Area Forecast Discussion
Issued by NWS Marquette, MI

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098
FXUS63 KMQT 011136
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
736 AM EDT Sat Oct 1 2016

.SHORT TERM...(Today and tonight)
Issued at 331 AM EDT SAT OCT 1 2016

Upper low over southern IN moves to lower MI tonight. Associated sfc
low will also drift north, possibly as far as northern lower MI late
tonight. Plenty of mid clouds rotating west across Upper Michigan
today as the upper low drifts north. Enough low-level moisture and
radiational cooling to lead to patchy fog far west early on today.
Band of showers currently over southeast Upper Michigan should
continue westward across central Upper Michigan this morning. May be
a break as these showers dissipate over west half of Upper Michigan
late morning into the aftn. Suppose during that break there could
even be partial sunshine. Eventually though, area of showers over
southern lower MI to Lk Erie look to rotate far enough northwest to
bring some showers back to mainly eastern half of cwa late today
into tonight. Highs today in the low to mid 60s, boosted a bit with
any substantial clearing. Lows tonight 40s west and 50s elsewhere.
Easterly winds will stay gusty on Bay of Green Bay and northern Lk
Michigan, but generally light otherwise.

.LONG TERM...(Sunday through Friday)
Issued at 442 AM EDT SAT OCT 1 2016

Until late in the upcoming week, above normal heights will dominate
the Upper Great Lakes downstream of a trof currently approaching the
W Coast. This trof will reach the central CONUS midweek and the
Great Lakes late week. Meanwhile, the mid level low that brought
unsettled weather to the area early in the week and which is
currently centered over the Ohio Valley will drift n, then e,
crossing the Lower Great Lakes region Sun into early Mon. Shra
associated with this feature, affecting the eastern fcst area, will
end by Sun aftn. Dry weather will follow early next week as ridging
sharpens up ahead of the trof progressing across the western CONUS.
As this trof and associated cold front continue eastward, a period
of shra appears likely at some point late Wed into Thu. After cold
fropa, shra chances are more uncertain, hinging on degree of cooling
to generate a lake component to pcpn and how deep and progressive
the trof is as it moves across the Great Lakes. As for temps,
solidly above normal heights will support above normal temps thru
the midweek period. Arrival of the trof late week will send temps
down, back to normal or even blo normal. It does not look like any
period of blo normal temps will last long as NAEFS and CPC outlooks
indicate that above normal temps should overall be favored into mid
Oct. CFSv2 ensembles still indicate a strong/consistent signal for
above normal temps overall into late Oct.

Beginning Sun, center of aforementioned Ohio Valley mid level low
will have moved to just east of Detroit by 12z, and during the day,
it will drift e across the Lower Great Lakes. Under rising heights
and deep layer q-vector divergence, any shra that may be occurring
over the eastern fcst area to start the day will end by aftn. Fcst
soundings from the 00z model runs definitely show less column
moisture than 24hrs ago. This may not be unreasonable given the
subsidence. So, Sun is looking to trend more optimistic with respect
to cloud cover. Should see skies become mostly sunny over at least
the nw half of the fcst area and potentially across the entire area.
High temps will be in the 60s, and may reach 70F in a few spots over
the w where more sun is expected.

Mon/Tue, trof moving across the western CONUS will support ridging
downstream across the western Great Lakes on Mon, shifting to the
Lower Great Lakes on Tue. At the sfc, associated high pres center
will drift se over Quebec to the Canadian Maritimes/New England
while ridging extends back to the Great Lakes. Thus, dry weather is
expected during this time with warming. High temps in the 60s to
around 70F on Tue should increase to the mid 60s to lower 70s on
Wed. Only 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/fog development. Then, lower sun
angle at this time of year will lead to slower erosion of those
clouds. While GFS/NAM fcst soundings indicate less potential of low
clouds/fog Mon as winds are light/vrbl or winds off Lake Superior
are very light Sun night, they continue to have a stronger signal
for low clouds/fog Mon night into Tue due to the increasing upslope
sse winds off Lake MI Mon night as high pres ridge shifts e. Not out
of the question that low clouds could plague the eastern fcst area
for much of the day Tue. With more sun over the w, the w will be
warmest on Tue.

Wed/Thu, model trends over the last 24hrs point toward a faster trof
progression across the w and central CONUS with the exception of the
ECMWF. 00z GFS/CMC indicate cold front will reach western Upper MI
Wed aftn/evening as opposed to Thu morning. The ECMWF has the front
slowly moving across the area on Thu. This slower solution results
from a sharper trof with a more significant shortwave rounding the
base of the trof, supporting a somewhat better defined low pres wave
lifting along the cold front. To some degree, the GFS/CMC also have
this feature, but weaker and affecting mainly eastern Upper MI/nw
Lwr MI. The shortwave and trof structure will be a point of
contention for the next few days. At this point, utilized a model
consensus which brings chc pops into the w half of Upper MI Wed,
spreading e Wed night, then diminishing w to e on Thu. A period of
likely pops appears reasonable given possible shortwave/low pres
wave lifting along front and precipitable water increasing to 1.25
inches. However, given the timing differences btwn the ECMWF and
GFS/CMC, will mostly hold off on those higher pops. Potential is
there for mdt to hvy pcpn depending on speed of front and
timing of sfc wave lifting along it.

Agreement has improved on magnitude of the cooling late week with
both the ECMWF/GFS showing 850mb temps falling to around -3C which
would support development of lake effect/lake enhanced -shra off
Lake Superior. GFS fcst soundings show more of a well-mixed boundary
layer which typically results in less coverage of lake effect pcpn.
For now, fcst will show low pops for w to nw flow favored areas.
&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 735 AM EDT SAT OCT 1 2016

Expect VFR conditions through most of the period as mid clouds move
across Upper Michigan to the north of low pressure south of the
region. A few showers may affect SAW this morning. Late tonight
could see fog and stratus develop at IWD as mid clouds clear out.

&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 331 AM EDT SAT OCT 1 2016

A weak pressure gradient across Lake Superior through Mon will keep
east to northeast winds at 20 kts or less. Southeast winds increase
over 20 kts Tue into Wed ahead of front moving out the Northern
Plains. The strongest winds will occur over north central and
eastern Lk Superior. Behind the front on Thu, west winds may gust
to 25 kts.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...JLA
LONG TERM...Rolfson
AVIATION...JLA
MARINE...JLA



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