243
FXUS63 KMQT 290717
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
317 AM EDT Mon Apr 29 2024

.KEY MESSAGES...

- Occasional showers and some drizzle and fog today. Fog may be
  locally dense at times in high terrain.
- 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 THIS AFTERNOON/...
Issued at 316 AM EDT Mon Apr 29 2024

Water vapor imagery and RAP analysis show shortwave/mid-level low
over eastern SD. At the sfc, associated 1005mb low pres is over sw
MN. The low has started to occlude, and from the occluded front, a
warm front extends across northern IA to southern Lwr MI. Main push
of isentropic ascent in advance of the wave supported a solid area
of shra that has lifted n of Upper MI during the night, leaving
behind mostly just areas of -dz and some fog. This break in shra
extends into WI. More shra are developing closer to sfc low and
aforementioned fronts. These shra extend from sw MN into southern WI.
Current temps across the fcst area are in the mid 30s to lwr 40s F.

Mid-level low will begin to open up today as it lifts toward western
Lake Superior. At the sfc, the associated sfc low will track from sw
MN to the vcnty of Ironwood by 00z. It does not look like the warm
front will make it into the U.P. Instead, the occluded front will
lift to near the MI/WI stateline by 00z. As a result, being ahead of
the occluded front, expect a gloomy day for the most part with some
areas of -dz and fog. Fog may be locally dense at times in higher
terrain. There will be shra at times as well. Closer to axis of 850-
700mb moisture transport, eastern fcst area should generally be
favored for more frequent shra this morning into early aftn. A
subtle shortwave will also be lifting across that area. Shra will
become more nmrs mid to late aftn across the w and central as
opening mid-level low approaches. Approaching occluded front will
also aid this shra development. There is a little cape avbl for
parcels lifted from top of inversion, but cape profile is very thin,
suggesting little potential of thunder. Fcst will not reflect any
thunder mention today. With winds maintaining an easterly component
thru the day, knocked high temps down from previous fcst. Expect
highs around 40F across the Keweenaw, mid to upper 40s central and
e, and low 50s F w. These highs will occur late in the day,
closer to 00z.

&&

.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 /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 121 AM EDT Mon Apr 29 2024

Prolonged period of LIFR/VLIFR conditions will affect all sites this
forecast period as fog and low clouds continue to move through along
with some showers. At CMX, easterly winds overnight will be
sustained at around 20kt with gusts up to 35kt possible.

&&

.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/ this afternoon for
     LSZ162-242>246-263>266.

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

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

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

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

&&

$$

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