Area Forecast Discussion
Issued by NWS Marquette, MI
FXUS63 KMQT 010006
Area Forecast Discussion
National Weather Service Marquette MI
806 PM EDT Sun Apr 30 2017
.SHORT TERM...(This evening through Monday)
Issued at 353 PM EDT SUN APR 30 2017
Water vapor imagery shows a wrapped up low over the Central Plains
this afternoon with a well defined dry slot out ahead of it. Visible
satellite is continuing to show mainly high clouds flowing across
the area with thicker clouds over southern and central WI and MN and
slowly lifting northward. Radar is showing most of the precipitation
well to the south of the U.P., mainly over central IL westward to
NE. This will be the main band of moderate rain that will slide
through tonight into Monday. There are a few showers sliding over
the far west and over the far east, but these should just slide just
along the edges of the CWA, with the best chance of seeing showers
this afternoon near Ironwood.
Tonight and Monday: A vertically stacked surface low and 500mb low
over the Central Plains tonight, is progged to lift north and
eastward into the central U.P. by late Monday afternoon. As this
happens, moisture will continue to increase from the south across
the U.P. This increase in moisture transport along with increased
isentropic upglide will allow rain to overspread the area by late
this evening with system forcing progged to slide into the area
Monday, helping to keep the rain in place. There may be a bit of a
break Monday afternoon over the east half as the dry slot passes
through the area; however, the added instability with the dry slot
may allow for a few rumbles of thunder. Again, the best chance of
hear some thunder would central and east close to the dry slot.
The heaviest rainfall totals are expected to remain over the far
east and the far west where strongest upglide and moisture transport
is progged to be located. Areas far west and far east may see three-
quarters of an inch to an inch, while the central portion of the
U.P. will probably end up seeing around a half inch to three-
quarters of an inch. At this point, river levels are still running
high with fairly saturated soils, so expect some rivers to rise,
possibly to bank full; however, widespread river flooding is not
expected across the CWA. Precipitation type doesn`t look to be too
much of a concern until Monday afternoon as colder air advects
through the thermal profile over the western U.P.; however, not
really expecting much in the way of snowfall accumulation. The
central and east will only see precipitation in the form of rainfall
through this time period. In addition to the rain potential, winds
may be gusty to 25 to 35 mph over the higher terrain and mainly over
the Keweenaw as LLJ of 40 kts or better is set to be just above the
.LONG TERM...(Monday night through Sunday)
Issued at 327 PM EDT SUN APR 30 2017
The slowly departing closed lo wl cause pcpn chcs thru at least Tue,
along with blo normal temps and a good chance of some accumulating
wet snow over the hier terrain of the nw half of Upr MI on Mon ngt
into Tue mrng. Trailing hi pres wl then bring a dring trend Tue ngt/
Wed before another aprchg disturbance results in a chc for more
showers on Thu. There is a general consensus among the longer range
guidance that the upr pattern wl change to one that features a bldg
upr rdg in the Rockies/wrn Plains to the w of a deep ern trof by
late this week. The resulting nnw flow wl cause aob normal temps and
drier than normal wx even though shrtwvs embedded in the nnw flow
alf wl bring shower chcs fm time to time.
Mon ngt/Tue...Deep closed lo is fcst to drift fm over Upr MI at 00Z
Tue to far wrn Quebec by 00Z Wed. Although accompanying deep lyr
forcing wl exit to the ne with this feature during Mon ngt, the
lingering deep cyc nw flow and moist lyr arnd the departing lo
justifies keeping hier likely pops thru the ngt and into Tue,
especially over the hier terrain of the nw cwa, which wl experience
the sharpest upslope wind component/llvl cnvgc. Dvlpg downslope flow
wl result in more drying/falling pops over the scentral. As h85
temps fall to as lo as -4 to -5C over the w by 12Z Tue, expect rain
to mix with/change to sn over the nw cwa. Not out of the question
there could be several inches of wet sn accums over the hier terrain
of the nw half on Mon ngt/Tue mrng. As the closed lo moves farther
away and gives way to steady h5 hgt rises that reach 100m fm 12Z-24Z
on Tue, the pcpn intensity wl diminish. Although this pcpn may still
be mixed with sn into the aftn, daytime heating wl minimize the
potential for additional accums. Temps peaking fm near 40 over the
hier terrain of the nw to arnd 50 over the scentral wl be well blo
Tue ngt...Although many of the models show a weak shrtwv/
accompanying forcing digging thru the Upr Lks in the nw flow alf
left behind the exiting closed lo in Quebec, the larger scale drying
under continuing hgt rises and weakening cyc flow with aprch of
trailing sfc hi pres wl limit pcpn chcs. With pwat falling aob 0.25
inch/clrg skies/lgt winds under the incoming hi pres, temps over the
interior w half could fall well into the 20s. Lowered the consensus
fcst min temps a couple degrees in that area.
Wed...The passing sfc hi pres/accompanying dry airmass wl bring a
mosunny day. With h85 temps near 0C, expect daytime maxes to climb
well into the 50s away fm the cooling influence of the lks as lk
breezes form under the relatively flat pres gradient in place.
Wed ngt/Thu...Some clds in advance of another shrtwv digging sewd
into the Upr Lks wl arrive as early as Wed ngt over the wrn cwa.
Although mstr inflow wl be limited, the passage of some dynamic
support during peak heating wl allow for a chc of some showers,
especially if the medium range guidance verifies that show a passing
cold fnt that would be a focus for sharper llvl cnvgc.
Extended...The majority of the longer range models have trended
toward a hier amplitude wrn rdg/ern trof upr pattern for late this
week into the weekend. This flow wl support aob normal temps. While
shrtwvs embedded in this flow wl bring ocnl chcs for showers, a lack
of deep mstr wl result in blo normal pcpn. Timing differences among
the models wl preclude more than lo chcs pops at any given time for
Fri thru Sun.
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 801 PM EDT SUN APR 30 2017
The main area of heavier precipitation will slide across the TAF
sites late tonight into Monday morning. Ceilings and visibilities
are expected to drop first at IWD and SAW before moving into CMX
overnight. IFR dropping to LIFR conditions are expected as the
heavier rain moves in to each site overnight into Monday morning.
Low cigs should then linger through Monday afternoon.
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 353 PM EDT SUN APR 30 2017
As low pressure tracks northeast from the Central Plains, expect
increasing east to northeast winds tonight. Winds will gust as high
as 20 to 30 knots this evening before increasing to 35 to 40 knot
gales over much of the lake tonight through Monday as pressure
gradient tightens as the low slide into the Upper Peninsula. Winds
will slowly diminish over the east half of Lake Superior Monday as
the low moves directly over the area; however, gales are expected to
linger over the west half. Nne winds as hi as 25-30 kts, and perhaps
near gale force over at least the western Lake, under a tight pres
gradient behind slowly departing lo pres on Mon night will slowly
back and subside to under 20 kts on Tue night as a hi pres ridge
builds into the western Great Lakes. Since a relatively flat pres
gradient will predominate the rest of the week, plan on winds under
20 kts on Wed thru Fri.
Gale Warning from 2 AM to 2 PM EDT Monday for LSZ265-266.
Gale Warning until 5 PM EDT /4 PM CDT/ Monday for LSZ162.
Gale Warning from 2 AM to 8 PM EDT Monday for LSZ263-264.
Gale Warning from 5 AM to 2 PM EDT Monday for LSZ243>246.
Gale Warning until 8 AM EDT Monday for LMZ221-248-250.