Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 231144
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
744 AM 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 forcasts 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 12Z TAFS through 12Z Thursday morning)
Issued at 743 AM EDT WED MAY 23 2018

VFR conditions are expected to prevail at all TAF sites through the
forecast period. Just a small chance IWD will see isold showers
and t-storms around daybreak on Thu. Went with VCSH for now. Will
see lake breezes develop at all sites this afternoon but winds
should remain light at 10 kts or less.

&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 438 AM EDT WED MAY 23 2018

Winds are expected to stay below 20 knots through the entire
forecast period. Expect areas of fog to develop late this week into
the weekend as some rainfall occurs over the lake and a humid air
mass arrives over the area. Could be looking at dense fog at
times.
&&

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

$$

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



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