Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 231953
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
353 PM EDT Wed May 23 2018

.SHORT TERM...(Today and tonight)
Issued at 438 AM EDT WED MAY 23 2018

Quiet start to the day with some cirrus over western Upper Michigan
and some stratus and patchy fog on Lk Michigan. Temps inland over
Upper Michigan are in the 40s. Temps near Lk Superior are staying up
in the 50s, even near 60F around Marquette, due to southerly return
flow between high pressure over southern Lk Michigan/lower MI and
weak front dropping over northern Lk Superior. Closest precip in the
form of t-storms is occurring over southwest MN into northern IA.
Storms are firing in area of focused H85 warm air advection on edge
of elevated mixed layer and higher MUCAPE. Sfc warm front is still
southwest of this elevated activity. Another area of t-storms are
over SD closer to main trough aloft and shortwaves lifting across
the northern Plains.

For Upper Michigan today, temps aloft look warmer than Tue by 1-2C
so expect highs well into the 80s inland and upper 60s/near 70F
along Lk Superior. Coolest temps today near Lk Michigan but even
there should get mid 60s. Could be some fog affecting immediate
shore of Lk Michigan east side of Garden Peninsula eastward. Looking
at another day of elevated fire weather concerns with min RH dipping
to around 20 pct inland. Winds gusting to 10-15 mph along lake
breezes this aftn look too light to justify any kind of Special
Weather Statement. This should be the last day until next week of
seeing persistent low RH blo 25 pct.

Signs of this change to a more warm, humid summerlike pattern begin
to show up tonight, though as it always seems, model forecasts of
convection show little agreement, even less than 24 hours out.
Aloft tonight we are in region of building heights as main trough
aloft is still well to the west over the Rockies and just
beginning to affect the northern Plains, but there should be
significant warm and moist advection ongoing in low levels ahead
of strengthening plains sfc- H85 trough. Similar to what is
occurring this morning to the southwest over IA and MN, expect
shra/t-storms to develop on nose of low-level jet/moisture
transport and on edge of reservoir of elevated instability with
1-6km MUCAPES of at least 1000 j/kg forecast. Differences in the
models tie into how far east this moisture/instability gradient
reach. NAM seems too aggressive with its low-level jet and in its
resulting cluster of elevated t-storms over much of the west half
of UPper Michigan by 12z Thu. Instead like the GEM/ECMWF idea of
showing similar idea to NAM but just shifted more over mainly MN
into far western Lk Superior. GFS seems too muted with overall
developing of shra/t-storms given instability that is building
over the plains currently. As always will have to watch for
convectively induced shortwaves that could trigger activity as far
east as NAM indicate, but for now will bring low chance pops into
western Upper Michigan late tonight. Effective shear late tonight
is weak under 15 kts, so maybe looking at small hail as updrafts
will not be able to persist too long.

Low temperatures tonight will be in the 40s to 50s, but given the
warmth already seen this morning, forecast lows in the low to mid
50s along Lk Superior may end up being too cool since the pressure
pattern is pretty similar with even a stronger south wind.

.LONG TERM...(Thursday through Tuesday)
Issued at 459 AM EDT WED MAY 23 2018

Mean western Canada ridge/eastern Canada trof that has dominated for
some time will progress downstream and breakdown over the next
several days as mean troffing tends to become established from the
Gulf of AK into western Canada/Pacific NW. This will support a
change in the weather for the Upper Great Lakes late week thru the
Memorial Day holiday weekend. Underneath the current western Canada
ridge, a southern stream trof is over the western CONUS. With the
flow to the n in Canada becoming progressive and another shortwave
trof moving off the N Pacific toward the sw CONUS, the current
western CONUS trof will get kicked ne then eastward along the
U.S./Canada border region, bringing an unsettled period of weather
to Upper MI late week thru the weekend. With large portions of west
and central Upper MI only receiving less than 25pct of normal
rainfall over the last 30 days, widespread decent rainfall is
needed. That probably won`t happen, but at least the potential is
there for some areas to receive much needed rainfall with sct
showers and thunderstorms Thu thru Sun, an unfortunate setup for
those planning outdoor activities during the holiday weekend after
having weeks of mostly dry weather prevailing. With shortwave
slipping e of the area Sun, dry weather should return for Memorial
Day. The shortwave trof that kicks the current trof out of the
western CONUS to the Upper Lakes will establish a new western CONUS
trof this weekend. With the aforementioned troffing setting up off
the Gulf of AK into western N America next week, this western CONUS
trof should eventually get forced ne like its predecessor, providing
Upper MI with another opportunity of shra/tsra at some point during
the last half of next week. As for temps, with the departure of the
eastern Canada trof, the mechanism for sending cooler air into the
Upper Lakes will be gone. Overall, the upcoming 7-10 day period
looks solidly above normal, though the typical cooler by the lake
will occur frequently. Many days will see more summerlike dwpts
readings as well.

