545
FXUS63 KDLH 100323
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1023 PM CDT Thu May 9 2024

.UPDATE...
Issued at 1022 PM CDT Thu May 9 2024

Temperatures have fallen into the mid-thirties at Grand Marais
and Two Harbors so we added the Coastal Cook and Lake Counties
to the Frost Advisory tonight.

&&

.KEY MESSAGES...

- An active spring weather pattern persists through the next
  7-10 days with continued chances for showers/thunderstorms
  most days and seasonable temperatures. A few stronger
  thunderstorms could produce small hail and gusty winds on
  Friday afternoon (northeast Minnesota) and again on Sunday
  afternoon (mainly northwest Wisconsin).

- Temperatures will fall below the freezing mark in much of
  inland northwest Wisconsin overnight. A Freeze Warning is in
  effect for most of northwest Wisconsin, with a Frost Advisory
  for parts of northeast Minnesota.

&&

.DISCUSSION...
Issued at 157 PM CDT Thu May 9 2024

On the synoptic scale a very spring-like weather pattern continues,
with many chances for precip but no particular day looking like a
complete washout.

Mainly sunny skies today with a weak area of high pressure over Lake
Superior causing a lake breeze/lake influence well inland, with
north-northeast winds gusting to around 20 knots this afternoon for
areas near the lake and into parts of northwest Wisconsin. Temps
will fall below freezing given clear skies tonight, with a freeze in
northwest Wisconsin and frost (temps in the 33-36 range) in
northeast Minnesota. Increasing clouds in northern Minnesota will
prevent a freeze, though some higher elevations of the Minnesota
Arrowhead region may reach below freezing.

On Friday a fairly fast-moving mid-level shortwave trough will move
from almost north to south from Manitoba/northern Ontario down
through the Upper Mississippi River Valley. While the thermal fields
don`t reflect much of a gradient ahead of this wave, the broad-scale
lift from the approaching wave combined with steep low level lapse
rates will lead to scattered showers and a few thunderstorms, though
the limited instability (perhaps 200-400 j/kg SBCAPE) and dry air at
low levels will mean the amount of precip that falls will be limited
and individual showers/storms will be fairly short-lived. Gusty
winds likely to be the main threat from the strongest storms -
perhaps producing 40-45 mph gusts at most, with some pea-size hail
also possible. Precipitation will be mainly diurnally-driven, with
showers/storms diminishing towards sunset and skies clearing out on
Friday night.

The shortwave trough is followed by some mid-level ridging over
northern Ontario into the Upper Great Lakes, with otherwise
northwest flow at mid levels and warm air advecting in from the west
at lower levels. Sunny skies to start on Saturday with diurnally
driven cumulus in the afternoon given some residual moisture in the
column, with a spotty shower possible Saturday afternoon/early
evening across northern Minnesota (15-25 percent chance) but nothing
to ruin a great day to get outside as highs reach into the 60s to as
warm as the low 70s for parts of north-central Minnesota.

Late weekend into early next week a slower-moving upper low with an
associated surface low deepening over far northern Ontario/Hudson
Bay will draw down a surge of unseasonably cooler air at low levels,
with a strong surface cold front moving from north to south across
the region late Sunday into Monday. In the warm sector ahead of this
cold front another round of diurnally-driven showers and
thunderstorms are expected on Sunday afternoon, mainly in east-
central Minnesota and northwest Wisconsin. With two days of west
winds at low to mid levels ahead of this front, a decent EML will be
present - nothing to write home about but still favorable mid-level
lapse rates, strong surface heating leading to steep low level lapse
rates, and a decent amount of moisture in the column will lead to
instability on the order of 500-1200 j/kg. While deep-layer shear
will be weak (15-20 knots), some stronger thunderstorms producing
heavy rainfall rates are possible in northwest Wisconsin, and a few
of the first storms could produce gusty winds and small hail
depending on the the timing of the arrival of the large-scale lift
from the cold front moving in from the north.

While the closed mature low briefly pauses over northern Ontario a
weak mid-level shortwave embedded in the northwest flow over
southern Manitoba into the Dakotas late Sunday moves across the
region on Monday leading to yet another round of precipitation on
Monday afternoon. Through the rest of the work week it`s much more
of the same - a longwave trough enters southern Canada and the
Pacific Northwest early in the week then slowly tracks eastward into
the Great Plains and Midwest mid-week leading to more widespread
precipitation, with a 60-70% chance for at least a tenth of an inch
of precipitation across the Northland mid-week, with some ensemble
guidance solutions producing as much as a half inch or more (10-20%
chance). Highs in the 60s to low 70s most days, cooler near Lake
Superior. Lows in the 40s with little to no chance for frost/freeze
late weekend through next week.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 629 PM CDT Thu May 9 2024

Mostly clear skies will occur well into tonight with mid-clouds
moving in from the northwest late tonight into Friday morning
along and ahead of a cold front. Winds will diminish tonight and
become light or calm for most. Some patchy fog is possible in
spots but chances are too low to include a mention at this time.
Showers will develop from northwest to southeast through the
Northland on Friday with a few thunderstorms in the afternoon
and evening. Forecast soundings show drier low levels so we
expect VFR conditions for most with the showers. Some brief
dips to MVFR will be possible with any of the stronger showers
or thunderstorms. Gusty and erratic winds and small hail will
also be possible with any thunderstorms.

Winds will veer through the day Friday as the cold front moves
through.

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
Issued at 1021 PM CDT Thu May 9 2024

East-northeast winds diminish this evening, with winds becoming
westerly at 5 to 10 knots on Friday as a weak cold front moves
across Lake Superior bringing with it scattered showers and an
isolated thunderstorm. Southwest winds through the weekend, around
10 knots on Saturday then stronger Sunday at 15-18 knots. Conditions
are not anticipated to reach Small Craft Advisory level through the
weekend.

Next week a prolonged period of easterly winds will lead to
gradually building waves across western Lake Superior, but hazardous
marine conditions are not anticipated.

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

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...Frost Advisory until 8 AM CDT Friday for MNZ012-019>021-037-
     038.
WI...Frost Advisory until 8 AM CDT Friday for WIZ006.
     Freeze Warning until 9 AM CDT Friday for WIZ001>004-007>009.
MARINE...None.

&&

$$

UPDATE...Melde
DISCUSSION...JJM
AVIATION...Melde
MARINE...JJM