000
FXUS63 KMQT 182311
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
711 PM EDT Thu Apr 18 2024

.KEY MESSAGES...

- Another round of light rain showers develops this evening and
through the first half of the night, mainly across the central and
eastern UP.
- Cooler temps Friday and Saturday with low (30%) chances for light
diurnal showers this afternoon/evening and perhaps a light lake
effect rain/snow mix for Friday/Saturday.
- Some localized fire wx concerns could resurface again Friday into
Saturday with more widespread concerns Sunday and Monday as a drier
airmass moves in with breezy W to NW winds.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 239 PM EDT Thu Apr 18 2024

The surface low that has brought rounds of rain over the past couple
of days has moved north of Lake Superior with weak ridging in its
wake. Aloft, broad troughing centered over the Canadian Prairies
continues to send weak shortwaves out of the Plains. One of these is
currently moving through central WI, touching off another round of
light rain showers. Water vapor shows an impressive dry slot across
eastern MN/western Lake Superior/far western Upper Michigan, while
surface observations indicate a diffuse frontal boundary draped over
the area. That is all to say that additional PoPs associated with
the shortwave moving through WI should stay contained to the central
and eastern UP. Weak radar returns have been streaming into the
south-central UP for most of the afternoon, but nothing appears to
be reaching the ground with just lingering lower to midlevel cloud
cover. However, will not rule out some sprinkles and light rain
showers this afternoon and evening. Otherwise, temperatures
seem to be behaving, hovering in the upper 40s and lower 50s
across most of the area. Where we can see some breaks in the
clouds, temperatures may be able to peak a couple degrees higher
in the mid 50s.

Tonight, the weak cold front off to our west moves through the UP,
while the right entrance region of an upper jet core slides over the
area. This may expand the coverage of rain showers, though rain
totals stay light; model soundings over the eastern half of the UP
only briefly moisten up enough at lower levels for my liking, and
the grand ensemble has a 70-100% chance for rain totals below a
quarter inch and around a 50% chance for totals less than a tenth of
an inch where we do pick up rain showers overnight. With a cooler
airmass moving in, expect temperatures to fall back more than last
night with lows ranging generally in the lower to mid 30s. Our
typically cooler spots throughout the western UP, where we`ll also
stand the best chance for skies to clear out, may drop into the 20s.

&&

.LONG TERM /FRIDAY THROUGH THURSDAY/...
Issued at 529 PM EDT Thu Apr 18 2024

The extended period is looking to be fairly calm, although we could
see some showers Friday into Saturday, and late Monday into Tuesday.
Drier lower levels Friday through this weekend into early next week
could lead to some fire weather concerns, particularly Sunday when
min RHs get down into the mid 20 percents. Overall, temps are
looking to be around normal to above normal, but tonight through
Saturday are looking to be below normal. Additional details on the
forecast follow below.

Starting with Friday, breezy west winds are expected across the area
due to deep mixing up to 8-9 kft across the interior. While mixing
won`t be as deep on the Keweenaw, westerly winds take advantage of a
long fetch off the lake. EPS is noticeably stronger than GEFS
with ensemble mean peak wind gusts up to 45 mph. Deep mixing and
some lingering moisture suggests potential for diurnal
showers/sprinkles, but deep inverted-Vs profiles up to around
5kft suggests raindrops will struggle to reach the ground and
shouldn`t be measurable. The exception is where lake breeze
boundaries add extra convergence, mainly across the eastern UP
where west winds favor converging lake breeze boundaries. Precip
types could be interesting with surface temps around 40F while
wet bulb temps are near freezing. This could result in showers
being a mix of rain/graupel/snow pellets before transitioning to
all snow as the column saturates to the wet bulb profile. A
pocket of synoptic moisture is still slated to pivot across the
area Friday night enhancing the isolated/scattered shower
activity, especially at higher elevation locations. QPF amounts
still appear very light and recent warmth should prevent
accumulations on roads, but a dusting on grassy/elevated
surfaces seems plausible wherever the most persistent showers
set up.

