Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Marquette Michigan
548 PM EST Thursday Jan 29 2015
Short term...(this evening through friday)
issued at 331 PM EST Thursday Jan 29 2015
Cold front has blown through. Temperatures are falling steadily into the
upper teens west and in the 20s near Lake Michigan. Northwest winds are
gusting near 50 miles per hour close to Lake Superior and even above 30 miles per hour
farther inland. Attention is on snow amounts and low visibility tonight as lake
effect snow increases. Radar shows increasing echoes this afternoon. Had
some fzdz into early afternoon...but seems to have faded now as colder
air at h9-850 mb spills across Upper Michigan. Upstream the soundings from
12z showed inversions around h9 or maybe slightly higher. There is a
wave aloft producing light snow over Minnesota arrowhead and Western
Lake Superior and this disturbance swings across this evening. Expect
to see increasing les in northwest-north-northwest flow areas of north central Upper Michigan.
Soundings show majority of lake convective layer within the dgz so
that will help out accums...but strong winds will also act to break
apart snowflakes. Smaller flakes and gusty winds will lead to poor
visibility especially near Lake Superior where ice is just offshore.
Went ahead and issued a lake effect Snow and Blowing Snow Advisory for
Alger and northern Schoolcraft counties as expected increase of snow
showers will occur this evening when people will still be out
traveling. May see a few hour period where snowfall rates push up
toward 1 inch per hour. Even so...total snow amounts into late
tonight will only top out at 3 to 5 inches. Based on snow amounts
alone would not have went with the advisory...but given the gusty
winds/blowing snow and poor visibility along with expected snow amounts
thought it would be good to have advisory out for where heaviest snow is
expected this evening. Visibility at times this evening may fall to one-
quarter mile or less in the heavier snow showers. Snow amounts
elsewhere along Lake Superior will be held down by the lowering
inversions and drying moving in behind the disturbance. Large high
pressure currently over the Canadian prairies moving in will also
result in diminishing trend. By late tonight only les of note will
likely be in the snowbelts of Alger through Luce County...at a
diminished state compared to this evening. Lows tonight kind of
tricky given flow of lake clouds still around which will offset cold
air advection. Some zero readings possible with any clearing
late...especially away from Lake Superior in the scntrl and also in the
Les continues to diminish on Friday and should lift to only far
northern Luce County by afternoon as low-level winds back west with the
high moving in. Temperatures will only reach low to middle teens as the lake
effect clouds are replaced with increasing middle clouds tied to warm
air advection ahead of next system that will move over the
area on Friday night.
Long term...(friday night through thursday)
issued at 502 PM EST Thursday Jan 29 2015
A cold pattern is setting in for the long term portion of the
forecast as the flow over namerica will feature a West Coast ridge and
cntl/eastern trough. The resulting northwest flow into the Great Lakes will
result in a steady feed of Canadian air. While it will be cold with
temperatures below to at times much below normal...temperatures will not be unusually
cold for this time of year. As for precipitation...this is a dry pattern with
little in the way of synoptic precipitation expected. The cold will however
lead to persistent les off Lake Superior. Most the les will be
on the light side...but there will be the occasional boost due to
passage of shortwaves.
Beginning Friday night/Sat...shortwave embedded in the northwest flow aloft
will track from northwest Minnesota in the evening to northern lower Michigan by Sat morning.
At the same time...another stronger shortwave trough will swing into
northern Ontario. Upper Michigan will be impacted mainly by the weaker southern
disturbance. Although a band of modest qvector convergence is forecast
to slide across Upper Michigan Friday night into Sat morning on the cyclonic
side of the southern shortwave...accompanying isentropic ascent/moisture
inflow is relatively weak. Still...will probably see an area of -sn
spread across much of the area. For now...forecast will show generally
higher end chance probability of precipitation. Accumulations should range from 0.5 to 1.5
inches. Surface cold front will pass Sat morning. There should be the
typical quick burst of MDT to possibly heavy lake enhanced snow
accompany cold front onshore. Although 850mb temperatures fall to -20 to
-25c by 00z sun...quick transition to a more diffluent/anticyclonic
925mb northerly flow and a falling inversion to 4kft will limit les
intensity after the burst of heavier snow associated with cold frontal passage.
Snow accumulations Sat should be in the 1-2 to possibly 3
inch range. After early highs...temperatures will fall through the day as
brisk north to northwest winds usher Arctic air mass into the area. Gusty winds
will also create blsn in open areas near Lake Superior.
Sat night through Sun night...Upper Michigan will be dominated by Arctic
air mass with northerly low-level flow backing west-northwest. Low inversion
around 4kft combined with dgz being mostly eliminated by the cold
air mass will keep lake effect snow accumulations on the light
side...generally 1-2 to perhaps locally 3 inches per 12hrs. Only
item of note is the potential for land breeze to push out over Lake
Superior from around Munising eastward late Sat night/Sun morning as
pressure gradient/wind slacken. If this happens...a mesolow could spin
up over scntrl Lake Superior and lead to heavier snow near the
shore between Marquette and Munising...depending on the circulation
structure. Sat night could be particularly chilly over the east as
clouds/les could shift west if winds become easterly due to drainage
of cold air into that area off Ontario.
Monday...les will begin to shift out over Lake Superior as winds
back due to high pressure moving from the middle Mississippi Valley to
the Ohio Valley. By the end of the afternoon...les may only be affecting
Tue-Thu...medium range guidance is trending a little more robust
with the next shortwave diving southeast out of Canada. If this is a trend
that holds up...there will be a widespread -sn across the forecast area
Tuesday/Tuesday night with the potential for a period of more significant
lake enancement near Lake Superior. Whatever happens...a solid shot
of Arctic air with 850mb temperatures of -25 to -30c will surge into the
area behind the shortwave Wednesday into early Thursday. With loss of dgz and
low inversions setting up behind shortwave...les accumulations will
be light Wednesday into Thursday. Although light...the very cold air will result
in small snowflakes that are very effective at reducing visibility.
Lowest temperatures of the week should occur Wed/Thu.
Aviation...(for the 00z tafs through 00z Friday evening)
issued at 548 PM EST Thursday Jan 29 2015
Snow showers will diminish by late evening as high pressure and
drier low-level air arrive from the northwest. At ksaw...will have
lake effect snow showers into the evening and expect diminishing and
ending trend to snow showers overnight tonight. Winds will remain
gusty at all the taf sites until later tonight. Visibility mainly MVFR at
all the sites though may dip to IFR briefly in the early evening. By
late tonight into Friday...mainly MVFR or VFR flying conditions are
Marine...(for the 4 PM Lake Superior forecast issuance)
issued at 402 PM EST Thursday Jan 29 2015
Cold front has moved east of Lake Superior. Northwest-north gales to 45 kts
through the evening then these diminish to 35 kts overnight. Heavy
freezing spray as well. Gale and heavy freezing spray warnings are in
effect through late tonight. Winds diminish below gales by around
daybreak on Friday. Next push of gale winds expected behind another
cold front on Saturday into Saturday evening. Strongest winds over
east half of Lake Superior and there will be more heavy freezing spray.
Otherwise...winds are expected to remain 30 kts or less over Lake
Superior through the forecast period.
lake effect Snow Advisory until 5 am EST Friday for miz006-085.
heavy freezing spray warning until 7 am EST Friday for lsz264-
Gale Warning until 4 am EST Friday for lsz265>267.
Gale Warning until 1 am EST Friday for lsz263-264.
Heavy freezing spray warning until 5 am EST Friday for lsz263.