Beginning Thu, sw flow will bring 850mb theta-e advection across the
fcst area. The sharp 850mb instability gradient noted within the
theta-e advection regime should be a key location for elevated
convection potential thru the morning, and chc pops will follow
along in this gradient zone. While 1000-1500/kg of cape is avbl for
the potential elevated storms, effective deep layer shear is blo
25kt. So, not expecting any svr storms. Stronger storms may produce
some small hail. Whether any sfc based storms manage to develop in
the aftn remains to be seen. If some morning storms do occur, any
boundary generated by that convection could provide a focusing for
possible redevelopment. Otherwise, there`s not much to generate
convection. Away from southerly flow off Lake MI, temps will rise
into the 80s. With dwpts rising thru the 50s, it will begin to feel
much more summerlike.

With 850mb flow oriented more anticyclonically Thu night and with
the 850mb instability gradient shifted n and ne of the area, not
convinced there will be much convection around. Only schc/low chc
pops were utilized. Certainly could end up being a dry night across
the board. Will be a warm night w and n central with mins above 60F.
Will be cooler toward Lake MI, probably 40s lakeside e of the Garden
Peninsula.

Shortwave swinging across the area on Fri will provide the forcing
for sct shra/tsra development. MLCAPES increase to 1000-1500j/kg,
but with deep layer shear aob 25kt, well-organized svr convection is
not expected. If any svr storms manage to develop, they would be
over the western fcst area and short-lived/isolated. Will be a very
warm day with highs well into the 80s away from southerly flow off
Lake MI.

Another shortwave will move across the area on Sat, and mlcape will
probably end up similar to Fri in the 1000-1500j/kg. There are hints
that deep layer shear may be up around 30kt, though models don`t
agree on that aspect. If so, there would be a slightly better chc of
isold svr storms Sat aftn.

Whether any shra/tsra linger into Sun will depend on progress of
cold front thru the Upper Lakes. The drier ECMWF scenario is
probably more likely with earlier fropa, but until there is better
model agreement, will linger chc/schc pops on Sun.

Building mid-level ridge into the Upper Mississippi Valley/western
Great Lakes should support dry weather for Memorial Day and Tue.
With associated sfc high pres setting up over the area, lake breezes
will provide cooling near the Great Lakes while interior locations
still rise above 80F.

Some shra may arrive Wed, depending on timing of the trof lifting
out of the western CONUS as discussed above.
&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 133 PM EDT WED MAY 23 2018

Other than the lake breeze expected to traverse through KSAW this
afternoon, not too many aviation concerns expected for much of the
early part of the TAF period. However, as tomorrow morning
approaches and the Upper Peninsula becomes under the influence of
a more unsettled pattern, could see some morning showers popping
up around the vicinity of the area terminals. KIWD and KCMX
currently appear the most likely to be directly affected by any
showers that might develop, but confidence is not there quite yet
to include anything more than VCSH for this TAF issuance. Look for
winds to prevail out of the southwest after sunrise Thursday
morning.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 347 PM EDT WED MAY 23 2018

Fog currently engulfing northern Lake Michigan has continued to
advect northward, pooling along the Schoolcraft/Mackinac County
land/water boundaries. This fog is anticipated to persist through
the overnight hours into early tomorrow morning before finally
dissipating. Otherwise, no significant marine hazards are expected
for the next couple of days with winds topping out at around 10-15
knots through tomorrow, briefly becoming stronger across eastern
Lake Superior and Lake Michigan/Bay of Green bay overnight
tomorrow.


&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
  Dense Fog Advisory until noon EDT Thursday for LMZ248-250.

&&

$$

SHORT TERM...JLA
LONG TERM...Rolfson
AVIATION...lg
MARINE...lg


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