448
FXUS63 KMQT 030712
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
312 AM EDT Mon Jun 3 2024

.KEY MESSAGES...

- Showers and a few thunderstorms progress eastward across west
  and central Upper MI today. Greatest coverage will be over
  the west. Severe storms not expected.
- Frequent opportunities for showers and thunderstorms over the
  next 7 days, with a break expected possible on Tuesday.
- Above normal temperatures through Wednesday, then turning
  cooler for the second half of the week.

&&

.SHORT TERM /THROUGH THIS AFTERNOON/...
Issued at 312 AM EDT Mon Jun 3 2024

Water vapor imagery and RAP analysis show weak mid-level troffing
over the Northern Plains. One vort max is noted over eastern ND, but
it`s difficult to pick out clearly any others. Radar imagery shows
shra/tsra from MN to Nebraska/KS with greatest coverage across MN
within 40-50kt low-level jet and the resulting 850mb theta-e
advection that has developed in response to the aforementioned ND
vort max. Radar imagery has occasionally been suggestive of
potentially one or two convectively induced weak vort maxes within
the shra/tsra area. The shra/tsra have spread out over nw WI, and
shra have recently arrived over far western Upper MI. Temps across
the fcst area currently range from the mid/upper 40s F at a few of
the traditional cold spots across the e to the mid 60s F at KIWD.

As shortwave over eastern ND lifts ene today, stronger core of the
low-level jet will mostly pass just nw and n of Upper MI, suggesting
that wider coverage of heavier rainfall will brush w and nw Upper MI
this morning. Meanwhile, with the southern end of the low-level jet
weakening to around 30kt at it translates over Upper MI today, would
anticipate a diminishing of shra as they progress across the area,
and much of the guidance indicates that. If a weak vort max is
concealed in the convection in MN, that would work to delay the
expected diminishing of shra. Of note is a better defined
convectively induced vort max over eastern Nebraska. Models indicate
that this feature will lift to Upper MI later this aftn, potentially
reinvigorating shra across the central and/or eastern fcst area.
Models have mixed signals on whether this feature will hold together
and/or aid shra. Will be something to monitor for an increase in
rainfall later aftn. Whatever the case, shra won`t reach the far
eastern fcst area until late in the day. CAPE is meager today with
abundant cloud cover limiting heating, but enough is present for non
sfc-based parcels or potentially sfc based parcels this aftn if
there is some thinning of clouds to maintain mostly just a schc
thunder mention. With expectation of clouds mostly dominating,
knocked high temps down a little. Expect upper 60s/lwr 70s F for the
most part, though eastern areas away from Lake MI should reach the
mid 70s due to thinner cloud cover thru at least the morning.

&&

.LONG TERM /MONDAY THROUGH SUNDAY/...
Issued at 416 PM EDT Sun Jun 2 2024

Warm and moist southwest flow ahead of an upper level trough lingers
through Wednesday resulting in almost daily chances for showers and
embedded thunderstorms. There should be a general lull on Tuesday,
but rain chances linger into Tuesday morning across the east and the
next disturbance arrives Tuesday afternoon/evening across the west.
Tuesday looks to be the warmest day this week with highs warming to
near or above 80F except for 70s downwind of Lake MI. A chance for
strong thunderstorms and locally heavy rainfall accompanies a cold
front passage Tuesday night. A cooler but still humid air mass
follows the front as an upper level low establishes a broader trough
across the Great Lakes region late this week. As a result, rain
chances late this week appear much lighter with limited thunder
potential and primarily diurnal in timing.

Starting with Monday morning, the UP will be positioned between
surface ridging to the east and a surface low to the west. A fairly
tight pressure gradient is accompanied by a ~45-50 kt low level
jet that translates east and weakens to 35-40 kts during the
day. This suggests some potential for stronger winds/gusts, but
considerable cloud cover and rain showers inhibit mixing so kept
forecast winds close to NBM. I considered removing thunder
chances on Monday due to meager CAPE values around or less than
100 J/kg, but any breaks in cloud cover could allow for greater
destabilization. Rain showers gradually diminish while tracking
across the eastern UP Monday evening and clearing skies expected
shortly after the front passes. Conceptually, this scenario
suggests potential for terrestrial radiation fog and maritime
advection fog by Tuesday morning.

