296
FXUS63 KDLH 161815
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
115 PM CDT Sun Jun 16 2024

.KEY MESSAGES...

- Scattered storms are possible this afternoon and evening
  (~50% chance). A few storms may become strong to severe (5-15%
  chance) with large hail being the main threat, but damaging
  winds and perhaps a tornado also possible.

- Very heavy rain and potential for locally considerable flash
  flooding is possible (40-60% chance), especially in northeast
  Minnesota. Scattered strong to severe storms are possible as
  well (15% chance), with large hail being the main threat.

- Rain and storm chances will continue through the end of the
  week and into next weekend.

&&

.DISCUSSION...
Issued at 400 AM CDT Sun Jun 16 2024

The first of several rounds of heavy rain is happening right
now, mainly impacting northwest Wisconsin. This initial surge of
rain and embedded non-severe thunderstorms will continue
northeast through the morning, eventually ending as the upper
level wave moves off to the northeast. Rainfall amounts thus far
have been about as expected, with higher observed amounts just
over 0.7". Radar estimates suggest totals around or just over
an inch may have fallen across parts of southern Price County.
All-in-all, this is transpiring as expected, and we could end up
with localized amounts up to ~2" before this ends later this
morning. Hydro-wise, no major concerns at this time, but some
localized minor flooding still can`t be ruled out.

In the wake of this first round of rain, strong southerly warm
and moist air advection will bring some pretty impressive
instability for this afternoon, especially so in northwest
Wisconsin where MUCAPE values around 2000-3000 J/kg, possibly
approaching 4000 J/kg, will lead to the potential for some
strong to severe storms. As has been mentioned in previous
discussions, this will be a conditional threat with strong
capping aloft in place. We also have some weak subsidence aloft
that negates some synoptic influence. But, models have been
persistent enough about having some frontal boundaries around
this afternoon, which will likely be enough to bust the cap and
lead to the potential for isolated to scattered strong to severe
storms this afternoon and evening. The initial threat, and the
most likely threat, will be for very large hail (2" in diameter
or more) with the strong instability in place, especially with
the first discrete cells that form. There`s also enough veering
in the low-levels, particularly northwest Wisconsin, such that a
tornado can`t be completely ruled out (though hodographs are not
perfectly favorable for tornadic supercells). Damaging winds
can`t be ruled out if storms are able to organize into a line,
which would be most likely in the evening.

Temperatures will be quite warm today, topping out in the mid to
upper 80s for east-central Minnesota into northwest Wisconsin.
This isn`t warm enough to warrant a heat advisory, but the heat
could be hazardous for sensitive groups, especially for those
without good access to hydration or air conditioning.

After sunset, we should lose most instability for a while,
leading to perhaps a brief break in rain for many places. We
then get another strong push of warm and moist air attendant
with passing upper-level shortwaves that will be favorable for
widespread rain and thunderstorms. This is looking like it will
start off as a widespread cluster of rain and non-severe storms
through mid-day Monday, then perhaps another reorganization that
will favor northeast Minnesota as we go into Monday evening and
night as strong low-level frontogenesis sets up. This is when we
will see the greatest threat for flooding, and with excessive
PWAT values around or perhaps slightly higher than 1.75"
(near or at maximum climatology), we will be looking at the
potential for 2-3" of rainfall (perhaps locally higher) through
Tuesday, with the best potential for this just north of the
Brainerd Lakes, stretching into the Iron Range, north towards
International Falls, and east towards Ely. The WPC has placed
this area under a moderate risk for flash flooding (40-60%
chance). The latest trends suggest that the warm front will be
at least somewhat transient, so that will reduce the threat for
extreme flash flooding to some extent, favoring instead a
broader risk for considerable flash flooding. We decided not to
issue a Flash Flood Watch for this update as we continue to
narrow down the area most susceptible for flash flooding, but a
Flash Flood Watch will likely be needed.

In addition to the flooding threat, instability will increase
again Monday night into Tuesday morning, and there will be a
threat mainly for large hail with some of the thunderstorms most
likely on the southern end of the rain closer to the warm front.
Couldn`t rule out some strong winds as well, but right now large
hail seems to be the biggest threat (5-15% chance).

There remains a threat for isolated to scattered severe storms
on Tuesday as a cold front passes through, and this is still
looking more likely to be a damaging wind threat moreso than any
other hazard, though some large hail could be possible. We
retain a slight risk (15-40% chance) for excessive rainfall from
the WPC for much of the region with the combination of rain
expected Monday night, then finishing off on Tuesday with the
storms moving from west to east.

We are still looking to see a brief break from the active
weather with high pressure on Wednesday, but looking ahead
through the end of the week and next weekend, models suggest
that the active pattern will continue with more rain and storm
chances.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 116 PM CDT Sun Jun 16 2024

Stubborn onshore flow off of Lake Superior has led to periodic
intrusions of dense fog into KDLH and North Shore terminals along
with LIFR to VLIFR ceilings. Expect these low ceilings and fog
to hang around into mid afternoon until winds can take on a more
southerly direction. IFR ceilings at KHIB should also rise to
MVFR by mid-afternoon. Otherwise, the remainder of the area is
sitting under MVFR ceilings. Confidence has increased in the
development of scattered showers and thunderstorms along a cold
front in north-central Minnesota later this afternoon initially
as individual storms, and then potentially growing into a line
of storms this evening as storms and the front push southeast.
Still need to pinpoint the exact timing of storms to terminals
downstream, so amendments are likely later this afternoon and
evening. There is a 15% chance that some of these storms could
be strong to severe, containing very large hail (2"+ in
diameter initially during the afternoon in NE MN). Damaging
winds are also possible, but would become the primary threat this
evening as storms transition into a line. Ceilings are expected
to lift to VFR this evening. Some MVFR to locally IFR visibilities
likely with the storms. There will be a brief break in
precipitation tonight before another round of showers and storms
move in from the southwest later tonight into Monday morning.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 116 PM CDT Sun Jun 16 2024

Dense fog continues to persist along the Twin Ports and North
Shore, so have extended the Marine Dense Fog Advisory through
this evening due to the weather pattern not really changing
until storms move over the Lake this evening. Scattered storms,
with a 15% chance of becoming strong to severe, develop along a
cold front over north-central Minnesota this afternoon and push
east into western Lake Superior this evening. Still expect the
strong to severe storm threat to end around mid-evening as
storms push southeast and weaken. Large hail and gusty, erratic
winds will be the main threats with the storms. Expect onshore
flow for most places the rest of today, with a shift to
southwesterly overnight, then back to onshore flow out of the
east to northeast on Monday. Winds may gust to around 15 kt
today, decreasing tonight, and then gust to around 15 knots
again on Monday.

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...Dense Fog Advisory until 1 AM CDT Monday for LSZ140>145.

&&

$$

DISCUSSION...JDS
AVIATION...Rothstein
MARINE...Rothstein