397
FXUS63 KMQT 042259
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
659 PM EDT Tue Jun 4 2024

.KEY MESSAGES...

-A few strong to severe thunderstorms expected in the far
 western UP today. Not much severe weather is expected, but a
 few isolated damaging wind gusts and/or marginally severe hail
 cannot be ruled out (10%).
-Cold front spreads from west to east across the UP tonight and
 tomorrow morning, bringing some thunder and occasional
 downpours but otherwise no severe weather.
-Showery weather through at least this weekend with a trend
 toward much cooler temperatures as a closed low sets up shop
 over the Great Lakes.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 250 PM EDT Tue Jun 4 2024

GOES-16 Day Cloud Phase RGB imagery shows a mixture of cloud forms
over Upper Michigan and Lake Superior this afternoon. Patches of
dense fog are over much of the open waters of Lake Superior
with some other lower stratus advecting north. Meanwhile,
stratus is breaking into stratocu over the central and eastern
areas of Upper Michigan while Gogebic and Ontonagon are starting
to see some cu fields bubbling up. This latter area will be the
area of most impactful weather this afternoon as CAMs resolve a
few strong thunderstorms over the far west later on this
afternoon, though some differ in strength. With WAA under warm,
southerly flow, temperatures have climbed well into the 70s
across the UP with a few spots already in the 80s, especially in
areas with downsloping in the far east and far west where
clearing was seen earlier than in the central.

With all of this surface warming, lapse rates at the low and mid
levels have resulted in significant gains in instability. RAP
mesoanalysis shows up to 2500 J/kg of SBCAPE along the MI/WI state
line at 18Z with some SBCIN present, but less than 25 J/kg. The wind
shear is a different story however, with effective bulk shear values
less than 20 knots except for after 22Z in the far west. Hodographs
are curved, but the magnitude is quite small. Despite this, the 12Z
members HREF has been more aggressive than the 00Z counterparts with
convective initiation this afternoon in the west, with paintball
plots of 40+ dBZ simulated reflectivity showing a smattering of
cellular convection over the western third of the UP from 21Z to
03Z. At this time, leaning towards a scattered to isolated cellular
convective mode, with a few "core dumps" that may produce an
isolated severe wind gust or marginally severe hail, but
probabilities only around 10%.

By around 06Z tonight, a cold front will arrive from the west and
spread a line of showers and weakening thunderstorms from west to
east through the west half of the UP through 12Z. No severe weather
is expected from the cold frontal line of showers, but some locally
heavy downpours are possible as mean NBM precipitation from 06Z-12Z
is over a half inch over the far west, with high-end (top 10% of
solutions) estimates of over an inch. This is still less than the
flash flood guidance, so widespread flash flooding is not a threat
with this system. This will begin to veer the winds westerly and
bring some temperature falls to the west, but the eastern two thirds
of the UP will only see lows in the low 60s to upper 50s.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 447 PM EDT Tue Jun 4 2024

Models and ensembles trending toward a blocky pattern in the high
latitudes of North America from the middle of this week into at
least the early part of next week. Models indicate mid-level
ridging/positive height anomalies, first from ne Canada across the
Arctic Ocean, and then over western N America will force mid-
level troughing to develop from s central Canada across the
Great Lakes/eastern U.S. The western ridging deamplifies next
week, but the EPS is slower to deamplify that ridge and is less
progressive with it than the GEFS/GEPS. The positive height
anomalies will remain across the Arctic Ocean thru ne
Canada/Labrador Sea next week. For Upper MI, this pattern will
lead to above normal temps through Wed trending down to an
extended period of blo normal temps (seasonably cool) most days
thru next week. However, the large scale pattern does suggest
the potential of unseasonably cool days in the mix, particularly
Thu thru the weekend. Would not be surprised to see a day or
two with highs widespread in the 50s F w and n. The less
progressive EPS solution would allow the cool weather to persist
longer thru next week than the GEFS/GEPS. As for pcpn, the
development of the mid-level troughing will support
showers/t-storms late tonight/Wed as the lead cold front passes
across the area. Models advertise a mid-level low closing off
over the Great Lakes region by Thu, leading to showery weather.
Generally, the pattern of mid-level troughing or a mid-level low
near the area through at least the first half of next week will
support frequent opportunities of showers. Model details will
be muddied on the timing/track of shortwave impulses circulating
around mid-level low into Upper MI, so pcpn fcst will have much
more uncertainty than normal. At this time, widespread, all day
rains appear unlikely unless a well organized wave develops
within this pattern. Many areas will be dry much of the time as
showers are likely to be scattered in coverage on most days.

