Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 231930

Area Forecast Discussion
National Weather Service Marquette MI
330 PM EDT Thu Mar 23 2017

.SHORT TERM...(Today and tonight)
Issued at 326 AM EDT THU MAR 23 2017

Upper air pattern consists of a 500 mb ridge over the plains and a
trough in the western U.S. this morning. There is also a shortwave
over Saskatchewan and Manitoba. The trough will move east into the
central plains on Fri with the area on the top of the upper ridge
through tonight. Weak 850-500 mb q-vector convergence moves across
the area through tonight. Deeper moisture tries to move through this
morning and then returns again tonight.

Complicated forecast with pcpn types for tonight. Looked at some
soundings and they all point to a warm layer aloft over a lower
layer of air that is around freezing. This will mean that most of
the pcpn tonight will be in a rain/freezing rain form. Right now,
not comfortable going with an advisory for freezing rain as the sfc
temperatures continue to be tricky being one or two degrees either
side of freezing. If temperatures are above freezing, there would be
no problem. Below freezing, could see up to 0.25 inch of ice. The
temperatures depend on how much we warm up today and then also
depend tonight on how much we evaporatively cool as the dry air at
the sfc will have to moisten up when pcpn starts. Will continue with
a special weather statement for now and mention the icing potential.
Will go with dry dew points into this afternoon. For this morning,
dry air continues to make a dent on the pcpn headed this way as very
little is hitting the ground in Wisconsin and eastern Minnesota.
Will still keep slight chance pops in for this morning and early
afternoon for this.

.LONG TERM...(Friday night through Thursday)
Issued at 327 PM EDT THU MAR 23 2017

A split upr flow wl dominate areas near the Cndn border thru the
coming week. Recent model trends indicate more aggressive mid lvl
drying associated with a nrn branch shrtwv rdg axis/hi pres in
Ontario wl push the tight mstr gradient on the nrn flank of a closed
lo embedded in the srn branch flow dominating the CONUS and tracking
toward the Lower Great Lks farther to the s on Fri ngt/Sat, reducing
the potential for freezing ra/icing during this time. However, as
the closed lo drifts toward srn Lower MI later in the weekend
following the passage of the shrtwv rdg/sfc hi pres to the e toward
Quebec, more mid lvl mstr and the potential for some light freezing
rain wl return. A bdlg upr rdg/sfc Hudson Bay hi pres wl then bring
a drying trend mid next week, but more pcpn may return later in the
week depending on the track/timing of another srn branch closed lo
moving thru the scentral Plains. Expect temps thru the medium/
extended range to average above normal, mainly due to relatively
warm overngt temps.

Fri night/Sat...Upr MI wl be situated near the edge of a sharp mid
lvl mstr gradient btwn a srn branch slow moving closed lo moving
near the mid MS River Valley and dry hi pres moving thru nw Ontario
under an upr rdg axis in the nrn branch flow dominating srn Canada.
The latest model runs have trended toward more aggressive mid lvl
drying as a more expansive sfc hi pres in Ontario depresses farther
to the s the axis of deeper mstr associated with the warm fnt
extending fm the srn branch lo into the Lower Lks. As a result, pops
wl be mainly confined to the scentral. Fcst sdngs for this area
continues to show an elevated warm lyr above a near sfc based invrn
with sfc temps not far fm 32, so some freezing rain/drizzle will
be psbl. An upslope ene wind into the ncentral may also cause some
light drizzle/freezing drizzle in these areas depending on the
degree of near sfc drying within the shallow sub invrn lyr.

Sat ngt thru Mon ngt...Although there are some differences among the
medium range guidance, these models in general show another shrtwv
moving within the srn branch trof over the sw states kicking the
closed lo in the mid MS River Valley up to srn Lower MI on Sun. As a
result, mid lvl mstr is fcst to expand slowly back into the Upr Lks
beginning Sat ngt as the sfc hi pres in Ontario shifts into Quebec.
The main fcst challenge is that the llvl flow wl remain out of the
ene, which wl act to maintain some colder near sfc temps blo an
elevated warm lyr with h85 temps above 0C, allowing the potential
for more freezing rain, especially at ngt in the absence of any
insolation/hier early spring sun angle. Fortunately, the sharper
deep lyr forcing is progged to remain to the s, so there should be
no sgnft qpf/icing.

Extended...An upr rdg axis in the nrn and srn streams is fcst to
build back into nw Ontario and the mid MS River Valley the middle of
next week, allowing a Hudson Bay sfc hi pres to expand into the wrn
Great Lks. So after any lingering pcpn ends by early on Tue, expect
dry wx to prevail into at least early on Thu, when some of the
longer range models hint another srn branch closed lo may aprch fm
the sw.

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 135 PM EDT THU MAR 23 2017

The main aviation concerns over the next 24 hour will be lowering
ceiling and visibilities as rain and freezing rain move across
Upper Michigan tonight into Friday morning. KSAW will have the best
chance at seeing freezing rain develop tonight and linger through
much of the overnight hours. Further west at KIWD/KCMX, confidence
is not as high, as wet-bulb temperatures look like they will remain
just above freezing, so have opted to maintain the trends of the
inherited TAFs and keep mentions of rain. Overall, as precipitation
moves across the area tonight ceilings are expecting to drop rapidly
down into the LIFR category late tonight as dry air erodes as the
low-level saturate. Do not expect these ceilings to improve much
through the morning hours on Friday as low-levels will remain fairly
saturated and winds veer around to the northwest.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 327 PM EDT THU MAR 23 2017

The strongest southerly winds will be confined to the eastern half
of the lake with speeds of 20 to 30 knots. These winds will diminish
to around 5 to 10 knots and veer to the west overnight into Friday
morning. West winds will veer north-northeasterly and increase to 20
to 25 knots through the afternoon hours on Friday. Then expect ne
veering e winds to increase up to 25 to perhaps 30 kts on Fri night
into Sun under the tightening pres gradient between hi pres passing
from Ontario into Quebec and lo pres in the lower Great Lakes. The
strongest winds are most likely over western Lake Superior, where
the lake topography will enhance the ene flow. As these features
weaken and exit to the e, winds will diminish on Sun and Mon. Winds
on Tue should remain relatively light as hi pres builds into Ontario.

Upper Michigan...
  Winter Weather Advisory from 11 PM EDT /10 PM CDT/ this evening
     to 11 AM EDT /10 AM CDT/ Friday for MIZ004>007-009>014-084-

Lake Superior...
Lake Michigan...


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