Grand Rapids, MI

Weather Forecast Office

GRR Winter Weather Forecasts

Probabilistic Snowfall Forecasts
MI Probabilistic Snowfall Forecasts
Probabilistic Ice Forecasts
MI Probabilistic Ice Forecasts
Winter Storm Outlook and Winter Storm Severity Index
Snow and Ice Observations
Medium/Long Range Forecast
Event Based Storm Total Snow Forecasts

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72 Hour Snow Amount Potential Experimental - Leave feedback Click here for more information on these products Click here for the NWS Probabilistic Precipitation Portal
Expected 72 Hour Snowfall - Official NWS Forecast What's this?	High End 72 Hour Amount 1 in 10 Chance (10%) of Higher Snowfall What's this?
	Low End 72 Hour Amount 9 in 10 Chance (90%) of Higher Snowfall What's this?
Low End Amount – 9 in 10 Chance (90%) of Higher Snowfall over 72 hours This map depicts a reasonable lower-end snowfall amount for the time period shown on the graphic, based on many computer model simulations of possible snowfall totals. This lower amount is an unlikely scenario with a 9 in 10, or 90% chance that more snow will fall, and only a 1 in 10, or 10% chance that less snow will fall. This number can help serve as a lower-end scenario for planning purposes. "Point Map" is Expected Snowfall - 72hr Official NWS Forecast The "Point" map is the official 72 hour NWS snowfall forecast in inches during the time period shown on the graphic. This snowfall amount is determined by NWS forecasters to be the most likely outcome based on evaluation of data from computer models, satellite, radar, and other observations. "Range Map" is Experimental Probabilistic Snowfall Range Amounts over 72 hours The "Range" map is the 25th percentile (lower number) to 75th percentile (higher number) of possible snowfall amounts based on the Weather Prediction Center (WPC) Super Ensemble output during the time period of the graphic. The official NWS snowfall forecast influences this range of values either up or down depending upon how closely they match. High End Amount – Only a 1 in 10 Chance (10%) of Higher Snowfall over 72 hours This map depicts a reasonable upper-end snowfall amount for the time period shown on the graphic, based on many computer model simulations of possible snowfall totals. This higher amount is an unlikely scenario, with only a 1 in 10, or 10% chance that more snow will fall, and a 9 in 10, or 90% chance that less snow will fall. This number can help serve as an upper-end scenario for planning purposes.

The purpose of these experimental probabilistic snowfall products is to provide customers and partners a range of snowfall possibilities, in complement to existing NWS deterministic snowfall graphics, to better communicate forecast uncertainties during winter weather events. For more information visit this project's Product/Service Description Document, and please provide us your feedback here.

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Percent Chance That 72 Hour Snow Amounts in Will Be Greater Than...

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>=0.1"	>=1"	>=2"	>=4"	>=6"	>=8"	>=12"	>=18"

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72 Hour Snowfall Totals by Location

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Location	Low-End Amount	Expected Amount	High-End Amount	Chance of Seeing More Than
Location	Low-End Amount	Expected Amount	High-End Amount

