Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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000
FXUS63 KGRR 202303
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
603 PM EST Mon Nov 20 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 325 PM EST Mon Nov 20 2017

A predominately dry and benign weather pattern will prevail this
week, including the Thanksgiving travel period. A cold front will
pass through on Tuesday but will have little precipitation
associated with it. Another cold front over the weekend will bring
some rain and snow showers, although minimal travel impacts
are expected at this time.

&&

.SHORT TERM...(This evening through Wednesday night)
Issued at 325 PM EST Mon Nov 20 2017

Strong southwest flow off lake MI will lead to a temperature
contrast across the area tonight, with overnight min temps
ranging form the mid 30s inland where boundary decoupling occurs
to the mid 40s along the lakeshore.

The pesky area of stratocumulus clouds which was north and west of
a Holland to Harrison early today has mixed out, but may return
again late tonight due to Lk MI effects.

The cold front on Tuesday is moisture starved as it comes through
Michigan but models do suggest a band of rain showers developing
along the front about the time it`s exiting the state late in the
day. Best pops tomorrow therefore, although still just chance,
will be around JXN in the afternoon.

The air behind the cold front late Tuesday and Tuesday night is
plenty cold enough for lake effect, but as with the last few
pushes of cold air the moisture is quite shallow. So while we will
have some lake effect snow showers on Tuesday evening, they will
be mostly light with little or no accumulation expected.

Surface ridging returns on Wednesday, although with the center of
the high being south of Michigan and our low level flow remaining
westerly, some lake effect cloudiness may linger.

.LONG TERM...(Thursday through Monday)
Issued at 325 PM EST Mon Nov 20 2017

The only weather in the extended period is a clipper moving across
southern Canada which brings a trailing cold front through Michigan
Friday night.

Warm advection ahead of the front should bring max temps to near 50
on Friday then strong cold advection kicks in for Saturday with a
reinforcing cold shot behind an arctic front coming through Saturday
night. Lowered model blend temperatures for Saturday through Sunday
as 850 mb temps tumble to about minus 15C Sunday afternoon. Maxes
should remain below freezing Sunday afternoon. Also bumped up POPs
as light lake effect snow showers in northwest flow will continue
into Sunday evening before sfc ridging builds in and inversion
heights lower.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 603 PM EST Mon Nov 20 2017

I expect VFR conditions to prevail at all of our TAF sites
overnight. There is a chance that MKG, more so than any other of
our TAF sites, may see MVFR cigs develop by midnight partly due to
the lake wind speed convergence and shallow moist layer seen in
the model soundings. Otherwise all taf sites will be impacted by a
very strong low level jet, between 03z and 06z there is 50 to 60
knots down as low as 1500 agl. Given winds at the surface will be
only 10 to 20 knots, that would be significant low level wind
shear. I included that in all of our tafs.

On Tuesday a cold front quickly moves west to east across the TAF
sites between 12z at MKG and 16z at JXN. Once the cold front comes
through I expect MVFR cigs to follow quickly. The low clouds will
last past 00z. I do not at this point believe there will be any
precipitation through.

Bottom line is low level wind shear tonight and mvfr cigs Tuesday
with no significant precipitation.


&&

.MARINE...
Issued at 325 PM EST Mon Nov 20 2017

Wind speeds have not reached gale force yet, but the winds are
forecast to further increase late this afternoon and evening. Will
not be making any changes to the ongoing Gale Warning. Winds and
waves will subside below gales on Tuesday afternoon but will
remain strong enough to warrant Small Craft Advisories after the
Gale Warning expires.


&&

.HYDROLOGY...
Issued at 1145 AM EST Mon Nov 20 2017

Few rivers continue to rise, but rises have slowed, while others
are showing signs of stabilizing. There are small chances for
precipitation Tuesday afternoon and Wednesday. Amounts, if
measurable, should not have any impact on rivers. Beyond
Wednesday, weather looks relatively quiet.

Despite elevated river levels, additional river flooding is of low
concern. Rivers are likely to recede through the course of the
upcoming week.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Gale Warning until 10 AM EST Tuesday for LMZ844>849.

&&

$$

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


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