Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 281139

Area Forecast Discussion
National Weather Service Marquette MI
739 AM EDT Wed Jun 28 2017

.SHORT TERM...(Today and tonight)
Issued at 452 AM EDT WED JUN 28 2017

This morning, surface low pressure was located along the North and
South Dakota borders, with a large swatch of precipitation spanning
much of Minnesota and down into Iowa and Nebraska along the axis of
a 50 knot low-level jet. With ample moisture transport and warm air
advection accompanying the enhanced 850mb flow, this precipitation
is expected to track across Wisconsin today and eventually up into
portions of Upper Michigan. While the area will be under broad lift
as warm air advection out ahead of the system spread across Upper
Michigan, the track of the 850-700mb moisture transport and enhanced
850mb flow will determine where the heaviest precipitation falls
later this afternoon and overnight. Ahead of the surface low, winds
will increase across the area throughout the day and become gusty.
The gusty southwesterly winds across Lake Michigan will create a
high swim risk along the northern shores.

Confidence in how precipitation amounts will play out this afternoon
and evening are rather low as both the high-res and medium range
models are not in good agreement this morning, likely due to the
complex nature of early morning convection. Later this morning and
into the afternoon hours, a wave of precipitation is expected to
push west to east across Upper Michigan as warm air advection
increases. As PWATs increase to around 1-1.5 inches, rain may fall
moderately at times. This precipitation is expected to linger
through much of the afternoon and into the evening hours across the
central and east. However, further west after the initial round of
rain showers moves through, depending on the track of the low
pressure system another round of showers and perhaps a few storms
may be possible, as additional development is expected along the
trailing cold front later this evening. The SPC has included far
southern portions of Upper Michigan within a marginal risk for
severe storms, but the best instability and shear looks like it
should remain just south of Upper Michigan where the better low-
level moisture will push northward across the warm sector. Upon
collaboration, opted to update the ESF (hydrologic outlook) instead
of issuing a flash flood watch as things look like should remain
rather progressive across the area, that coupled with the
uncertainty in where the heaviest rain will track.

As the surface low tracks east across Upper Michigan tonight,
showers and perhaps a rumble of thunder will be possible. The best
chances for additional moderate rainfall will be across the central
and eastern half of the area as the low-level jet and deeper
moisture attempt to lift northeast ahead of the surface low. Any
ongoing convection along the surface cold front and into the warm
sector should push south of the area across Wisconsin. Therefore,
precipitation chances should begin to wane from west to east during
the overnight hours.

.LONG TERM...(Thursday through Tuesday)
Issued at 337 AM EDT WED JUN 28 2017

Models indicate a slowly progressive pattern will prevail with zonal
flow during the middle of the week giving way to troughing through
the north central CONUS this weekend as a mid level low moves from
Alberta into the Upper Great Lakes. A ridge will then build from the
Northern Plains into the Upper Great Lakes for the first half of
next week. Temperatures will remain below normal with moderation
closer to seasonal averages early next week.

Beginning Thursday, Additional wrap-around moisture and light rain
could continue across the northern tier of the cwa into early
Thursday afternoon as the compact mid level low moves across eastern
Lake Superior. Ridging and q-vector divergence spreading in from
the west in the afternoon will lead to drier conditions.

Friday-Sunday, as the larger scale mid level trough deepens from the
Northern Plains into the Upper Great Lakes, a shortwave trough and
associated sfc low is expected to lift from the Central Plains into
the western Great Lakes. The models have trended farther north with
this feature and associated pcpn compared to previous runs. The
heaviest pcpn is again expected over southeast Upper Mi based on
model consensus track of the sfc low and fcst of stronger 305k-310k
isentropic ascent over se half of the cwa. With the mid-level trough
deepening over the northern Great Lakes, rain chances will increase
Saturday, especially inland during peak heating. Isolated t-storms
will also be possible se half as MLCAPE values approach 500 J/Kg.
Enough moisture/instability will linger into Sunday with cyclonic
mid level wnw flow and potential of weak shortwaves moving through
region to warrant low chc pops for mainly afternoon isold to
scattered showers.

Monday-Wednesday, Models and ensembles in good agreement with the
drying trend expected at least for the first half of next week as
mid-level and sfc ridging build into the area. Sunshine should push
temps well into the 70s with a gradual warming trend into Tuesday.

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 737 AM EDT WED JUN 28 2017

Conditions are expected to deteriorate through the morning and
afternoon hours across all terminals as rain showers move east
across the area. Forecast soundings show the low-levels saturating
quickly, and down into the IFR category, and possibly even lower as
these showers push through the area. Visibilities will be highly
dependent on where the heavier bands of rain set up, so opted to
leave visibilities up for now as confidence is not high that the
band of heavier rain will impact KSAW/KIWD/KCMX. The IFR ceilings
may lower into the LIFR category through the overnight hours, with
visibilities dropping as well.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 452 AM EDT WED JUN 28 2017

As low pressure approaches the area from the west winds will increase
to around 20 to 25 knots by the afternoon/evening hours. A few gusts
upward of 30 knots cannot be ruled out, but there is some
uncertainty in the track of this low and the resulting winds that
will develop. Depending on where heavy rain develops later today,
some locations may see fog develop across the lake. Given the
uncertainty in where this precipitation will develop, opted to leave
mentions out of the forecast for now. By Thursday morning/afternoon,
winds will decrease to around 10 to 15 knots, and then should remain
below 20 knots through the first half of next week.

Upper Michigan...
  Beach Hazards Statement from 11 AM EDT this morning through this
     evening for MIZ014.

Lake Superior...
Lake Michigan...


SHORT TERM...Ritzman
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