FXUS63 KGRR 121700

AFDGRR



Area Forecast Discussion

National Weather Service Grand Rapids MI

1200 PM EST Fri Dec 12 2025



.KEY MESSAGES...



- Lake Effect Snow through the Weekend



- Arctic Air this Weekend, Warming Trend Next Week



&&



.DISCUSSION...

Issued at 310 AM EST Fri Dec 12 2025



- Lake Effect Snow through the Weekend



A quick moving shortwave trough will move through this evening

bringing with it a round of snow. Within the southwest flow this

afternoon, a band of snow showers is expected to develop around

the Muskegon area. There initially could be some freezing rain as

moisture flirts with the dendritic growth zone. Deeper moisture

moves in during the late afternoon and early evening along with 

positive vorticity advection. Winds will also shift to the west 

northwest. This will cause snow showers to spread along the 

lakeshore and expand eastward. Deep moisture will be brief as 

shown in 700mb moisture fields and soundings which will limit 

amounts. Snowfall rates will largely be about 0.1 inch per hour 

with 0.25 to 0.50 inch per hour possible between 7pm and midnight.

Overall amounts along and west of US-131 are expected to be in 

the 1 to 3 inch range through Saturday morning. The probability of

4 inches or more is low (20 to 30 percent) with isolated higher 

probabilities of 40 percent as seen in the WPC super ensemble and 

HREF. Therefore not planning any headlines at this time. 



Saturday afternoon a clipper system passes mainly to our south

bringing another front through the region. We'll have to monitor

the track as it could potentially bring higher amounts to

southwest Michigan, otherwise light lake effect snow and flurries

will continue into Sunday with amounts largely under an inch and 1

to 2 inches along the lakeshore through Sunday afternoon. With the

snowfall and cold temperatures as mentioned below, any snow will

cause slick conditions.



- Arctic Air this Weekend, Warming Trend Next Week



Cold air filters in for the weekend with 925mb temperatures around

-15 C resulting in lows in the single digits Saturday night and

 Sunday night and highs in the teens on Saturday and low 20s on

 Sunday. Wind chills will be around 0 and in the single digits

 below 0 potentially hitting minus 10 Saturday morning into Monday

 morning. Slight improvements in the wind chills are possible

 Sunday afternoon with the "warmer" temperatures.



The overall pattern shifts to more westerly flow next week

bringing milder temperatures with highs in the 30s Tuesday and 

then upper 30s to 40s Wednesday and Thursday. Looking at the

cluster analysis there is some uncertainty with the timing and

strength of the shortwave troughs and ridges in the flow. With

these shortwaves there is the potential for rain/snow. With any

rain we'll need to monitor the timing. With the cold ground there

could the be potential for freezing rain even with air 

temperatures above freezing.



&&



.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...

Issued at 1200 PM EST Fri Dec 12 2025



A mix of MVFR and VFR cigs are expected across the terminals this

afternoon before solid MVFR sets in overnight through the end of

the TAF period. After 00z, lake effect snow showers set in from 

northwest to southeast with periods of MVFR visbys likely and a 

20-30% chance of IFR visbys. Light snow showers likely linger near

the lakeshore through the day but become less widespread and 

robust after 12z Saturday through the end of the TAF window. Wind

gusts increase tonight into Saturday to 20-25 knots, possibly as

high as 30 knots near the lakeshore, in post frontal cold air 

advection.



&&



.GRR WATCHES/WARNINGS/ADVISORIES...

MI...None.

MARINE...Small Craft Advisory from 7 PM this evening to 7 PM EST Saturday 

     for LMZ844>849.



&&



$$



DISCUSSION...RAH

AVIATION...Thomas