NWS Marquette, MI wrote its last area forecast discussion before the first event at Aug 31, 3:23 PM EST, 1 hour 7 minutes earlier.
Area forecast discussion, Aug 31, 3:23 PM EST, 1 hour 7 minutes before
Area Forecast Discussion
National Weather Service Marquette MI
423 PM EDT Mon Aug 31 2020
.SHORT TERM...(This evening through Tuesday)
Issued at 352 PM EDT MON AUG 31 2020
Water vapor satellite this afternoon shows a distinct dry punch
aloft over Wisconsin and the western UP, this associated with a
strong negatively-tilted mid-level short wave that is lifting
northeastward across the western UP and Lake Superior. At the
surface, this takes the shape of a narrow trough accompanied by a
tight wind shift as evidenced by south winds at Passage Island (east
end of Isle Royale) and NW winds at Rock of Ages (west end of Isle
Royale). Strong fgen is providing maple lift for showers moving
across the area. Initially, these were in a broader, more stratiform
area. However in the past hour or so some scattered heavier showers
have developed over western Marquette County where SPC Mesoanalysis
indicates up to 250 J/kg MUCAPE. Even the most generous HRRR
sounding wrt instability keeps ELs below the hail growth zone, and
with cloud-phase satellite showing only very little ice growth, felt
ok keeping thunder out of the forecast. However, some briefly
heavier rainfall rates will be possible the next couple of hours.
This evening, precip will clear out from west to east as the front
races through. Initially skies will be clear, allowing for some
cooling. However, satellite and models show a thick patch of cirrus
racing in from the west that will move over the area by late
evening, inhibiting cooling somewhat. Still, given the cool air
aloft behind this front it will be a seasonably chilly night (lows
in the 40s interior and 50s lakeshores). Despite today's rainfall,
think that we will maintain a few kts of gradient wind which, along
with this cirrus, should prevent much if any fog from forming.
Tomorrow, temps begin warming aloft again, from about 8 C in the
morning to about 11 C by late afternoon at 850 mb. However, this
comes as the next short wave (this one much more strung out) bring
more mid-level cloud cover in by afternoon, keeping temps from
warming too much. Highs should make it into the low 70s across the
board.
.LONG TERM...(Tuesday night through Monday)
Issued at 355 PM EDT MON AUG 31 2020
At the start of this forecast period, Upper Michigan will be
sitting in between two bouts of precip to the NW and SE. The one
sliding northeastward to the southeast of the area may skim
portions of the far southeastern U.P., with this round courtesy of
being triggered by the leading edge of an upper trough axis
swinging overhead. To the NW, that precip is more directly
associated with the trough axis itself as an upper jet moves in.
This jet/trough looks to weaken as it crosses the Upper Great
Lakes, with not a whole lot of atmospheric moisture accompanying
it, thereby reducing more widespread precip chances with this
system.
Brief benign period then occurs before the next, potentially more
robust system knocks on the door, although similar to how the
models have been handling these more fall-like system tracks as of
late, may be a bit overdone, particularly the GFS. Nonetheless,
it'll be windy with some rain in the area, but the extent of the
wind and rain is yet to be seen. All of the models are in
agreement in intensification of the low, but differ on its track
(i.e. if further north, less rain chances, lower wind speeds).
Stay tuned, particularly those with marine interests (see below).
In the extended period, the pattern looks to remain unsettled with
repeated visits from shortwaves and other disturbances, keeping
the chances for rain somewhat persistent. Not a washout every day
by any means, but just nuisance-type shower activity is what is
currently looking to occur. As for temps, it will wobble between
near to a few degrees below normal through the entire forecast
period, with the warmest day likely happening on Wednesday. If a
fan of the warmer temps, enjoy it while it lasts as early next
week could usher in much cooler weather. Expect 40s and 50s for
lows through the period.
&&
.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 158 PM EDT MON AUG 31 2020
Cold front moving across the area early this afternoon has brought
showers and MVFR cigs to the terminals with occasional vis
reductions into IFR as well at CMX and IWD. The front is knocking on
IWD now, will move through CMX around 20z, and SAW around 21z.
Satellite shows some low-level mist and stratus that will keep
things MVFR for about 1-2 hours after the wind shift with the front.
But once that clears out, conditions go VFR by this evening and stay
VFR through the end of this TAF period.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 422 PM EDT MON AUG 31 2020
The active pattern continues. A sharp trough/occluded front is
moving quickly northeastward across the lake this afternoon.
Southerly winds out ahead of it have been in the 20-30 kt range, now
confined to the eastern half of the lake, while immediately behind
the trough there has been a quick wind shift to westerly and an hour
or two period of gales. Have observed gale force gusts at the
western lake buoy, Rock of Ages, and Houghton this afternoon,
however winds have already relaxed back into the 20-30 kt range at
all three of these sites. Winds will continue to relax into the 15-
20 kt range this evening and through the day tomorrow.
Winds, particularly across the western portions of Lake Superior,
will be on the increase late tomorrow night into early Wednesday
with a few gusts to gale-force possible. Elsewhere across the lake,
gusts look to generally range in the 25 to near 30 knot range. By
early Thursday, more widespread gale-force gusts look likely,
spreading from west to east as the day progresses. However, there is
some uncertainty as to just how high these gusts will get given some
model discrepancies in the track of the low pressure system
responsible for these winds. Regardless of these finer details,
expect gales for this time period, tapering off by late Thursday
into early Friday.
For the first half of the weekend, gusts should top out around 20
knots, with the next system of interest potentially ushering in
higher winds toward the tail end of next weekend.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Beach Hazards Statement until 9 PM EDT this evening for MIZ014.
Lake Superior...
None.
Lake Michigan...
None.
&&
SHORT TERM...RJC
LONG TERM...lg
AVIATION...RJC
MARINE...RJC/lg