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Area forecast discussion 
National Weather Service Grand Rapids Michigan
949 PM EST Friday Dec 19 2014

Latest update...

issued at 339 PM EST Friday Dec 19 2014

Fairly quiet weather is expected to continue into the weekend as
high pressure slides off to the east of the Great Lakes. Clouds will
become more prevalent as we head into Saturday. There may be a
little bit of light snow across central lower Michigan Sunday
afternoon and evening...but any accumulation would be trace amounts.
High temperatures this weekend will be near seasonable values in the
lower to middle 30s.

The weather looks to turn more active next week with a system
forecast to move through the Great Lakes region. Warm air initially
will bring rain from Monday into Tuesday before changing over to
snow towards Christmas.


Short term...(this evening through Sunday night)
issued at 339 PM EST Friday Dec 19 2014

Short term concerns primarily pertain to cloud cover. A secondary
item of note are small chances for light snow Sunday afternoon and

In regard to clouds a general theme in the models to to expand the
low clouds across the south tonight and even spread them back into
portions of the west late. So...expecting mostly cloudy skies in the
south and becoming mostly cloudy in the west. Northeast sections of
the County Warning Area may stay mainly clear all night and have the coldest
readings up there. Lows in the teens in the northeast.

As the flow turns southwesterly on Saturday expect that the low
clouds will slide over the entire County Warning Area with cloudy skies prevailing
in all areas by sunset.

Saturday night into Sunday skies will remain mostly cloudy as well.
Precipitation chances exist Sunday afternoon into Sunday evening as
a warm frontal feature lifts through the area. Not expecting
significant precipitation...but model soundings would indicate chances for
some light snow. It may try to mix with a bit of light rain if we
can warm just enough. Only have a 30 percent chance for snow in the
forecast for these periods.

Long term...(monday through friday)
issued at 339 PM EST Friday Dec 19 2014

Confidence in a storm impacting the region remains high in the
Monday night through Christmas day time frame. However due to the
large spread in solutions...precipitation type issues remain as we approach
the Holiday.

The models continue to show the energy that is now over the Gulf of
Alaska intensifying again as the system reaches the middle of the
nation and collides with additional Gulf moisture by Monday night.
Good confidence that we will see mainly rain Monday/Tuesday as
southerly flow should bring temperatures into the 40s. The precipitation could
start as a mix on Monday...but then just rain is expected by Monday

The system bombs out somewhere over the Great Lakes...with the track
of the surface low spread from the western u.P. To northwest PA...depending
on the model. The trend has been slightly warmer as the upper
trough does not go negatively tilt until Wednesday...when the colder
air finally arrives. So have keep a mostly rain forecast through
Tuesday night...then we should transition to snow from west to east
into Wednesday afternoon/evening. Quiet a wet system for sure...
with around an inch of rain very plausible prior to any snow

Will still go with mostly snow from Christmas evening to Christmas day
evening as the low is forecast moves north and drags colder air in.
There remains the possibility that we see a Transfer of energy to an
East Coast the amount of snow is also in question. If this
Transfer occurs we will see a weaker system impact the Great Lakes.
If this Transfer does not occur we could remain in th trowel of the
storm for a longer period...resulting in more snow. 800 mb temperatures appear
to only become marginal for US to see much lake effect this does not appears to be a Hugh factor.

A second surface low from the SW is shown by the Euro and GFS into
Friday. We should see some warm advection ahead of the storm...
making precipitation type questionable again with this system. As of now
have gone with a rain/snow mix south...and snow north.


Aviation...(for the 00z tafs through 00z Saturday evening)
issued at 944 PM EST Friday Dec 19 2014

The low clouds have scattered out across much of southwest lower
Michigan...but high level clouds...over 15k feet...were moving in. There
is a risk that fog could form in the next few hours...but this
risk is limited by the higher level clouds moving in. Thus I did
not include the fog in the forecast at this time.

MVFR clouds will gradually move in late tonight from the south and
west. This will likely persist through Sat am. For now I kept the
return to VFR for most taf sites Sat afternoon...but this is not
certain to happen as the low levels remain fairly moist.

Aviators may encounter some icing in these lower clouds.


issued at 339 PM EST Friday Dec 19 2014

High pressure will bring fairly light winds and low wave action
tonight into Saturday. Southerly flow begins to pick up on Sunday.
Small Craft Advisory conditions may develop as early as Sunday
afternoon in the north. Sunday night it appears Small Craft Advisory conditions will
be likely...north of Holland. Will hold off at this point on a
fourth period Small Craft Advisory...but one will likely be needed going forward.
Next week looks rough on Lake Michigan given a deep low moving
through the region.


issued at 339 PM EST Friday Dec 19 2014

River levels across the area are near normal for this time of year
with no significant precipitation expected through the weekend.
Hydro issues through Monday. Deep low pressure will likely bring
soaking rains to the area Monday night into Tuesday with rainfall
amounts of a half to one inch. Given the low flows currently this
should be able to be absorbed without much issue.


GRR watches/warnings/advisories...


short term...Duke
long term...jk

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