249
FXUS63 KMPX 301741
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1241 PM CDT Tue Apr 30 2024

.KEY MESSAGES...

- Slight Risk (Level 2 of 5) of severe weather across south
  central Minnesota this afternoon for the next round of showers
  & thunderstorms. The main threats are damaging wind and large
  hail, along with the chance for an isolated tornado or two.

- Unsettled weather pattern continues, with multiple chances for
  rain in the upcoming forecast. The next round of widespread
  rain will be Thursday, followed by additional rain chances
  Saturday and again early next week.

&&

.DISCUSSION...
Issued at 340 AM CDT Tue Apr 30 2024

The dreary Monday weather is exiting stage left this morning, as the
surface low has now drifted into northern Wisconsin. Latest
observations reveal the mist/drizzle has lifted north and all that
is left is a slow moving layer of stratus. This cloud layer will
continue to drift eastward over the coming hours. Winds have become
light following the departure of the surface low and forecast
soundings have hinted at the potential for some patchy fog
developing across central Minnesota. Any fog that develops will mix
out of the picture as southeasterly winds increase today, ahead of
the next round of active weather.

Our attention remains focused on a potent shortwave trough that is
captured on GOES water vapor imagery as it begins to advance east of
the Rockies. Ahead of this feature is a mid-level thermal ridge,
which will will be a key player in a notable warm-up on tap heading
into this afternoon. The latest forecast calls for highs in the 60s
to low 70s across the area. Following a dry and warm period for much
of the day, the focus will shift to an incoming line of rain and
thunderstorms. The shortwave trough is progged to slide to the east
of the Dakotas this afternoon, becoming negatively tilted as it
lifts northeast through Minnesota. Strong diffluence will aid in
creating broad ascent east of the trough. A line of showers and
thunderstorms will develop east of the this feature as the trough
interacts with the wing of ongoing warm/moisture advection. CAM
guidance is in stellar agreement with the expected evolution of
today`s convective event, likely due to the synoptic nature of the
forcing. Starting early this afternoon, a line of convection will
move into western Minnesota. The line of storms will continue
east into the evening, with the leading edge set to cross I-35
around 00z. Showers and storms will then persist east into western
Wisconsin and should end shortly before midnight. Not many
changes to report with the latest Day 1 outlook from the SPC, as a
Slight Risk for severe weather remains in place across the
southern 3 tiers of counties in Minnesota. Forecast soundings
across this area depict an environment that is very much in the
character of a low CAPE/high shear event, given the expected
500-1000 J/kg of MLCAPE and ~50 knots of 0-6km bulk shear. While
instability will be lacking, low- level curvature in the
hodographs indicates an atmosphere that will be capable of
producing severe weather. Damaging winds and large hail will serve
at the primary threats, however we cannot rule out an isolated
tornado or two given the forecast wind profiles. It`s reasonable
to say the expected "scattered" nature to the severe weather
threat is likely the ceiling for this event given the stable lapse
rates aloft and lack of moisture (forecast dew points reach the
mid 50s along I-90). HREF guidance supports the idea that limited
instability will put a lid on the overall threat, with a greater
signal for much stronger updrafts to the south in Iowa. A Marginal
Risk remains in place roughly to I-94 in Minnesota and Wisconsin.
While we cannot rule out an isolated instance of damaging wind or
hail in the Marginal Risk area, the presence of only a few
hundred joules of MUCAPE should significantly limit the severe
weather potential (including in the Twin Cities Metro). Rainfall
amounts between 0.5" to 0.75" remain the expectation for most
locations, though the HREF LPMM QPF parameter illustrates the
possibility of higher amounts given convection/training.

Dry weather returns for much of Wednesday and the temperatures will
remain mild, with highs in the 60s across south central Minnesota
and western Wisconsin. Of course, it`s only fitting that we "Rinse
and Repeat" again on Thursday, as the next storm system of interest
brings the return of widespread soaking rains and cooler
temperatures. The latest global ensemble suite indicates that the
storm may track a bit further to the southeast when compared to the
last three storm systems. This would mean that most, if not all of
the forecast area is on the cooler side of the storm and as a
result, severe weather is not expected locally at this time. Early
indications are that another half inch to inch of rain may fall from
early Thursday through Friday morning, which is supported by
forecast PWATs well into the 90th percentile of sounding
climatology.

The forecast will dry out again on Friday, but the departure of the
Thursday storm system and yet another disturbance on Saturday will
make for a breezy end of the work week. Speaking of the disturbance
on Saturday, it does not look like the type of weather system that
could produce soaking rains, rather scattered showery type precip
for the first half of the weekend. Perhaps it comes as no surprise
that another, yes... another more notable storm system will move
through the Upper Midwest early next week and the early read from
the ensemble suite is that we could be looking at a fifth widespread
soaking rain event (dating back to this past Friday). The new NBM
output features "likely" PoPs for the Monday/Tuesday system. It does
not look like we are taking a break from needing the umbrella
anytime soon...

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1226 PM CDT Tue Apr 30 2024

While conditions are currently VFR, showers have already begun
to develop and move into southern MN. Continual development is
expected through this afternoon, with an eventual line of
thunderstorms moving west to east across the southern half of MN
and into WI late this afternoon and into this evening.
Conditions will fall to at least MVFR with IFR likely within
heavier storms. For southern MN terminals (MKT, RWF, and MSP),
VFR expected after midnight after storms move through as skies
clear out. Farther north, MVFR cigs will continue through
Wednesday morning as overcast skies will be slower to clear.
Southeasterly winds will increase to near 10 knots this
afternoon and then flip to westerly after the storms and cold
frontal passage this evening. Winds will increase overnight with
sustained values of 15-20 knots and gusts of 25 to 30 knots
before slowing towards sunrise Wednesday. 40 knot southwesterly
LLWS is also likely for our southern and eastern terminals.

KMSP...Adjusted TEMPO for thunderstorms to be from 00-02Z with
conditions falling to IFR. Showers should end by 04Z while
westerly winds will strengthen into Wednesday morning with gusts
approaching 25-30 knots.

/OUTLOOK FOR KMSP/
WED...VFR. Wind W 10-15G25kts.
THU...MVFR/-SHRA. Chc IFR. Wind E 10-20G30 kts.
FRI...VFR. Wind W 10-15G25kts.

&&

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

&&

$$

DISCUSSION...Strus
AVIATION...CTG