Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 212002

Area Forecast Discussion
National Weather Service Marquette MI
402 PM EDT Tue Mar 21 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 401 PM EDT TUE MAR 21 2017

Deep upper trough has moved across eastern Canada but ridging is
already building upstream over western North America. Sfc cold front
crossed Upper Michigan this morning and the cold air continues to
sweep in this aftn. Certainly cold enough for lake effect but it
also very dry upstream. Thus, have seen lake effect snow showers
spread well inland helped out by daytime heating/instability while
snow showers and even cloud cover over northwest cwa and most
recently into ncntrl cwa have diminished. NW-NNW winds have been
gusty behind the front with gusts many areas over 30 mph today and
over 40 mph across Lk Superior. Temps as of late this aftn have
fallen below the freezing mark over all of Upper Michigan except
far scntrl. Dry air upstream is really taking toll on ongoing snow
showers. Expect current isold-scattered snow showers to continue
diminishing late this aftn and possibly tapering off to flurries
by early this evening.

Despite dry air overhead, expect lake clouds and some snow showers
to redevelop later evening and overnight with nighttime cooling over
mainly ncntrl cwa with N winds and temps at top of inverion/h9 down
to at least -15c. Low inversions will result in light snow amounts
to 1 inch or less in most locaitons, though if snow showers persist
any one area later tonight there could be accums up to 2 inches. As
it looks now, best chance of stronger convergence and persistent
snow showers would be far eastern Marquette county and mostly across
Alger county. Where skies become clear and stay that way through the
night, min temps could drop to around zero as dry airmass tied to
incoming high pressure dominates away from lake effect processes.
Leaned on GEM regional for min temps. That model typically does very
well with radiational cooling situations and shows temps over
interior west and maybe far eastern Luce county dropping to zero to
5 below.

NNW flow and moisture to h9 will keep lake clouds and flurries going
on Wed morning, mostly to the east of Marquette. Eventually h9 winds
back more WNW in the aftn which will disrupt the lake effect as dry
air is advected into the lake effect convective layer. Otherwise,
with the 1035-1040mb high settling overhead, expect lake breezes
near the Great Lakes. Temps will stay near 30 where winds come off
the chilly lake waters and even ice cover in some NSH areas (near Lk
Superior and northern Lk Michigan and into the eastern cwa). Temps
inland west and toward WI border will rise into the mid 30s and
maybe even upper 30s with enough sunshine.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 328 PM EDT TUE MAR 21 2017

The most sgnft challenge in the longer term remains the potential
for mixed pcpn/some freezing ra in the Thu ngt/Fri time period to
the n of a warm fnt associated with a srn branch closed lo fcst to
lift enewd fm the srn Rockies toward the OH River Valley this
weekend. Overall confidence is lo into this weekend because the fcst
wl depend on the interaction btwn this closed lo and hi pres
expanding into nw Ontario under a separate nrn branch flow that wl
prevail acrs srn Canada. Although Wed ngt wl be quite chilly under
passing sfc hi pres, overall temps into next week should run aoa
normal due mainly to warm overngt temps.

Wed ngt...The combination of incrsg hi clds sprilling over an aprchg
upr rdg axis and an incrsg sly flow on the wrn flank of the sfc hi
pres retreating toward the ern Great Lks wl limit the diurnal temp
fall. Expect the lowest temps over the interior e closer to the
departing hi and lighter winds/core of drier air with pwat holding
in the 0.10-0.25 inch range thru the ngt. Dropped min temps toward
the lo end of guidance in this area.

Thu...Some of the latest models are generating some lgt pcpn over
the area as the incrsg sly flow/waa btwn the departing hi and a nrn
branch lo pres tracking thru far nw Ontario results in quite a bit
of mid lvl moistening. But the acyc, dry llvl flow wl limit
pops/qpf. Given these limitations and passage of sharper deep lyr
qvector cnvgc to the n closer to the Ontario lo/associated shrtwv
track, suspect the drier 12Z NAM model is on the right track. But
the fcst wl include some lo chc pops over the w half for mainly some
aftn light ra.