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Snow Amount Potential Experimental - Leave feedback Click here for more information on these products Click here for the NWS Probabilistic Precipitation Portal
Expected 72 Hour Snowfall - Official NWS Forecast What's this?	High End 72 Hour Amount 1 in 10 Chance (10%) of Higher Snowfall What's this?
	Low End 72 Hour Amount 9 in 10 Chance (90%) of Higher Snowfall What's this?
Low End 72 Hour Amount – 9 in 10 Chance (90%) of Higher Snowfall This map depicts a reasonable lower-end snowfall amount for the time period shown on the graphic, based on many computer model simulations of possible snowfall totals. This lower amount is an unlikely scenario with a 9 in 10, or 90% chance that more snow will fall, and only a 1 in 10, or 10% chance that less snow will fall. This number can help serve as a lower-end scenario for planning purposes. "Point Map" is Expected Snowfall - 72hr Official NWS Forecast The "Point" map is the official 72 hour NWS snowfall forecast in inches during the time period shown on the graphic. This snowfall amount is determined by NWS forecasters to be the most likely outcome based on evaluation of data from computer models, satellite, radar, and other observations. "Range Map" is Experimental Probabilistic Snowfall Range Amounts over 72 hours The "Range" map is the 25th percentile (lower number) to 75th percentile (higher number) of possible snowfall amounts based on the Weather Prediction Center (WPC) Super Ensemble output during the time period of the graphic. The official NWS snowfall forecast influences this range of values either up or down depending upon how closely they match. High End 72 HourAmount – Only a 1 in 10 Chance (10%) of Higher Snowfall This map depicts a reasonable upper-end snowfall amount for the time period shown on the graphic, based on many computer model simulations of possible snowfall totals. This higher amount is an unlikely scenario, with only a 1 in 10, or 10% chance that more snow will fall, and a 9 in 10, or 90% chance that less snow will fall. This number can help serve as an upper-end scenario for planning purposes.

The purpose of these experimental probabilistic snowfall products is to provide customers and partners a range of snowfall possibilities, in complement to existing NWS deterministic snowfall graphics, to better communicate forecast uncertainties during winter weather events. For more information visit this project's Product/Service Description Document, and please provide us your feedback here.

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Percent Chance That 72 Hour Snow Amounts Will Be Greater Than...

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Hover over thumbnails below to view larger image.

>=0.1"	>=1"	>=2"	>=4"	>=6"	>=8"	>=12"	>=18"

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72 Hour Ice Accumulation Potential Experimental - Leave feedback Click here for more information on these products Click here for the NWS Probabilistic Precipitation Portal
Expected 72 Hour Ice Accumulation - Official NWS Forecast What's this? This is the elevated flat surface ice accumulation. It is not radial/line ice. Radial/line ice is typically 39% of the elevated flat surface ice. For more information on this, see this module.	High End 72 Hour Amount 1 in 10 Chance (10%) of Higher Ice Accumulation What's this?
	Low End 72 Hour Amount 9 in 10 Chance (90%) of Higher Ice Accumulation What's this?
Low End 72 Hour Amount – 9 in 10 Chance (90%) of Higher Ice Accumulation This map depicts a reasonable lower-end ice accumulation amount for the time period shown on the graphic, based on many computer model simulations of possible ice accumulation totals. This lower amount is an unlikely scenario with a 9 in 10, or 90% chance that more snow will fall, and only a 1 in 10, or 10% chance that less snow will fall. This number can help serve as a lower-end scenario for planning purposes. "Point Map" is Expected 72 Hour Ice Accumulation - Official NWS Forecast The "Point" map is the official NWS ice accumulation forecast in inches during the time period shown on the graphic. This ice accumulation amount is determined by NWS forecasters to be the most likely outcome based on evaluation of data from computer models, satellite, radar, and other observations. "Range Map" is Experimental Probabilistic Ice Accumulation Range Amounts over 72 hours The "Range" map is the 25th percentile (lower number) to 75th percentile (higher number) of possible ice accumulation amounts based on the Weather Prediction Center (WPC) Super Ensemble output during the time period of the graphic. The official NWS ice accumulation forecast influences this range of values either up or down depending upon how closely they match. High End 72 Hour Amount – Only a 1 in 10 Chance (10%) of Higher Ice Accumulation This map depicts a reasonable upper-end ice accumulation amount for the time period shown on the graphic, based on many computer model simulations of possible ice accumulation totals. This higher amount is an unlikely scenario, with only a 1 in 10, or 10% chance that more snow will fall, and a 9 in 10, or 90% chance that less snow will fall. This number can help serve as an upper-end scenario for planning purposes.

The purpose of these experimental probabilistic ice accumulation products is to provide customers and partners a range of ice accumulation possibilities, in complement to existing NWS deterministic ice accumulation graphics, to better communicate forecast uncertainties during winter weather events. For more information visit this project's Product/Service Description Document, and please provide us your feedback here.

