726 
FXUS63 KGRR 081958
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
358 PM EDT Sat Oct 8 2022

LATEST UPDATE...
Discussion/Marine

.DISCUSSION...(This evening through next Saturday)
Issued at 357 PM EDT Sat Oct 8 2022

- Warmer than colder than warmer but not much rain -

For the most part it will be warmer for the next few days with
little in the way of rainfall. I do not expect any significant 
frost of freezing temperatures in the GRR forecast area tonight. 
The next northern stream shortwave tracks well north of the 
Canadian board Sunday, with it's primary jet core tracking just 
south of James Bay Monday morning. This boots out the cold air we 
are currently in, so we see rising low and mid level temperatures 
and thickness values into Sunday evening. Yes, even the thickness 
in the 1000/925 rise during the night tonight over SW MI. Really 
this is a warm front sort of event but there is little mid level 
moisture so mostly it will just not get all that cold tonight. 
However all that warmer dry air will clear out the clouds by early
this evening. 

There is weak northern stream shortwave traveling in tandum with
the farther north shortwave. That system becomes a rather sharp
upper trough as is passes just south of Michigan Sunday night.
This too is seriously moisture staved. Even so it has a fair
amount of lift with it so we get a lot of mid clouds as it comes
through. Thus Sunday will not really be all that sunny actually. 
The mid clouds move in just before sunrise. This system is strong
enough that it will likely create precipitation aloft by Sunday
evening. That will mostly pass south of I-96 since the shortwave
will track south of I-94. Maybe we get some very light rain
showers to reach the ground near and south of I-94 Sunday evening.
We have low chance pops for that event. 

- Brief cool down Monday- 

The cold front that trails the Canadian system comes through this
area Monday morning. With the polar jet well north it Canada at
that point we only get brief push of cooler air from this. Largely
this would be on Monday. There is likely to be freezing or below 
freezing temperatures Monday morning north of Route 20. Since the 
polar jet is so far north with this expect little in the way of 
clouds and quick warm up by Monday afternoon.


- Widespread significant rainfall is expected midweek then colder-

Our next system is a fairly strong Pacific storm currently. The
jet streak from that crosses the Aleutian Islands Sunday evening.
The associated jet streak digs strongly southward into western MT
by Tuesday morning. That of course results in rising low and mid 
level heights over the Great Lakes. That in turn means warmer 
temperatures. Tuesday will likely be a the warmest day of the week
since there will be a fair amount of sunshine yet. 

Wednesday is when the rain moves in from this storm. That happens 
since that next major Pacific storm system's jet core digs west 
of Michigan. That puts us on the warm advection and good moisture
transport side of this system. We expect a significant (over a 
quarter inch of rainfall) over the entire forecast area from this 
system on Wednesday. We may even get enough instability for 
thunderstorms.

This system is expected to majorly close off a deep upper storm
over the southern Canada north of the Great Lakes into the area
well south of the Great Lakes by Friday. That system will be
locked in place into next weekend. We will likely have lake effect
showers from this and maybe even some wet snow mix it at times. To
early to put details on this. 




&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 148 PM EDT Sat Oct 8 2022

Winds have become gusty as forecast thanks to the strong gradient
with the low to our north and high to our south , in combination
with a shortwave tracking just north of the area this afternoon.
There is a 25 to 30 knot wind speed max between now and 06z in the
500 ft to over 8000 ft agl layer that comes trough this area to
help the cause of those stronger winds. 

The passing of this system will clear the skies from northwest to
southeast through the rest of the afternoon. All areas should be
clear or nearly so between 22z and 06z.

The next shortwave comes through Sunday evening. That is stronger
and brings a cold front through the area late Sunday night into
mid morning Monday. There will be mid clouds that move into the
area ahead of that front but I do not expect any precipitation at
any of our TAF sites through 18z. It is possible in the 23z to 06z
time frame there could be showers for the I-94 TAF sites however.


&&

.MARINE...
Issued at 357 PM EDT Sat Oct 8 2022

Winds and waves will remain hazardous to small craft into late
Sunday night. There will be a break in that but by mid week expect
possible gales and dangerous surf conditions. 



&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 11 AM EDT Sunday for LMZ844>849.

&&

$$

DISCUSSION...WDM
AVIATION...WDM
MARINE...wdm