117
FXUS63 KDLH 161541
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1041 AM 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 /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 650 AM CDT Sun Jun 16 2024

Fog at DLH/HIB will persist for another 1-3 hours, but is
expected to lift with southerly flow increasing this morning.
Otherwise, the IFR ceilings are expected to be rather slow to
lift through the morning and afternoon. This afternoon, there is
a chance (~50%) for scattered thunderstorms to develop. Timing
and location of these remains somewhat difficult because their
development is conditional on clouds clearing out and the
presence of frontal boundaries that could trigger the storms.
But, the latest guidance suggests that storms may develop around
INL mid-afternoon, then spread southeast through the afternoon
and evening. There is a 5-15% chance that some of these storms
could be strong to severe, containing very large hail (2"+ in
diameter). Damaging winds are also possible. Ceilings are
expected to lift to VFR this evening. The next round of rain and
storms may approach from the southwest later Sunday night.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 1036 AM CDT Sun Jun 16 2024

Moisture and onshore flow has kept dense fog persisting along
the North Shore into Twin Ports this morning, so opted to extend
the Marine Dense Fog Advisory through 1 PM this afternoon. Models
do show some fog lingering through the afternoon, as well, but
look to keep the denser fog offshore, though confidence is still
low in how long the dense fog hangs on. Chances for scattered
storms (a few strong to severe; ~15% chance) redevelop and push
into the western Lake Superior vicinity very late this afternoon
into evening, though the strong to severe storm threat should
end by mid-evening. Large hail will be the main threat with
these, though gusty and erratic winds will be possible as well.
Otherwise, expect onshore flow for most places today (southeast
to northeast winds), becoming variable tonight, then similar
directions again on Monday. Winds may gust to around 15 kt
today, decreasing tonight.

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 PM CDT this afternoon for
     LSZ140>145.

&&

$$

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