Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 271901

Area Forecast Discussion
National Weather Service Marquette MI
301 PM EDT Tue Jun 27 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 300 PM EDT TUE JUN 27 2017

WV loop and 12z RAOBS indiate broad upper trough over eastern Canada
into Great Lakes and northeast CONUS. Ridging is upstream fm scntrl
Canada to the northern Plains but more trougning is present western
Canada to Idaho/Montana/Wyoming. At the sfc, high pressure is
centered over Ohio Valley while low pressure trough swinging
eastward across Montana/Wyoming is moving toward the northern
Plains. Cu has bubbled up along the lake breeze over eastern U.P.
and suppose there may be a shower there in the next few hours.
Otherwise no other shra have been seen over rest of cwa as dry air
seen in upstream soundings has overwhelmed any daytime heating and
shallow instability.

High pressure ridge still west of here so expect conditions to stay
dry through tonight as the ridge crosses. Lows will mainly be in the
50s though some inland areas could drop into upper 40s.

Shortwave trough over the Rockies and associated low pressure system
will reach the eastern Dakotas by daybreak on Wed. The forcing along
with axis of elevated instability should support clusters of showers
and thunderstorms from northern Missouri north into parts of western
Minnesota. As low-level jet ahead of the low pressure/trough veers
more sw expect this convection to lift toward Upper Great Lakes,
reaching western forecast area in the morning. Moisture advection
ahead of the system overall will be strong with pwats over 1.50
inches and h85 dwpnts of 14-16c lifting toward Upper Mississippi
River Valley. Shortwave trough and sfc low/trough slide across
Minnesota through Wed morning while sfc warm front stays well to the
southwest of Upper Michigan. Strong moisture transport on nose of
h85 jet, along with pva from the shortwave trough and divergence
from jet streak from northern Ontario to lower Great Lakes will
support moderate to heavy rain moving west to east across Upper
Michigan through the day though rain likely will not make it to the
eastern cwa until at least mid aftn. Appears the thunderstorms will
likely outrun axis of greater instability aloft as the day wears on.
Expect widespread showers but only isold embedded thunder. Greatest
chances for seeing a cluster of thunderstorms would be in the aftn
from scntrl to southeast forecast area.

Heavy rain is a concern with recent heavy rain that occurred this
weekend in some areas and very wet month seen thus far in many areas
(over 7 inches at least for portions of scntrl forecast area). Right
now with most guidance pointing to rain totals Wed morning through
Wed evening of 1-2 inches and overall progressive system think the
chances for flooding is too low to justify any kind of flood watch.
However, since rivers and streams are running high and any heavy
rain will add to the higher flows, will opt to issue a hydrologic
outlook statement which is kind of like a special weather statement
for hydro concerns. WFO GRB already had one out and decided to
follow suit. Mid shift then can continue the ESF or if needed go
with a flash flood watch.

One additional concern on Wed will be increasing south winds and
high waves over northern Lk Michigan. Will continue to mention the
hazard in the HWO but will not issue beach hazard statement due to
marginally cool high temps in the low 60s and since when the
greatest hazard will be occurring the weather will be not very
friendly for beach goers with widespread moderate to heavy rain.

.LONG TERM...(Wednesday through Monday)
Issued at 340 AM EDT TUE JUN 27 2017

An active pattern with multiple waves traversing the area will keep
rain chances in the forecast through at least the weekend with
temperatures running 5 to 10 degrees below normal. The best chance
for widespread moderate to heavy rain will be Wednesday into
Thursday, then precipitation chances will be periodic into early
next week. Early next week, temperatures will gradually return to
near normal.

Widespread moderate to heavy rainfall is expected to develop on
Wednesday and push east across Upper Michigan into Thursday morning
as low pressure tracks across the area. Expect the rain showers to
move into western portions of Upper Michigan during the late
morning/early afternoon hours on Wednesday, and then gradually push
east across the central and east into the afternoon and evening
hours. With a warm, moisture rich air mass overhead, PWATs will
increase to around 1.5+ inches, along with deepening of the warm
cloud depth. These ingredients, coupled with increased lift along
the warm front as it lifts across the area will allow for high
rainfall rates. Right now, the highest rainfall totals are expected
to be across the central and east, where 1-2`` of rain looks
possible. There may be some isolated thunder embedded within the
widespread rain, but the threat for any severe thunderstorms will
remain well south of the area. Into early Thursday morning, as
moisture transport lifts northeast into Ontario, the threat for
heavy rain will wave, but with upper-level energy will still linger
overhead, so cannot rule out scattered showers through the day on
Thursday, but depending on the speed of the wave exiting the area
and track of the surface low, things could dry out a bit sooner than
currently reflected on Thursday. Thankfully, the band of moderate to
heavy rain looks to remain fairly progressive as it moves across the
area. However, given the antecedent wet conditions across the area,
and rivers and their respective tributaries running high flooding
may still be an issues in some locations, especially those that
see the highest rainfall rates.

Friday through the weekend, a number of upper-level waves are
progged to move across the Great Lakes region bringing additional
chances for showers and perhaps a few rumbles of thunder. With a
leading shortwave lifting north out of the middle Mississippi Valley
and up into the western Great Lakes Friday afternoon, expect showers
to become a bit more widespread. Progressing into Saturday, a more
potent upper-level wave will pivot across Upper Michigan and allow
precipitation chances to linger through the day on Saturday and into
Sunday. Right now, it certainly looks like the end of the weekend
will be much drier than the beginning.

Early next week, there may be a slight chance for rain showers as
another shortwave digs south across the area, but behind this
exiting wave it looks like we may start to dry out and warm up a
bit. By Monday afternoon/evening, the GFS and ECMWF have increasing
large-scale subsidence across the area with surface high pressure
moving overhead. Also, with ridging progged to build across the
Plains, this may allow the jet stream to shift a bit further north
and the return of more seasonable weather.

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 147 PM EDT TUE JUN 27 2017

All TAF sites will be VFR through late tonight. Weather becomes more
inclement on Wed as a low pressure system crosses the region. Rain
showers move into TAF sites late on Wed morning but only IWD will
become MVFR by midday on Wed. Conditions further deteriorate at all
TAF sites to IFR by Wed evening as heavier rain showers move through.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 300 PM EDT TUE JUN 27 2017

Winds should remain blo 20 knots through Wed morning as sfc high
pressure continues to dominate the area. By Wed afternoon and Wed
night se to e winds could increase to 20 to 25 knots over the east
half of Lake Superior and also far western Lake Superior as a low
pressure system lifts across the Upper Great Lakes. Winds will then
decrease to 20 knots or less towards the end of the week and weekend
as the pressure gradient relaxes once again.

Upper Michigan...
Lake Superior...
Lake Michigan...


LONG TERM...Ritzman
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