Area Forecast Discussion
Issued by NWS Grand Rapids, MI

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FXUS63 KGRR 151811
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
111 PM EST Wed Nov 15 2017

LATEST UPDATE...
Aviation

.SYNOPSIS...
Issued at 324 AM EST Wed Nov 15 2017

Expect a windy, rainy day today as a developing low pressure
system tracks from southern Minnesota early this morning to
eastern Lake Superior this evening. The cold front assoicated with
the primary system will bring and end to the rain by late
afternoon. However an arctic front comes through this evening as
the storm continues to deepen. That will bring lake enhanced
showers which will change to snow by midnight and bring as much as
an inch of snow to some areas near and west of US-131 by mid
morning Thursday.

High pressure behind the system will bring clearing and cooler
temperatures into Friday afternoon. That will be followed by a
much stronger system that will track through the Great Lakes
Saturday with rain and wind Friday night into Saturday morning.
The cold air comes in Saturday afternoon increasing the winds.
There will likely be some lake effect snow showers with some
accumulations Saturday night into Sunday morning.

&&

.SHORT TERM...(Today through Friday)
Issued at 324 AM EST Wed Nov 15 2017

There is little question we will have rain this morning and there
is also little question the rain will come to an end for a few
hours late this afternoon only to be followed by lake enhanced
rain showers that will change to snow showers by midnight.

The phasing of a northern and southern stream shortwave over
Michigan today will result and upper trough that becomes slightly
negatively tilted by late this afternoon as a 110 knot jet core
dives into the back side of the upper trough. This process
enhances the deep lift over Michigan from mid morning into this
afternoon. There is a 40 to 50 knot low level jet helping the
cause too. Bring in the jet exit region does not hurt our cause
for a period of moderate to heavy rain late this morning into
early this afternoon either. That combined with precipitable
water values near 0.90 inch for the 15th of November helps to
bring us the heavier rainfall. This will mean a period of moderate
to heavy rainfall for most of the area between 9 am and 2 pm.
Most areas should get over a half inch of rain today.

Since the system is deepening as it moves away and the northern
stream air gets drawn into the system it will also be windy,
epically once the cold air moves in later this afternoon. Also
since the jet core goes south of Michigan we will be in the upper
level cold pool tonight and in deep cyclonic flow. This brings in
850 temps down to -7c. That is more than enough to result in rain
showers changing to snow showers by midnight. With northwest winds
this will mean all areas near and west of US-131 will see the
precipitation tonight.

This system moves out quickly Thursday so any snow showers should
end by mid morning. In fact skies should clear due to shortwave
ridging Thursday night. That will bring temperatures down into the
lower to mid 20s.

Friday will see increasing clouds as the next system approaches.
Any rain will hold off until Friday night.

.LONG TERM...(Friday night through Tuesday)
Issued at 324 AM EST Wed Nov 15 2017

Rain showers are likely Friday night as the sfc low continues to
strengthen and move east with southerly flow waa and moisture
advection out ahead of it. A few thunderstorms may also develop late
Friday night over our south/southeastern fcst area, but the better
chance for convection should stay further south of our area.

With the sfc low being somewhat weaker/faster and taking a further
southward track across southern Michigan, we now expect less in
terms of impacts from wind and snow showers. Nevertheless it will
become windy late Saturday through Saturday evening on the back side
of the departing and strengthening sfc low. Scattered snow showers
are also still expected late Saturday through Saturday night into
Sunday but with little if any snow accumulation.

A high pressure ridge will build in Monday and bring fair weather
with seasonable temperatures. Overall medium range guidance trends
also now suggest that fair and tranquil wx will likely continue
Tuesday into midweek with near normal temps.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 110 PM EST Wed Nov 15 2017

Widespread IFR cigs/vsbys will continue this afternoon. Even
though the heavier rain will shift off to the east soon, the
lower cigs and ocnl drizzle/light rain should persist until the
cold front passes though late in the day.

Shortly after Fropa (roughly 21z at MKG and 00Z at JXN) we will
see cigs improve to MVFR levels and vsbys to at or above 6 miles.
The winds will shift westerly and become strong with gusts of
25-35 kts tonight.

Lake effect snow and rain showers will develop behind the
front tonight but was not confident enough to go with reduced
vsbys in snow. The DGZ is not saturated in the fcst soundings and
the sfc temps hold up around 40 much of the night per latest LAMP
guidance, which supports more rain than snow.

If there were to be any decent vsby-reducing snow showers tonight
it would probably be between roughly 04Z and 08Z when a fairly
potent shortwave will be passing through the region. This feature
could briefly provide deep enough moisture to saturate the DGZ
with some convective bursts of heavier precipitation and stronger
wind gusts possible as cells pass through.


&&

.MARINE...
Issued at 324 AM EST Wed Nov 15 2017

The deepening storm pulling in polar air from southern Canada this
evening into Thursday will help increase the winds so I see no
problem with our gales late this afternoon into tonight. Thus I
continued our forecast as is.


&&

.HYDROLOGY...
Issued at 108 PM EST Tue Nov 14 2017

Model QPFs with the Wednesday cold front have trended up, with
widespread amounts near 0.50 now expected. This should bring an
end to the current slowly receding river levels and probably bring
about some slight/minor rises. The system for Friday and Saturday
could produce around an inch of rain, and that may lead to more
notable rises in the days following. At this time, it appears the
Kalamazoo and St. Joseph rivers would be most susceptible.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 4 PM EST this afternoon for
     LMZ844>849.

     Gale Warning from 4 PM this afternoon to 8 AM EST Thursday for
     LMZ844>849.

&&

$$

SYNOPSIS...WDM
SHORT TERM...WDM
LONG TERM...Laurens
AVIATION...Meade
HYDROLOGY...Meade
MARINE...WDM



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