditions very
likely at best MVFR and at worst LIFR with degraded
visibilities. Winds could also run VRB25G40kts with the line
as it moves across but will see how models evolve the system
before adding in wind impacts.

/OUTLOOK FOR KMSP/
WED...VFR. Chc SHRA. Wind W 15-20G30 kts.
THU...VFR. Wind NW 15-20G35 kts.
FRI...VFR. Wind NW 10-15G25 kts.

&&

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

&&

$$

DISCUSSION...ETA
AVIATION...JPC