380
FXUS63 KMPX 190356
AFDMPX

Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1056 PM CDT Sat May 18 2024

.KEY MESSAGES...

- Showers and thunderstorms, some possibly severe, in WI this
  afternoon with the best chance near and to the east of Eau
  Claire, Chippewa, and Rusk counties.

- An active pattern set to begin Sunday night. Multiple chances
  for rain, possibly heavy, and thunderstorms over the next
  week. Greatest risk for heavy rain will be on Tuesday.

&&

.DISCUSSION...
Issued at 210 PM CDT Sat May 18 2024

Today and tonight... A cold front continues to move across
Minnesota this afternoon. Ahead of the front has more warm air
advection and moisture with drier air behind it. The temperature
gradient of this front is not as obvious at this point of the
day, as much of the area along and ahead of it has had
significant daytime heating and is above 80 degrees. The front
is well defined by the cumulus clouds along and ahead of it.
Building instability will allow for these cumulus clouds to
start to tower this afternoon. Some have already started to gain
some height across Wisconsin as seen on GOES cloud phase RGBs.
This will continue through to the evening as peak heating and
convective temperatures are achieved. The timing of where the
cold front is will be key, as has been mentioned in all the
previous discussions. Currently expecting this timing to work
out near or to the east of Rusk, Chip, Eau Claire Counties. Some
of these storms as seen in the SPC marginal risk could be
strong to severe. This would likely favor hail in the early more
discrete phase, but isolated high wind gusts are possible as
well with favorable mixing from today`s heat.

Sunday through Wednesday... This will be the focus of the week
with inches of rain forecast. First on Sunday another LLJ will
pick up with a warm front moving in from Iowa. This will provide
for a setup not unlike what we saw Friday evening and night. It
does look like a better forcing and moisture setup though, so
more confident in the occurrence of this rain and totals will be
higher as seen in out QPF forecast. This whole period will be
supported by an upper low over the Canadian Prairies. Short wave
after short wave will pass through the Upper Midwest along the
south side of this larger circulation. The strongest of these
waves comes on Tuesday. This is helped with surface support as
the main low that remains rather stationary on Monday starts to
move out to the north towards us on Tuesday. As this moves we
will move into the most favorable area of lift. This is where we
see the highest QPF, with amounts in ensembles of 2 to 4 inches
possible, as mentioned in the previous discussion. The rain
part of this forecast looks very likely, but what is less
certain is how far north we can see severe weather. SPC has a
day 4 outlook across parts of southern Minnesota and western
Wisconsin. Good shear and as mentioned before forcing could
provide for this. Less certain on the instability front as
cloudy and rainy days often do not have the heat needed for
large amounts of CAPE and therefore this could be more marginal.
That`s why the risk area is to the south where it should be
warmer that the higher risk is present. This severe chance is
also seen in machine learning outlooks run by CSU. So Tuesday
will be the day to keep an eye on for multiple reasons. Rain
chances persist into Wednesday as this wave moves out of the
Upper Midwest. Wednesday will also be the coolest day of the
week with high temperatures in the upper 50s to mid 60s.

Thursday into next weekend... Models get much more dispersive in
this period. Still plenty of QPF among ensemble members, but not
as clear of a signal and much more spread. Overall it seems a
more active period is likely to continue, but confidence on
timing of when rain could fall remains low at this time.
Temperatures should be fairly steady this period with near to
maybe slightly below normal depending on cloud cover.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 1055 PM CDT Sat May 18 2024

Increasing mid level clouds Sunday morning, then showers/
thunderstorms become possible in the afternoon across western
MN, spreading east Sunday evening. Light and variable winds
tonight will turn south southeast Sunday.

KMSP...No concerns tonight.

/OUTLOOK FOR KMSP/
MON...Chc AM MVFR/-TSRA. VFR/chc SHRA aftn. Wind SE 5-10 kts.
TUE...MVFR or IFR/TSRA likely. Wind NE 10-15 kts.
WED...VFR. Chc MVFR/-SHRA. Wind WNW 15G25kts.

&&

.HYDROLOGY...
Issued at 253 AM CDT Sat May 18 2024

The heavy rain event for Tuesday currently highlights the
potential for a large footprint of 1 to 3 inches of rain, with
some locations pushing 4 inches to hit much of the upper MN
River Basin. Gauges at Montevideo, Granite Falls, and Morton are
still at or near minor flood stage and if the kind of rainfall
amounts we are currently seeing were to fall in the upper MN
basin, then renewed flooding along the Minnesota River upstream
of Mankato will be possible as we head into Memorial Day
weekend.

&&

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

&&

$$

DISCUSSION...NDC
AVIATION...Borghoff
HYDROLOGY...MPG