678
FXUS63 KDLH 192320
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
620 PM CDT Sun May 19 2024

.KEY MESSAGES...

- Rain arrives tonight and lingers through Monday. Total
  accumulations around 0.25" to 0.50"; locally higher and lower
  amounts possible.

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

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

&&

.DISCUSSION...
Issued at 407 PM CDT Sun May 19 2024

Today, we`re under the influence of southerly warm air advection
out ahead of an approaching low pressure system from the
southwest. A weak wave aloft has been kicking off some showers,
but the air has been so dry at the surface that most of it,
except the heaviest showers, has been virga. We can expect this
general cloudy and occasionally sprinkly weather to continue
through the evening.

Tonight, the upper level trough and low pressure passing by will
bring an area of rain to the region. The main swath of rain is
expected to be somewhat quick-hitting, lasting about 6-9 hours
through Monday late afternoon to early evening. PWATs will be
around 90th percentile of climatology, but without excessive
synoptic forcing and the aforementioned relatively quick
duration. So, totals around 0.25"-0.50" are likely to be common,
and there`s pretty reasonable ensemble consensus around that.
We`ll probably see some locally higher and lower amounts. Higher
amounts will be more likely in east-central Minnesota into
northwest Wisconsin where a bit of instability (<500 J/kg) may
promote a few embedded thunderstorms. Strong to severe storms
are not expected. We`ll probably also see some areas of fog with
this, though there isn`t a strong signal for dense fog anywhere
at this point.

There`s likely to be a brief break in the rainfall Monday night
such that it tapers off to scattered showers for most places. A
few models are hinting that we could retain some elevated
instability overnight though, so we`ll have to keep an eye on
that for the potential for some isolated non-severe storms,
which would be most likely in the east-central Minnesota to
northwest Wisconsin areas.

A much more potent low pressure system is still shaping up to
impact the region Tuesday through Wednesday with a broad warm
nose of moist Gulf of Mexico air headed towards the Northland.
PWATs will again be around that 90-95th percentile of
climatology, so plenty of moisture out there. This time, we`ll
see a longer duration of rainfall (up to 15-20 hours or so), so
it`ll add up more. A broad synoptic rainfall with some embedded
thunder will likely yield totals >1" for most areas (50-90% per
NBM). Several ensemble members paint the possibility for higher
totals approaching 3-4" as well locally. At this point, flash
flooding doesn`t seem like a big concern as the rainfall
intensity, in general, probably won`t be high enough to support
that. However, the long duration of it could lead to some
localized minor flooding. At the very least, areas that usually
get filled with water when it rains, such as ditches and other
low spots, will probably see some high water. The WPC has drawn
a marginal risk (at least 5%)for excessive rainfall across the
region, with a slight risk (at least 15%) for approximately the
Twin Ports and points south.

In addition to the rain, we`ll have higher potential for some
thunderstorms with higher instability. The caveat with this
system remains the storm track. Ensembles still have a fairly
large range of possibilities as far as the low track goes,
though funny enough, the inconsistency in low track has been
pretty consistent in the past several runs (namely the ECMWF).
This is important because the northern extent of convection
potential will depend on the track. If the track is further
north, a wedge of potential instability around 1000 to 1500 J/kg
or so could swing into our area Tuesday afternoon. There will
be plenty of 0-6 km shear to promote some strong to severe
thunderstorms, particularly in parts of northwest Wisconsin, if
this pans out. Right now, the probably for severe storms sits at
around 15% on Tuesday, with a slight risk for severe storms for
parts of northwest Wisconsin per the SPC.

The rain is expected to taper to scattered wraparound showers
Wednesday afternoon as low pressure moves into Ontario. Thursday
will likely be a drier day, but there`s still at least a 10-20%
chance for some sort of rain as an amplified upper-level pattern
remains. Another trough may swing through Friday, potentially
bringing a cold front and shower/storm chances. The weekend may
have some periodic rain as well.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 620 PM CDT Sun May 19 2024

VFR conditions currently across the Northland. Radar is picking up
on a few returns this evening but with stout dry air at the surface
most of this rain is not making it to the surface. We will continue
to see a few sprinkles over the next couple hours. A warm front will
be lifting through the area tonight lowering ceilings and brining
widespread rain. Some of the high res guidance also suggests some
embedded thunder with the most likely impacted terminals being
BRD/HYR. Rain will begin clearing out tomorrow morning but we may
see some lingering fog through the morning hours.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 407 PM CDT Sun May 19 2024

Breezy southwest winds are expected to persist from Grand
Portage to Grand Marais for the next few hours this afternoon.
Then, winds transition to northeasterly for Monday with speeds
around 10-15 kt. Winds become stronger from the northeast on
Tuesday with gusts 25-30 kt, increasing to around 35 kt Tuesday
afternoon and night. Headlines will likely be needed through
Wednesday afternoon/evening as gusty winds persist as low
pressure passes through. We will see rain later tonight through
Monday, then again Tuesday through Wednesday. There may be
thunderstorms Tuesday into Wednesday, and some stronger storms
can`t be ruled out.

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...Small Craft Advisory until 9 PM CDT this evening for LSZ140.

&&

$$

DISCUSSION...JDS
AVIATION...Britt
MARINE...JDS