Area Forecast Discussion
Issued by NWS Marquette, MI

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655
FXUS63 KMQT 240504
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
104 AM EDT Fri Mar 24 2017

.SHORT TERM...(This evening through Friday)
Issued at 402 PM EDT THU MAR 23 2017

This afternoon temperatures have been slow to warm, especially
across the interior central portions of the U.P. given the ample
cloud cover, as mid and upper level clouds continued to stream
northeast ahead of a developing lee cyclone across the High Plains
this afternoon. Current radar imagery shows returns beginning to
show up across much of Minnesota; however, given how dry the air
mass currently is only a few select sites are reporting
precipitation this afternoon.

The main forecast concern tonight through Friday is the potential
for freezing rain, and possibly some sleet, across much of Upper
Michigan tonight into the morning hours on Friday. This will likely
result in a slick commute during the morning hours. Models are in
good agreement with a convective band, currently developing in
central Minnesota, lifting northeast across much of Upper Michigan
tonight as warm air advection/isentropic lift increase and work
strengthen a mid-level baroclinic zone. A few of the models are
suggesting upwards of around or even great than 0.50`` of QPF with
this heavier band. However, given how dry the low-levels are,
currently thinking the models are likely overdoing amounts.
Therefore, have opted to run with a lower QPF, but given the thermal
profiles and expected wet-bulbing tonight this still resulted in
around quarter of an inch of ice accumulations across the central
portions of Upper Michigan. The highest ice accumulations are
expected to occur across the interior and central portions of the
area, especially across the higher terrain. These locations will see
more cooling this evening and once precipitation starts to fall, the
wet-bulbing process will allow for freezing rain to develop as warm
air advection aloft continues to stream northward. One concern is
that there may be periods when rain mixes in with the freezing rain,
and/or begin to transition over to rain towards the morning hours.
Therefore, there uncertainty still exists in the overall ice
accumulations. Further to the west, ice accumulations are still
possible; however, the thermal profiles point more towards a mix of
rain and freezing rain so ice accumulations are expected to be a bit
less. Across eastern portions of the area, a mixture of sleet and
freezing rain are expected to begin late tonight. Closer to the
lake, ice accumulations are expected to remain a bit less,
especially across western Gogebic county and north of Lake Michigan
as southerly winds should keep temperatures just above freezing.

Late Friday morning through the rest of the afternoon, warm air
advection will weaken as a weak back door cold front pushes south
across the area. This will allow the focus for additional
precipitation to be across south central and eastern potions of
Upper Michigan. The freezing rain will begin to transition over to
rain, with a few locations possibly seeing some snow mixed in the
afternoon near Lake Superior. Elsewhere, skies will remain cloudy.

.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 06Z TAFS through 06Z Friday night)
Issued at 102 AM EDT FRI MAR 24 2017

Expect conditions to deteriorate overnight as periods of rain at IWD
and freezing rain (SAW) or sleet/snow (CMX) results in low level
moistening and lower cigs. Expect mainly MVFR cigs should drop to
IFR and LIFR cigs by late tonight. Slight warming into Friday
morning should bring a transition to mainly rain at SAW/CMX. Drier
air moving in with nrly winds Friday will lift to cigs MVFR at
CMX/IWD by afternoon while upslope flow into SAW maintains IFR cigs.
&&

.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.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Weather Advisory until 11 AM EDT /10 AM CDT/ this morning
     for MIZ001>007-009>014-084-085.

Lake Superior...
None.
Lake Michigan...
None.
&&

$$

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



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