954
FXUS63 KDLH 200944
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
444 AM CDT Mon May 20 2024

.KEY MESSAGES...

- Rain with embedded thunderstorms continue to move across the
  area through today. Total rainfall accumulations around 0.25"
  to 0.50"; locally higher amounts possible.

- A larger spring system brings even more rain Tuesday through
  Wednesday with totals >1" likely for many areas. There could
  be some strong to severe storms on Tuesday as well.

- A little drier weather to end the week, but rain chances will
  persist into the weekend.

&&

.DISCUSSION...
Issued at 442 AM CDT Mon May 20 2024

A wave of showers and isolated thunderstorms is moving across
the area this morning as our first wave of precipitation
expected this week. This is associated with a weak shortwave in
combination with a surge of moisture and is ahead of an inverted
trough at the surface. Plenty of isentropic lift going on this
morning. Total rainfall amounts should range between 1 and 4
tenths of an inch, with a large portion of the Northland getting
at least a quarter inch of rainfall by this evening. Once this
band of precipitation moves out of the area this afternoon and
evening, we should get a short break in the active weather
tonight.

Tuesday into Wednesday is the most concerning time range, as a
much stronger upper level shortwave ejects out of a broader
upper level trough over the Rockies and develops a surface low
over western Kansas late tonight which drives northeast across
the western Great Lakes Tuesday night. This much stronger system
will combine with another surge of Gulf moisture to produce a
period of very busy weather for the Northland Tuesday through
Wednesday. Tuesday evening we should develop a narrow window of
instability with sufficient shear to produce strong to severe
storms Tuesday afternoon and evening, mainly over northwest
Wisconsin. For now it appears damaging winds and large hail are
our main risk, but depending on how the boundary layer develops
we could also have a tornado risk as well. SPC has kept the
slight risk of severe weather on the day 2 outlook this morning.
This system is also likely to generate generous rainfall
amounts with that Gulf moisture feed, and models are continuing
to shows precipitable water values of over 1.25", which is 2
standard deviations above normal values. As of this morning, the
event total rainfall for Tuesday through Wednesday evening has
some areas approaching 3 inches of rainfall. No surprise that
WPC has kept us in a slight risk of excessive rainfall. This
system exits the area Wendesday night, leaving us with some
lingering shower activity into Thursday. We are also looking at
some much cooler temperatures for Wednesday into Thursday, with
highs both days down into the 50s to low 60s, which may be as
much as 10 degrees below normal.

Our stretch of active weather continues into next weekend, with
a signal for the broad upper level trough over the Rockies
slowly shifting east over time, which should continue to push
shortwaves in our direction. Given their scale, the models are
not giving us a very clear signal for timing or track on any of
these features, so it should be no surprise that there are
chances for precipitation Friday through the weekend. However, I
expect we will be able to narrow these down somewhat this week
and be able to pick out some drier periods for outdoor
activities. Temperatures should be near to below normal through
the weekend.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1257 AM CDT Mon May 20 2024

Rain with embedded thunderstorms is moving into the Northland
this morning. As the rain spreads in, the currently VFR
conditions will slowly deteriorate overnight, with all sites
gradually lowering to IFR ceilings with MVFR visibilities,
generally in the 11z through 21z time frame, with approximately
6-9 hours of these lowered ceilings for each terminal. KDLH may
have IFR visibilities as well with wind flow off Lake Superior.
Visibilities improve during the afternoon as the rain moves out,
with improving ceilings a few hours later. Ceilings and
visibilities may deteriorate once again after 04z as east winds
increase once again and another round of showers and
thunderstorms move towards the area.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 442 AM CDT Mon May 20 2024

Rain with embedded thunderstorms is moving into the Northland
this morning. As the rain spreads in, the currently VFR
conditions will slowly deteriorate overnight, with all sites
gradually lowering to IFR ceilings with MVFR visibilities,
generally in the 11z through 21z time frame, with approximately
6-9 hours of these lowered ceilings for each terminal. KDLH may
have IFR visibilities as well with wind flow off Lake Superior.
Visibilities improve during the afternoon as the rain moves out,
with improving ceilings a few hours later. Ceilings and
visibilities may deteriorate once again after 04z as east winds
increase once again and another round of showers and
thunderstorms move towards the area.

For the open water discussion, refer to the NWS Marquette Area
Forecast Discussion at weather.gov/mqt.

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
MARINE...Gale Watch from Tuesday afternoon through Wednesday evening
     for LSZ140>146-150.

&&

$$

DISCUSSION...LE
AVIATION...LE
MARINE...LE