Area Forecast Discussion
Issued by NWS Marquette, MI
FXUS63 KMQT 280813
Area Forecast Discussion
National Weather Service Marquette MI
413 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...(Wednesday through Monday)
Issued at 411 AM EDT TUE MAR 28 2017
Confluent upper level flow in northern branch of split flow pattern
results in sfc high from Hudson Bay to upper Great Lakes on Wed.
Ridge then slides to Quebec and the lower Great Lakes on Thu. East
to northeast sfc flow into the upper Great Lakes keeps conditions
dry. Onshore flow results in temps staying in the mid to upper 30s
along Lk Superior for Wed while rest of the cwa sees readings rise
through the 40s. A 50 degree reading is possible over far west and
along the WI border.
Attn Wed night into Thu turns to upper low in the southern branch of
the split flow pattern and the associated sfc low. This low pressure
system which looked like it could bring wintry precip to parts of
Upper Michigan late this week now looks to remain south of Upper
Michigan as the confluent upper flow in northern stream and
associated sfc Hudson Bay high pressure continue to dominate. Now,
even the ECMWF and GEM which were showing the system farther north
all along only would bring wintry precip as far north as WI and
northern lower MI. 00z ECMWF did bump back some lighter precip into
the southeast U.P. for Thu, but looking at low-level moisture off
the ECMWF any precip would be hard pressed to make it much farther
north than immediate Lk Michigan shoreline. Southward trend on the
ECMWF and GEM began to emerge on Mon and dayshift already cut pops
based on those trends with more influence from the Hudson Bay high.
Consensus from latest models continues to show even lower pops, now
only grazing scntrl to far se cwa with mainly slight chance pops for
rain/snow mix Thu into Thu night. Even though low levels are dry and
minimal precip is expected should see bkn-ovc mid-high level clouds
later Wed aftn through Wed night and Thu as swath of h7-h5 moisture
(10-20kft agl) streams well to north of the southern stream system.
Clouds clear out west to east late Thu night into Fri resulting in
mostly sunny skies. Most areas will see temps in the 40s on Fri and
possibly near 50 along the WI border. Even with the increasing
sunshine compared to Wed and Thu, temps will stay on cool side in
upper 30s near Lk Superior with ENE winds on northern edge of sfc
low crossing the Ohio Valley and lower Great Lakes.
Split flow pattern does not back off for the weekend and on into
next week. Could be a smaller shortwave/weak sfc trough coming
through on Sat with a few rain showers. Next chance of precip would
be early next week. ECMWF has shown stronger system 3 out of last 5
with even a potential for snow, but GEM and GFS are not as insistent
on that. Split flow pattern will make it tough to pin down specifics
.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.