Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 191919 CCA
AFDGRR

Area Forecast Discussion...CORRECTED
National Weather Service Grand Rapids MI
219 PM EST Mon Nov 19 2018

LATEST UPDATE...
Aviation/Hydro

.SYNOPSIS...
Issued at 315 AM EST Mon Nov 19 2018

We will see a couple of weaker systems push through the area through
Wednesday. These systems will bring some light snow showers, with
some light accumulations closer to the lakeshore. Colder air over
the area will be reinforced with the passage of these systems. Drier
air will move in for Wednesday and Thanksgiving Day, but it will
remain colder than average.

We will see warmer air move in for Friday and remain in place
through the weekend. Friday will be dry, but rain showers will move
in for Saturday and Saturday night. Showers should diminish on
Sunday.

&&

.UPDATE...
Issued at 1209 PM EST Mon Nov 19 2018

A cold front will swing through the forecast area this afternoon
and evening. The front is associated with a clipper system moving
through Northern Lower Michigan. We will see light snow
primarily, but there may be a little light rain mixed in this
afternoon as well. Accumulations will be less than an inch. The
best chance for accumulating snow will be in the northwest CWA
towards Ludington and Pentwater. The precipitation is being forced
by the cold front but there will be some lake enhancement as well.
Overall, no major changes were made to the forecast.

&&

.DISCUSSION...(Today through next Sunday)
Issued at 315 AM EST Mon Nov 19 2018

The items of interest in the period leading up to Thanksgiving Day
will be on the two waves expected to impact the area later today and
Tuesday night. The general trend with regard to these waves has been
little change. We then will focus on a warm up, and bigger system
that will bring rain next weekend.

We continue to expect that an inch or so of snow accumulation is
likely along the lakeshore, while a dusting is possible inland for
late this afternoon and this evening. We will see one short wave
push in first, that will help to bring the front into the area.
Lower clouds and some snow showers will start to spread in from the
NW this afternoon. This system does not have a lot of moisture with
it, and only some moisture/instability will be drawn onshore from
Lake Michigan. The instability is limited as temps aloft are only
around -5C with the front. Once the front moves through, lake effect
develops, but goes offshore really quick with the low level flow
changing to become from the NNE.

We will see a break in the action from late tonight, until late
Tuesday evening. At that time, another frontal system will push
through the area with a strong short wave that stays well north of
the area. Onshore flow will bring some moisture and instability with
the front that will bring another round of snow showers to the area.
The favored area Tue night will be the NW portion of the area due to
the flow, and closer proximity to the upper wave. We still do not
expect anything more than an inch or two at most. This is because
the best forcing is well north with the wave, and we are on the anti-
cyclonic side of the upper jet. Inversion heights are quite low,
even with lake instability as part of the equation.

Once the front moves through by early Wed, we will see ridging at
the sfc and aloft take control of the weather. This will be dry, but
rather cold as the flow around the high will tap colder air from
over the snowpack across Canada, and bring it in. Many locations
will see lows in the teens on Thanksgiving morning.

We will see a decent change in the air mass on Friday compared to
Thanksgiving Day. The flow will become southerly, and strengthen
fairly decent. This will draw warmer air northward into the area. We
should stay dry still on Friday, as it will take a while to get
sufficient moisture advected into the area. Enough moisture should
arrive Friday night and Saturday ahead of the low lifting toward the
area from the south, that rain will be likely over the area. The
rain will diminish on Sunday as a quick ridge will move over the
area, in between the departing low, and the next one poised to move
in after the weekend.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 217 PM EST Mon Nov 19 2018

MVFR ceilings are in place across portions of Southwest Lower
Michigan at 18z. These lower ceilings will be a bit hit or miss
this afternoon, but will likely trend toward widespread as we head
towards 00z. A cold front is sweeping south through the area and
it will likely aid in development of these ceilings. Overnight,
the flow goes northerly in a lake effect type of regime. What this
will do is focus the MVFR ceilings toward the lakeshore and likely
try to scatter the lower clouds out or at least raise bases to VFR
towards KLAN and KJXN.

Periods of snow showers can be expected through the next 24 hours.
The first will come along the cold front moving south through the
area this afternoon and evening. Visibilities may dip into the
3-5SM range for a short time, but much of the activity will not
reduce visibility much. The better likelihood of lower visibility
will come with the second threat which will be lake effect moving
down the lakeshore this evening near the cold front. Some of this
activity may produce MVFR visibility for a 1-3 hour period.

&&

.MARINE...
Issued at 1223 PM EST Mon Nov 19 2018

Changes were made to the marine headlines to encompass the larger
waves expected tonight into Tuesday. The waves this afternoon will
be marginal, in the 2 to 4 foot range, but are expected to build
tonight into Tuesday. Waves will reach the 3 to 5 foot range in
all zones, with 4 to 7 footers likely up towards Big and Little
Sable Points. Winds will approach 30 knots tonight in north flow
behind the cold front.

&&

.HYDROLOGY...
Issued at 217 PM EST Mon Nov 19 2018

There are no hydrologic concerns through the end of the week. A
few rounds of light precipitation, mostly falling in the form of
snow, will affect the area through Wednesday. The first will be
this afternoon through tonight, with a few light showers lingering
near the lakeshore through early Tuesday. The second round will
occur Tuesday night into Wednesday morning. Thursday and most of
Friday look dry.

Longer range models then continue to show a wetter pattern setting
up Friday evening through early next week. Several rounds of
rainfall look to occur, although the timing from Saturday onward is
still uncertain as forecast models vary widely with the timing,
track, and strength of low pressure systems near the region. We will
continue to monitor potential rainfall amounts, but it does not look
like there will be flooding concerns.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory from 7 PM this evening to 1 PM EST Tuesday
     for LMZ849.

     Small Craft Advisory until 1 PM EST Tuesday for LMZ845>848.

     Small Craft Advisory from 1 AM to 1 PM EST Tuesday for LMZ844.

&&

$$

UPDATE...Duke
SYNOPSIS...NJJ
DISCUSSION...NJJ
AVIATION...Duke
HYDROLOGY...HLO
MARINE...NJJ


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