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Area forecast discussion 
National Weather Service Grand Rapids Michigan
330 PM EST Friday Dec 26 2014

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

Synopsis...
issued at 330 PM EST Friday Dec 26 2014

One more unseasonably mild day is in store for Saturday as a low
pressure system over Missouri tracks northeast through Wisconsin and
northern Michigan.

Moisture streaming north ahead of this system will bring clouds and
occasional light rain or drizzle beginning late tonight and
continuing through Saturday. The rain may mix with a little light
snow Saturday night before ending as a cold front passes through.

We will see some chilly air and light lake effect snow showers
arrive this week with highs mainly in the 20s. No significant snow
accumulations are expected at this time.

&&

Short term...(this evening through Sunday night)
issued at 330 PM EST Friday Dec 26 2014

No major changes in thinking to the going forecast. Widespread low
clouds develop later this evening as surface dew points around 40 stream
in from the southwest. Latest runs of the hrrr show scattered light
convective looking rain showers developing this evening across
Missouri and Illinois. These should will likely track into the area
from the southwest or develop overhead overnight and persist
Saturday within the warm advection zone ahead of the approaching surface
low and cold front. In addition to the convective rain showers...
some patchy drizzle may be squeezed out of the low clouds at times
late tonight and Saturday.

Deeper moisture moves east of the area after 00z Sunday about the
time the colder air is arriving. Precipitation behind the surface cold
front should trend toward just some very light mixed rain and snow
showers. No snow accumulations expected late Saturday night into
early Sunday due to very shallow moisture profiles and questionable
dgz saturation. Additionally...surface ridging/anticyclonic flow is
quick to build in which actually leads to decent Prospect for
sunshine developing Sunday afternoon.

Long term...(monday through friday)
issued at 330 PM EST Friday Dec 26 2014

We continue to expect a trend toward colder weather in the long term
with chances of snow showers through the period. Snow accumulations do
not look to be anything significant in the forecast period for now. We
will continue to monitor this potential as it would not take major
changes to bring a better potential of lake effect.

The chance of snow for SW lower on Monday does not look real good at this
time. A short wave trough will be moving into the Great Lakes region
from the west-northwest on Monday. However a strong 1050+ mb ridge to our west
will be in control of the lower levels here. NE flow and an
extension of the surface ridge in place will limit precipitation potential.

The period from Tuesday through Thursday then will feature the coldest temperatures
of the long term. The Monday short wave will complete the transition of
the upper air pattern to more of a northwest flow aloft over the area.
Colder air will continue to filter in on the nearly and eventually northwest
low level flow. The air will be plenty cold enough for lake
effect...however we will remain on the south side of the northern branch
of the jet. Short waves diving southeast are expected to remain just north
of the County warning forecast area. This will limit moisture depth significantly and also
the deep layer instability.

Lake effect could be more robust if the upper jet and the associated
short waves are able to dive just a little further south. We believe
that the strong cutoff upper low across the SW U.S. And the ridge
ahead of it will hold the northern branch of the jet just north of the
area.

We could see the initial effects of the cutoff upper low start to
move in as early as next Friday as warm and moisture advection ahead of
it starts to overrun the colder air expected to be in place. The
models typically eject these systems out too quick...so we will keep
the chance of precipitation low at this time for next Friday.

&&

Aviation...(for the 18z tafs through 18z Saturday afternoon)
issued at 1233 PM EST Friday Dec 26 2014

Area of low clouds continues to plague the north/northwest portion of the
area early this afternoon...affecting only kmkg at this time. Some
additional cumulus is forming just south of this cloud cover that will
affect kgrr more than any other location. We expect the cloud
cover to hold in at kmkg except for a few breaks at times. The
cloud cover will expand across all areas tonight as the next
system approaches the area from the SW.

Showers will become possible after 08-09z across the west. They
will then expand to the east thereafter. Ceilings will lower and will
likely end up IFR for the daylight hours on Sat and continue
through the end of this forecast period. Visibilities are not expected to be
too bad...mainly in the MVFR category.



&&

Marine...
issued at 330 PM EST Friday Dec 26 2014

The pressure gradient relaxes tonight so winds and waves are
expected to subside. However they will ramp up again late Saturday
and Saturday night as a cold front passes across Lake Michigan.

&&

Hydrology...
issued at 330 PM EST Friday Dec 26 2014

Have canceled the advisory for the Maple River at Maple Rapids as
latest forecast has it cresting a half foot below bankfull Sunday.
Sycamore Creek at Holt crested last night and is falling below
bankfull at this time. About a tenth of an inch of precipitation is
expected on Saturday which will not affect the rivers much. A lack
of significant precipitation into the New Year will allow the larger
rivers time to crest and fall without much impact.

&&

GRR watches/warnings/advisories...
Michigan...none.
Lm...Small Craft Advisory until 10 PM EST this evening for
lmz844>849.

&&

$$

Synopsis...Meade
short term...Meade
long term...njj
aviation...njj
hydrology...cas
marine...Meade

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