439
FXUS63 KGRR 231551
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1051 AM EST Mon Dec 23 2024

.KEY MESSAGES...

- Wintry mix of precipitation today into tonight

- Gradual moderating trend of temps midweek through the weekend

- Rain showers next weekend

&&

.UPDATE...
Issued at 1051 AM EST Mon Dec 23 2024

We will be holding on to the headlines as is for this morning.

More widespread precipitation has been a little delayed in
organizing this morning. That said, what has occurred has been
pretty much expected with freezing rain having been observed at
Grand Rapids and Eaton Rapids, and UP being reported at Kalamazoo
and Battle Creek which is likely sleet or freezing rain.

We believe that the layout of the precipitation types is still
good, with little change made to them. One thing we did hit a
little harder was freezing drizzle, especially up north. Latest
model guidance is indicating that we may not keep a saturated DGZ
during the entire time, leading to some fzdz at times up there
where sfc temps will stay below freezing.

It will be the case down south too, but it has been covered by the
freezing rain chances, and will become more drizzle as temps rise
above freezing later this afternoon.

The bottom line to all of this is that a lack of deep moisture at
times will likely eat into different p-type accumulations. The
potential impacts will remain with freezing rain/freezing drizzle
remaining possible everywhere, so no headline adjustments at this
time.

&&

.DISCUSSION...
Issued at 300 AM EST Mon Dec 23 2024

- Wintry mix of precipitation today into tonight

A low pressure system centered over far southern MN early this
morning will continue to move east and bring our area a wintry mix
of pcpn today. Very light warm air advection snow showers/flurries
will clip our far northern fcst area early this morning (prior to
daybreak).

Steadier pcpn will begin to develop during the mid to late morning
hours and will continue through the afternoon and evening. Fcst
soundings suggest pcpn will fall mainly in the form of snow
north of the I-96 corridor with potential for two to five inches
of accumulation (relatively highest amounts within that range
occurring over our far ne fcst area up around Clare).

A consensus blend of latest higher res model guidance and fcst
soundings suggest that a wintry mix of pcpn will occur near to
south of the I-96 corridor. This wintry mix will really cut down
on any snowfall (less than an inch of snow is fcst near to south
of I-96). The 00Z HREF FRAM suggests potential ice accretion
would be very light and confined to areas near/south of I-96 and
we are forecasting trace amounts to less than five hundredths of
an inch of -fzra. This is still sufficient enough to result in
some travel impacts.

Pcpn will wind down near to south of I-96 this evening but we
expect that deformation zone snow will linger over our northern
fcst area through most of the evening. This deformation zone
snowfall will taper off by around midnight as mid to upper level
deformation zone dynamics shift east of our area.

We decided to leave the winter wx adv start times (12Z this
morning) unchanged for our central/southern fcst area as latest
runs of the HRRR show potential for light freezing rain/freezing
drizzle to develop fairly quickly from west to east between 12Z
and 15Z.

- Gradual moderating trend of temps late week through the weekend

Overall trends in numerical guidance the past 24-48 hrs show a
bit slower of a moderating trend of temps through midweek. It now
appears that high temps will only reach the mid 30s on Christmas
Day and Wednesday. Predominantly dry wx is expected on Christmas
Day through midweek. Temps will only be around 1-3 degrees milder
incrementally Thursday and Friday before stronger waa boosts high
temps well into the 40s for the weekend.

- Rain showers next weekend

After potential for some warm air advection showers Friday we
expect better potential for some showers for the weekend as deeper
moisture will be in place by then. A low pressure system over the
Arklatex region will move ne and likely bring steadier rain by
Saturday night and Sunday.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 618 AM EST Mon Dec 23 2024

Snow and mixed precip moves in during the morning with MVFR
conditions expanding eastward and increasing LLWS. Expected IFR
conditions by the afternoon and perhaps even LIFR by evening.
Southeast winds will gust to 20 knots at times in the morning
before going west and northwest in the afternoon and evening.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory until 11 PM EST this evening for
     MIZ037>040-043>046-050>052-056>059.
     Winter Weather Advisory until 7 PM EST this evening for
     MIZ064>067-071>074.
MARINE...Small Craft Advisory until 10 PM EST this evening for LMZ844>849.

&&

$$

UPDATE...NJJ
DISCUSSION...Laurens
AVIATION...Ostuno