Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 200756

Area Forecast Discussion
National Weather Service Marquette MI
356 AM EDT Thu Oct 20 2016

.SHORT TERM...(This evening through Thursday)
Issued at 409 PM EDT WED OCT 19 2016

Pattern Synopsis/Forecast: Low amplitude pattern in place across
North America this afternoon.  Broad short wave troughing over the
central plains with flat ridging over the southeastern states/mid
Atlantic region...and another short wave ridge along the west coast
downstream of a rather substantial cyclone centered over the Gulf of
Alaska.  Surface analysis shows a cold front cutting across central
Upper Michigan and stretching back to the west into southern
Minnesota and South Dakota.

Pattern becomes more amplified over the next 24 hours as upstream
short wave ridge builds eastward...and a sharper short wave trough
advances into the Midwest/upper Great Lakes.  This will induced a
frontal wave along a cold front that currently lies along the Ohio
River...this cyclogenesis acting in concert with high pressure
building east into the Midwest downstream of the upper ridge axis
will continue to funnel northerly winds and colder air into the
upper Great Lakes through Thursday.

Primary Forecast Concerns:  The arrival of sub-zero temperatures at
850mb certainly brings the potential for lake convection into play
(with mean Lake Superior water temperature around 12C).  Narrow
surface ridge builds across the U.P. tonight...likely a consequence
of the land-lake temperature differential.  Current satellite trends
shows low clouds spilling out of Minnesota and across western Lake
Superior and northwest Upper Michigan...south edge of cloud deck has
mixed out allowing for more sun across southwest/south central
Upper.  Expect clouds to continue to spread east during the late
afternoon/evening along at least the Lake Superior shoreline
counties...then as winds veer more toward a more northerly component
tonight expect clouds to get pushed back farther inland.  Expect
cloud cover to be fairly prevalent through the day Thursday.

As for precipitation chances...given the arrival of cold air and
veering flow allowing for a longer northwesterly fetch over the
lake...can envision some shallow bands of showers developing later
tonight and especially Thursday with a bit of a diurnal component
and inversion heights getting pulled up a bit with more cyclonic
curvature aloft and a dynamic PV anomaly swinging into the upper
Lakes.  So will bump PoPs from the consensus forecast which looked a
bit dry (and increased temporal resolution to six hours during the
day Thursday so as not to get too cute).

.LONG TERM...(Friday through Wednesday)
Issued at 356 AM EDT THU OCT 20 2016

While no hi impact events are likely for Upr MI in the longer term
period, the expected pattern wl feature changeable wx. Lingering lk
effect clds/showers into Fri evng wl give way to some dry wx thru at
least Sat evng as a sfc hi pres rdg lingers nearby. There could be
more showers late in the weekend depending on the track of a shrtwv/
accompanying sfc lo pres aprchg fm the wnw. Temps during this time
wl be within a few degrees of normal. There could be some lk effect
clds/showers on Sun ngt into Mon in the cooler nw flow ahead of
trailing hi pres. After a brief dry period into Tue, another
disturbance/lo pres aprchg fm the w may bring some rain mid next

Fri...Ongoing lk effect pcpn in lingering cyc nne flow/under axis of
h85 temps arnd -5C wl diminish slowly w-e on Fri as larger scale
subsidence ahead of aprchg shrtwv rdg/sfc hi pres lowers invrn base/
diminishes the llvl cyc flow. Wl retain the hier likely pops over
the ncentral cwa favored by the upslope nne flow in the mrng before
disruptive insolation/lowering subsidence invrn reduces the pops.
There could be some snow mixed with the showers in the mrng over the
interior hier terrain, but ltl if any accum is expected.

Fri ngt...While sfc hi pres shifting over central Upr MI by 12Z Sat
wl end the lk effect pcpn over the w and central, maintained some
chc pops thru the evng over the e with a more resilient cyc nnw
flow/h85 temps near -5C btwn the sfc hi pres rdg and deepening lo
pres moving into New England. Some waa clds in the llvl ssw flow
btwn the sfc hi pres rdg and a shrtwv/sfc lo pres crossing scentral
Canada may move in the w late at ngt. Expect the lowest min temps
into the 20s over the interior central where skies are moclr/winds
lgt under the hi pres rdg axis.

Sat...While some clds associated with the waa on the srn flank of
the disturbance passing thru scentral Canada may impact the cwa,
lingering llvl dry air associated with persistent h5 rdg axis/sfc hi
pres shifting slowly to the e on the wrn flank of deep lo pres in
New England and passage of the shrtwv so far to the n favors a dry
fcst for Upr MI.

Sat ngt thru Sun ngt...Most of the medium range guidance shows a
fairly strong shrtwv embedded in the fast wnw flow aloft near the
Cndn border and associated sfc lo pres moving near the Upr Lks
during this time. Despite some fairly impressive dpva ahead of this
feature, absence of any sgnft mstr return wl restrict accompanying
pops. There are some fairly sharp differences on the track/intensity
of the sfc lo pres. With a more confluent nw flow aloft just to the
e on the wrn flank of the deep lo pres track tracking slowly n thru
Quebec, suspect the weaker and farther s depiction of the sfc lo is
on the right track. This scenario would further reduce pops. But
considering the uncertainty in the fcst, maintained consensus fcst
for now. A colder nw flow in the wake of the departing disturbance
and in advance of trailing hi pres that wl drop h85 temps toward -5C
could bring a return of some lk effect clds/showers on Sun ngt.

Next week...Some lk effect clds/showers could linger into Mon in the
nw flow ahead of aprchg hi pres. But as this sfc hi pres builds into
the Great Lks on Mon ngt into Tue under a bldg upr rdg left in the
wake of slowly departing upr trof/sfc lo pres in ern Canada, expect
a period of dry wx. If the hi pres rdg/axis of pwat under 0.50 inch
is ovhd on Mon ngt, Tue mrng could be quite chilly. But many of the
models show waa clds invading the area by then on the wrn flank of a
faster exiting sfc hi pres along with some lgt pcpn on Tue, so wl
stick with the consensus fcst for now. The longer range guidance
then hints another shrtwv/sfc lo pres moving thru a more zonal flow
over the w half of NAmerica could impact the area next Wed/Thu.

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 139 AM EDT THU OCT 20 2016

Anticipate mainly MVFR ceilings to persist through the forecast
period at IWD/CMX with VFR cigs at SAW tonight before veering low
level winds more to the northwest that should bring MVFR ceilings in
toward Thursday morning. Included a TEMPO group for lake effect showers
overnight at KCMX.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 409 PM EDT WED OCT 19 2016

Rising surface pressures and an associated weakening gradient
expected to keep marine concerns to a minimum beyond this
evening...where some gustiness will persist in a low level cold
advection pattern behind a departing cold front.  Some marginal
small craft conditions east of MQT this evening along the south
shore of Lake Superior.  Winds mostly below 20 knots expected by
Thursday...and 15 knots or less by Friday.  Surface ridging will
dominate this weekend...with relatively light winds expected
especially by October standards.  Depending on how pattern
evolves...will likely see an increase in winds in the Monday time

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


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