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209
FXUS63 KDLH 032334
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
634 PM CDT Fri May 3 2024

.KEY MESSAGES...

- An active weather pattern will lead to continued on and off
  precipitation chances through the next 7-10 days, with most
  of the precipitation falling tonight into Saturday and then
  Monday night into Tuesday.

- In between rounds of rainfall, dry conditions in combination
  with strong winds could lead to near-critical fire weather
  conditions on Monday.

- Thunderstorms are possible (20-30 percent chance) late Monday
  through Tuesday night, with severe weather potential very low
  - perhaps a 5 percent chance at most for isolated marginally
  severe storms in northwest Wisconsin.

&&

.DISCUSSION...
Issued at 122 PM CDT Fri May 3 2024

An active weather pattern continues through the first week of May,
which is helping to reduce the number of dry and windy days that
could lead to critical fire weather conditions. Today will be mainly
sunny to start across the Northland with the exception of parts of
Koochiching County where the closed low lifting north is still
causing cloudy skies and the occasional light rain shower. Highs
today in the 60s (perhaps a stray 70 in northwest Wisconsin) and
drying out with relative humidity values as low as 25-30 percent.
Windy with southwest winds 15-20 mph with winds gusting as high as
25-30 mph. Clouds return this afternoon from west to east.

On the synoptic scale a fairly progressive pattern across North
America to start the weekend as a closed low over northern Minnesota
lifts northward with the parent longwave mid/upper level trough over
the Canadian Prairie into the Dakotas gradually meanders eastward.
This eastward progression is accelerated this evening as a fast-
moving mid-level shortwave trough digs in across the central Rockies
and then ejects northeastward towards Lake Superior tonight into
Saturday. This impulse brings with it impressive broad-scale lift
across the region tonight with strong warm air advection at low
levels across northern Wisconsin and excellent positive vorticity
advection over MN/WI, with a surface front emerging/sharpening up
nearly in line with the MN/WI border Saturday morning.  The best
broad-scale lift is offset from the best area of low level moisture,
and combined with the fast-moving nature of this impulse there is an
atypically large spread in guidance for the precip amounts -
generally amounts of around a tenth to quarter inch expected along
and south/east of the Iron Range (highest from Brainerd/Lake Mille
Lacs to the Twin Ports and up the north shore), with the odds for a
half inch or more low (20-30 percent, highest across eastern MN) and
values over an inch unlikely (less than 5 percent chance). The
exception will be north and west of the Iron Range (which has missed
out of the highest precip amounts over the previous week) where
little to no precipitation is expected due to weaker broad-scale
lift.

The weekend won`t be a total washout, though - sunshine should start
to peak out of the clouds in central Minnesota by the afternoon
Saturday, and most locations across the Northland will be the sun
break out before sunset Saturday evening. Sunday will be a top-ten
weather day with sunny skies, highs in the 60s (50s for parts of the
north shore) and weak winds as a broad area of high pressure builds
in across the Upper Midwest. Warmer and breezy on Monday with highs
hitting the 70 degree mark for much of the Northland (except near
Lake Superior where east winds will keep temps in the 50s to low
60s). Near-critical fire weather conditions are possible as relative
humidity values fall to 25 to 35 percent and southeast winds gust as
strong as 20-30 mph.

Another round of precipitation arrives late Monday with
precipitation chances every day for the rest of the week. While
mid/upper level ridging builds in across the Midwest this weekend, a
very large closed upper level low enters the western CONUS, digging
into the Four Corners region and causing a resultant surface low to
deepen over the Great Plains, with the surface low probably develop
in the Central High Plains Monday, lifting north into the northern
Great Plains on Tuesday. This surface low will be anomalously deep
for this time of the year - a much more winter/early spring
evolution than late spring - and then the mature low over the
northern Great Plains just... hangs out for a few days. The closed
low essentially gets stuck as the "parent" upper level longwave
trough slowly moves eastward into the Great Plains through the rest
of the work week, with the weakening surface low tracking east from
the Dakotas into the Upper Great Lakes. This pattern evolution is
complicated, and with the complex nature there is a lot of
uncertainty in the details. However, in most scenarios there will be
off and on precipitation chances through the week with temperatures
near normal (highs in the upper 50s to 60s).

Most of the precipitation next week will fall late Monday and
through Tuesday, with elevated instability leading to a few embedded
thunderstorms. There MAY be scenario in which a few storms are
capable of small hail in northwest Wisconsin Tuesday afternoon, but
severe weather is unlikely. In total Mon night through Wednesday
morning around a quarter to half inch of rainfall is expected, but
locally higher amounts of an inch are possible.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
-- Changed Discussion --
Issued at 634 PM CDT Fri May 3 2024

High clouds are moving in from the west this evening out ahead of of
an approaching shortwave. This shortwave will swing in from the west
and bring rain showers through the overnight period and most of
tomorrow morning. Ceilings will drop to IFR with VIS fluctuating
from the rain. Lightning chances look to be negligible (less than
10%). Weather conditions will begin to improve as we head into the
afternoon hours.
-- End Changed Discussion --

&&

.MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/...
-- Changed Discussion --
Issued at 634 PM CDT Fri May 3 2024

Strong southwest winds today gradually weaken this evening, with
Small Craft Advisories in effect through the day. Another round of
rain tonight into Saturday with weak west winds 5-10 knots Saturday,
increasing and becoming more southerly at 10-15 knots on Sunday as
high pressure builds in. A change on Monday as northeast winds
increase through the day as an area of low pressure deepens across
the Dakotas, with steady winds around 15-20 knots developing Monday
and persisting through Tuesday/Tuesday night. Gale-force gusts are
possible (10 percent chance) on Tuesday afternoon, but widespread
gale force winds are not anticipated. With a long period of steady
northeast winds, waves will build to 3-6 feet Tuesday, possibly
larger for the north shore.

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

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
MARINE...Small Craft Advisory until 10 PM CDT this evening for LSZ121-
     140>147-150.

&&

$$

DISCUSSION...JJM
AVIATION...Britt
MARINE...JJM