Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 270751
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
351 AM EDT FRI MAY 27 2016

.SHORT TERM...(This evening through Friday)
Issued at 347 PM EDT THU MAY 26 2016

Complicated convective forecast as coverage and intensity depends on
smaller scale shortwaves within broad sw flow aloft. Those type of
features are tough to pin down even 12 hours out.

Currently, shortwave moving across became enhanced by convection
late last night and that shortwave with sharp drying has forced the
showers and thunderstorms this aftn. Wave will continue to north of
Upr Michigan this evening so overall should see downward trend to
shra/tsra over the area currently. Thus far the main hazards from
these storms have been lightning and heavy rain. Have had multiple
reports of heavy rain especially over western Upr Michigan. Since
heating has not been as much as expected, instability has been
meager with sfc/ML/MU CAPES staying blo 500j/kg. Effective shear
also around 30 kts which is on the low-end with the weak
instability. LCLs are low enough around 1000m for brief spin up
tornado due to the higher dwpnts around, but this is being offset by
limited low-level shear which is well under 20 kts. Away from these
initial showers/storms could see isold shra/tsra try to reform over
northwest WI where sfc based CAPES this aftn are rising back up to
1000j/kg in wake of the shra/tsra that moved through earlier. A lot
of subsidence behind this initial shortwave per WV loop, so not sure
on the coverage in this redevelopment area. A bit of an enhanced cu
field trying to form currently. Supercell composite (looks at
effective shear and instability) does indicate there could be
supercells, but mean storm motion and right moving motion point to
majority of this activity staying along WI border or farther into WI,
if it occurs at all.

By late evening overall setup should be more quiet. Lots of low-
level moisture with generally lack of cloud cover and light winds
points to widespread fog which may be dense. Any fog will linger
into Fri morning, especially where light winds are onshore off the
Great Lakes.

Looking upstream there is a minimum in convective activity until
southern Neb and northwest MO where more concentrated shortwaves are
along with upper level jet and stronger sfc low. Some remnants of
this with possible additonal waves due to showers and storms forming
farther north across Neb/IA/Ill should will allow chances for
showers and storms to increase by Fri aftn. We`ll see if clearing
is more widespread than today. If so, readings will be able to reach
mid-upr 70s while dwpnts are around 60 degrees. Result will be sfc
based CAPES more in the 1000-1500j/kg range which will be plenty
high enough for organized severe storms since deep layer shear is
forecast to be 35-45 kts. As was case today, everything will depend
on how much insolation we receive before the shortwave(s) arrive by
aftn.

.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 06Z TAFS through 06Z Friday night)
Issued at 132 AM EDT FRI MAY 27 2016

Expect low clouds and fog at all the TAF sites overnight into Friday
morning. Conditions will drop to LIFR/VLIFR, lowest at CMX where
light onshore winds are expected and widespread fog could advect in
fm Lk Superior. after improvement back to VFR late Friday
morning/afternoon expect another round of showers and thunderstorms
to move in late Friday afternoon/evening with deteriorating
conditions.
&&

.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.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Dense Fog Advisory until 6 PM EDT /5 PM CDT/ this evening for
     LSZ162-243>246-263>267.

Lake Michigan...
None.
&&

$$

SHORT TERM...JLA
LONG TERM...KC
AVIATION...Voss
MARINE...KC


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