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Area forecast discussion 
National Weather Service Grand Rapids Michigan
1220 am EST Thursday Nov 26 2015

Latest update...

issued at 226 PM EST Wednesday Nov 25 2015

An area of high pressure centered over the central Appalachians
will draw an unseasonably moist airmass out of the Gulf of Mexico
into the southern Great Lakes region through Thanksgiving day.
Meanwhile colder air will sink southward out of Ontario into the
northern Great Lakes region. Rain will develop over the area as a
result tonight and persist into Friday. As the colder airmass
filters into lower Michigan on Friday...a period of mixed
precipitation will be possible.


Short term...(this evening through Friday night)
issued at 226 PM EST Wednesday Nov 25 2015

The nearly stationary frontal boundary that sets up over northern
lower Michigan and WI tonight will become stronger as it slowly drifts
southeastward through Southern Lower Michigan through Friday. Gulf
moisture advect up and over this frontal rain some
of which will be heavy. The right entrance region of an upper jet
will be over this frontal...enhancing the rainfall. A shallow
subfreezing cold wedge shows up on the forecast soundings for
Friday roughly around 950 mb.

Not much upstream on radar right now...thus will start the night
off dry for most locations. By 06z the rain should be expanding
over the area...especially northwest parts of the County Warning Area. Wet weather
can be expected on Thanksgiving day as moisture advection
continues over the strengthening approaching frontal zone. Temperatures
could start off in the middle to upper 30s for Harrison with some
rain later tonight. Thus a close call for icy spots on the
roadways. This rain will continue on and off through Thursday
night...with the Jackson area seeing the least amount of rain
through 12z Friday. With snow on the ground and Gulf moisture
advecting over it...I did go with some fog in the forecast for
late tonight through Thanksgiving day.

I did add sleet to the weather grids for Friday as this shallow
cold airmass slips southward through the region. Some models have
it colder than -4 degree c 950 mb with an above freezing layer
above especially northwest of Grand Rapids. With surface temperatures
staying above freezing...I do not see much potential for impacts
to the roads at this time. Will need to monitor trends closely.

The upper jet does not sink south of the Great Lakes region Friday
night. Thus uncertainty exists as far as how much we will dry out
as this would open up the opportunity for another weak wave to
head in our direction. Will need to monitor trends closely. Will
hold onto a low risk for precipitation for southern counties for
the first half of the night.

Long term...(saturday through wednesday)
issued at 226 PM EST Wednesday Nov 25 2015

High pressure will build in to produce fair weather with seasonable
temperatures through the weekend. The next low pressure system will
move northeast toward the Great Lakes region and bring a chance of
rain showers as early as Monday.

A consensus of latest medium range guidance suggests that the best
chance for rain will come Monday night into Tuesday as the low moves
up through the Great Lakes region. Rain showers will likely become
mixed with then change over to light snow showers late Tuesday
through Tuesday night due to northwest flow cold air advection on the back side of the

Fair weather will return late Wednesday through Thursday as a high
pressure ridge builds in from the west. Temperatures will average
slightly above normal Monday into Tuesday before cooler air wraps
in behind the system for midweek.


Aviation...(for the 06z tafs through 06z Thursday night)
issued at 1220 am EST Thursday Nov 26 2015

Latest guidance has backed off a bit on the timing and
southeastward extent of IFR ceilings/visibilities later tonight and
Thursday. IFR is still expected to get into mkg and GRR and
linger much of Thursday where rain will be more persistent.

However the farther east and south you go from GRR the IFR
probabilities for Thanksgiving day decrease. Will leave IFR out
of the tafs at azo/btl/lan/jxn although would not rule out some
spotty IFR at times at these farther east sites in the morning
when showers are occurring.

There is some indication that ceilings will improve to VFR south and
east of GRR in the afternoon/evening Thursday as a wave moves
along the front in Wisconsin and stalls the boundary.

South winds will be 10-20 kts tonight and increase to 15 to 30
kts on Thursday.


issued at 226 PM EST Wednesday Nov 25 2015

Southerly winds will remain strong tonight and into Thursday night
but a sharp wind shift will occur on Friday or sooner as colder
air arrives from the north. Will maintain the headlines.


issued at 1150 am EST Wednesday Nov 25 2015

The focus continues to be on the anticipated rainfall late
tonight through addition to the snowmelt in the
hardest hit locations from saturdays snowfall.

Expectations for the upcoming rainfall have been fairly
consistent with a spread in totals...from about 0.75 inches in
the southeast (jackson) to around 1.50 inches in the northwest
(ludington). Though rainfall and snowmelt will cause within bank
rises on streams and rivers...the greatest potential for near or
above bankfull levels exists in the southeastern third of the County Warning Area.
Namely...the Maple River at Maple Rapids and Sycamore Creek at
Holt...are forecast to crest slightly above action state.

For now...the revise serving its purpose as some question still
lingers in the speed of the snowmelt and rate at which the rain
will fall. Some reports have reflected that about half the snow
depth has been consumed by melting in the last 24-48 hours. At
this rate...much of the feedback may gradually make into rivers
sparing any greater concern. It will continue to be monitored as
rainfall is realized through Friday.


GRR watches/warnings/advisories...
Lm...Small Craft Advisory until 7 am EST Friday for lmz844>849.



short term...mjs
long term...Laurens

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