851
FXUS63 KMQT 291136
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
736 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 /TONIGHT THROUGH SUNDAY/...
Issued at 411 AM EDT Mon Apr 29 2024

Ongoing period of active weather continues with only minor changes
to going forecast as three low pressures spin across the area this
week. Even though there are several chances for rain between 00z
Tuesday and 12z Thursday, total rainfall amounts are expected to be
light (less than 1/4 inch). The final low pressure that lifts across
the area Thursday and Friday is more likely (40-60%) chance to bring
moderate rainfall amounts (greater than 1/2 inch). The grand
ensemble also indicates a low (10-25%) chance for heavy rainfall
amounts (greater than 1 inch).

Starting with tonight, most of the rain associated with the first
low pressure will already be north/east of our area. However, the
surface low tracks directly across our area with low-level moisture
convergence implying a chance for fogginess. Confidence was too low
to include in the forecast at this time, but model soundings imply
better chances in the poorly mixed boundary ahead of the cold front.
A dry frontal passage is currently favored, but there may be some
sprinkles/drizzle along and ahead of the front. Model soundings also
show potential for a few hours of post-frontal upslope drizzle for
the Copper Country Tuesday morning associated with moisture wrapping
around the surface low. Elsewhere, morning stratus tries to scatter
to cumulus during the afternoon especially south-central where west
winds are downsloping. Cloudiness should be more stubborn
closer to Lake Superior so I shaved a few degrees off Tuesday`s
high temps.

A vigorous 500 mb shortwave approaches from the west Tuesday evening
and becomes negatively tilted as it pivots across the area Tuesday
night. 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 bubbling up along the cold front to our west Tuesday
afternoon. These storms appear to grow upscale into an MCS that
reaches the MI/WI state line a few hours after midnight. If a
sufficiently organized cold pool develops then favorable low level
shear vectors and impressive synoptic forcing may be adequate for
the MCS to persist across our area. At this time, that potential
appears most likely across the western UP mainly between Ironwood
and Houghton. Any storms that make it into our area should be
elevated and therefore are mostly a novelty instead of a hazard. The
window for rainfall is brief (~3 hours) leading to light rain
amounts less than 1/4 inch.

The mesoscale details of convection feedback onto the surface
pressure pattern leading to a low confidence forecast for Wednesday.
The main area of uncertainty is just how windy it will get as a much
drier air mass allows for deep mixing. Subjective analysis of model
guidance suggests the strength of overnight convection may be
directly correlated with magnitude of winds Wednesday afternoon. A
well-organized MCS may result in mesolow formation and locally
strong pressure gradients whereas a weak/dying MCS would not. It`s
worth noting that the probability of gusts >45 mph appears to have
diminished below 10%. Regardless of winds, mixing up to around 6kft
into a mid-level dry layer indicates RH values should dip below 30%
and perhaps even lower. The combination of gusty winds and low RH
indicates potential for elevated fire danger, but several rounds of
recent rainfall implies wet soils/fuels that should limit the
threat.

High pressure builds Wednesday night but increasing upper level
clouds should prevent temps from bottoming out, but they`ll still be
~25F cooler than Wednesday`s highs of 65-70F. Model guidance has
trended substantially toward a low pressure developing on Thursday
then tracking across our area Thursday night. As a result, rain
chances increase on Thursday as the warm front lifts north then rain
chances end behind Friday`s cold front. Additional generally light
rain chances continue through next weekend signaling a
continuation of the pattern bringing above-normal temps/precip
to Upper Michigan.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 736 AM EDT Mon Apr 29 2024

With low pres and occluded front lifting toward Upper MI today,
expect low stratus to dominate the area along with some fog,
especially where sfc winds are upsloping. There will be -shra and
-dz at times at well. LIFR will prevail at IWD/CMX/SAW thru this
aftn. With upsloping e to ese winds at CMX/SAW, conditions may slip
blo airfield landing mins at times, especially at CMX. As the low
lifts to the ne of the area tonight, expect improvement to IFR at
IWD/SAW. CMX may end up with LIFR thru the night as upsloping e
winds shift to upsloping w winds. The easterly winds today at CMX
will be gusty to 25-30kt thru mid aftn.

&&

.MARINE...
Issued at 411 AM EDT Mon Apr 29 2024

East-northeast gales to 40 kts are occurring across most of the lake
tonight with gusts up to 45 kts at the Twin Ports. Gales to 40 knots
continue this morning before diminishing around midday then ending
this afternoon. Significant wave heights up to 14 ft are possible
this morning between Duluth Harbor to the Bayfield Peninsula and
near Isle Royale. Waves fall below 8 ft this evening.

A low pressure tracks across the lake tonight switching easterly
winds to westerly and allowing winds to fall below 20 kts over the
west half this evening and after midnight across the east. West
winds are expected to remain mainly below 20 kts through Tuesday.
East to south east winds increase to 20-25 kts Tuesday night,
becoming westerly and increasing to 25-30 kts behind a cold front on
Wednesday. There is a low 10-30% chance for westerly gales up to 35
kts on Wednesday with the highest chances on the windward 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.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Gale Warning until 5 PM EDT /4 PM CDT/ this afternoon for
     LSZ162-243>246-263>266.

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

  Small Craft Advisory until 8 PM EDT this evening for LSZ242.

  Small Craft Advisory from 5 PM this afternoon to 4 AM EDT
     Tuesday for LSZ243>246.

  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...EK
AVIATION...Rolfson
MARINE...EK