Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 292034

Area Forecast Discussion
National Weather Service Marquette MI
434 PM EDT SUN MAY 29 2016

.SHORT TERM...(This evening through Monday)
Issued at 434 PM EDT SUN MAY 29 2016

Water vapor imagery and RAP analysis show a shortwave trof moving
over the Upper Great Lakes. At the sfc, broad low pres is just n of
Lake Superior with a weak cold front extending s thru central Upper
MI. Abundant cloud cover has helped to keep instability from
building significantly, especially over western Upper MI where
mlcape is less than 100j/kg per latest SPC mesoanalyis. Some
sunshine over central Upper MI has allowed mlcapes to increase to
500j/kg or so ahead of sfc cold front. With the increase in
instability, shra which began to develop nne from WI mid/late
morning have expanded considerably into central Upper MI this aftn
along/ahead of front. With deep layer shear mostly under 25kt,
storms have not been well organized to pose a svr risk, but some
brief, very heavy rainfall has been occurring with the strongest
cells. Fog continues be an issue on the Great Lakes with zone of
dense fog lifting up the western part of Lake MI into the shoreline
areas of se Delta and Schoolcraft counties. That fog appears to be
rapidly shrinking in coverage over the couple of hrs. On Lake
Superior, cloud cover is preventing a good view of the fog over the
w half of the lake, but webcams suggest fog is still widespread
except over the far w where increasing downslope westerly winds are
eroding the fog from the w. To the e, southerly winds have pushed
fog well offshore for the time being.

Tonight, lingering showers and isold tstms will end from w to e with
passage of shortwave trof/arrival of deep layer qvector divergence
and loss of daytime heating. Last of the -shra should be out of the
e shortly after 06z, if not sooner. Since daytime heating has been
helping to mix out low-level moisture/raise cigs to the w, skies
should trend to at least partly cloudy as the night progresses. Only
issue would be where winds maintain an onshore component off Lake
Superior as fog or stratus may affect those areas thru the night.

Memorial Day looks like a great day weather-wise to wrap up the
holiday weekend. A shortwave will be passing by n of the fcst area,
but with the wave n of Lake Superior and the fcst area on the
anticyclonic side of the supporting jet streak, shra activity will
remain n of the fcst area. Expect a mostly sunny day with high based
cu inland from Lake Superior. As with tonight, one possible issue
could be some low clouds/fog at Lake Superior shoreline locations.
By Mon morning, if there is fog still on Lake Superior, it should be
confined to the eastern part of the lake. So, shoreline locations
from around Munising eastward could be affected by low clouds/fog if
the fog has not cleared off the lake yet. Max temps away from lake
moderation will rise into the 70s, perhaps near 80f s central.

.LONG TERM...(Monday night through Sunday)
Issued at 314 PM EDT SUN MAY 29 2016

Nam forecasts a shortwave ridge moving into the upper Great Lakes
00z Tue with a trough moving into the northern plains. The trough
slowly moves east while the ridge remains over the upper Great Lakes
00z Wed. The trough then moves into the northern Mississippi River
valley 00z thu. Nam brings in some deeper moisture with the 850-500
mb q-vector convergence by Tue evening and keeps both around until
late Wed afternoon when the deeper moisture leaves the area. GFS and
ECMWF show about the same thing as the Nam does and will use a blend
of the models for this forecast.

Will keep Mon night dry and then bring in pops on Tue and have them
last through Wed with the next system moving in. Could see qpf
amounts of 0.67 inch to 1.00 inch of rain from Tue through Wed. Did
not make many changes to the going forecast overall for temperatures.

In the extended, GFS and ECMWF show a 500 mb trough over the upper
Great Lakes 12z Thu with a ridge in the desert sw. Upper air pattern
changes little for 12z Fri. On Sat, the 500 mb ridge builds in the
western U.S. with troughing in the ern U.S. and the pattern
continues to amplify for Sun. Temperatures will remain near normal
for this forecast period with unsettled weather at the beginning
part of the extended forecast into Thu night.

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 150 PM EDT SUN MAY 29 2016

A cold front passing across the Upper Great Lakes will bring
improving conditions to all terminals during this fcst period. With
an upslope westerly wind, lowest conditions this aftn will be at
KIWD/KCMX where low mvfr cigs will likely prevail for at least the
next few hrs along with the possibility of -shra. Since flow is more
sharply upsloping at KCMX, there may be some ifr cigs at that
terminal. Early this evening, KIWD/KCMX should improve to VFR and
remain that way for the remainder of the fcst period. However, will
need to watch for lower clouds to linger longer at KCMX. At KSAW,
mostly vfr conditions are expected thru the fcst period, though
passing shra thru the area may lead to some mvfr conditions at times
until evening.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 434 PM EDT SUN MAY 29 2016

Initially, with moist air lingering over the chilly lake waters,
fog, dense in some areas, persists over much of Lake Superior.
However, with a cold front passing across the lake, currently over
central Lake Superior, increasing w winds are beginning to bring
slightly drier air over western Lake Superior. This drier air should
work to clear fog off the lake tonight into Mon. However, there is
some uncertainty in whether the fog will clear off the eastern part
of the lake.

A relatively weak pres gradient and typical high stability over the
water at this time of year will dominate Lake Superior for much of
this forecast period. As a result, expect winds at or below 20kt
over most of the lake, but with some exceptions. One exception will
be this evening as winds may gust to 20-25kt for a time in the wake
of the passing cold front. Another exception will be over far
western Lake Superior late Mon night/Tue as the pres gradient
tightens ahead of an approaching low pres. With coastal
convergence/terrain funneling enhancing the winds, ne winds will
increase with gusts possibly up to 25-30kt. Then as the low moves
closer, se winds over eastern Lake Superior may gust up to 25kt Tue

Upper Michigan...
Lake Superior...
  Dense Fog Advisory until midnight EDT tonight for LSZ243-244-

  Dense Fog Advisory until 6 PM EDT this evening for LSZ245-246-

Lake Michigan...
  Dense Fog Advisory until 5 PM EDT this afternoon for LMZ248-250.



SHORT TERM...Rolfson
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