Terrestrial fog should dissipate Tuesday morning allowing for mostly
sunny skies and temperatures warming to around 80F across most of
the UP. Dew points around 60F indicate potential for unseasonable
destabilization during the day (perhaps in the 2000-3000 J/kg
range), consistent with EFI value of 0.5-0.7. Soundings suggest the
area stays capped on Tuesday until the cold front moves in Tuesday
night, but will need to monitor potential for a pop-up storm along
any lake breeze boundaries that develop. Bulk shear also increases
as the front approaches indicating an increasingly favorable
environment for strong to perhaps severe thunderstorms. Diurnal
timing is more favorable for severe storms to our west, but the warm
sector of a ~990 mb surface low in early June seems more threatening
than the marginal risk currently outlooked by the SPC suggests.
NAEFS guidance also indicates pwats increasing above the 90th
percentile Tuesday evening implying a heavy rain threat.

Model spread increases by Wednesday morning, presumably due to
differences in convective development late on Tuesday. Most
operational 12z models indicate the cold front will still be
overhead or at least nearby Wednesday afternoon implying potential
for afternoon redevelopment, mainly east. Modest mid-level cold air
advection may dynamically destabilize the area on Wednesday leading
to a round of diurnal showers/storms. However, I decided to pull
thunder chances for Wednesday night onward as dew points fall below
50F and cool/dry air advection continues. The upper level low tracks
southeast across the UP Wednesday thru Thursday night resulting in
an extended period of unsettled and showery weather. Total rain
amounts are expected to be light due to lack of quality moisture
while temperatures trend below normal, especially daytime highs.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 134 AM EDT Mon Jun 3 2024

VFR conditions should hold through mid to late morning when they
begin to deteriorate to MVFR starting with IWD.  An approaching
disturbance will spread rain showers into the area early this
morning, and cigs will eventually deteriorate as the environment
becomes saturated.  Best chances for any thunderstorms will be
confined to IWD where best forcing will be concentrated with strong
low-level jet.  Will, however, carry a LLWS mention at both IWD and
CMX this morning in association with said low-level jet.  At the
surface, southerly winds will also exceed the 12 kt threshold with
gusts up to 22 kts later this morning through this afternoon. And
for now, will lean toward a downward trend in cigs with IFR
conditions by Tue 03Z.

&&

.MARINE...
Issued at 416 PM EDT Sun Jun 2 2024

Light winds of 20 knots or less continue today into tonight as weak
surface high pressure continues over Lake Superior. However, as a
cold front moves through late tonight into Monday, southerly winds
gust up to 20 to 25 knots Monday, particularly over the north-
central lake and near tip of the Keweenaw. By Monday evening, winds
diminish to 20 knots or less and stay light until a cold front
approaches the lake Tuesday afternoon with southeast winds gusting
to around 20 kts. The front cross the lake late Tuesday night and
Wednesday with southwest winds to gusting up to 20 to 25 knots over
the western half of the lake behind the front. A low pressure stalls
over northern Ontario for the latter half of the week, resulting in
a prolonged period of unsettled weather including west or southwest
winds gusting to 15-25 kts through Friday evening. A few stronger
gusts up to 30 kts are possible on Thursday.

As for other marine hazards, patches of dense marine fog are
occurring across northeastern Lake Superior this evening. Dew point
temperatures well above lake water temperatures and several periods
of rain indicate potential for fog redevelopment on Monday through
Tuesday night. A few thunderstorms are possible across the western
lake tonight before spreading across the remainder of the lake
Monday and Monday evening. Another cold front Tuesday night brings
scattered thunderstorms across the lake from west to east from
Tuesday afternoon through Wednesday. While severe thunderstorms are
not expected at this time, a few stronger storms capable of hail,
gusty winds, and frequent lightning are possible Tuesday night into
Wednesday

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.

&&

$$

SHORT TERM...Rolfson
LONG TERM...EK
AVIATION...TDUD
MARINE...EK