Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 221958

Area Forecast Discussion
National Weather Service Marquette MI
358 PM EDT Wed Mar 22 2017

.SHORT TERM...(This evening through Thursday)
Issued at 348 PM EDT WED MAR 22 2017

As high pressure continued to push east across the area today, lake
effect snow showers east of Marquette diminished rapidly throughout
the late morning and early afternoon. Afternoon water vapor imagery
shows a fairly amplified pattern with a longwave trough across the
western CONUS, a ridge extending northward towards the Canadian
border and spanning much of the central CONUS, and another longwave
trough across the east. As the westernmost longwave trough slowly
continues to move east across the Rockies, a lee cyclone has begun
to develop across the northern Plains with a swath of mid-level
moisture returning northward into the northern Plains and upper
Mississippi River Valley.

As we remain under the influence of surface high pressure, expect
the pleasant weather to continue through the rest of the evening!
Late tonight into Thursday morning, as warm air advection begins to
lift across the area, expect skies to become cloudy from west to
east across the area. Overnight temperatures will be highly
dependent on how fast/thick the mid and upper level clouds come
in/will be. Confidence is highest in temperatures across the east
where cloud cover will be last to arrive and ample radiational
cooling will allow temperatures to drop into the lower teens.

As the leading edge of the warm air advection/isentropic accent
approach area from the southwest Thursday morning, expect the a band
of snow showers to develop across the western U.P. and gradually
move across the central and east through mid/late morning and
afternoon hours, respectively. Forecast soundings show ample dry low-
level air, so the initial timing for precipitation onset across the
west looks like it will occur after midnight tonight into the early
morning hours. With temperature profiles being between -10 and 0C,
do not expect the SLRs to be terribly impressive, but upwards of
half an inch of wet, slushy snow will be possible across the west
through the morning and into the central and eastern U.P. later in
the morning/afternoon. Expect the snow to transition over to rain in
locations that see temperatures climb above freezing through the
afternoon, and possibly even a break in precipitation during the day
across the west.

.LONG TERM...(Thursday night through Wednesday)
Issued at 358 PM EDT WED MAR 22 2017

Overall confidence in the longer term fcst is lo because the wx into
early next week wl depend on the track/intensity/timing of a closed
lo in the srn branch flow dominating the CONUS, a hi pres passing
thru scentral Canada under a separate nrn branch flow, and the sharp
gradient of mstr btwn these features that wl be near Upr MI thru the
weekend. Because some llvl cold air associated with the hi pres may
bleed into/linger over Upr MI, there could be some mixed pcpn
including freezing ra at times. However, temps into at least early
next week should run aoa normal due mainly to relatively warm
overngt temps. There is likely to be a drying trend next Tue/Wed as
an upr rdg builds over the wrn Great Lks, but there is uncertainty
as to how much cold air wl return on the srn flank of accompanyin hi
pres bldg into nw Ontario.

Thu ngt into Fri ngt...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 sgnft 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/Fri ngt. Since h85
temps are fcst to rise above 0C over the area and lingering llvl dry
air wl allow for evaporative cooling on Thu ngt that allows for sub
freezing near sfc temps under the elevated warm lyr, there is the
potential for freezing ra/ice accums then before diminished
evaporative cooling with llvl moistening on Fri allows the pcpn to
change to mainly ra.  Considering model qpf, there appears to be a
potential for 0.10 to 0.20 ice accum on Thu night over the interior
w and central cwa. Opted to issue an SPS to highlight the potential
for this icing. Although the 12Z NAM shows more sgnft pcpn farther
to the n into Fri ngt, the bulk of the recent model runs indicate
the most persistent pcpn into Fri ngt wl occur over the scentral
closer to the area of deeper mstr with more aggressive mid lvl
drying over the nrn tier. Considering the far s placement of the upr
lo and the trend for the axis of h85-7 fgen to drift to the s with
time, the farther s model consensus seems on the right track for
Fri/Fri ngt. But Upslope ene winds on the srn flank of hi pres bldg
into nw Ontario ahead of a bldg nrn branch upr rdg axis over
scentral Canada may allow some lgt pcpn to linger a bit longer over
the hier terrain of the ncentral.

Sat into Mon...There remain sgnft differences as to how quickly and
far to the n the srn branch closed lo wl lift thru the weekend. In
general, the medium range guidance has trended toward a farther n
drift into Lower MI, which would allow a gradual return of deeper
mstr and expansion of pops to the n over Upr MI as the drying
influence of the Ontario hi pres diminishes with its shift into
Quebec. Since h85 temps wl be over 0C, accompanying pcpn should be
mainly liquid. The question remains as to how much and how long
colder/drier near sfc air associated with the departing sfc hi pres
wl linger acrs the area that could allow for some freezing ra.

Extended...As an upr rdg blds over the wrn Great Lks on Tue/Wed, the
longer range guidance indicates bldg hi pres in nw Ontario wl expand
over the wrn Great Lks and bring a drying trend to Upr MI. But there
are sgnft differences as to how much cold air wl spill into the area.

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 140 PM EDT WED MAR 22 2017

VFR ceilings and visibilities will prevail for the rest of the
afternoon and evening. Mid and high clouds will spread from west to
east overnight with winds becoming southerly at all terminals.
KIWD/KCMX have the potential to see a brief band of snow showers
move across the terminal Thursday morning, so have included mentions
of -SHSN along with MVFR ceilings/visibilities. Further to the east,
have opted to leave mentions of show showers out of KSAW for now as
it looks to occur towards the very end of this TAF period.
Therefore, will let subsident TAF issuance fine tune the potential
at KSAW. Otherwise, expect southerly winds to increase and become
gusty on Thursday.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 348 PM EDT WED MAR 22 2017

As high pressure continues to drop southeast of the area tonight,
winds will become southerly and increase to 15 to 25 knots by
Thursday morning. Expect the winds to increase through the afternoon
to around 25 to 30 knots. Expect s winds as hi as 30 kts, with a
few gale force gusts to 35 kts possible, on Thu evening over the
east half of Lake Superior to diminish on Thu night thru Fri as a
flatter pres gradient dominates. 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 by Mon will diminish.

Upper Michigan...
Lake Superior...
Lake Michigan...


SHORT TERM...Ritzman
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