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Percent Chance That 72 Hour Ice Accumulation Will Be Greater Than...

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>=0.01"	>=0.1"	>=0.25"	>=0.5"	>=0.75"	>=1"	>=1.25"	>=1.5"

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72 Hour Ice Accumulation by Location

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Location	Low-End Amount	Expected Amount	High-End Amount	Chance of Seeing More Than
Location	Low-End Amount	Expected Amount	High-End Amount

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72 Hour Ice Accumulation Potential Experimental - Leave feedback Click here for more information on these products Click here for the NWS Probabilistic Precipitation Portal
Expected 72 Hour Ice Accumulation - Official NWS Forecast What's this? This is the elevated flat surface ice accumulation. It is not radial/line ice. Radial/line ice is typically 39% of the elevated flat surface ice. For more information on this, see this module.	High End 72 Hour Amount 1 in 10 Chance (10%) of Higher Ice Accumulation What's this?
	Low End 72 Hour Amount 9 in 10 Chance (90%) of Higher Ice Accumulation What's this?
Low End 72 Hour Amount – 9 in 10 Chance (90%) of Higher Ice Accumulation This map depicts a reasonable lower-end ice accumulation amount for the time period shown on the graphic, based on many computer model simulations of possible ice accumulation totals. This lower amount is an unlikely scenario with a 9 in 10, or 90% chance that more snow will fall, and only a 1 in 10, or 10% chance that less snow will fall. This number can help serve as a lower-end scenario for planning purposes. "Point Map" is Expected 72 Hour Ice Accumulation - Official NWS Forecast The "Point" map is the official NWS ice accumulation forecast in inches during the time period shown on the graphic. This ice accumulation amount is determined by NWS forecasters to be the most likely outcome based on evaluation of data from computer models, satellite, radar, and other observations. "Range Map" is Experimental Probabilistic Ice Accumulation Range Amounts over 72 hours The "Range" map is the 25th percentile (lower number) to 75th percentile (higher number) of possible ice accumulation amounts based on the Weather Prediction Center (WPC) Super Ensemble output during the time period of the graphic. The official NWS ice accumulation forecast influences this range of values either up or down depending upon how closely they match. High End 72 Hour Amount – Only a 1 in 10 Chance (10%) of Higher Ice Accumulation This map depicts a reasonable upper-end ice accumulation amount for the time period shown on the graphic, based on many computer model simulations of possible ice accumulation totals. This higher amount is an unlikely scenario, with only a 1 in 10, or 10% chance that more snow will fall, and a 9 in 10, or 90% chance that less snow will fall. This number can help serve as an upper-end scenario for planning purposes.

The purpose of these experimental probabilistic ice accumulation products is to provide customers and partners a range of ice accumulation possibilities, in complement to existing NWS deterministic ice accumulation graphics, to better communicate forecast uncertainties during winter weather events. For more information visit this project's Product/Service Description Document, and please provide us your feedback here.

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Percent Chance That 72 Hour Ice Accumulations Will Be Greater Than...

Experimental - Leave feedback

Click here for more information on these products

What's this?

Hover over thumbnails below to view larger image.

>=0.01"	>=0.1"	>=0.25"	>=0.5"	>=0.75"	>=1"	>=1.25"	>=1.5"

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Winter Storm Severity Index (WSSI)	Winter Storm Outlook (WSO)

Local Snow Reports	National Snowfall Analysis

Days 4-7 Winter Weather Outlook

Day 4 Winter Weather Outlook	Day 5 Winter Weather Outlook


Day 6 Winter Weather Outlook	Day 7 Winter Weather Outlook

Click here for an interactive map

CPC Week-2 Experimental Heavy Snow Risk



CPC Temperature & Precipitation Maps

Days 6-10
Temperature	Precipitation



Days 8-14
TEMPERATURE	PRECIPITATION



Week 3-4
TEMPERATURE	PRECIPITATION