Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Marquette Michigan
348 PM EST Wednesday Nov 26 2014
Short term...(today and tonight)
issued at 610 am EST Wednesday Nov 26 2014
..moderate to heavy lake effect for north flow areas tonight...
Radiosonde observations and WV/infrared satellite loop indicate western Continental U.S. Ridge and
central and eastern Continental U.S. Trough. Two main jet cores...a strong
near 200 knots 300 mb jet racing SW-NE from southeast United States to
Quebec and another 150 knots 300 mb jet diving northwest-southeast into the Southern
Plains. Lead jet is supporting the strong system moving up the
eastern Seaboard while plains jet is supporting compact low
pressure system near Omaha Nebraska producing swath of precipitation from Minnesota
into MO. Farther north...shortwave working along in northern stream
pushing into northwest Ontario is resuling in swath of light snow
northern Minnesota into Northern Lake Superior. Another two shortwaves within
the northern stream are over dropping southeast over Saskatchewan and
Manitoba and also over northern Manitoba. Though low pressure system
over plains stays south of here...weak trough is extending to the
northeast of it will affect weather over Upper Michigan today. Other
main surface feature is Arctic high pressure expanding across Canadian
prairie provinces and nosing a ridge over northwest Ontario to north
of Lake Superior and also into northern plains.
Weak gradient over Upper Michigan and some areas of clear skies has
allowed temperatures to fall to around 10 below over interior sections of
central and east County Warning Area this morning. Quiet over the area as lake effect
clouds are north of Keweenaw thanks to SW winds ahead of trough set
up over Western Lake Superior. Weak srly flow is bringing low clouds
into Lake Michigan zones and over parts of east County Warning Area.
Later today...expect the trough over Western Lake Superior to sink
slowly over Keweenaw and far West County warning area this afternoon...probably not until
after 21z at kiwd. This will occur as deeper layer moisture/forcing
spreads over western Upper Michigan as the two shortwaves upstream in
Canada and the one just to the west of here move across. Soundings
indicate shallow layer up to h9 for favorable wind trajectories for
les over western County Warning Area this afternoon. By 00z over far West County warning area...north-northeast winds
to h9 with temperatures near -15c support lake enhanced snow as the better
large scale forcing crosses. Slr/S increase to 20:1 as most lift is
within dgz. Enough instability and sharp convergence developing with
larger scale forcing along with affects from shortwave will support
period of heavier snow in the evening far west...from iwd to White
Pine/Porcupine mts. Additionally...once the shortwaves exits by
midnight...soundings show all of lake convective layer is within
dgz. Slr/S may reach 30:1 as winds are also diminishing at that
time. High slr/S could allow for good tack on snow later tonight.
Due to the heavy snow in the evening and the potential for a lot of
fluffy snow overnight into early Thanksgiving day...setup seemed
good enough to upgrade to lake effect warning for Gogebic/Ontonagon.
Only marginal snow amounts over the Keweenaw but with a period of
strong gusty winds to 30 miles per hour behind the trough this evening and the
fluffy snow issued a lake effect advisory to cover the snow and blsn on
a busier than normal travel day ahead of Thanksgiving.
Trough sinks into north central Upper Michigan this evening and that brings
at least a period of heavier les into Baraga and northern Marquette
coutnies. Similar to far West County warning area...sufficient instabiilty and
upslope north-northeast flow supported snow amounts up to 6 inches over Baraga
County and put out an advisory for tonight to cover that. Heaviest snow
expected for L'Anse area and especially over the favored higher
terrain of eastern Baraga County. Continued the advisory for
Marquette County that was issued on Tuesday afternoon...but with the
sharper low-level upslope flow and since the trough convergence will
be synced up with the shortwave...setup seemed good for lake
enhancement in the evening...especially over the higher terrain from
the Huron mts to Negaunee and possibly along the shore at Marquette.
North-northeast winds do become north-northwest-northwest fairly quick overnight tonight and the
shortwave will be exiting at that time as well. Thought the
potential for persistent heavier snow would be too low to do any
kind of upgrade to Marquette even though it should snow around
inch/hour rates in the evening. Wild card for Marquette County is
the stronger nearly winds/blsn. Could see gusts to around 30 miles per hour vicinity
of Marquette and Harvey late tonight and with the fluffy snow...that
could be big visibility reducer into Thanksgiving morning. Will let later
shifts decide on need for upgrade though. Setup for Marquette is
similar for Alger. Trough just arrives later tonight and heavier les
lingers into Thanksgiving longer. Heaviest snow focuses mainly over
western snow belts of the County.
Finally...south flow les still expected off Lake Michigan mainly
affecting far east County Warning Area. Convergence appears too weak to support
anything more than light snow accums into tonight with perhaps up to
a few inches. Lack of strong winds though will curtail blsn
issues...so did not see need for any headline for Schoolcraft or
Luce counties. Inland areas will also see some snow...but amounts
will be less than 1 inch due to limited overall moisture with the
system moving through this evening.