Beginning Wednesday, a vigorous shortwave now moving out across the
Northern Plains today will take on a negative tilt as it swings into
the western Great Lakes Wed morning. With the arrival of the
negative tilt shortwave there will be uptick in forcing/upper
diffluence along the associated cold front as it moves w-e across
the area. Precipitable water increasing to around 200pct of normal
will support locally heavy downpours. HREF 90th percentile has
streaks of 1.5 inch or higher pcpn amounts, indicating the heavier
rainfall potential with some of the convection. Elevated cape of
several hundred j/kg along and ahead of the cold front will also
support isolated t-storms. In the wake of the fropa showers/t-storms
will abruptly end, followed by clearing from w to e early Wed
morning thru early to mid aftn on Wed. Attention then turns to
secondary cold front arriving late Wed afternoon/evening in
association with another shortwave. Aloft, height falls continue
thru the day with Upper MI becoming situated under expanding mid-
level low and cooling mid-levels. With fcst soundings showing
potentially several hundred j/kg of MLCAPE building, deep layer
shear 25-35kt, and a drier profile blo cloud layer, there is a
potential for gusty wind producing storms late Wed aftn/evening
across the west half of Upper MI. While winds probably won`t reach
severe criteria, it will definitely be something to monitor late Wed
afternoon, especially if instability ends up on the higher end of
current guidance which would raise the potential of isolated
severe wind gusts. Showers/t-storms will spread into the eastern
fcst area during Wed evening with the gusty wind risk
diminishing as instability wanes.

On Thu, Upper MI will be situated firmly under mid-level low
circulation with recent guidance now showing the center over or very
near to Upper MI. Some shower activity will be ongoing to start the
day. Under cold pool aloft combined with any shortwaves swinging
around the circulation and the building of weak sfc based
instability, showers will take on a diurnal component and expand in
coverage away from the stabilizing influence of Lake Superior under
nw winds. Would expect s central and se Upper MI to see most
numerous shower coverage. Will be a cooler day with highs in the 50s
near Lake Superior for areas where nw winds are directly onshore
ranging up to the mid/upper 60s F s central. If showers/clouds are
more widespread than currently expected, highs will be lower.
Showers should diminish Thu night with the loss of diurnal
instability.

Friday into Saturday will likely be very similar to Thursday, but
with the mid-level low shifting slightly e, though diurnal shower
coverage will likely decrease a bit each day from Thursday`s
coverage. As with Thursday, if clouds/shower coverage are more
widespread, highs Fri and Sat will be lower than the current
forecast of upper 50s to mid 60s F.

Over the late weekend thru early next week, details of the structure
of the mid-level flow from s central Canada thru the Great Lakes
region is very uncertain. Models have shown little agreement or run-
to-run consistency on the expansiveness, location, movement of mid-
level low and shortwave timing/amplitude in the flow. Pattern is
certainly suggestive of daily shower potential and the ensembles
also support this by indicating persistent mid-level troughing into
early next week. Similar to the previous days, if showers and clouds
are more widespread or persistent on Sunday, high temps will only be
in the 50s across the w and n and 60s s central. Overall, it appears
the influence of the mid-level low should diminish during the early
part of next week, so would expect showers to become more
isolated at that time.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 659 PM EDT Tue Jun 4 2024

Tonight, SAW and CMX will remain VFR and dry. Overnight, a cold
front will spread west to east across the TAF sites, and the showers
and thunderstorms from that front will usher in lower ceilings and
potentially low visibility. IWD and CMX will fall to MVFR by late
tonight and possibly to IFR Wed morning. SAW will fall to IFR by Wed
morning and then go to MVFR Wed afternoon.

&&

.MARINE...
Issued at 447 PM EDT Tue Jun 4 2024

Other than some 20-25 kt ne wind gusts over western Lake Superior
and se winds over eastern Lake Superior, winds tonight will
generally be less than 20 kts. Thunderstorms moving out over western
Lake Superior this evening ahead of an approaching trough will pose
a risk of strong wind gusts. This trough will then sweep across Lake
Superior late this evening thru early Wed aftn with more storms
possible. While wind gusts to around 20kt will continue, the showers
and thunderstorms along/ahead of the front may result in locally
enhanced winds ahead of and just behind the trough. More
thunderstorms developing over MN and moving out across western Lake
Superior Wed afternoon/evening will also pose a risk of locally
strong wind gusts. Thereafter from Wed night thru Fri, fairly steady
w to nw winds of mostly 20-25kt are anticipated with occasional
gusts to 30kt. Winds may die down slightly by Sat.

Also of note, fog will be dense at times on western and central Lake
Superior into this evening. This fog should depart with passage of
the trough late this evening through early Wed afternoon.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Dense Fog Advisory until 11 PM EDT /10 PM CDT/ this evening
     for LSZ162-263-264.

Lake Michigan...
None.

&&

$$

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