Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Grand Rapids Michigan
310 PM EST sun Feb 1 2015
synopsis/short term/long term/Hydro/climate
issued at 305 PM EST sun Feb 1 2015
A major winter storm will continue to impact the region through
early Monday morning before departing. Blowing and drifting snow
will continue to lead to dangerous travel especially near and
south of I-96 and toward I-94. Storm total accumulations
(including what has fallen already) by Monday morning will range from a
couple inches along Route 10 to as much as 12 to 16 inches along
I-94. Wind chill readings will frequently be below zero for most
mornings this week. Occasional snow showers are possible through
middle week with additional snow showers once again for the weekend.
Short term...(this evening through Tuesday night)
issued at 305 PM EST sun Feb 1 2015
Storm term discussion: little change to our existing
forecast...with continued snow and blowing snow through tonight
with snow covered roads and drifting snow leading to dangerous
travel. Residual impacts to the Monday morning commute are
likely...especially for secondary and rural roads where unplowed
snow may be a significant problem for travel. The GFS has led the
way with this system and will continue to be followed closely. WV
and infrared imagery show the western edge of this storm still extends
into eastern Nebraska and western Iowa...so still a ways to go yet
as the deformation zone works into the southern County Warning Area tonight.
Looking at the 12z GFS multi- layer fn vector convergence from
h925 up to h500...there are indications that both the I-94 region
and also a separate area from South Haven to GRR will be
underneath deep forcing...with some mesoscale heavy bands possible
with enhanced snowfall rates of 1" or more per hour. That
said...this is a very fine snow...and settling/compression
undoubtedly will occur. Nevertheless...amounts will continue
piling up through tonight as the worst of the storm is expected to
manifest from 21z through 06z.
The dry slot is expected to move as far north as extreme Southeast
Michigan...and as such...weakly positive or even negative epv on
the nose of this dry slot will impact areas along/east of an azo to
lan line through 06z. This will be coincident with complete
saturation through the column and also strong fgen with the
deformation zone forecast to move into the southern/southeast County Warning Area by both
the NAM and GFS. All this adds confidence to steady snowfall rates
of around or even a bit more than 1"/hour tonight near and south
of I-96 and particularly near/east of an azo to lan line. By 00z
or shortly thereafter...the dgz splits into two regions as low
level temperatures continue to decline...so a "bonus" region for
dendritic growth will exist for a short time before the storm
winds down. Not sure how much this will add to the accums...but
some enhancement is possible.
Amounts so far near/south of I-96 have generally been 4 to 8
inches. An additional 4 to 8 inches is expected tonight...bringing
storm total accumulations in the 8 to 16 inch range. This is based
on a weighted blend of all available short/long range models as
well as wpc guidance. North of I-96...where an advisory is in
place...storm total amounts will tail off to around 8 inches
across the very southern portion of the advisory area to as little
as 2 or 3 inches near Route 10.
Winds...as anticipated...have been on the upswing today. GRR and
mkg have already gusted to 30 knots or greater. Although hrrr wind
gusts are too high by 5-10 knots...will keep the general theme in
mind with our grids and hold onto gusty winds through at least
06z. Wind gusts to 40 miles per hour are possible based on trends this
afternoon...mainly from mkg to GRR to lan...where NE flow seems to
be maximized in these types of systems. Blowing and drifting
snow...especially in rural/open areas...will be a significant
problem for the duration of this event given the dry nature of the
snow and the wind gusts.
Short term discussion: after the storm moves out around
12z...expecting a much quieter Monday aside from some lake effect
snow showers that will blow inland as winds back from north to west with
a ridge moving into the Ohio Valley region. Accums are only
expected to be a few tenths of an inch. By Tuesday night...a
clipper will be moving through the Midwest and will spread some
light snow into Southern Lower Michigan. Light accumulations look
probable at this point based on medium range model quantitative precipitation forecast.
Long term...(wednesday through sunday)
issued at 305 PM EST sun Feb 1 2015
A few light snow showers and flurries will linger Wednesday as a
strong upper level pv anomaly moves across the northern Great Lakes
region and in the wake of the Arctic cold front. Widespread sub zero
readings are quite possible by early Thursday morning as a result of
clearing skies and a dry airmass in place as high pressure builds in
in conjunction with with extensive snow cover across much of our
forecast area by then.
High pressure will bring fair weather Thursday but it will be quite
cold with maximum temperatures only reaching the teens. Temperatures will moderate
Friday and Saturday as the upper level pattern becomes zonal. A
cold front dropping down from the northwest will bring a chance of light
snow Friday night and/or Saturday followed by the arrival of another
colder airmass by Sunday.
Aviation...(for the 18z tafs through 18z monday)
issued at 1145 am EST sun Feb 1 2015
A snowstorm will continue in progress this afternoon through this
evening resulting in widespread LIFR conditions through late this
evening due to moderate to heavy snow and blowing snow. Northeast
winds will continue to increase to 15 to 25 kts with frequent gusts
to around 30 kts late this afternoon and evening which will further
reduce visibilities in blowing snow. Light rime icing will be
possible generally below 2000 feet above ground level.
Conditions will gradually improve to IFR then MVFR during the early
morning hours Monday as the snow moves out and ceilings begin to
improve. North winds will remain brisk at 15 to 25 kts overnight.
Conditions will gradually improve to VFR middle to late Monday morning
when wind speeds will diminish a little bit out of the north-northwest at 15 to
20 kts. Conditions should then remain VFR through 18z Monday.
issued at 300 PM EST sun Feb 1 2015
Ice formation on rivers is the immediate Hydro concern. Arctic air
has arrived with the coldest temperatures expected Monday with similar
temperatures for Thursday as another Arctic front moves through. Lows
tonight and Monday morning will drop into the single digits. Cold
temperatures are expected through the rest of the week so ice
development will continue...plus the snow that falls through
Monday morning will also help with ice development. Ice is
expected to remain fairly stable as temperatures stay chilly.
issued at 153 PM EST sun Feb 1 2015
Feb 1st record snowfall for GRR is 6.1" in 2001.
Feb 1st record snowfall for lan is 6.2" in 1967.
Feb 1st record snowfall for mkg is 14.2" in 1965.
While official long term snowfall records are not maintained
outside of these local climatological data (lcd) stations...snowfall
amounts of 10" or more in a single calendar day will likely rank
in the top 10 or top 5 for the entire month of February for many
Michigan...Winter Storm Warning until 6 am EST Monday for miz056>059-
Winter Weather Advisory until 6 am EST Monday for miz037>040-