296
FXUS63 KMQT 292016
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
416 PM EDT Mon Apr 29 2024

.KEY MESSAGES...

- Isolated to scattered showers, some drizzle, and patchy fog continues
  into tonight. Some fog may be locally dense at times in high
  terrain, especailly in the Keweenaw.
- Active pattern continues as a series of low pressure systems
  track across the region into early 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 /WEDNESDAY THROUGH MONDAY/...
Issued at 415 PM EDT Mon Apr 29 2024

Period of active weather continues with a series of low
pressures systems tracking across the area into early next week.
There will be several chances for rain with these systems with
the best chance of widespread moderate rainfall likely occurring
with the system Thursday into Friday as models indicate a feed
of Gulf moisture ahead of it drawing in PWAT values in excess of
an inch.

Starting Tuesday, a mostly dry frontal passage will be moving across
the area tonight, but there may be some sprinkles/drizzle along and
ahead of the front. Model soundings indicate a potential for a few
hours of post-frontal upslope drizzle for the Copper Country Tuesday
morning associated with moisture wrapping around the surface low
tracking north of the area. Otherwise, expect mostly cloudy skies
with highs ranging from the 50s near Lake Superior and east to the
lower to mid 60s interior west and south central.

A vigorous 500 mb shortwave trough approaches from the Northern
Plains Tuesday evening as it becomes negatively tilted and pivots
across the area late Tuesday night into early Wednesday. There`s
very little time for moisture to return ahead of this disturbance
for destabilization and the nocturnal timing further limits thunder
potential. However, there`s very good agreement in convection riding
into the area along the cold front to our west Tuesday afternoon.
These storms appear to grow upscale into an MCS that moves fairly
rapidly across the area late Tue night into early Wed. At this
point, it looks like the best chance for widespread rainfall will be
aligned over the western counties and maybe some of the north
central counties closer to the system`s track and where the better
deep layer qvector convergence and isentropic ascent is fcst. Any
storms that make it into our area should be elevated and shouldn`t
pose a hazard. The window for rainfall is brief (~3 hours) leading
to light rain amounts less than 1/4 inch.

Not great agreement among the models with how much mixing will occur
on the backside of this system on Wednesday afternoon. The GFS
soundings show the potential of mixing to 6-7 kft through a fairly
dry airmass which could drop dew points into the lower 30s (and
perhaps lower) over the interior west with min RHs dipping to 30 pct
or less over the interior west half. Deep mixing off GFS soundings
also suggests westerly gusts could reach near 35 mph. Meanwhile, NAM
soundings depict more clouds with less mixing (only to 3-4 kft)
yielding lesser wind gusts (20 mph or less) and less afternoon
drying of dew points. If the GFS scenario of deeper mixing pans out
the combination of gusty winds and lower RHs could potentially lead
to elevated fire danger, however the recent moderate rainfalls over
the last week could also imply wetter soils/fuels that could limit
the threat.

High pressure builds in Wednesday night resulting in dry conditions,
but then the focus shifts to a low pressure developing over the
Plains on Thursday then tracking across our area Thursday night. As
a result, rain chances increase on Thursday ahead of the warm front
as it lifts north then rain chances end behind Friday`s cold frontal
passage. Ensemble probabilities indicate it`s likely that much of
the area should see QPF totaling a quarter inch or more during this
period with a chance (near 50 pct) of QPF reaching a half inch or
more south central.

Additional generally light rain chances look to continue through
next weekend as weak shortwave impulses continue to move through the
mid-level trough hanging over the area.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 206 PM EDT Mon Apr 29 2024

A low pressure system currently centered over northwest WI this
afternoon will slowly meander northeast over Upper MI through this
evening, then Lake Superior overnight into Tuesday. During this
period, low clouds and fog will impact flight conditions. As the
occluded front lifts northeast with the sfc low, a round of isolated
to scattered showers will lift with it into the evening hours. SAW
and IWD will see periods of IFR to LIFR cigs and vis with these
showers as well as lingering drizzle/fog, but both sites are expected
to fall to LIFR tonight. CMX is expected to remain in VLIFR through
most of tonight as plenty of moisture and upslope flow keeps fog
around and cigs low. All sites are expected improve to MVFR by
Tuesday afternoon.

&&

.MARINE...
Issued at 415 PM EDT Mon Apr 29 2024

East-northeast gales will quickly fall blo gales late this
afternoon/evening as the sfc low now over northwest WI gradually
lifts over central Lake Superior later tonight and winds become less
than 20 kts. East to southeast winds increase to 20-25 kts Tuesday
night, becoming westerly and increasing to 25-30 kts behind a cold
front on Wednesday. There is now less than 20% chance for westerly
gales up to 35 kts could occur on the windward side of the Keweenaw
shoreline. Winds quickly diminish below 20 kts Wednesday night and
stay light until the next low pressure approaches on Thursday
bringing another episode of gusty easterly to northeasterly winds
Thursday night into Friday with maybe a few low-end gale gusts to 35
kts possible over north central and eastern portions of the lake.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Small Craft Advisory until 11 PM EDT /10 PM CDT/ this evening
     for LSZ240-241.

  Small Craft Advisory until 4 AM EDT Tuesday for LSZ243>246.

  Small Craft Advisory until 2 AM EDT Tuesday for LSZ247-248.

Lake Michigan...
  Dense Fog Advisory until 11 PM EDT this evening for LMZ221-248-
     250.

&&

$$

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