Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 200523

Area Forecast Discussion
National Weather Service Marquette MI
123 AM EDT SAT AUG 20 2016

.SHORT TERM...(This evening through Saturday)
Issued at 355 PM EDT FRI AUG 19 2016

Today`s weather has been driven by a group of MCV centers
originating from multiple convective complexes last night. As of
1930Z, the first is lifting NE near Manistique, while the second is
centered over SW Baraga County. A third center has formed with a
self-maintaining heavy rain/storm complex now over Whitefish Bay.

With some clearing between the first and second MCV, the boundary
layer has recovered to some extent as temps across the south-central
have risen into the mid to upper 70s. This will be a focus for
further convective initiation ahead of the second MCV. In fact,
recent radar trends show activity already increasing. Meanwhile, the
main cold front is draped across the western Upper MI counties.

Expect showers and some storms to track eastward through the early
evening across the south-central. Isolated to scattered showers will
also occur along the cold front as it drifts SE across the CWA
through the evening. With decreasing upper-level support late this
evening into the overnight, most of the CWA will experience a dry

Focus then turns to widespread rain for Saturday. The
aforementioned cold front will stall across northern Lake MI to
central WI overnight as a sharp trough over ND shifts across the
Upper MS Valley. A rapidly strengthening sfc low is expected to
develop along the front late tonight through Saturday. Model
guidance continues to waver on the location of the sfc low, but
solutions are converging on a track from SW WI late Saturday morning
to around the bay of Green Bay at 00Z Sunday. Signs point to the
potential for a band of heavy rain across central Upper MI in
response to decent isentropic lift and deformation under a passing
right entrance to an upper jet axis. At this time, rainfall amounts
of 1.5-2 inches late tonight into Saturday evening will be possible
across a swath of the central U.P.

.LONG TERM...(Saturday night through Friday)
Issued at 340 PM EDT FRI AUG 19 2016

Main focus in the medium/extended range wl be on winds/pops/lk
enhanced pcpn associated with deepening sfc lo pres that is fcst to
lift thru ern Upr MI and into Ontario on Sat ngt into Sun. If some
of the deeper fcst scenarios for this lo come to pass, there may be
a need for wind headlines on Sat ngt into Sun, especially near Lk
Sup E of the Keweenaw. A period of more tranquil, drier wx wl follow
early next week associated with trailing hi pres before shower/TS
chcs return by mid week as the SW flow btwn this departing hi and a
vigorous shrtwv moving acrs Scentral Canada draws warmer and moister
air back into the area.

Sat ngt/Sun...The 12Z NAM/GFS/Cndn models have come into reasonable
agreement with the 00Z ECWMF showing a deepening sfc lo pres lifting
NEwd on Sat evng thru the ern cwa and into Ontario later at ngt just
E of Lk Sup ahead of vigorous shrtwv moving into the wrn Great Lks.
Although the dvpa/deep lyr forcing associated with the shrtwv are
fcst to lift to the NE after midngt, lingering cyc NNW flow/falling
h85 temps toward 5C by 12Z Sun that wl likely add a lk enhanced
component to the pcpn/Lk Sup water temps are within a few degrees of
20C even n the cooler open waters/ and maintain an axis of likely/
categorical pops especially in the upslope areas near Lk Sup. Some
of the hier res models show an even deeper sfc lo pres exiting
slower, a scenario that can`t be ruled out given the warm waters of
the Great Lks and vigorous shrtwv that is fcst to drop h5 hgts up to
100m btwn 00Z and 12Z Sun. Main impact the deeper fcsts would have
is to result in stronger winds under a tighter pres gradient with
the more efficient mixing of the hier momentum to the sfc over the
relatively warm lk waters. In fact, the 12Z regional WRF-ARW fcsts
h925 winds/potential sfc wind gusts up to 50-60kts. If this deeper
sfc lo verifies, future shifts may need to consider wind headlines
for at least a portion of the cwa, especially near Lk Sup E of the
Keweenaw. As the lo and sharp cyc flow continue to the NE on Sun and
give way to a weaker, more acyc flow in the aftn, winds/pops wl

Sun ngt thru Mon ngt...The deep upr trof centered fm Hudson Bay into
the ern Great Lks at 00Z Mon is progged to lift steadily to the NE,
allowing for steady hgt rises ahead of aprchg upr rdg axis during
this time. The associated sfc hi pres rdg is fcst to shift steadily
E as well, fm NW Ontario into the mid MS River Valley on Sun evng to
the mid Atlantic States into wrn Quebec by sunrise on Tue. Sun ngt
wl be cool under the rdg axis/pwat as lo as 0.5 inch, but a bit
tighter pres gradient to the N of the hi center moving into the OH
River Valley wl likely prevent temps fm falling farther than about
45 over the interior. Return SW flow/WAA on the wrn flank of the
retreating rdg wl then cause some mid clds on Mon/Mon ngt. Some of
the medium range guidance even generates some showers as early as
Mon ngt, but prefer a dry scenario given the fcst hgt rises/overall
relative dryness and capping of the airmass shown on fcst sdngs. H85
temps rebounding to near 14C on Mon wl support max temps aprchg 80
over the W, where the bulk of the mid clds may shift to the NE.
Steady SW winds, pwat rising toward 1.25 inches and some clds on Mon
ngt wl greatly limit nocturnal cooling.

Extended...Bldg upr rdg across the wrn Great Lks ahead of a potent
shrtwv drifting thru Scentral Canada and over an acyc SW h85 flow
arnd the departing hi pres rdg that is progged to lift h85 temps
near 20C should bring about a dry and even warmer day on Tue. As the
shrtwv continues E and toward NW Ontario by late Wed, shower/TS chcs
wl be on the incrs ahead of aprchg cold fnt. Since the fnt wl
probably drift only slowly thru the wrn Great Lks to the S of slow
moving disturbance in NW Ontario, shower/TS chcs wl linger into Thu.
Temps look to remain above normal into Thu. Cooler wx should arrive
on Fri in the wake of the fropa, but there could still be some
showers as upr trof axis lingers nearby.

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 123 AM EDT SAT AUG 20 2016

Showers will move back into the area before daybreak this morning.
Periods of rain will then continue into the evening as a strong
low pressure system lifts across Upper Michigan. Have backed off
of low clouds at SAW for rest of tonight. VFR conditions at all the
terminals will quickly trend to MVFR late tonight then IFR on Sat
due to the rain and some fog at times, especially at SAW with moist
upslope flow off Lk Superior. As the low moves over eastern Lk
Superior later tonight, expect north winds to increase sharply at
SAW with gusts to 25 kts or higher.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 355 PM EDT FRI AUG 19 2016

As a cold front drifts southeastward across Lake Superior through
this evening, expect winds to become NW less than 15 knots through
tonight. Then, a low pressure system rapidly developing along the
cold front Saturday will track from SW WI Saturday morning, to near
Green Bay Saturday evening, to east of Sault Ste. Marie by Sunday
morning. In response, NE winds will increase to 25 knots through
Saturday afternoon. After the low passes Saturday evening, N to NNW
gales of 35 knots are expected to develop across much of the east
half of Lake Superior. As high pressure then slowly builds in from
the west through Monday, NW winds will gradually diminish from
around 30 knots Sunday morning to less than 15 knots by Monday
morning. A period of southerly winds of 10 to 20 knots is then
expected Tuesday and  Wednesday as the high pressure drifts to the
SE and low pressure develops over south-central Canada.

Upper Michigan...
Lake Superior...
  Gale Watch from late tonight through Sunday morning for LSZ251-

  Gale Watch from this evening through Sunday morning for LSZ249-

Lake Michigan...


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