Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 190819
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
419 AM EDT Wed Apr 19 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 305 PM EDT TUE APR 18 2017

Low pressure continues to track towards western portions of the area
this afternoon as a robust shortwave, evident on the water vapor
imagery, continues to lift northeast. With warm, moist air advecting
in ahead of this system, fairly widespread rain developed across
Minnesota and Wisconsin and streamed northeast into western portions
of the area throughout the late morning and early afternoon hours.

Through the rest of the afternoon and into the overnight hours,
expect the ongoing rain to lift northeast across the west and
central portions of Upper Michigan as warm, moist accent continues
ahead of the upper level vort-max. Across the west, rain is expected
to remain light, but training precipitation will allow precipitation
amounts to possibly exceed a quarter of an inch through the rest of
the afternoon and overnight hours. Further east across central and
eastern portions of the area, rainfall amounts are expected to be
much lower as the main forcing lift northeast across central Lake
Superior. During the overnight hours, as the trailing cold front
pushes east across the area, expect the widespread rain to come to
an end from west to east. However, with increasing cold air
advection behind the system, forecast soundings are consistent with
stratus settling into the area. Therefore, we could see some spotty
drizzle develop and linger into early Wednesday morning across the
west and central, especially across the higher terrain.

On Wednesday things will dry out, but models are fairly persistent
in maintaining stratus through a good portion of the day. Could see
a few pockets of clearing, especially across the south where
downsloping winds will be persistent, but upper-level clouds will
begin to stream northward ahead of another approaching system.

.LONG TERM...(Thursday through Tuesday)
Issued at 418 AM EDT WED APR 19 2017

A split upper flow wl dominate the wx pattern across NAmerica during
the medium/extended range. Recent model runs have trended farther
north with the track of the next southern branch shrtwv/sfc low pres
to impact Upr MI tonight into Thu, bringing the potential for some
moderate wet snow to mainly the higher terrain of the ncentral/nw
cwa. Hudson Bay hi pres expanding into the area in the wake of this
disturbance wl then bring a period of dry wx for at least Fri and
Sat. Although a cold front associated with a northern branch shrtwv
may pass Upper MI Sat night or early Sun, accompanying pcpn should
be on the light side. The next disturbance to impact the area will
likely arrive late Mon into Tue. Expect temps to run at or blo
normal during the medium/extended range.

Thu and Thu night...GFS/NAM and regional CMC all coming into better
agreement on track of Plains shortwave and associated sfc low for
Thu into Thu evening taking the sfc low across northern Lake Mi into
eastern Upper Mi by early Thu evening.  Models show a significant
amount of qpf over much of Upr MI under large scale dpva and
diffluent upper flow ahead of the shortwave that wl result in 12hr
h5 height falls of 120-140m along the projected track of the
associated h85 low track. An upslope, strengthening cyclonic e-ne
flow wl enhance pcpn rates over the higher terrain of ncentral
counties, particularly Baraga and western Marquette counties and
over the Keweenaw Peninsula. The forecast thermal profiles suggest
the pcpn wl begin as ra but then mix with or change to sn over at
least the higher terrain of the nw half by sometime on Thu morning
as the vigorous uvv results in sufficient dynamic cooling thru a
deep enough layer. Models including SREF products and WPC snow
accumulation progs seem to be pegging Huron Mountains and even the
Keweenaw Peninsula as areas with greatest potential for significant
snowfall with upslope ene to ne flow and mid-level fgen as driving
forces.  However, there are concerns looking at the NAM and GFS bufr
soundings that the model QPF may be overforecast as both models have
drier air working into the area by 12Z Thu and the depth of moisture
does not reach to the -10C isotherm. At this point, do not feel
comfortable issuing a winter weather advisory given considerable
model uncertainty regarding marginal thermal profiles and
possibility of drying mid-levels on Thu. Feel inclined to keep SPS
going with a mention of a potential for moderate wet snow at times
into the Keweenaw and possibly Baraga and western Marquette
counties.

Expect the pcpn to diminish w-e on Thu night as the
shortwave/dynamic support exit to the e. But clouds and some lighter
sn wl persist thru the night especially over the northern tier with
lingering cyclonic upslope northerly flow.

Fri thru Sat...Hudson Bay high pres bldg into the Upr Lakes in the
wake of the departing low pres will bring a drying trend to Upr MI
on Fri, with some clrg as the llvl flow becomes more anticyclonic.
There could be some lingering -shsn/shra mainly east of MQT in the
morning where cyclonic nw will hang on a bit longer. Lingering clds
and llvl n winds off Lk Superior wl hold down the rise in max temps,
especially near the lake. The combination of light winds/clrg skies
and pwat falling under 0.25 inch in the subsidence behind the shrtwv
wl allow temps on Fri night to fall into the chilly 20s over the
interior. A good deal of sunshine and h85 temps rebounding to near
4C on Sat will allow max temps to rebound as high as the low 60s
over the western interior away fm the cooling influence of the lakes.

Late Weekend...The medium range guidance indicates a shortwave in
the nrn branch flow wl push thru Ontario and drag a cold front
across the Upr Lakes on Sat night/Sun morning. Although there are
timing differences, all the models generally show an absence of
moisture inflow that wl diminish the potential for any significant
pcpn, especially since the sharper forcing ahead of the shortwave wl
remain to the n. Even if there is a return of at least some sunshine
with trailing high pres on Sun, a north wind off Lk Superior and h85
temps falling as low as -8C wl result in blo normal temps.

Early next week...Models coming into better agreement, particularly
the 00Z GFS and ECMWF, on timing of the next shortwave/low pres that
is fcst to approach fm the w with the next best chance of pcpn
appearing to be Mon night into Tue.
&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 132 AM EDT WED APR 19 2017

At KIWD and KCMX, conditions will gradually improve. At SAW, where
the wrly winds will downslope, mainly MVFR cigs are expected until
late with IFR late tonight. Enough low level mixing will persist to
minimize vsby reduction. High pressure building into the region with
drier air will bring improving conditions, to MVFR in the morning
and VFR by late afternoon.
&&

.MARINE..

Southeast gales to 35 knots over the e half of Lake Superior this
afternoon under the tight pres gradient ahead of a lo pres tracking
thru MN toward the Upper Lakes will diminish this evening following
the passage of the lo pres. In its wake, expect winds to shift to
the nnw up to 25-30 knots tonight before further diminishing and
veering to the ne on Wed as trailing high pres crosses Ontario/Lake
Superior. Depending on the track of another lo pres approaching the
Lower Great Lakes on Thu, ene winds up to 25-30 kts are likely then.
If the lo pres is deep enough, there could be some gales. As hi pres
builds back into the Upper Lakes late in the week following this lo
pres, winds will diminish under 25 kts on Fri and Sat. N winds could
increase up to 25 kts Sat night and Sun following a cold frontal
passage.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Gale Warning from 8 AM to 6 PM EDT Thursday for LSZ250-251-266-
     267.

  Gale Warning from 6 AM EDT /5 AM CDT/ to 3 PM EDT /2 PM CDT/
     Thursday for LSZ162-263.

  Gale Warning from 8 AM to 4 PM EDT Thursday for LSZ244>248-264-
     265.

Lake Michigan...
  Gale Warning from 5 AM to 2 PM EDT Thursday for LMZ248-250.

  Gale Warning from 5 AM to 1 PM EDT Thursday for LMZ221.

&&

$$

SHORT TERM...Ritzman
LONG TERM...Voss
AVIATION...JLB
MARINE...KC



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