Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 151831
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
131 PM EST Wed Feb 15 2017

LATEST UPDATE...
Hydro

.SYNOPSIS...
Issued at 229 AM EST Wed Feb 15 2017

A cold front passed through the area Tuesday evening and this has
brought down from Central Canada some seasonably cold air for two
day. We will have snow showers around today into this evening,
accumulations will be limited and temperatures will remain below
freezing through the day. Tonight should be the coldest night of
the week with most locations having lows below 20 degrees. The
Canadian origin high will pass over Michigan Thursday ending the
snow showers by sunrise but it will remain cold with highs around
freezing. The passage of warm front on Friday brings us into the
warm air. Southwest Michigan will likely stay in the warm air
until at least Thursday of next week. We could have periods of
showers next week starting on Tuesday. Highs will mostly be in the
50s and 60s from Saturday through at least Wednesday.

&&

.SHORT TERM...(Today through Friday)
Issued at 335 AM EST Wed Feb 15 2017

Our main issue today will be the snow showers as the cold air
continues to come into the area. It was already decided to drop
the winter weather headline as we have only flurries around as I
write this and the snow showers I do expect today should not be
all that impactful.

A shortwave dropping south around the upper low is bringing the
colder air into Southwest Michigan as I write this. Most of the
high resolution models show inversion heights increasing to
around 6000 to 7000 ft late this morning into this afternoon.
Since 850 temperatures will fall to around -15c during this time,
that will be in the DGZ so as just about all the models show, snow
showers will become widespread today. The NCAR ensembles show 60
to 80 pct pops west of US-131 all day today. With winds from the
northwest and not much directional change with height that will
help the snow showers to form northwest to southeast bands. Since
there is not much lift in the DGZ through it is saturated today,
I would expect snowfall amounts to be rather limited, mostly an
inch or less. NCAR ensembles most areas east of US-131 having less
than a half inch of snow today but the lake shore areas could see
as much as an inch and a half. We will have enough wind to cause
some blowing and drifting but with such limited snowfall I do not
see this as being much of a travel issue. So the bottom line is
frequent light snow showers today with minimal impacts (no
headline needed).

The upper jet gets east of the area by midnight or so thus the
snow showers will come to an end as inversion heights fall below
3000 ft. It will be the coldest night of the week too, most areas
will see lows in the teens.

A slow warming trend follows through Friday. The warm front will
be to dry to bring us any precipitation so just partly cloudy
skies are expected. Thu through Friday.

.LONG TERM...(Friday night through Tuesday)
Issued at 335 AM EST Wed Feb 15 2017

Friday night through Monday is fairly straight forward. The entire
period includes well above normal temperatures with the potential
for precipitation coming in late Monday and Tuesday.

The anticipated upper ridge will continue building in with southerly
flow ramping up into Saturday. Dry air throughout the mid and upper
levels will support mostly clear skies much of the time. There are
only a couple of notes to make in the Saturday through Monday
timeframe.

The first note is with respect to ample low level moisture that is
in place behind the warm front early Saturday morning. Provided
mainly clear skies and strongly inverted temperature profiles, fog
would be suggested. This would mix out quickly after sunrise, but is
something to keep an eye on.

The second thing to note would be the upper level short wave well to
our north. A surface trough extends south of this wave and swings
through late Saturday. This will act as a temporary wind shift with
winds out of a north through Sunday. This all passes through
dry and only hold temps a couple degrees cooler. We will quickly get
back to business with southerly flow, as it returns Sunday night
into Monday. Monday could be the warmest day  with a layer of +10C
air deepening to around 10k feet (875mb) Monday afternoon.

We get back into a busier pattern late Monday as a cold front
extends south from a system well to the north of Lake Superior. This
front pushes through early Tuesday before stalling south of the
Great Lakes. Another surface low then approaches from Iowa late
Tuesday, dragging the boundary back to the north as a warm front.
All precipitation looks to be rain with plenty of mild air in
place.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1245 PM EST Wed Feb 15 2017

MVFR conditions expected into this evening with light snow
showers and ceilings around 2500 feet AGL. Expect VFR later
tonight and on Thursday. Winds will be northwest today gusting to
20 knots this afternoon then diminishing to around 10 knots this
evening.

&&

.MARINE...
Issued at 335 AM EST Wed Feb 15 2017

Recent marine observations show no gales being reported and based
on numerous model sounding forecasts it would seem to me gales are
not expected today so I will have a SCA till around 5 am Thursday
and call that good.

&&

.HYDROLOGY...
Issued at 131 PM EST Wed Feb 15 2017

River levels continue above normal, but no flooding is expected
into next week. Little precipitation is expected, so river levels
should fall into next week.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 5 AM EST Thursday for LMZ844>849.

&&

$$

SYNOPSIS...WDM
SHORT TERM...WDM
LONG TERM...JAM
AVIATION...Ostuno
HYDROLOGY...63
MARINE...WDM



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