370
FXUS63 KMQT 041913
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
313 PM EDT Sat May 4 2024

.KEY MESSAGES...

-Rain overspreading the UP from west to east this afternoon/evening
 as a low pressure system moves through the area.
-The UP remains under the preferred path for low pressure systems,
 with multiple notable features passing through the next week.
-In between systems, dry conditions will be expected, though mostly
 low winds and antecedent rainfall should broadly limit fire
 concerns.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 312 PM EDT Sat May 4 2024

A shortwave trough moving through the Northern and Central Plains as
noted on water vapor imagery will be propelling a cold front across
Upper Mi this afternoon and evening, spreading showers from west to
east across the fcst area. The leading edge of showers is into
southern Houghton and western Iron counties as noted on the latest
radar imagery as will continue to move through central Upper Mi from
20-00z and then into the eastern U.P. counties 00-03Z before exiting
the eastern cwa by 09Z. Ridging and subsidence behind the shortwave
and associated cold front will support drier conditions behind the
front tonight and maybe some partial clearing over portions of the
western U.P. later tonight. The moist low levels from the showers
along with the prospect of partial clearing however could also
support the development of stratus/patchy fog behind the front. Min
temps tonight will generally range from the upper 30s west to the
lower 40s central and east.

&&

.LONG TERM /TONIGHT THROUGH FRIDAY/...
Issued at 436 AM EDT Sat May 4 2024

Starting tonight, a broad trough will expand over the Upper Midwest
and central Canada with a ridge over the eastern U.S. coast and a
closed low over the western U.S. coast. A shortwave riding the
middle trough will be progressing eastward over the U.P. with
another shortwave not long behind it over Manitoba. The associated
cold front finish progressing east across the U.P. by Sunday
morning, bringing a line of showers eastward as well as a brief
period of northeast gusts to 20-25 mph; a few rumbles of thunder are
possible mainly earlier in the period. Lows overnight are expected
in the mid 30s to mid 40s, warmest east where the cloud cover is
expected to hold on the longest.

The second shortwave passes just north of Lake Superior on Sunday,
but no precip is expected as sfc high pressure builds in over the
Upper Great Lakes. This should see cloud cover diminish, light
winds, and highs in the mid 50s to mid 60s; warmest south central.
Mixing increasing in the afternoon, stronger over the interior west,
will bring RHs down around 40% in the east/Keweenaw with near 30-35%
in the interior west. No fire weather concerns are expected at this
time. With mid level ridging moving east over the Great Lakes and
high pressure shifting to expand over the entire basin, the quiet
weather continues with lows in the mid 30s to low 40s. Meanwhile,
the closed low will have made it onshore and moved east over the
Rockies, beginning to open up into a trough and take on a negative
tilt.

By Monday morning, the trough will be situated just over the lee
side of the Rockies. High pressure means another dry day with better
mixing up to ~850 mb. Stronger winds mixing down from aloft are not
going to be an issue, but lower dew points will be. Minimum RHs are
expected around 30-35% in the afternoon/evening hours. With highs in
the upper 50s to low 70s, cooler by the lakeshores, we flirt with
borderline elevated fire weather conditions. Will want to monitor
these conditions in future forecast packages. The trough is expected
to pivot northeast over the Plains through Monday night supporting
sfc low cyclogenesis, but the U.P. stays dry yet. Monday night will
be warmer than the previous night with temps only settling into the
40s, warmer in the west as clouds increase ahead of the next system.

Chances for showers increase in the far west on Tuesday with
increasing q-vector convergence, but likely will hold off until late
morning/early afternoon when the trough begins to develop back into
a closed low over the northern Plains. PVA over our region increases
at this point into Wednesday morning as a shortwave cycles around
the low, eventually passing northeast over the Upper Great Lakes. An
approaching left exit region of the upper level jet also looks to
support additional cyclogenesis over the Central Plains Tuesday
night. This second sfc low then lifts northeast on Tuesday, crossing
northeast over the Great Lakes Tuesday night resulting in an uptick
in PoPs Wednesday night. Meanwhile, the stronger sfc low associated
with the mid level low will spin over the Northern Plains. With the
given spread in the guidance, opted to leave the NBM PoPs Tuesday
onward. There is a chance for thunderstorms on Tuesday and
Wednesday, but confidence remains low at this point given the spotty
instability noted in the guidance; best chances are on Tuesday when
the mid level lapse rates and bulk shear are higher.

Slight chances for showers gradually diminish through the end of the
work week as we begin to see a pattern shift. Longer range ensemble
guidance hints at positive 500 mb height anomalies over the western
U.S. with negative height anomalies moving toward the east coast
toward the latter part of May. This means less moisture from the
Gulf of Mexico to support precip chances and cooler northwest flow
over the Great Lakes. The drier trend is captured well by CPC precip
outlooks out to 3-4 weeks with a cooler pattern more within the next
8-14 days.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 142 PM EDT Sat May 4 2024

VFR conditions will slowly deteriorate to low-end MVFR and
possible IFR starting mid to late this afternoon at IWD and
toward this evening (22Z-00Z) at SAW and CMX as rain overspreads
Upper Michigan from west to east. Expect improvement back to
VFR late this evening/overnight as drying and clearing occurs in
the wake of a cold front.

&&

.MARINE...
Issued at 436 AM EDT Sat May 4 2024

Southwest winds this morning become northwest mid morning over
the west half of Lake Superior as a weak low pressure lifts
northeast into the region. Winds across the rest of the lake
turn northeast behind a cold front this evening as the low lifts
northeast into northern Ontario. The eastern portions of Lake
Superior could briefly see some northwest wind gusts up to 25 kt
tonight into Sunday morning. As high pressure settles over the
lake Sunday and Monday, winds will be below 20 kt until Monday
afternoon. A strong low pressure system over the Northern Great
Plains will cause gusty northeasterly winds to funnel towards
Duluth Harbor to around 20-25 kts monday afternoon into Monday
night. Meanwhile, a second weaker low pressure develops over the
Central Plains, lifting northeast toward the Upper Great Lakes
on Tuesday. The track and timing of this secondary low is still
not totally solid, but east winds to 20-30 kts are likely
Tuesday into Tuesday evening as it moves through the Great Lakes
Basin. Probability of Gales remains low at this time. (<20%
chance of winds exceeding 34 kts). Winds look to hold around
15-25 kts through the rest of the work week.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Small Craft Advisory from 5 AM to 2 PM EDT Sunday for LSZ250-
     251.

Lake Michigan...
None.

&&

$$

SHORT TERM...Voss
LONG TERM...Jablonski
AVIATION...Voss
MARINE...Jablonski