Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 242039

Area Forecast Discussion
National Weather Service Marquette MI
439 PM EDT Mon Jun 24 2019

.SHORT TERM...(This evening through Tuesday)
Issued at 427 PM EDT MON JUN 24 2019

Water vapor imagery and RAP analysis show a vigorous shortwave
beginning to take on a negative tilt as it lifts thru the Upper
Mississippi Valley. At the sfc, low pres trof extends across western
Upper MI from e side of the Keweenaw Peninsula s to around
Watersmeet. Increasing deep layer forcing ahead of the shortwave
is beginning to support an expansion of shra and some isold
thunder ne from WI into central Upper MI. Fortunately, abundant
low-level moisture and resulting cloud cover has kept instability
in check today. Latest SPC mesoanalysis shows MLCAPES up to around
500j/kg and MUCAPE into the 500-1000j/kg range. Upstream, next
shortwave of interest is over MT, and this feature will play a
role in the weather here on Tue as it may lead to strong to svr

Expect shra to continue expanding over the next several hrs and
spread e and ne in association with shortwave lifting across the
Upper Great Lakes. Expect some locally hvy rainfall. After the
overall dry conditions that have prevailed this month across the
fcst area (month to date pcpn is running under 50% of normal over
the w half of Upper MI with a good portion under 25% of normal), the
rainfall is needed to alleviate the short term dryness.
Unfortunately, heavier rainfall will miss some of the driest areas
over the w. Svr risk appears to be very limited based on current
instability and widespread cloud cover limiting any additional
buildup of instability. In addition, deep layer shear has fallen off
to under 25kt this aftn. Shra will wind down overnight, but may
linger for most of the night over the e in cyclonic flow immediately
following passage of the low-level trof. Fog is likely present over
western Lake Superior after the rainfall of the last 24hrs, and this
fog will affect areas near the lake thru the evening under wnw
winds. Fog may expand inland for a time toward and after sunset.

Active late aftn is likely on the way Tue. Shortwave currently over
MT will move across northern MN Tue aftn and will reach Upper MI Tue
evening. W and WNW mid-level flow are the most favorable regimes for
warm season strong to svr storms in Upper MI, and westerly flow will
be present on Tue. In addition, low-level wind fields will be
westerly, supporting better low-level convergence as aftn winds
develop a lake breeze component off the Lakes. This is especially so
over the e half of the fcst area. Consensus of 12z guidance is for
MLCAPES to increase to around 1000j/kg in an environment of 30-40kt
of deep layer shear. Expect sct shra/tstms to develop after 18z.
However, Keweenaw likely won`t see any shra under stabilizing
westerly winds off Lake Superior. Hail will be the main risk with
wetbulb zero heights favorably positioned in the 8-10ft layer. Dry
mid-levels are missing to enhance wind risk, but strong winds still
a possibility. Will be warm, summer day with highs mostly in the
upper 70s/lwr 80s. Will also be breezy with mixed layer winds
supporting gusts to 20-25mph and at times 30mph.

.LONG TERM...(Tuesday night through Monday)
Issued at 433 PM EDT MON JUN 24 2019

The active convective weather continues into this forecast period,
with a brief break likely for most in Upper Michigan on Wednesday,
save a slight chance of thunderstorms in the east (low confidence in
this coming to fruition). From Thursday into the weekend, the U.P.
will linger in an unsettled pattern that consists of weak shortwaves
riding along the periphery of mid- to upper-level ridging,
increasingly amplifying by the end of this weekend. Given this type
of setup, longer-range models are struggling to come into agreement
on the finer details, as is typical, yielding nearly daily PoPs, but
only due to the sporadic nature of the expected activity.

Summer has finally arrived (and not just officially) as temperatures
steadily rise and linger in the 70s (near the lakeshores) and 80s
(more widespread, inland) for highs each day. Lows will respond
accordingly, with widespread 50s to around the 60 degree mark
closest to the WI border. As already alluded to, instability will
become increasingly available as well, allowing for those
aforementioned thunderstorm chances to ramp up throughout this
forecast period.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 133 PM EDT MON JUN 24 2019

With low pres lifting thru the Upper Great Lakes this aftn/evening,
shra and a few tsra are expected, mainly at KSAW. Coverage of shra
will be more limited to the w, so only VCSH was mentioned in fcst at
KIWD/KCMX. While KIWD should improve from prevailing IFR to MVFR by
late aftn as somewhat drier air works into the area, KCMX will
likely see conditions fall from MVFR to IFR as cool/moist marine
layer upslopes under wnw winds to that terminal. KSAW should see
prevailing MVFR conditions into this evening, though some brief
periods of IFR are possible late aftn/evening with the pcpn. Drier
air will spread e across the area tonight. This will result in
improvement to VFR at KIWD late evening and at KCMX/KSAW overnight.
Breezy w winds gusting to 20-30kt are expected at all terminals on
Tue. VFR conditions will prevail thru the early aftn.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 427 PM EDT MON JUN 24 2019

Sfc low pres will lift ne of Lake Superior tonight. Until the low
passes, se winds over the e half of Lake Superior will continue to
gust to 15-25kt, and up to 30kt at high obs platforms. As the low
lifts ne, westerly winds gusting to around 20kt will develop from w
to e. High obs platforms could see gusts to 25-30kt. Westerly
winds will continue Tue, mostly in the 10-20kt range though gusts
to 20- 25kt are expected across the w half of the lake, especially
around the w and n side of the Keweenaw. Winds will be slightly
weaker on Wed, then light on Thu as high pres ridging arrives.
Light winds will continue on Fri.

Areas of fog have developed on Lake Superior. This fog may be
locally dense tonight, but the fog will clear out from w to e late
tonight and Tue.

Upper Michigan...
Lake Superior...
Lake Michigan...
  Dense Fog Advisory until 11 PM EDT this evening for LMZ221-248-



SHORT TERM...Rolfson
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