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Area forecast discussion
National Weather Service Grand Rapids Michigan
100 am EST Tue Feb 28 2017

Latest update...
aviation

Synopsis...
issued at 330 PM EST Mon Feb 27 2017

A wet weather system will arrive late tonight with rain spreading in
from the southwest. Periods of rain and perhaps a few rumbles of
thunder are expected to continue through Tuesday night. Then as the
system departs it will drag colder air into the region Wednesday
into Wednesday night. The rain will gradually switch to snow on
Wednesday, with some areas seeing as much as two inches by Thursday
morning.

Additional snowfall should linger Thursday and Thursday night,
before finally ending, leading to a quiet weekend. Warmer air and
rain should occur by Monday.

After temperatures from 50 to 55 Tuesday and Wednesday morning,
Thursday and Friday will be much colder with highs in the 30s.
Temperatures are expected to warm for the weekend into Monday with
highs back to around 50.

&&

Short term...(this evening through Wednesday night)
issued at 330 PM EST Mon Feb 27 2017

A period of steady rain is expected toward daybreak Tuesday, then
again toward sunset, with pleasant weather for mid day. Tuesday
night will see a soaking rain before temps drop on Wednesday,
leading to the rain changing to snow. Some snow accums are expected
Wed afternoon and evening mainly north of I-94.

Solid warm advection tonight will help keep temps in the mid and
upper 30s for lows tonight. This flow will bring increasingly moist
air from the Gulf. Combined with this will be a 45 knot low level
jet nosing into the SW corner of the state and anticyclonic upper
jet leading to divergence. Showers will expand over the region from
the southwest by about 09z and there could even be a few embedded
thunderstorms within this pattern.

The first wave of pcpn moves through during Tuesday morning, with
about a six hour break, before the next round arrives around sunset
Tuesday. Temps will manage to get well in the 50s mid day, between
the two rain periods.

A steady rainfall is expected into Tuesday night as the surface low
and front moves in. Outside chance we could see some stronger
storms in the evening south of I-96 with another low level jet supporting the
storms. Pcpn totals across much of the County Warning Area should be around an inch
from the multiple waves of rain.

Max temps on Wed should occur in the morning of 45 to 50, with temps
falling through the afternoon as the surface low pulls away and
drags in the colder air. The rain will switch to snow from
northwest to southeast through the day. This snow will come to an
end Wednesday evening as the upper trough moves through. Expect two
inches or less of snow, most in the northwest cwa, and probably no accums
closer to I-94.

Long term...(thursday through monday)
issued at 330 PM EST Mon Feb 27 2017

Our "roller-coaster" type weather pattern will continue well
beyond this forecast period. We will start out colder than normal
with snow showers from a system moving out of the area by late
morning Thursday. A cold front comes through Thursday night, which
means even colder temperatures Friday with more snow showers.
Then comes the warm-up over the weekend. However the warm front
may bring US more snow Saturday morning before we get back into
highs in the 50s Sunday. A wave on the front brings showers Sunday
but then another deep storm heads our way for Monday with the
chance of late day thunderstorms, after that cold air comes back
and we get more snow.

The mjo remains in quad 2 (cold for eastern Continental U.S. In late Feb and
march) and will head to quad 3 by the middle of next week (also cold
for this area). Meanwhile we have another stratospheric warming
event developing over Canada that builds into the Continental U.S. Next week.
Also, we have a building upper high near Greenland (currently
developing). All of this tells ME we should be colder than normal.
Which may mean the system on Sunday into Monday may end up
tracking farther south, we will have to watch that, as this has
been a recent problem of late with the models.

As for the Thursday night into Friday cold front the models all show
some sort of snow with this but do not agree on how developed the
surface wave will be. There is a similar story for the warm front
on Saturday. I am thinking we do get some light snow from both of
these but not enough to cause major travel issues. The next big
system on Monday would have thunderstorms with it if it tracks far
enough north but again, given the other factors (blocking
Greenland highs, mjo etc...I have to wounder if that will be true.

So, the bottom line is we are in a stormy pattern and we will more
than likely see some precipitation nearly every day the next week
or so. The snow behind the system on Monday could be significant
if the surface low tracks a touch farther south.

&&

Aviation...(for the 06z tafs through 06z Tuesday night)
issued at 1258 am EST Tue Feb 28 2017

Conditions will deteriorate tonioght and Tuesday as moisture
increases ahead of another low moving toward Michigan. Instability
will also increase and thunderstorms are possible after 21z. Look
for IFR conditions to develop this morning as showers and fog
develop.

&&

Marine...
issued at 330 PM EST Mon Feb 27 2017

No problems on the lake until Wednesday. Until then a southerly
flow will stay 15 knots or less. However by Wednesday winds will
swing to the north northwest and increase toward 20 knots. The cold
advection will lead to conditions favorable for a Small Craft
Advisory.



&&

Hydrology...
issued at 330 PM EST Mon Feb 27 2017

Many rivers in the region continue to experience higher flows due to
continued runoff from rainfall late last week. Additional rises
will develop later this week as another rainfall event brings one
half to one inch of rain across a large portion of west Michigan.
Flooding is not expected at time...but several locations will see
above bankfull rises.

&&

GRR watches/warnings/advisories...
Michigan...none.
Lm...none.
&&

$$

Synopsis...jk
short term...jk

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