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Area forecast discussion 
National Weather Service Marquette Michigan
513 PM EST Monday Dec 22 2014

Short term...(this evening through tuesday)
issued at 400 PM EST Monday Dec 22 2014

Upper Michigan is in a lull between waves of precipitation at this
time...with the next precipitation producer tied to the surface low
that currently stretches from eastern South Dakota to Omaha
Nebraska. Southeasterly flow ahead of this low continues to pull
warmer air into the upper Great Lakes area...with 3pm temperatures
in the middle 30s under mostly cloudy skies and fog over the western
and central u.P. Over the east...dry low level air from lower
Michigan has nosed into that area and started to scattered the
clouds out. That drier air will try to work its way west into the
central County Warning Area and break up some of the low clouds and fog for this

As this low drifts southeast this evening...a couple shortwaves
rounding the base of the upper trough over the northern/Central
Plains will intensify the southern extent of the low over southern
Iowa and northern Missouri around 06z tonight and then lift the low
to the northeast and into east central Wisconsin by 00z Wednesday.
As this occurs...a surface trough will lift north into Upper
Michigan during the day. There will be a couple waves of
precipitation in the short term period. The first one will arrive
late this evening and into the overnight hours over the southern
u.P. As middle level warm air advection pushes north into the area and
weakens. The second and stronger wave of warm air advection will be
tied to the surface-700mb trough and moves into the region on
Tuesday. Models seem to be converging on the solution of the
heaviest band of precipitation moving north through the area from
middle morning through the late afternoon hours. While much of the County Warning Area
will see over 0.33 inch of liquid equivalent...expect the heaviest
quantitative precipitation forecast to be over the southeast third of the County Warning Area and also over the
north central where there will be some added terrain enhancement
with the east-northeast winds. 09z sref probabilities support the
idea of the heaviest precipitation falling over the central/eastern
County Warning Area.

Looking at model soundings for that time appears that
much of this precipitation will fall as snow...except for some
locations right along Lake Michigan and more specifically over
southern Menominee County. In those areas...there appears that there
will be a pocket of warmer air around 950-875mb that will warm the
low level temperatures up to 3c and eliminate most if not all snow
potential. But as you travel north-northeast along the Lake Michigan
shoreline...that amount of warm air really begins to
weaken...especially as the main area of precipitation wraps up. Many
of those areas over the south central and southeast have their
wetbulb temperatures within the vertical profile struggling to rise
above 0c...which would indicate as that moderate precipitation
begins to fall it would cool towards that. Thus...will trend the
forecast to mainly snow over the rest of the southeast and eastern
part of the County Warning Area as that heaviest precipitation rotates north through
the area during the day tomorrow. But as the heavy snow shifts
north-northwest in the afternoon...the warmer air will spread into
the southeast u.P. Along/behind the inverted trough while a dry
slot moves in aloft. Think this warm air will arrive after the
heaviest precipitation (limit potential for that precipitation to change
to rain)...but it will transition any lingering precipitation to a
light rain or drizzle as ice crystals are removed from the clouds.
Since most of the forcing and cloud will be below the dgz...expect
snow ratios to be around the 10 to 1 range for much of the period
and will follow that for the forecast. With that precipitation type
expectation and location of the heaviest quantitative precipitation forecast...have snowfall amounts
in the advisory range for much of the County Warning Area. Think some of the areas
out west (and also where it mixes with rain) will be on the low end
of our advisory criteria (3in per 12hrs)...but otherwise have
snowfall amounts of 3 to 5 inches in most locations for late
tonight through Tuesday. With rates around one inch an hour over the
central/eastern County Warning Area (during the late morning through middle afternoon
time period) think the accumulation will be fast enough to make for
hazardous travel in those areas during the early evening commute.
Winter Weather Advisory has already been issued for overnight
tonight through Tuesday...with a focus on the snow for Tuesday.

Long term...(tuesday night through monday)
issued at 511 PM EST Monday Dec 22 2014

Highs will remain in the 30s through the day Friday...with plenty of
going on precipitation wise this period. Slushy to wet roadways will greet
Holiday travelers through Friday...unless a quick burst of snow

Initially have the exiting surface low shifting from WI at 00z
Wednesday...shifting across Lake Michigan overnight into
Wednesday...becoming a part of the next low nearing from the Tennessee
Valley Wednesday morning. Drizzle/freezing drizzle will linger
through Wednesday over the east third of the County Warning Area...before changing to
snow late in the day.

