Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 300839

Area Forecast Discussion
National Weather Service Marquette MI
439 AM EDT Fri Sep 30 2016

.SHORT TERM...(Today and tonight)
Issued at 438 AM EDT FRI SEP 30 2016

Upper low and sfc low spinning over Ohio Valley vcnty of northern KY
this morning while high pressure ridge is stationed north of Lk
Superior. NE winds btwn these features and nighttime cooling and
lingering low-level moisture is supporting low clouds and patchy fog
over parts of western and north central Upper Michigan. Low-level
winds change little into tonight and there is minimal dry air
advection occurring so expect sct-bkn low clouds to persist over
western Upper Michigan through tonight. Elsewhere should see
generally partly cloudy skies as h85-h7 moisture on north edge of
upper low drifts across. May be enough saturation and weak lift to
help develop a few showers late today far scntrl. Not a great chance
of rain by any stretch though.

The Upper low and sfc low drift slowly back to the north later
tonight toward the Lower Great Lakes, but model trends and forecast
soundings indicate that even though clouds will steadily increase
from se to nw through the night, chances of rain will be confined to
scntrl and east cwa and those will be late at night aft 09z Sat.
Since upper low will be still south of lower Michigan through
daybreak, any rain that occurs this far north will be very light or
probably just a few sprinkles. Lowest temps tonight in the mid to
upper 40s over interior west while temps elsewhere will stay in the
low or even mid 50s with increasing and thickening cloud cover.

.LONG TERM...(Saturday through Thursday)
Issued at 430 AM EDT FRI SEP 30 2016

For much of the long term the Upper Lakes will be under above normal
heights/ridging downstream of a trof currently approaching the W
Coast. This trof will reach the central CONUS mid week and the Great
Lakes late week. Despite the overall ridging/above normal heights,
the mid level low that brought unsettled weather to the area early
in the week and which is now centered over the Ohio Valley will
drift n, then e, crossing the Lower Great Lakes region Sun/Mon. As
it does so, some shra will probably spread back into at least the s
central and eastern fcst area over the weekend. Dry weather will
then return early next week as ridging sharpens up ahead of the trof
progressing across the western CONUS. As trof and associated cold
front continue eastward, shra will return late Wed/Thu/Fri. As for
temps, solidly above normal heights will support above normal temps
during the long term. Depending on timing of aforementioned
trof/cold front, temps will eventually fall back to normal or even
blo normal late next week. Farther out, NAEFS and CPC outlooks
indicate that above normal temps should continue to be favored
overall into mid Oct. CFSv2 ensembles go on to indicate a fairly
strong/consistent signal for above normal temps overall into late

Over the weekend, mid level high over the western Atlantic and trof
moving onshore over the western CONUS will work to force the mid
level low now over the Ohio Valley n. Model consensus is for the
center to sneak into far southern Lower MI on Sat before shifting e
across the lower Great Lakes later Sun into Mon. Guidance is in good
agreement showing increasing/deepening mid level moisture, but deep
layer forcing per q-vectors only brushes the e half of the fcst
area. While lower levels are dry initially, it`s not especially dry,
so the prospect of shra spreading into the s central and eastern
fcst area seems reasonable. Farther w and nw, lack of forcing should
support continued dry weather. Shra will tend to end from the w on
Sun as the mid level low begins to shift e/heights rise and sfc high
pres ridge begins to become more dominant. Despite more clouds, max
temps will likely still be a little above normal.

Mon/Tue, trof moving across the western CONUS will support ridging
downstream thru the Great Lakes, and at the sfc, associated high
pres center will drift se over Quebec to the Canadian Maritimes
while ridging extends back to the Great Lakes. Thus, dry weather is
expected during this time with warming. High temps in the 60s on Tue
should increase to the mid 60s to lower 70s on Wed. Only potential
concern is cloud cover. With stronger cooling over land at night at
this time of year and with Great Lakes waters relatively warm, any
advection of the warmer/more humid marine modified air inland will
result in low cloud development. Then, lower sun angle at this time
of year will lead to slower erosion of those clouds. Will need to
keep in mind the possibility of more cloud cover, especially since
GFS fcst soundings suggest that idea. On Mon, possibility of more
cloud cover will be due to flow off Lake Superior under more of a ne
wind while on Tue, cloud cover will be due to southerly flow off
Lake Michigan which would affect mostly the e half of the fcst area.

Wed thru Fri, fcst will depend on the timing of the western trof and
associated cold front. Considering how far out in the model runs
this system is, 00z medium range guidance for now is in fairly good
agreement with timing, suggesting pcpn may reach western Upper MI
Wed aftn. Shra chances will then continue Thu/Fri, initially with
fropa on Thu, and then into Fri under deep cyclonic flow and arrival
of cooler air that will probably add a lake component to shra. With
the front w of the area, Wed could be the warmest day of the week
depending on cloud cover and pcpn timing. Temps will begin to trend
down Thu, though still above normal. Highs on Fri will be aob
normal. ECMWF is most aggressive with cooling, sending 850mb temps
blo 0C.

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 139 AM EDT FRI SEP 30 2016

Expect low MVFR to IFR cloud decks overnight at IWD and eventually
likely SAW too in upslope ne flow. Conditions will improve to VFR
late Fri morning with diurnal heating/mixing. Downslope ne flow will
keep conditions VFR through the forecast period at CMX.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 438 AM EDT FRI SEP 30 2016

Weak pressure gradient across Lake Superior through the weekend and
early next week will keep east to northeast winds at 20 kts or less.
South-southeast winds may increase over 20 kts Tue into Wed ahead of
front moving out the Northern Plains. Strongest winds would be over
north central and eastern Lk Superior.

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


LONG TERM...Rolfson
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