Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 250542

Area Forecast Discussion
National Weather Service Marquette MI
142 AM EDT Fri May 25 2018

.SHORT TERM...(This evening through Friday)
Issued at 437 PM EDT THU MAY 24 2018

Forecast concerns in the short term will focus on chances and
timing of convection and potential for any strong to severe storms.

Remnant outflow boundary as noted on sfc obs has become the focus
for another round of convection this afternoon over central MN and
northern WI along 1000-2000 j/kg MLCAPE gradient and area of strong
850 mb moisture transport and 25 kt 850 mb jet. Isolated t-storm
ahead of area of convection has moved into central MNM county in
past hour.

RAP model indicates MLCAPE values increasing to 500-1000 j/kg range
into the western half of Upper MI this evening with effective shear
values increasing to 25-30 knots as a weak shortwave rotates across
the area. Believe this will support redevelopment of shra/tsra into
western half of Upper MI this evening and a few stronger storms
could produce dime-sized hail with wet-bulb-zero heights 9.5-11kft.
SPC has included the western U.P. in a marginal risk for svr storms
mainly this evening. As shortwave moves east overnight and
evening/overnight and warmer 8h temps of 16-18C move in later
tonight believe atmosphere will become more capped leading to a lull
in convection later tonight into Fri morning. Arrival of another
shortwave from the west could lead to another round of scattered
to numerous showers/t-storms Fri mid-afternoon into early evening
as MLCAPE values increase to 1500-2000 j/kg. These higher CAPE
values combined with fcst deep layer shear of 25-35 knots and WB
zero heights 9.5-10.5 kft could yield isolated severe storms over
the interior western two-thirds of Upper Mi with damaging winds
and large hail. SPC has this area of Upper Mi in a marginal risk
for severe storms on Fri.

.LONG TERM...(Friday night through Thursday)
Issued at 333 PM EDT THU MAY 24 2018

Above normal temperatures expected to continue through the extended
forecast along with scattered showers and thunderstorms through much
of the Memorial Day weekend.

Saturday: A shortwave is set to slide across the area Saturday
morning into the early afternoon hours, helping mlcape values reach
to around 1000J/kg. Models are showing that 0-6km deep layer shear
may be up to around 30 knots; however, with the shortwave set to
slide east of the area by the late afternoon hours. If enough
sunshine breaks out during the morning hours, then instability could
be enhanced enough to allow for some organization in the
thunderstorm activity across the area. There will be a conditional
risk for at least some isolated severe thunderstorms for late
Saturday morning into the afternoon for the central and eastern
U.P.with the increased shear values.

Sunday: There may be a few rain showers and possibly a thunderstorm
on Sunday morning; however, coverage and intensity will likely be
much more muted as the lingering shortwave will continue to slide to
the east. During the afternoon hours, under very weak pressure
gradient, convergent lake breeze boundaries may touch off a few
showers and a remote chance of an afternoon thunderstorm across the
area. Overall coverage will be minimal and mainly confined to the
central and eastern U.P.

Monday: There is a hint that a subtle shortwave may try to slide
through the Upper Great Lakes by Monday afternoon. This will help to
increase CAPE values a bit, probably in the 500 - 1000 J/kg range by
Monday afternoon. The instability along with lake breeze boundaries
under light flow, will lead to a few pop up afternoon showers across
the area, with a couple rumbles of thunder possible.

Tuesday through early Wednesday: Fairly quiet weather will be in
place for Tuesday and early Wednesday as high pressure slides
through the area and temperatures will continue to be above normal
for this time of year, by about 15 to 20 degrees.

Wednesday afternoon through Thursday: A deepening upper-level trough
is progged to approach the Upper Great Lakes region Wednesday
afternoon and slide through the area Wednesday night into Thursday.
This will be basically the same time frame that the associated low
pressure system and cold front slides through the area. Instability
is progged to be increased with the moisture advection into the area
and steepening lapse rates; therefore, there will likely be
thunderstorms ahead of the cold front. Shear looks marginally
favorable for severe weather; however, exact details will be ironed
out as we get closer to this time period and models converge on the

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 141 AM EDT FRI MAY 25 2018

Scattered showers and isolated thunderstorms will move through the
area off and on, although VFR conditions should prevail. LLWS will
continue at all sites overnight. Timing the onset of showers
and thunderstorms will be difficult.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 437 PM EDT THU MAY 24 2018

Winds less than 20 kts are expected into next week. Expect areas of
fog to develop late tonight into the weekend as some rainfall occurs
over the lake and a humid air mass arrives. May have dense fog at
times with best chance setting up Fri night and Sat as a trough
slides across the lake.

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


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