Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 131903

Area Forecast Discussion
National Weather Service Marquette MI
303 PM EDT Sun Aug 13 2017

.SHORT TERM...(This evening through Monday)
Issued at 302 PM EDT SUN AUG 13 2017

Upper air pattern consists of a shortwave over the northern plains
this morning which moves into the upper Great Lakes tonight and Mon.
Nam shows some 850-500 mb q-vector convergence along with deeper
moisture on Mon moving into the area. With isolated showers popping
up this afternoon along lake breeze boundaries, will continue the
slight chance pops until this evening until the peak heating ends.
Did back off on pops tonight and push them back in the west until
late tonight and keep it slight chance only. Looks like tomorrow
with dynamics and lake breezes again that the pops would be confined
to mainly inland areas and also will be highest in the south.
Overall, did not make too many changes to the going forecast.

.LONG TERM...(Monday through Saturday)
Issued at 423 AM EDT SUN AUG 13 2017

In response to a trof moving out of the Gulf of Alaska,
ridging/positive 500mb height anomalies that were over western
Canada are shifting toward central Canada with the peak anomaly now
centered over n central Canada. To the e, a trof remains over
eastern Canada into the ne CONUS and northern Plains. Medium range
guidance has not deviated much in indicating that the area of
positive 500mb height anomalies over n central Canada will gradually
settle to the Hudson Bay vcnty and eastern Canada during this week.
Main change has been to drift these anomalies a bit farther n late
week, allowing for weak negative height anomalies/troffing to shift
from the Rockies mid week to the Great Lakes and northeast CONUS
late week and weekend underneath the ridging to the n. For Upper MI,
these changes mean temps will generally not stray far from mid Aug
normals this week. For the most part, expect readings to be on the
warm side of normal more often than not. Looking farther ahead,
GFS/CMC/CFSv2 ensemble means still suggest positive 500mb height
anomalies may hold on thru late Aug over eastern Canada, which would
tend to favor above normal temps across the Upper Lakes during the
latter part of this month. As for pcpn over the next 7 days,
potential of pcpn has increased for Mon. Then, progression of the
aforementioned trof/negative height anomalies into the Great Lakes
later this week will bring the next potential of more organized pcpn
in the late Wed to early Thu time frame. Some risk of pcpn will then
linger late week with troffiness over the area.

Beginning Mon, shortwave trof now over the Dakotas will move into
the western Great Lakes while another shortwave drops sse thru
northern Ontario into the Upper Lakes. Deep layer forcing provided
by these 2 features will aid diurnally driven sct shra during Mon.
Not out the question that there could be a few tsra with that
possibility probably greatest over the interior e half which should
see a little more daytime heating to boost instability a bit.

Exiting of shortwave trof to the e will bring an end to pcpn from w
to e Mon evening. With high pres settling over the area during the
night, radiational fog may develop if skies clear out, mainly in
areas where rainfall occurs Mon aftn.

As has been the case for a few days, Tue still looks like a dry day
with shortwave ridging approaching the Upper Lakes btwn departing
eastern trof and trof moving across western Canada and the western

While models have agreed on at least one period of more organized
pcpn during the last half of the week, run-to-run consistency has
been poor on the structure of the shortwave trof reaching the Upper
Lakes. Model runs in recent days have ranged from mid-level lows
approaching the area to broader trofs with embedded shortwaves. Over
the last 2-3 days, medium range model runs have most frequently
pointed toward the late Wed to early Thu time frame for the best chc
of pcpn, and today`s 00z models generally fit into that consensus.
As a result, fcst will show highest pops, in the likely category,
shifting across the area during that time. Thunder potential looks
rather limited. In the wake of this shortwave, there will be some
potential of at least isold shra at times Fri thru Sun with troffing
over the Great Lakes.

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1259 PM EDT SUN AUG 13 2017

VFR conditions will prevail at the TAF sites through the period.
Isold afternoon shra/tsra could occur over north central Upper
Michigan near lake breeze boundaries. KSAW will see best chance but
probability remains too low for mention in the TAF at this time.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 302 PM EDT SUN AUG 13 2017

Winds will remain at 20 knots through much of next week. The
strongest winds of 15 to 25 knots will occur late Wednesday into
Wednesday Night ahead of a low pressure system moving in from the
Northern Plains.

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


LONG TERM...Rolfson
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