Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 252339
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
739 PM EDT Fri May 25 2018

.SHORT TERM...(This evening through Saturday)
Issued at 506 PM EDT FRI MAY 25 2018

Thunderstorms this afternoon fired over south central and eastern
Upper Mi where there was better insolation and increased instability
with MLCAPEs 1000-1500 j/kg. Also deep layer shear values close to
30 knots supported isolated stronger storms which likely contained
dime-sized hail at a few locations. The rest of the U.P has stayed
under a veil of mid-high clouds which has helped limit instability
and thus kept a cap on most convection this afternoon.

Mesoscale model trends indicate convection could continue for the
next hour or so over the eastern counties, but then focus will shift
to the potential for isolated to scattered storms generating over
the western counties toward early evening as mid-high clouds erode
and instability increases to MLCAPE in excess of 1500 j/kg. If these
storms develop it looks like shear will be weak (around 20kt) which
will limit severe potential and lead to generally pulse-type storms.
Expect any lingering convection to erode shortly after sunset as
diurnal instability wanes. The rest of the night should see clearing
skies, although eastern counties could see some fog/stratus
development later tonight with southerly flow off Lake Michigan
continuing feed of moist air into those counties.

Muggy and very warm conditions will be on tap for Saturday as sunny
skies in the morning will lead to a quick warmup late morning into
early afternoon. The increased warming will also lead to increased
instability again by afternoon with close to 1000 j/kg SBCAPE into
the central counties of the U.P. Deep layer shear values of 30 knots
or possibly higher into the central U.P could lead to isolated
stronger storms with gusty winds to 40 knots possible at a few
locations.

Deep mixing as noted on fcst soundings and 850 mb temps near 18c
will lead to high temps Sat into the upper 80s and possibly lower
90s over much of the interior west half of Upper Mi. Southerly flow
off Lake Mi will keep inland temps over the east half in the lower
to mid 80s and in the 60s to lower 70s along Lake Mi and the Bay of
Green Bay. Dewpoints in the upper 50s to lower 60s will again result
in very muggy conditions across the region.

.LONG TERM...(Saturday night through Friday)
Issued at 236 PM EDT FRI MAY 25 2018

Warm/Humid conditions appear to be the main story for the next few
days, or at least through the bulk of the Holiday Weekend for the
Upper Peninsula. Upper level pattern is setup with steadily
increasing heights, with operational solutions lifting a weak lobe
of vorticity northeast during the day Sat that could touch off a
couple showers and thunderstorms. Instability is marginal, with
weakly sheared wind field but some energy present which could
product a few stronger storms with small hail and wind gusts to 40
mph. Otherwise very summer like weather is expected, as temps may
warm into the mid/upr 80s across much of the UP. The exception will
be areas adjacent to Lake Superior and Michigan, due to the onshore
flow from midday lake breezes. The gradient does start to tighten up
Mon aftn/eve; however, a frontal boundary will be sliding south from
Ontario.

Mon ngt thru Wed: Weak frontal boundary will try to slide south
across the UP late Mon; however, with the overall larger scale
forcing showing a trough across the Plains, expect this frontal
boundary to lift back north later in the week with continued warmth
and humidity returning to the UP. Temps thru the remainder of the
extended will be generally in the 70s to lower 80s, with overnight
lows in the 50s. A few scattered showers and thunderstorms will be
possible throughout the extended, but mainly Mon and again Wed thru
Fri.
&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 730 PM EDT FRI MAY 25 2018

Immediate aviation concern for the start of this TAF period will
be the ongoing isolated showers/thunderstorms across the Upper
Peninsula. KIWD and KSAW will have the greatest chances of
VCTS/VCSH, respectively, occurring for the next few hours, until
just after sunset. Once this diurnally-driven activity winds down,
the rather moist atmosphere, in addition to today`s rain, could
allow for some low clouds and/or fog to develop. However,
confidence is not high in this panning out in and around the
terminals, and will monitor conditions through the overnight hours
to determine if lowering categories in the subsequent TAF
issuance and/or an amendment is needed. Bottom line: don`t be
surprised if there ends up being a reduction in ceilings and/or
visbys, particularly at KIWD and KSAW, by the pre-dawn hours
tomorrow.

&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 506 PM EDT FRI MAY 25 2018

Winds less than 20 kts are expected through the middle of next week.
Expect areas of fog to develop and linger at times into the weekend
as multiple rounds of rain are expected over the lake and the humid
airmass lingers. Fog may be dense at times, especially this morning
across the far west half. Thunderstorms are possible Saturday
afternoon into sat night, and then again early next week.
&&

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

$$

SHORT TERM...Voss
LONG TERM...Beachler
AVIATION...lg
MARINE...Voss



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