Long term...(thursday night through wednesday)
issued at 342 PM EST Wednesday Nov 26 2014
Thursday night...the lingering les will diminish as the surface ridge axis
slides through the western lakes and low level winds back to the SW.
With light winds and a period of clearing over the interior west
during the evening...temperatures will drop quickly to mins below guidance
before recovering overnight as clouds move in. Models were
consistent in bringing potential for some light snow into the west
late with the developing warm air advection pattern.
Friday...snow is expected to spread across the region with favorable
moisture advection and isentropic lift through the 850-700 mb
frontal zone. 3 g/kg moisture available in the 285k-295k layer
during the period of strongest lift is consistent with potential for
2 to 4 inches of snow with models consensus quantitative precipitation forecast of 0.10 to 0.20
inches and slr values from around 15/1-20/1. There is still some
uncertainty where the band of heavier snow will develop as the 12z
NAM brings greater amounts of precipitation into southern Upper Michigan compared to the
GFS and European model (ecmwf). There will also be the potential for a band of lake
enhanced snow off of Lake Michigan that could spread eastward from near
the Garden Peninsula into Luce County. Since the strongest low
level conv is expected to move steadily to the east...snow amounts
in any one location should be limited. However...confidence is lower
for the position/strength of this feature that could add several
inches to the snow totals.
Friday night into Sat...surface low pressure is forecast to spread from the northern
plains to the upper MS valley with continued warm air advection bringing
substantial 850 mb warming. NAM/GFS 285-295k isentropic forecasts
suggest that the strongest lift and deepest moisture will remain
across Lake Superior and far northern Upper Michigan. With a prominent 850-700
mb dry layer developing to the south...freezing drizzle will be
possible along with some light snow or flurries as ice nuclei become
more scarce. Any precipitation amounts are expected to be light with
only a few hundredths of an inch at most. There may also be enough
900-700 mb warming into the area of deeper moisture for some
Sat night and sun...low pressure lifting NE toward James Bay Sat night
will drag a cold front through the northern lakes with much colder air
moving in on northwest winds. With 850 mb temperatures falling to near -18c...les
will be likely for northwest wind snow belts. A limiting factor for heavier
snow will be substantial 850-700 mb drying with backing and
increasing anti-cyclonic low level winds from late sun into Sun night.
Mon-Wed...the GFS/gefs and European model (ecmwf) were in reasonable agreement with
the pattern into next week with high pressure building into the region
Monday into Monday night bringing diminishing les. Another middle level and
surface trough moving through Tuesday into Tuesday night could bring some light
snow to the area. The models have trended toward keeping colder
across region that would keep any precipitation as snow with maximum temperatures
recovering into the middle 20s to around 30 by Tuesday and Wednesday.
Aviation...(for the 18z tafs through 18z Thursday afternoon)
issued at 1245 PM EST Wednesday Nov 26 2014
Disturbance and associated surface trough will swing across Upper Michigan this
aftn/evening. Increasing lake enhanced snow will affect all
terminals as the trough pushes across the area...beginning latest at
ksaw. At kiwd/kcmx...IFR conditions are expected to become the
prevailing condition this afternoon...though some LIFR will occur as
well. Wind flow this evening will favor kiwd for heaviest
snow/lowest conditions...and LIFR will likely prevail there this
evening while kcmx remains IFR. Lowering inversion/drying air mass
will result in diminishing lake effect snow later in the period...
allowing impovement to VFR. At ksaw...VFR conditions will prevail
this afternoon. With trough passage...expect conditions to fall to IFR late
this evening along with periods of LIFR. As winds begin to back late
tonight and especially Thursday morning...lake effect snow will shift
mostly east of ksaw...allowing improvement to MVFR.
Marine...(for the 4 PM Lake Superior forecast issuance)
issued at 348 PM EST Wednesday Nov 26 2014
A surface trough will slide south over Lake Superior tonight.
Behind the trough...expect northerly winds to 30 kts. Winds will
then diminish to under 20 knots west to east Thursday/Thursday night as high pressure ridge
arrives. With another cold front pushing across the upper lakes Sat
night...expect increasing S/SW winds to 15-25kt Friday into Sat ahead
of front. Behind the front...northwest winds may reach 20-30kt late Sat
night and sun and increase to gales by Sun night into Monday.
lake effect Snow Advisory from 10 PM this evening to 1 PM EST
Thursday for miz006.
Lake effect Snow Advisory from 7 PM this evening to 7 am EST
Thursday for miz004.
Lake effect Snow Advisory from 7 PM this evening to 10 am EST
Thursday for miz005.
Lake effect snow warning until 1 PM EST /noon CST/ Thursday for
Lake effect Snow Advisory until 7 am EST Thursday for miz001-003.