Area Forecast Discussion
Issued by NWS Marquette, MI
FXUS63 KMQT 150721
Area Forecast Discussion
National Weather Service Marquette MI
321 AM EDT Sat Oct 15 2016
.SHORT TERM...(This evening through Saturday)
Issued at 343 PM EDT FRI OCT 14 2016
The main forecast concerns through the short term is the potential
for gusty south winds across the area tonight into Saturday.
Additionally, the winds will cause waves to build close to 10 ft
along the Lake Michigan shoreline, which may lead to minor beach
erosion/lake shore flooding.
Tonight: Dry high pressure will continue to slowly slide to the east
of the U.P. tonight, allowing warm southerly flow to increase across
the area. As the high departs, low pressure will slide across
central Canada toward central Manitoba. The pressure gradient
between the two systems will cause winds to become gusty out of the
south across much of the Upper Great Lakes region. 925mb winds are
progged to be around 30 to 40 knots out of the south tonight. The
main question continues to be how much of this actually mixes down
to the surface. 850mb temperatures will continue to steadily warm on
WAA into the region, warming from around 10C at 00Z/15 to around 15-
16C by 12Z/15, which would be warmer than Lake Superior water
temperatures and very near the Lake Michigan water tempertures. Even
with the increasing stability, it still looks like winds will be
fairly gusty across both inland areas and over the Great Lakes. The
strongest gusts will be over the Great Lakes before profiles become
more stable, with up to 40 knot gusts possible over northern Lake
Michigan this evening into the early overnight hours. Therefore, the
Gale Warning will continue over eastern Lake Superior and
northwestern Lake Michigan. Another issue associated with the
increased southerly winds will be the potential for minor beach
erosion/lake shore flooding, mainly along the Lake Michigan
shoreline as waves build to around 10 ft. Otherwise, conditions
should remain dry across the area with steadily increasing cloud
cover from the west.
Saturday: The low pressure system will slide from central Manitoba
around 12Z/15 to near James Bay by 00Z/16. At the same time, strong
southerly winds will remain in place across much of the Upper Great
Lakes region as the pressure gradient remains strong and a cold
front slowly approaches from the west. Waves will continue to be
around 10 ft along the Lake Michigan shoreline through the day
Saturday which will continue to lead to minor beach
erosion/lakeshore flooding potential. Moisture will slowly increase
into the area during the afternoon hours. This, combined with
increased forcing along the cold front, will allow showers to slide
into the western half of the U.P. MU Cape values look to be very
marginal for thunder Saturday, so have only slight chances of
thunderstorms south central for Saturday afternoon. Dry air looks to
be fairly prevalent in the mid layers so any rainfall that does
occur Saturday afternoon should remain on the light side.
.LONG TERM...(Sunday through Friday)
Issued at 320 AM EDT SAT OCT 15 2016
A fairly active medium range period is in store for Upr MI along
with above normal temps until at least Wed. Aprchg sfc hi pres rdg
axis wl bring mosunny wx for Sun, but then some fairly sharp
waa/isentropic ascent btwn this hi departing to the e and an aprchg
lo pres wl bring a return of some showers/a few TS on Sun ngt into
Mon. An aprchg shrtwv wl cause lingering showers on Mon ngt into Tue
before a more acyc nw flow results in a trend toward cooler and
drier wx at mid week. The arrival of h85 temps down to -5C in the
nly flow ahead of aprchg hi pres could cause some lk induced
troffing/showers later on Wed into Fri before this hi pres arrives
and causes a better chc for dry wx toward the end of the coming week.
Sun...Large scale dnva/deep lyr qvector dvgc ahead of an aprchg
shrtwv rdg axis and under a sfc rdg extending into the Upr Lks fm
sfc hi pres centered over Hudson Bay wl bring a dry wx to Upr MI.
The combination of a good deal of sunshine and mild h85 temps not
far fm 10C wl result in another warm day with max temps rising into
the 60s except over the nrn tier. The strengthening sly flow/waa
btwn the sfc hi pres rdg shifting to the e and falling mslp in the
nrn Plains wl cause some mid/hi clds to roll back into the w by late
in the day.
