Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 280533

Area Forecast Discussion
National Weather Service Marquette MI
133 AM EDT Tue Mar 28 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 319 PM EDT MON MAR 27 2017

The evolution of low clouds continues to be the challenge of this
forecast as low-level moisture lingers under a strengthening
inversion. Isolated showers have developed across the west this
afternoon as a 700hPa trough drifts ESE across the CWA. Isolated to
possibly scattered showers along this line will continue eastward
into this evening before clearing the CWA by midnight.

As for cloud cover, low-level clouds have struggled to erode today
as mid-level clouds limit surface insolation. Where mid-level clouds
have thinned across the far west, low-level clouds scattered out and
temps quickly responded. This trend should slowly continue eastward
before loss of daytime heating. Where clearing occurs across the
west half, fog is expected to develop overnight. The potential for
dense fog will be conditional on how much clearing occurs over the
next several hours.

Another surge of low-level moisture currently evident by low-clouds
over far northern Ontario will shift southward through the night.
This reinforcing shot of moisture will likely keep skies rather
cloudy across at least the north-central well into Tuesday. Given
the late March sun angle and dry air above the shallow, 1kft,
inversion, expectation is that clouds will eventually mix out. Where
clearing occurs early enough away from N to NE winds off Lake
Superior, temps should approach 50F. Along the immediate shores of
Lake Superior, some locations will struggle to get out of the mid

.LONG TERM...(Tuesday night through Monday)
Issued at 336 PM EDT MON MAR 27 2017

A split flow pattern wl dominate the CONUS/srn Canada during the
medium/extended range. Sprawling Hudson Bay hi pres under shrtwv
rdging in the nrn branch flow wl bring dry wx into at least Thu.
Depending on the degree of phasing btwn a closed srn branch closed
lo tracking fm the scentral Plains toward the OH River Valley/Lower
Great Lks later in this week and a disturbance in the nrn branch
flow moving thru Ontario, some wintry pcpn on the nrn fringes of
this disturbance could impact Upr MI, especially the se half. But
the trends among the 12Z model guidance is for there to be less
phasing btwn these shrtwvs, with a dry fcst for Thu into Fri now
more likely. Although a shrtwv or two in the nrn branch flow could
impact the cwa in the longer term, an absence of deep mstr would
result in only clds/light pcpn. Overall, temps in the medium/
extended range wl be aoa normal.

Tue ngt into Thu...A sprawling Hudson Bay hi pres stretching fm
Hudson Bay hi pres into the Upr Lks under shrtwv ridging in the
zonal nrn branch flow over srn Canada wl bring dry wx to Upr MI
during this time. The main challenge wl be on whether any lo cld wl
linger under a lo subsidence invrn base. Given the acyc/diffluent
nature of the fcst llvl flow and the slow drying fcst in the h95-9
lyr during a time of strengthening insolation/mixing, suspect any lo
clds wl tend to diminish with time. The best chc for more persistent
lo cld wl be over the hier terrain of the ncentral, with the llvl
nne flow wl present a greater upslope wind component.

Thu thru Fri...The main concern during this time wl be on the track
of a srn branch closed lo that wl be moving enewd thru the scentral
Plains on Wed ngt/Thu and toward the lower Lks on Thu ngt. How far n
this lo pres shifts and whether this disturbance wl impact the cwa
wl depend on the degree of phasing btwn this srn branch disturbance
and a nrn branch shrtwv moving into nw Ontario. The guidance that
shows minimal or no interaction btwn the branches, especially recent
GFS runs, indicate the lo pres/deeper mstr and pcpn wl remain to the
s, perhaps just brushing the srn cwa with some snow. On the other
hand, the models hinting at more phasing depict the pcpn shield
impacting all of the cwa except the Keweenaw/far nw within an
airmass that is sufficiently cold (h85 temps as lo as -5C) to bring
mainly sn, especially during the period of nocturnal cooling. The
12Z Cndn and ECMWF runs have trended toward the consistently less
phased GFS guidance, so lowered pops blo the consensus fcst to
reflect a hier prob of the srn branch lo remaining to the s.

Sat thru Mon...Following the exit of the srn branch disturbance/lo
pres into the ne states, a wnw nrn branch flow wl once again
dominate the Upr Great Lks. Some of the extended models show at
least one mstr starved disturbance influencing Upr MI during this
time, psbly bringing some light mixed pcpn to the area. But overall,
this period should be rather dry with aoa normal temps as h85 temps
are fcst to be arnd 0C.

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 130 AM EDT TUE MAR 28 2017

Mainly mid clouds with VFR conditions will prevail at
KIWD/KCMX/KSAW. Another area of low-level moisture is expected to
move in from the north late in the night into the morning hrs.
However, model trends and upstream obs suggest that conditions
will be less likely to drop into the MVFR range. The best chance
for any cigs blo 3k ft will be at KSAW where weak upslope flow
will prevail. Also, shallow radiational fog will be possible at
all sites overnight into the early morning hrs though vsby
restriction should be minimal, mainly in the 3-5sm range.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 336 PM EDT MON MAR 27 2017

A sprawling Hudson Bay hi pres/flat pres gradient over the Upper
Lakes will result in light n-e winds under 20 kts into at least Thu.
If a lo pres moving toward the Lower Great Lks later in the week
moves a bit farther to the n, the pres gradient could tighten enough
to bring e-ne winds up to 25 kts. But if this disturbance remains
farther to the s and a hi pres ridge remains over the Upper Lakes,
winds under 20 kts will linger into the weekend.

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


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