355
FXUS63 KMPX 312016
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
316 PM CDT Fri May 31 2024

.KEY MESSAGES...

- Showers & thunderstorms become more widespread this evening.
  Localized heavy rainfall possible from south-central Minnesota
  through western Wisconsin.

- Severe thunderstorms & localized heavy rain possible Sunday
  evening, especially across western and southern Minnesota.

- Another chance for widespread rain likely Tuesday night.

&&

.DISCUSSION...
Issued at 240 PM CDT Fri May 31 2024

TONIGHT/SATURDAY MORNING...Showers and thunderstorms are
becoming more widespread across southern Minnesota this
afternoon, as frontogenesis & moisture convergence increase
along a slow moving front. This activity will continue to spread
north and east along the front this evening, with showers and
thunderstorms continuing into tomorrow morning as the front
slowly exits the area to the east. Storm motion & low-level
moisture return vectors are oriented parallel to the slow
moving front, meaning showers & thunderstorms are likely to
train over the same areas tonight. Precipitable water values in
the 90th percentile are high, but not extreme, so while
localized heavy rain & flash flooding fare a potential concern -
it does not appear to be a widespread threat. High resolution
ensemble guidance continues to highlight a swath of 1-2" of rain
from south-central Minnesota, through the southern reaches of
the Twin Cities metro, & into west-central Wisconsin. Individual
high-res models depict localized pockets of 3-4" where training
of the heaviest thunderstorms occur, so while we can`t say
exactly where these heaviest amounts may occur, our confidence
is fairly high that we will see some localized heavy rain
impacts tonight through tomorrow morning. CAPE & shear values
are fairly paltry for a severe weather threat, but can`t rule
out isolated small hail and/or gusty winds from a few storms
this afternoon & evening.

SATURDAY-SUNDAY MORNING...The rain will be out of eastern
Minnesota by mid-morning & western Wisconsin by early
afternoon, with dry weather then expected into Sunday afternoon.
Guidance continues to indicate an environment favorable for
severe weather developing across western Minnesota by late
Sunday afternoon, ahead of a cold front/surface low approaching
out of the eastern Dakotas. MLCAPE values around 2000 J/kg &
effective bulk shear of 30-40 kts will support all modes of
severe weather, although the threat for large hail/tornadoes
looks to mainly be limited to discrete supercells early in the
event across eastern SD/far-southwest MN. Early long-range CAM
guidance suggests that these initial discrete storms will merge
into a MCS by the evening, which will move into western &
southern Minnesota through the evening. Instability values are
forecast to drop off across central Minnesota, so the severe
threat is not really anticipated to continue into eastern
Minnesota & western Wisconsin Sunday night, but we`ll have to
see if this trend continues. Heavy rain could also be a concern
given PW values forecast to be above the 90th percentile, but
the progressive nature of the MCS & its expected weakening
through the night should act to limit rainfall amounts to the
1-2" range. While the severe threat may diminish across central
& eastern Minnesota, the thunderstorm complex is still expected
to persist as it heads east, with stormy weather continuing
into Monday morning across western Wisconsin.

MONDAY THROUGH FRIDAY...Monday will be dry in the wake of the
departing storm system, however this will be short-lived as
another system approaches the area Tuesday. The surface low with
this system is actually forecast to be stronger than the one
Sunday night, but displaced more to the north over southern
Canada. Widespread convection is again expected along the cold
front draped to its south, which will bring good chances for
another 1" of rain (at least) through Tuesday night. Confidence
is still fairly low on the potential for severe weather and
heavy rain/flooding concerns, given differences in the timing of
the front & uncertainty on the quality of deep shear this far
south along the front. Beyond Wednesday, cooler northwest flow
develops aloft as a broad & persistent trough lingers over the
Great Lakes & eastern CONUS through next weekend. Temperatures
will be cooler, with periodic shower chances but lesser chances
for organized thunderstorms/heavy rain.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1222 PM CDT Fri May 31 2024

VFR turning MVFR with periods of SHRA & TSRA for the TAF period
as a front stalls over the area today. TSRA is most likely after
20z through around 02-03z before we lose instability and SHRA
lingers through 10-12z tomorrow. The main uncertainty within the
TAF will be CIG heights throughout with a high probability of
MVFR for most sites that see SHRA and around a 20-25 percent
chance of IFR mainly during the period of SHRA before 12z.
Visibility could also briefly drop to low MVFR/IFR this
afternoon depending on the strength of storms, however
instability is fairly limited so rainfall rates dropping
visibility below 2sm is not expected for now.

KMSP...SHRA into TSRA coverage is expected to increase this
afternoon as the front stalls over the area, with currently
high-res guidance keeping the line directly over the Twin
Cities. The current TAF keeps us MVFR at the lowest, however
there is still a possibility of some IFR visibility with some
stronger TSRA or even tomorrow morning with the lingering -SHRA.

/OUTLOOK FOR KMSP/
SUN...VFR, MVFR/-TSRA likely late. Wind S 5-10kts.
MON...MVFR/-TSRA early, then VFR. Wind SW to NW 10-15kts.
TUE...VFR early, then MVFR/SHRA/-TSRA. Wind SE 10kts.

&&

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

&&

$$

DISCUSSION...ETA
AVIATION...TDH