685
FXUS63 KMQT 282243
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
643 PM EDT Sun Apr 28 2024

.KEY MESSAGES...

- Much cooler today with showers lifting from south to north
  during the afternoon.
- Active pattern continues as three low pressure systems track
  across the region over the next week. Above normal
  temps/precip are expected including thunderstorm chances.
- Elevated fire weather conditions are possible over the west
  half of Upper Michigan on Wednesday, but will depend on the
  preceding precipitation.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 346 PM EDT Sun Apr 28 2024

Upslope/onshore ne winds have lead to chilly temps today (mid to
upper 30s) into west and north central portions with even some
patchy dz at times into north central portions. Downsloping into
the eastern portion of the cwa has allowed temps there to reach
into the lower 50s under abundant cloud cover.

Water vapor imagery and RAP analysis show a shortwave over the
eastern NE and eastern KS that models project will be lifting ne
toward the Upper Great Lakes later tonight and Monday. As the
associated sfc low pres centered over eastern NE and southern IA
lifts nne into southern MN and southern/central WI late tonight,
strengthening WAA/isentropic ascent ahead of the system`s
advancing sfc-850 mb warm front and increasing transport of Gulf
moisture and PWAT values around an inch or more will result in
steady showers (now over into the south central UP) to lift
north across most of the cwa later this afternoon and evening.
In turn, will have categorical PoPs lifting north for
widespread showers across the cwa. Models mid-level RH plots hint
at dry-slotting reaching into the western UP later this evening
and overnight which could result in a break from the steadier
showers so have lowered PoPs back to chance over these zones.
Overall, from this afternoon through tonight have QPF totals
ranging from around a .25 inch over the Keweenaw to more than an
inch over se portions of the cwa where best isentropic lift
will be focused the longest across the sharp 850 mb thermal
gradient along the warm front. Elevated CAPE values of a couple
hundred j/kg could lead to isolated t-storms late tonight into
se portions, also boosting QPF totals. Expect lows tonight
mostly in the mid to upper 30s, except for some lower 40s
readings south central and east.

Despite a very shallow mixed layer of 1-2 kft off the sfc as
depicted on soundings, the arrival of a 45-50 kt LLJ could
result in easterly wind gusts approaching near advisory criteria
later tonight across the Keweenaw Peninsula, particularly on
the downslope westerly side of the Keweenaw. Not enough
confidence to issue a wind advisory at this point for the
Keweenaw as it looks the higher gusts may be just localized on
the western side of the Keweenaw but this will be something to
monitor on the evening and mid shifts. The rest of the cwa will
see easterly gusts more in the 20-30 mph range.

&&

.LONG TERM /MONDAY THROUGH SUNDAY/...
Issued at 445 PM EDT Sun Apr 28 2024

With three different low pressure systems in the extended forecast,
there is fairly good agreement in the medium range model guidance
for plenty of precip chances. Uncertainty builds in the latter part
of the week as guidance begins to diverge ahead of the third low
pressure system.

The first low pressure system will be ongoing at the beginning of
the extended forecast. Starting on Monday, a negatively tilted mid
level trough will be situated over the Dakotas/MN state line,
extending south into IA with weak ridging over the east U.S. coast
and a trough over the Pacific Northwest. The midwest trough pivots
over the UP on Monday and the sfc low slowly follows northward
behind it. Better q-vector convergence will be located over Lake
Superior already Monday morning with a dry slot highlighted in PWATs
dropping ~0.2" behind the warm front. This leads to diminishing
showers over the west in the morning hours. With increasing PVA in
the afternoon, showers are reinvigorated mainly over the west half
of the UP. This may be enough forcing to provide some thunder and
lightning, however severe weather is not expected. Lingering showers
and cloud cover will limit instability with model guidance hinting
at ~200-300 j/kg of MUCAPE and mid level lapse rates mainly below 6
C/km. Also, by the time the low level inversion is eroded, the very
limited instability will have nearly diminished. The 4/28 0z ECMWF
EFI still highlights this period under anomalous QPF with SoT>0 and
shaded values to 0.7 to 0.9. Morning showers look to add 0.01" to
0.15" in the west with 0.15" to 0.5" in the Keweenaw and eastern UP.
Showers in the afternoon could result in an additional 0.25" in
heavier downpours. That said, hydro hazards are not expected.

