Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 250924
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
524 AM EDT Sun Jun 25 2017

.SHORT TERM...(Today and tonight)
Issued at 523 AM EDT SUN JUN 25 2017

09Z Water vapor imagery reveals the shortwave/closed low that was
just south of Upper Michigan last evening has now slid e into
central Lower Mi. Wraparound showers associated with this feature
have showed a diminishing trend over the east half of Upper Mi in
the past hour or two as best deep layer q-vector convergence has
moved e with movement of the shortwave.  Expect this diminishing
trend to continue through 12z this morning as weak mid-level ridging
and q-vector divergence spread in fm the w behind the shortwave.
Also expect some patchy dense fog this morning given abundant low-
level moisture fm recent rains.

Today: A surface trough lingering over the area will become the
focus for more showers and thunderstorms across the Upper Peninsula
this afternoon as yet another shortwave over southern Manitoba
rotates across the Upper Great Lakes during the period of peak
heating. The combination of the cooler air aloft associated with the
shortwave along with surface heating during the afternoon, will
yield MLCAPES of 300-700 j/kg per RAP soundings and increasing
chances for showers and thunderstorms into the afternoon and early
evening hours. Freezing hgts and wet bulb zero hgts fm 5.5kft to
7kft agl will increase chances for stronger storms to produce small
hail. Similar to yesterday, weak deep layer shear values in the 10
to 15 knot range will support only pulse/unorganized thunderstorm
activity so not expecting any severe storms, just mainly small hail.
Some of the storms that pulse may cause some heavy downpours in the
afternoon into the early evening hours, mainly inland from the Great
Lakes. Look for high temps ranging from the mid to upper 50s far w
and nw to the mid to upper 60s south central and east under mostly.
cloudy skies.

Tonight: Could see a repeat of last night, with moderate to heavy
wraparound showers persisting across much of the area into the
overnight hours as the Manitoba shortwave slides se along the WI
border and deep layer q-vector convergence lingers across the area.
Support for t-storms should wane after the evening hours with loss
of diurnal instability. Lows tonight will be mostly in the 40s,
except for a few lower 50s south central.

.LONG TERM...(Monday through Saturday)
Issued at 337 AM EDT SUN JUN 25 2017

Overall, there will be a brief warming and drying trend through the
early part of the week, before another system rolls across the Upper
Mississippi Valley and into the Great Lakes region late Wednesday
and Thursday. Depending on the track of this system moving across
the Great Lakes, we could see heavy rain move across Upper Michigan
that may lead to some hydro concerns. Still a bit early as model
trends continue to fluctuation from run to run, but the medium range
models are in good agreement with the placement of this heavy rain
across Upper Michigan late Wednesday afternoon into Thursday
morning. Towards the end of the week and into the weekend, we will
then see periodic chances for precipitation, with seasonable
temperatures.

On Monday, expect showers to linger across the central and eastern
portions of Upper Michigan as surface low pressure and its
associated upper-level wave are slow to exit the area. The lingering
cloud cover and precipitation should keep temperatures in the 60s yet
again. Locations across the west will see the warmest temperatures,
as they will have the best chance at seeing decreasing cloud cover
in the afternoon hours. Monday night into Tuesday, shortwave energy
will finally dig south across lower Michigan and into southern
Ontario, and surface high pressure will drop south from the northern
Plains. This will allow skies to clear and precipitation to come to
an end from west to east. Heights will rise a bit, but with flow
aloft still progged to be out of the northwest, a few subtle, weak
impulses will dig across the area and allow cloud cover to increase
through the day on Tuesday. Given the amount of dry mid-level air
advecting into the region as surface ridging slides off to our south
on Tuesday, expect much of the area to remain dry.

Wednesday through Thursday, a more potent shortwave will push east
across the Upper Mississippi Valley and Great Lakes regions with
medium range models showing the *potential* for a heavy rain event
across Upper Michigan. Ahead of this system PWATs will increase to
around 1.5 inches as strong warm air advection and 850-700mb
moisture transport lifts northeast towards Upper Michigan. The
medium range models, based off their 00z runs, are in good agreement
with a band of heavy rain developing along the surface warm front as
it lifts north across Wisconsin and into Upper Michigan late
Wednesday afternoon. Wednesday evening and overnight into Thursday,
as a 30-50 knot low-level jet impinges northward, this will sharpen
the mid-level front and allow the sloping baroclinic zone to deepen
to around 500mb. Large scale lift should also increase across the
area as a coupled jet structure develops aloft with shortwave energy
lifting northeast across Wisconsin and another shortwave digging
south across southeast Ontario. Given the antecedent wet conditions
across the area, with many locations over the past week and a half
picking up around 5-8+ inches of rainfall, if this band of heavy
rain does come to fruition across Upper Michigan it could lead to
hydro/flooding concerns. Model trends through this time period will
need to be monitored as a shift either north or south will have a
big impact on how things will play out.

Unfortunately it doesn`t look like this active pattern will release
its grip on the region as additional shortwaves are progged to track
across the area towards the end of the week and through the weekend.
This will bring additional chances for showers and perhaps a few
rumbles of thunder.
&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 142 AM EDT SUN JUN 25 2017

Ceilings will be in the IFR/LIFR range at SAW and CMX overnight and
will fall to IFR late tonight at IWD. The next system approaches
this afternoon. Visibility may be restricted at times under
heavier rain showers; however visibility should generally be in
the VFR range. Cigs may be slow to improve today at SAW with
continued moist northerly upslope flow off Lake Superior.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 523 AM EDT SUN JUN 25 2017

Winds of 10 to 15 knots are expected to continue through the first
half of next week as the pressure gradient decreases and high
pressure builds in for the first part of the work week. Towards the
middle of the week, winds will start to increase to around 20 to 25
knots as a system lifts across the Upper Great Lakes. Winds will
then decrease to around or less than 15 knots towards the end of the
week and next weekend as the pressure gradient relaxes again.
&&

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

$$

SHORT TERM...Voss
LONG TERM...Ritzman
AVIATION...07
MARINE...Voss


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