Although there are still some discrepancies in even the Wednesday
night forecast...I did take out the mention of the low pushing northward
over east lower Michigan and Lake Huron late Wednesday into Wednesday evening
for the east half of Upper Michigan in the severe weather potential statement. The 22/00z European model (ecmwf) is
stronger/more wrapped up...and as a result keeps wrap around precipitation
Wednesday night into Thursday over or just east of the County Warning Area. The 22/12z
run was slower...and still kept much of the precipitation around Luce
County and east. The 18z GFS went back to a slightly more west idea with
the precipitation. Still looks like the counties along Lake Michigan...and Luce
County will be the main impacts...with some lake enhancement over north
central Upper Michigan. If the 18z GFS pans out...more significant changes
back to our previous forecast/severe weather potential statement discussion will be needed. The 12z
runs however were more consistent on keeping the widespread precipitation east.

Low pressure tracking northeastward from the Central Plains Thursday
night through the upper Great Lakes late Friday afternoon and Friday
night will bring the potential for widespread light to moderate
snowfall to all of Upper Michigan. There is still plenty of
discrepancy...with the 22/12z European model (ecmwf) keeping much of the precipitation over
the west third to half of the County Warning Area. The GFS is a bit more
generous...with a healthy swath of 0.1in liquid. Added the light to
moderate snow potential to the severe weather potential statement for Holiday travelers. Rain may
mix in over Lake Michigan Friday afternoon...before much cooler air pushes
in across the entire area Friday night. 850mb temperatures west at 12z
Saturday could be around -16c on a favorable northwest wind...extending
snow over the west into Sunday.

Aviation...(for the 18z tafs through 18z Tuesday afternoon)
issued at 1257 PM EST Monday Dec 22 2014

MVFR to IFR ceilings cover much of Upper Michigan as moist
southeasterly flow is occurring ahead of a low pressure system in
eastern South Dakota. At ksaw...ceilings and visibilites are lower
due to the favorable upslope wind direction. Expect these lower
clouds to remain into the evening hours...although they may raise
some towards late afternoon as drier air from lower Michigan
attempts to work into the area. Had the greatest confidence at
conditions staying at or below MVFR...but there could be a period of
VFR ceilings if the drier air can work into the area.

Snow will work into the area overnight into Tuesday as the low
pressure system lifts northeast towards the area. There will likely
be two surges of precipitation with this low...the first coming
during the overnight hours and the second arriving by late morning
or early afternoon. The second wave will produce the strongest snow
and did drop ksaw down to LIFR visibilites to account for that
moving through late in the taf period.

Marine...(for the 4 PM Lake Superior forecast issuance)
issued at 400 PM EST Monday Dec 22 2014

A low pressure system over the Missouri River valley will lift
northeast on Tuesday through eastern Upper Michigan while
weakening. Winds will turn to the east-northeast tonight and
continue through Tuesday. While most locations will see winds in
the 20-30kt range...there may be a few gale force gusts to 35kts
over Western Lake Superior. As the low continues to weaken on
Tuesday night...another low will develop in the lower Mississippi
Valley. This low will quickly lift northeast on
Wednesday...crossing Lake Huron on Wednesday night and moving into
northern Quebec on Thursday. At this time...expect northerly winds
to stay below 25kts over Lake Superior during that period. Another
low will take shape in the Central Plains on Thursday night and
then move northeast through the upper Great Lakes region on Friday
night. Northeast winds up to 30 knots are expected Friday night into
Saturday behind this low.

MQT watches/warnings/advisories...
Upper Michigan...
Winter Weather Advisory from 1 am EST /midnight CST/ to 7 PM EST
/6 PM CST/ Tuesday for miz001>007-009>011-084-085.

Winter Weather Advisory from 11 PM EST /10 PM CST/ this evening
to 4 PM EST /3 PM CST/ Tuesday for miz012>014.

Lake Superior...
Lake Michigan...


Short term...srf
long term...kf

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