Showers lift north out of the UP Monday night as the trough and sfc
low lift over Lake Superior, temporarily bringing dry weather back
to the UP for Tuesday. WAA during the day accompanied by clearing
skies will bring above normal highs in the 50s near Lake Superior
and in the east with 60s in the interior west and south central.
Meanwhile, a shortwave will quickly ride east off the Northern
Rockies toward the Upper Great Lakes during the day as it takes on a
negative tilt and replacing the dry weather Tuesday night into
Wednesday as it swings northeast over the UP. While there is some
spread yet in the associated sfc low pressure, the general consensus
is to take it northeast from MN into northern Ontario, but both GEFS
and ECMWF ensembles have members that take the low further to the
east over Lake Superior. The ECMWF also is a bit slower with the
timing, which would drag precip longer into Wednesday. This means
that timing and track still have some uncertainty yet, but a brief
round of showers Tuesday night into Wednesday is expected, with
better odds over the northwestern UP. Instability again is fairly
low (MUCAPE below 100 j/kg), but the support of the cold front
moving east across the UP may support a few rumbles of thunder near
the WI/MI state line.

Dry weather then returns on Wednesday, likely continuing through
Wednesday night. Pressure rises behind the cold front and clearing
skies will result deep mixing. This will yield warmer than normal
temps in the 60s to low 70s and some breezy west winds during the
day. Sounding analysis shows the interior west mixing up to around
800-850mb with up to 900mb in the east and the Keweenaw. The last
two runs of ECMWF ensemble probabilities of wind gusts exceeding 34
kts were around 20-40% in the west with the 4/28 13Z NBM
probabilities around a similar magnitude, except higher to 60% in
the Keweenaw. This would also result in lower dew point temps in the
west and thus RHs dropping near 25%. The combination of gusts and
low RHs would increase fire weather concerns. The limiting factor
here is the timing of the previous low pressure system. If the ECMWF
solution is favored, precip will linger further into Wednesday
resulting in delayed mixing, lower wind speeds, and higher RHs.

Uncertainty continues to grow in the forecast Wednesday night
onward, but chances for precip increase Thursday with 20-50% PoPs
continuing into the weekend as we track out the third low pressure
system.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 642 PM EDT Sun Apr 28 2024

An advancing warm front and increasing moisture ahead of low
pressure lifting ne through the Upper Mississippi Valley will result
in MVFR cigs at IWD and CMX lowering to IFR and as low as LIFR/VLIFR
late tonight after widespread rain into the region later this
evening and overnight. Lingering LIFR conditions at SAW will
continue under steady rain. ENE winds this afternoon will be gusty
to around 20kt. At CMX, easterly winds tonight will become sustained
at 20-25kt with gusts to 35-40kt possible. LLWS will set in at SAW
this evening into the early overnight.

&&

.MARINE...
Issued at 445 PM EDT Sun Apr 28 2024

Northeast gales to 35 kt are expected across the western third of
the lake this afternoon increasing to easterly gales to 40 kts
across most of the lake tonight, continuing into Monday morning.
While a few gusts may exceed 40 kts late tonight into Monday,
probabilities remain on the low end (25-50%). The strongest winds
are expected in the far west as well as the north central portion of
the lake between the Keweenaw and Isle Royale where there could be
some channeling. The far eastern zone may see a few gale force gusts
to 35 kts Monday morning, but confidence was not high enough to
issue a Gale Warning for that zone. Gales quickly diminish Monday
afternoon as the low pressure moves over western Lake Superior.

Significant wave heights up to 14 ft are possible Monday morning
between Duluth Harbor to the Bayfield Peninsula and near Isle
Royale. Waves fall below 8 ft Monday evening.

Winds fall below 20 kts in the west half of the lake Monday evening
and after midnight in the east. Winds are then expected to remain
mainly below 20 kts through Tuesday. East to south east winds
increase to 20-30 kts Tuesday night, becoming west behind a cold
front on Wednesday. With stronger pressure rises behind the cold
front, west gales to 35 kts are possible on Wednesday over the west
half of the lake. Highest probabilities of winds exceeding 33 kts
are around 50-75% between the Keweenaw and Isle Royale. Winds
quickly return below 20 kts Wednesday night.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Gale Warning until 5 PM EDT /4 PM CDT/ Monday for LSZ162.

  Small Craft Advisory until 11 PM EDT /10 PM CDT/ Monday for
     LSZ240-241-247-248.

  Small Craft Advisory until 11 PM EDT this evening for
     LSZ242>246.

  Gale Warning from 11 PM this evening to 5 PM EDT Monday for
     LSZ242>246-263>266.

  Small Craft Advisory until 5 PM EDT Monday for LSZ249>251.

Lake Michigan...
  Small Craft Advisory until 11 AM EDT Monday for LMZ221.

  Small Craft Advisory until 4 PM EDT Monday for LMZ248-250.

&&

$$

SHORT TERM...Voss
LONG TERM...Jablonski
AVIATION...07
MARINE...Jablonski