Thu ngt into Sat...As a closed lo over the srn Rockies embedded in
the srn branch flow dominating the CONUS shifts slowly toward the
mid MS River Valley, guidance indicates an area of pcpn wl dvlp on
Thu ngt over Upr MI to the n of its accompanying warm fnt that wl
extend into the Lower Lks. There remain some differences as to how
far n the main, most persistent waa/mid lvl fgen pcpn band wl drift
on Thu ngt into Fri as well as the thermal profile/ptype/impact of
llvl evaporative cooling and then on how quickly expanding sfc hi
pres over scentral Canada under the large scale subsidence behind
the passing nrn branch shrtwv wl advect drier air into the Upr Lks
and push this pcpn band to the s on Fri into Sat. A consensus of
recent model runs show the most persistent waa pcpn band wl impact
mainly the scentral closer to the axis of sharper h85-7 fgen. Since
h85 temps are fcst to rise above 0C over the area and lingering llvl
dry air wl allow for evaporative cooling, there is the potential for
freezing ra/some ice accumulation before diminished evaporative
cooling with llvl moistening on Fri allows the pcpn to change to
mainly ra. Pcpn chcs wl then diminish on Fri ngt into Sat as the nrn
branch sfc hi pres expands into nw Ontario. Some of the guidance
indicates some lgt pcpn may linger on Sat over the ncentral with an
upslope ene wind on the srn flank of the Ontario hi pres.

Extended...Uncertainty lingers into Sun related to whether and how
far to the n the srn branch closed lo wl drift. The GFS remains the
most aggressive at lifting a stronger closed lo farther to the n and
causing more wdsprd mixed pcpn changing to ra over the area
following the passage of the hi pres and retreat of the core of the
dry air into Quebec. For next Mon/Tue, pcpn chcs wl linger as many
of the extended models show a disturbance tracking thru the Upr Lks.
But much uncertainty remains on the track/intensity of this feature
and the impact on the mslp field, so no changes were made to the
consensus fcst.

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 152 PM EDT TUE MAR 21 2017

At IWD and CMX, conditions have already improved as very dry air
upstream moves over Lk Superior and Upper Michigan. Both of those
sites will see cigs around 030 or higher this aftn along with
minimal vsby reductions as light snow comes to an end. Only a few
clouds will linger late this aftn into tonight as air remains dry
closer to approaching high pressure ridge.

At SAW, expect more persistent snow showers through late this aftn
before dry air eventually takes toll on ongoing lake effect.
Conditions will mostly be MVFR through the aftn, though brief IFR
vsby is possible during heavier snow showers. Clouds should scatter
out by early evening as the dry air moves in. Then later tonight
into Wed morning expect MVFR to lower VFR clouds and flurries to
return as winds turn out of the N off Lk Superior. Skies will
graudally clear out on Wed aftn though it may take some time as
onshore winds persist off Lk Superior.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 401 PM EDT TUE MAR 21 2017

NW gales to 35 kts over eastern Lk Superior will diminish this
evening. Winds will continue to diminish to less than to 25 kts late
tonight and to 20 kts or less on Wed as high pressure settles
overhead. S winds up to 25-30 kts will be possible late Wed night
into Thu under the tightening pres gradient on the western flank of
hi pres departing to the e. Expect winds to diminish on Thu night
thru Fri as a flatter pres gradient dominates. Expect ne winds to
increase up to 25-30 kts on Fri night into Sat night under the
tightening pres gradient on the southern flank of hi pres building
into Ontario. Depending on if and how quickly the Ontario hi pres
builds toward the area on Sun, winds may diminish then.


Upper Michigan...
Lake Superior...
  Gale Warning until 2 AM EDT Wednesday for LSZ249>251-266-267.

Lake Michigan...


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