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Area forecast discussion 
National Weather Service Grand Rapids Michigan
329 PM EST Thursday Mar 5 2015

Latest update...
synopsis/short term/long term/Hydro

issued at 329 PM EST Thursday Mar 5 2015

Another cold night is expected tonight...then a moderating trend is
expected through the weekend and into next week. Highs tomorrow will
reach the 20s...with 30s over the weekend. By the middle of next
week we should warm into the 40s...with the southern portion of the
state nearing 50 on Wednesday and Thursday. Only light precipitation
is expected into early next week. Very weak systems moving through
the Great Lakes tomorrow and Saturday may bring brief periods of
light snow. Any accumulations each day should be an inch or less.


Short term...(this evening through Saturday night)
issued at 329 PM EST Thursday Mar 5 2015

Limited concerns through the short term. Northwest upper flow
remains in place...but temperatures will be moderating as the cold
core of air lifts out. The shortwave seen over the Dakotas this
afternoon will swing through our area tomorrow. Only expecting small
chances for snow. Confined the probability of precipitation to the northwest half of the
forecast area as Delta T/S may be just enough to aid in snow
generation. Lingered flurries area wide Friday night.

Next shortwave is seen in the water vapor imagery coming ashore in
British Columbia. The shortwave dives southeast and moves through
our area on Saturday. Moisture increases in the 1000-700mb layer in
both time frames...Friday and Saturday. Not expecting much either
period...but some chances for a little light snow for sure.
Overall...a pretty quiet period.

Long term...(sunday through thursday)
issued at 329 PM EST Thursday Mar 5 2015

Warmer temperatures are expected by Tuesday after our final clipper
system brings some light snow to the area on Sunday.

One good sign of a warm up is looking into the stratosphere the 30mb
and 50mb circulation around the polar vortex...which has featured a
deep trough over the eastern United States retreats into southern
Canada by the middle of next week. Meanwhile at 10mb there were two over northeastern Russia and the other northern Hudson
Bay. By the middle of next week that considerate over the North
Pole. All this tells ME the deep cold air retreats to the north over
the next week. This GOES along with what one would forecast using
the mjo...which is warming for about 2 weeks. Thus I am more in
favor the European model (ecmwf) idea of not bringing down so much cold air later
next week.

The other issue that leads ME to want to follow the European model (ecmwf) over the
GFS is that the northern stream shortwave that creates the cold
outbreak later next week was sharper on yesterdays run than today.
That suggests to ME the tendency of the model is to flatten
that shortwave over time. That would favor the European model (ecmwf) idea of warm
verses colder surface temperatures later next week.

One other issue is the GFS model sounding compared to the ecwmf
suggest the GFS is cooling the lower levels to much due to the
current snow cover. The negative for that though is we are under
surface high pressure during the middle of next week. That leads to
less deep mixing so highs in the middle 40s...that GOES nicely with the
1000/925 mb thickness tool...which is my favorite high temperature
forecasting tool.

As for the system on Sunday...the best dynamics and jet core pass
north of Michigan in southern Canada. Even so both the European model (ecmwf) and GFS
show some workable moisture transport vectors nearly parallel to
Interstate 96/94 Sunday during the day. So I expect some light snow
but nothing one would have to shovel. After that moves out warmer
temperature begin.

Bottom line is expect some of the warmest temperature since
Christmas week (you may remember highs in the 50s on the 23rd of
december). Dew points should not get above freezing so the snow melt
will be slow...even with those warm temperatures.


Aviation...(for the 18z tafs through 18z Friday afternoon)
issued at 1249 PM EST Thursday Mar 5 2015

Currently skies are mostly clear at all of the taf sites except
mkg which has a VFR ceiling and has has few flurries. I expect winds
become more westerly at the surface the snow band over the lake
will move inland before dissipating and impact the mkg taf site in
the 2 PM to 6 PM time frame. I would expect some IFR visibility with the
snow showers there. I do not think these will make it to GRR so I
did not include them at GRR.

As for the clouds associated with the snow band...they will move
inland like the snow band itself will but winds turn to the
southwest by this evening and that will keep most of the low
clouds (mvfr / VFR ceilings) from mkg north and northeast. I did
bring some VFR ceilings into the GRR taf site with a few flurries
possible during the late afternoon. Otherwise I have clear to
mostly clear skies at the other taf sites with mostly light winds.


issued at 329 PM EST Thursday Mar 5 2015

Low ice jam potential/flooding risk over the next 7 days.

Latest snow water equivalent analyses indicate around an inch or two
is contained within the snowpack inland with 2-4 inches of liquid
equivalent closer to the Lakeshore. Swe values of 4+ inches are most
likely in the white and pere Marquette river basins.

A gradual warm up is expected Friday into the middle of next
week...but the latest models are less bullish with the warm air.
Highs generally in the 40s to around 50 degrees seems reasonable
with lows near or below freezing. Given the mostly dry forecast
through next Thursday...this could be an ideal forecast to slowly
melt the snowpack and chip away at ice thickness on area rivers and
streams. Rises in area rivers mostly below bankfull are expected
next week. A few smaller streams could reach advisory
stage...especially from around March 11 into the following weekend.
But the major stems of the grand and Muskegon rivers are not
expected to exceed bankfull next week.

Until further notice...any significant rainfall events change the
dynamic and increase the risk for flooding.


GRR watches/warnings/advisories...


short term...Duke
long term...wdm

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