Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 261955

Area Forecast Discussion
National Weather Service Marquette MI
355 PM EDT FRI AUG 26 2016

.SHORT TERM...(This evening through Saturday)
Issued at 355 PM EDT FRI AUG 26 2016

Still seeing drizzle and isolated-scattered rain shower along a SFC
trough oriented from eastern to north-central Upper MI. Will see
these showers diminish over the next few hours.

Definitely have seen a trend for precip to be mainly confined to the
SE-E portions of the CWA late tonight and Saturday as shown by all
models except the NAM (which brings the main area of precip right
over the central CWA). The NAM was not incorporated into the
forecast since it was an outlier. Some subtle shortwave energy
coupled with FGEN forcing looks to result in showers moving into the
southeastern CWA late tonight. That precip then should spread over
mainly the south to southeastern CWA through the rest of the day.
Also see some potential for light rain or drizzle over north-central
Upper MI as southeasterly flow upslopes into the area. Should see
showers move in or approach the far western CWA late in the day as
a strong shortwave moves into NW MN.

.LONG TERM...(Saturday through Thursday)
Issued at 435 AM EDT FRI AUG 26 2016

Current pattern features a ridge/strong positive height anomaly over
the Gulf of Alaska extending n and e across the Arctic to Greenland.
To the s, a broad mid level low is centered in the vcnty of northern
Hudson Bay with trof extending sw into the southern Rockies. Over
the next few days, the swath of positive height anomalies across the
Canadian arctic region will strengthen in response to a powerful
storm moving from Siberia across the North Pole. The strengthening
positive height anomalies will lead to an elongated trof setting up
to the s from the Gulf of Alaska eastward across Canada early next
week, and farther s, a lower amplitude/zonally oriented flow across
southern Canada and the northern CONUS. As this occurs, one last
shortwave ejecting the current trof over the w will move across the
Upper Great Lakes this weekend. During the middle and later part of
next week, the flow will amplify as troffing deepens along the W
Coast, forcing a building ridge over central N America and a trof
over eastern N America. Under these expected changes, the current
cool down will transition to warmer conditions/above normal temps
early next week as westerlies retreat northward. Mid and late next
week, temps will depend on the amplitude and placement of the
trof/ridge/trof pattern across N America. If the central ridge and
eastern trof is displaced westward (eastward), the Upper Lakes will
be under cooler nw flow associated with the trof (warmer/more humid
conditions associated with the ridge). There is plenty of uncertainty
in this regard, and while above normal temps remain favored for now,
the 00z model runs are mostly trending toward greater amplification
and a westward shift of the ridge/trof so that the cooler scenario
may play out for a time. As for pcpn, aforementioned shortwave
lifting into the Upper Lakes will provide an opportunity for pcpn
this weekend, mainly Sat. Next shortwave will be moving across
southern Canada Mon/Tue. Associated cold front swinging across the
area will bring the next chc of pcpn, probably later Mon. As with the
temp uncertainty, pcpn chances for the remainder of next week will
depend on amplitude/placement of the trof/ridge/trof pattern. If the
area is more firmly under nw flow, it will be a drier pattern. If
not, there will be the potential for active tstm clusters at times as
disturbances ride around the ridge/hot air over the central CONUS.

Beginning Sat/Sat night, shortwave over the Dakotas Sat morning will
shift ene, crossing the Upper Lakes late Sat Night and reaching
Quebec Sun evening. The high res NAM window is a nw outlier bringing
a more defined sfc low and heavier pcpn ne across western Upper MI.
Other guidance generally points toward an ill-defined sfc low on
track farther e, yielding 2 areas of greater concentrated pcpn, one
associated with the ill-defined sfc low affecting more of WI/lower
MI/eastern Upper MI and the other more closely tied to the
approaching shortwave across MN. This could lead to gap of
dimimished pcpn coverage across a good portion of the fcst area.
For now, fcst will show pops generally chc w half/likely e half,
mainly Sat aftn/evening. Cloud cover/limited instability will keep
thunder potential low.

There should be some lingering morning low clouds Sun, especially if
the NAM is correct, but arrival of larger scale drying in the wake
of shortwave will result in increasing sunshine thru the day. GFS
looks too aggressive/quick in pushing a stronger WAA pattern into
the western Great Lakes already in the aftn, resulting in pcpn
developing across the w half of Upper MI Sun aftn. This solution was
discarded in favor of the majority drier idea.

Next shortwave tracking from s central Canada Sun night to northern
Ontario by Tue morning will push a cold front across the area,
probably Mon night. While there could be some convection in the waa
pattern ahead of shortwave, better chc of shra/tsra should occur
vcnty of cold front as it moves across the area Mon night. Max temps
Mon will be back to aoa 80F for much of the area.

If the model trend toward greater pattern amplification and westward
shift of central ridge/eastern trof is correct, front will be pushed
far enough s with sfc high pres building more strongly into the
Upper Lakes to allow dry weather to prevail for Tue/Wed and perhaps
even into Thu. Previous runs of the ECMWF had a flatter ridge,
allowing a shortwave and convective complex to round the ridge and
reach the area Thu. The more amplified ridge in the 00z run, similar
to the GFS, greatly diminishes that potential. In contrast, pcpn
potential could be tied to shortwave energy dropping s into the
deeper trof over se Canada.

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 620 AM EDT FRI AUG 26 2016

A low pressure trough will slowly settle across Upper Michigan
today. Cool and moist air behind the trough flowing across Lk
Superior will result in sct-bkn MVFR clouds today with a chance of
some showers. The greatest chances for showers will be at SAW this
aftn. High pressure arriving this evening will improve conditions to
VFR at all the TAF sites. Mid to high clouds will increase late in
the TAF period ahead of another system that will bring more rain to
the area Sat into Sat night.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 355 PM EDT FRI AUG 26 2016

Expect winds through this weekend and early next week to remain at
20 kts or less as the overall pressure gradient will remain weak.

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


LONG TERM...Rolfson
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