Sun ngt/Mon...Sharpening pres gradient btwn lo pres moving e fm the
nrn Plains toward Upr MI and retreating hi pres rdg responsible for
the dry wx on Sun wl allow for axis of vigorous waa powered by h925-
85 winds up to 40-45 kts/isentropic lift best shown on the 300-305K
sfcs/area of deep lyr qvector cnvgc to pass across the Upr Lks and
bring a period of showers later Sun ngt into Mon mrng. Maintained a
mention of some elevated TS as many of the models show SSIs a few
degrees blo 0C/mucapes aoa 500 j/kg with h85 temps as hi as 13-14C.
On Mon, the axis of sharpest isentropic lift/deep lyr qvector
cnvgc/deep mstr is progged to shift to the e of Upr MI, so expect
diminishing pops w-e with the arrival of some mid lvl drying/deep
lyr qvector dvgc. But since many of the models continue to generate
some pcpn thru the aftn, maintained some lo chc pops. Although some
lo clds are likely to linger within relatively humid llvl airmass to
the n of stnry fnt just to the s of Upr MI, temps during this time
wl run well above normal.
Mon ngt/Tue...A shrtwv aprchg within the wsw flow aloft and over
stnry fnt just to the se of Upr MI wl bring the threat of more
showers during this time. However, models show quite a bit of
disagreement on how much deep mstr wl be present, so model qpf is
very inconsistent. Some of the medium range models also show a more
acyc flow beginning to dvlp on Tue in the wake of a faster exiting
shrtwv/sfc fnt, introducing more uncertainty in the fcst. Overall,
fcst wl show the the hiest pops on Mon evng ahead of the aprchg
shrtwv, with diminishing pops thru the rest of this period. Since
h85 temps are progged to fall no lower than about 7-8C over the nw
cwa by 00Z Wed, well above normal temps wl persist thru this time.
Tue ngt/Wed...Although another shrtwv may pass on Tue ngt, model
trends toward deep lyr drying/a more acyc llvl nw flow to the e of
hi pres bldg into the Plains justifies pops no hier than the schc
category as shown by consensus fcst. Expect a slow return toward
more seasonable wx as h85 temps dip toward -2C over the nw cwa by
Extended...Although sfc hi pres to the w is progged to slowly drift
toward the wrn Great Lks on Thu into Fri, cooler nly flow fcst to
drop h85 temps toward -5C in advance of this rdg may result in some
lk induced troffing/pcpn near Lk Sup under slowly falling upr hgts.
Not out of the question some snow could mix with the pcpn over the
hier terrain. The closer aprch of this sfc hi pres rdg on Fri wl end
the threat for this pcpn. Some of the longer range guidance hints
another shrtwv embedded in the wnw flow alf may aprch next weekend,
but limited mstr wl restrict any accompanying pops.
.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 145 AM EDT SAT OCT 15 2016
Tight pres gradient and relatively stable conditions near the sfc
will result in LLWS into the morning hrs at KIWD/KCMX/KSAW. KMQT VAD
wind profile has been showing 40-50kt winds at 500ft AGL for the
last several hrs. The southerly winds will also gradually transport
low-level moisture into the area, eventually bringing MVFR cigs to
all 3 terminals during the morning. With more of an upslope
component to the winds, cigs at KSAW may fall to IFR in the evening.
There may be some -shra this aftn as a cold front arrives, but
confidence in development and coverage is still low, only supporting
a VCSH mention at best.
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 343 PM EDT FRI OCT 14 2016
Southerly winds will increase pressure gradient tightens ahead of an
approaching Plains trough. Expect winds to increase to 30 knots this
afternoon over the east half of Lake Superior with gale force gusts
possible late in the afternoon. South gales to 35 knots are expected
over the east half of the lake tonight; therefore, have continued
the gale warning late this afternoon through much of tonight.
Elsewhere up to 30 knot southerly winds are expected.
Gales will continue to be possible Saturday over Lake Michigan while
the rest of the area will remain below gales for the remainder of
the forecast period.
Gale Warning until 6 AM EDT early this morning for LSZ249>251-
Gale Warning until 11 PM EDT this evening for LMZ248-250.
Gale Warning until 8 PM EDT this evening for LMZ221.