The cool air mass aided by synoptic moisture shift east on Saturday
bringing potential for fire wx back to the area, especially near the
WI state line. The exact timing of a mid-level dry layers arrival
remains unclear, but NAM guidance gets quite dry across the west
during the afternoon. Forecaster confidence decreased to only medium
for Sunday as an energetic shortwave or lobe of the PV dives
southeast across Ontario. Models seem to be trending toward a more
significant cold front passage on Sunday that could result in a non-
diurnal temperature pattern, but there`s still enough spread that
maintaining fire wx potential (especially near the WI state line)
seemed most prudent. In addition to temperature implications,
modeled wind profiles appear stronger with potential for another
breezy day. Even if the front makes it into our area on Sunday, a
system approaching on Monday will lift the front back to our north.
The dry air mass and fire wx concerns return on Monday, but winds
are lighter limiting the fire wx potential.

Models continued trending toward a better developed cyclone
approaching the area late on Monday. 00z guidance trended south of
our area but the 12z suite was right back in our neighborhood.
Ensembles don`t show any obvious clusters of solutions, but it`s
worth noting that this system could have a tap of sufficiently cold
air for accumulating snow. The past two operational ECMWF runs
advertised a post-system air mass cold enough for pure lake effect
snow. A very quick first glimpse suggests shallow/light LES, but it
should be monitored.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 710 PM EDT Thu Apr 18 2024

VFR conditions are expected to prevail across all of the TAF sites
tonight through Friday. However, some light lake-effect/diurnal snow
showers could bring some high-end MVFR cigs across the area come
Friday morning through the rest of the day for each of the TAF sites
from time to time (chance of this occurring around 30%). Otherwise,
expect some light rain showers across KSAW the next few hours as the
cold front continues pushing through Upper Michigan this evening.
KCMX could see some marginal LLWS from time to time tonight as winds
at around 2 kft could reach up to speeds of around 35 knots.
However, given the possible periodic mixing and the marginal LLWS
(which has about a 50% chance of occurring from time to time), I
decided to leave the mention of LLWS out of the TAF for KCMX at this
time.

&&

.MARINE...
Issued at 529 PM EDT Thu Apr 18 2024

SSW winds of 20 to 30 knots are occurring over the western half of
the lake this afternoon. Winds over the western lake veer WSWerly
tonight, the winds increase to 20 to 30 knots. The winds continue
increasing to 35 kt gales over the east-central lake on Friday as
cold air advection reduces over lake stability. The strongest winds
are expected along the northern shore of the Keweenaw Friday due to
funneling. Winds veer NWerly and weakening to 20-30 kts Friday
night into Saturday, the winds weaken to 20 to 30 knots across
the lake before backing to the SW over the central lake early
Saturday evening. A period of lighter winds is possible Sunday
morning ahead of a potentially strong cold front that may move
across the lake late on Sunday. Timing and position of this
front have important forecast implications with our local tool
advertising a 20-40% chance of gales across the eastern lake
late on Sunday. As ridging builds in Sunday night, winds die
down to 20 knots or less and remain that way until possibly
Monday night, when a shortwave low moving through the Upper
Midwest increases N`rly winds to 20 to 30 knots across the lake
through Tuesday night.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Small Craft Advisory from 2 AM EDT /1 AM CDT/ Friday to 8 AM
     EDT /7 AM CDT/ Saturday for LSZ240-241.

  Small Craft Advisory until 11 AM EDT Friday for LSZ242>244.

  Gale Warning from 11 AM to 11 PM EDT Friday for LSZ242>244-263-
     264.

  Small Craft Advisory from 5 AM to 1 PM EDT Friday for LSZ245-
     246.

  Gale Warning from 1 PM Friday to 2 AM EDT Saturday for LSZ245-
     246-265>267.

  Small Craft Advisory from 5 AM Friday to 8 AM EDT Saturday for
     LSZ247-248.

  Small Craft Advisory from noon Friday to 8 AM EDT Saturday for
     LSZ249.

  Small Craft Advisory from 9 AM Friday to 8 AM EDT Saturday for
     LSZ250-251.

Lake Michigan...
  Small Craft Advisory from 11 AM to 8 PM EDT Friday for LMZ221-
     250.

&&

$$

SHORT TERM...LC
LONG TERM...EK
AVIATION...TAP
MARINE...EK