Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 271746

Area Forecast Discussion
National Weather Service Marquette MI
146 PM EDT FRI MAY 27 2016

.SHORT TERM...(Today and tonight)
Issued at 456 AM EDT FRI MAY 27 2016

Continued difficult forecast as convection will be driven by subtle
shortwave energy that will be modified by upstream convection.
Prediction of convection from these shortwaves is difficult even
within 12 hours, so confidence is limited. Generally followed a
blend of mesoscale models for pops through the short term.

Looking for 2-3 very subtle waves to move through this afternoon
through tonight. Sfc and upper ridging this afternoon will help
somewhat limit convection, as will limited instability less than 500
J/kg as shown by all models. Have scattered showers and
thunderstorms over the west and central to 00Z tonight. Highs today
in the 70s away from the Great Lakes shores will be dependent on
cloud cover and precip.

Have likely pops moving in tonight as another shortwave moves in and
sfc ridging gives way to troughing. Fog redevelopment is also
expected over land tonight.

.LONG TERM...(Saturday through Thursday)
Issued at 349 AM EDT FRI MAY 27 2016

Upr MI wl be dominated by a SW flow aloft this weekend, resulting in
above normal temps and shower/TS chcs thru Sun. Drier/cooler air wl
move in early next week as a shrtwv rdg/sfc hi pres follows an
exiting shrtwv. More showers wl arrive toward mid week.

Sat...Upr MI wl still be under the deep SW flow of warm, moist air
btwn an Upr Rdg over the E and a slowly deamplifying upr trof over
the central CONUS. Combination of pwat fcst up to 1.75 inches
/nearly 250 pct of normal/, aprchg shrtwv/exit region of 60kt h3 jet
max lifting out of the trof/accompanying DPVA, and sfc lo pres trof
extending into the Upr Lks in the presence of diurnal heating should
result in numerous showers/TS with h85 temps near 15C. The main
limiting factor for convective coverage/intensity despite 0-6km
shear fcst as hi as 30-4kts over the W wl be extensive cld cover
that limits the diurnal temp recovery despite some late day mid lvl
drying associated with the mid lvl jet surge. Greatest coverage
should be over the W, where the dynamic forcing is fcst to be more
substantial. Cooling off Lk MI and weaker forcing over the E should
hold down pops there. Models indicate the mid lvl drying wl also
tend to hold down convective coverage later in the day despite
diurnal heating.

Sat ngt...Models in fairly good agreement showing some mid lvl
drying wl occur under h3 jet max during this time of nocturnal
cooling. These factors wl tend to cause any lingering evng
showers/TS to diminish. More fog is likely to dvlp under this mid
lvl drying. Main limiting factor for widespread fog wl be a fairly
steady S wind that wl tend to limit the diurnal temp fall.

Sun...Shrtwv lifting out of deamplifying central trof is fcst to
aprch. Although arrival of the drier mid lvl air may tend to limit
the coverage of showers/TS, the prospect of more aftn sunshine/
daytime heating wl probably result in more aftn convection along
passing cold fnt attendant to slowly departing sfc lo in Ontario and
in area of DPVA/deep lyr qvector cnvgc ahead of the aprchg shrtwv.
The GFS fcst MUCape is near 1700j/kg. Although deep lyr shear fcst
no hier than 30-35 kts may tend to limit the severity of any TS,
presence of mid lvl drying/greater sfc-theta-e difference could
cause some of the stronger storms to drop at least marginally svr
hail along the fnt, where shear may be locally enhanced.

Sun ngt...Arrival of hgt rises/DNVA/deep lyr qvector dvgc/mid lvl
drying in the wake of passing shrtwv/cold fropa wl diminish
shower/TS chances. Since llvl dry advection is fcst to be marginal,
some lo clds may linger, especially where the llvl WNW flow wl
upslope into the Keweenaw.

Mon into Tue...Although models show shrtwv rdging/hgt rises with sfc
hi pres rdg dominating, the GFS does generate some lgt pcpn on Mon
aftn over the scentral CWA along a Lk MI breeze. Considering the
negative dynamics, favor the pcpn-free fcsts. This period wl be
cooler and drier as h85 temps are progged to dip as lo as 5C.

Tue night thru Thu...Not surprisingly, there are timing differences
on the aprch of the next shrtwv fcst to move E along the CONUS/Cndn
border. Some of the extended models show area of pcpn arriving as
soon as Tue ngt, with drying by Tue. The slower guidance shows pcpn
moving in on Wed and lingering thru Thu. Wl rely on the consensus
fcst for now. Temps look to run close to normal before turning
cooler following the shrtwv/attendant cold fropa.

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 145 PM EDT FRI MAY 27 2016

Isolated showers and perhaps a TSRA is expected this aftn into
tonight. Best chance of TSRA will be at KSAW late this aftn. VFR
conditions into early evening will follow trends of last couple
nights by deteriorating to IFR/LIFR overnight in low clouds and
fog. Light easterly flow off fog covered Lk Superior will result
in VLIFR conditions around airport minimums at KCMX. Should see
very low clouds and fog diminish mid morning Saturday but lower
MVFR deck may persist along with chance for showers.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 349 AM EDT FRI MAY 27 2016

A relatively weak pres gradient/hi stability will dominate the Upper
Great Lakes this forecast period, so expect winds at or below 20kts.
Since moist air will linger over the chilly lake waters, fog will
linger into at least Sun.

Upper Michigan...
Lake Superior...
  Dense Fog Advisory until 6 PM EDT /5 PM CDT/ this evening for

Lake Michigan...
  Dense Fog Advisory until 4 AM EDT Saturday for LMZ248-250.



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