National Weather Service United States Department of Commerce

Heavy Rain and Mountain Snow Lingers in California; Winter Storm Impacting the Great Lakes and Northeast U.S.

An atmospheric river will wind down through today across California with lingering heavy rainfall, heavy mountain snow, and gusty winds. A wintry mix of freezing rain, sleet, and snow will cause hazardous travel conditions for the Great Lakes into the northern Mid-Atlantic and southern New England today through Saturday morning. Areas of tree damage and power outages are possible. Read More >

San Francisco Bay Area, CA

Weather Forecast Office

Probabilistic Snowfall Forecasts

Weather.gov > San Francisco Bay Area, CA > Probabilistic Snowfall Forecasts

Snow Amount Potential
Experimental -
Expected Snowfall - Official NWS Forecast
 

What's this? 		High End Amount
1 in 10 Chance (10%) of Higher Snowfall

What's this?
Low End Amount
9 in 10 Chance (90%) of Higher Snowfall

What's this?

Low End 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.

Expected Snowfall - Official NWS Forecast

 

This map is the official 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.

High End Amount – 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.
Percent Chance That Snow Amounts Will Be Greater Than...
Experimental -
What's this?

Percent Chance That Snow Amounts Will Be Greater Than

 

This series of maps shows the probability (that is, the likelihood) that snowfall will equal or exceed specific amounts during the time period shown on the graphic. These forecasts are based on many computer model simulations of possible snowfall totals.
Hover over thumbnails below to view larger image.
>=0.1"
>=1"
>=2"
>=4"
>=6"
>=8"
>=12"
>=18"

Snowfall Totals by Location
Experimental -
What's this?

Snowfall Totals by Location

 

These tables show the snowfall forecast for individual locations, and provide the same information as the graphics on this web page, just shown in a different way. All of these values are valid for the same time period as depicted on the graphics.

 

Location Low-End
Amount		 Expected
Amount		 High-End
Amount		 Chance of Seeing More Than
 
Ice Accumulation Potential
Experimental -
Expected 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 Amount
1 in 10 Chance (10%) of Higher Ice Accumulation

What's this?
Low End Amount
9 in 10 Chance (90%) of Higher Ice Accumulation

What's this?

Low End 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.

Expected Ice Accumulation - Official NWS Forecast

 

This 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.

High End 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.
Percent Chance That Ice Accumulation Will Be Greater Than...
Experimental -
What's this?

Percent Chance That Ice Accumulation Will Be Greater Than

 

This series of maps shows the probability (that is, the likelihood) that ice accumulation will equal or exceed specific amounts during the time period shown on the graphic. These forecasts are based on many computer model simulations of possible snowfall totals.
Hover over thumbnails below to view larger image.
>=0.01"
>=0.1"
>=0.25"
>=0.5"
>=0.75"
>=1"
>=1.25"
>=1.5"
Ice Accumulation by Location
Experimental -
What's this?

Ice Accumulation Totals by Location

 

These tables show the ice accumulation forecast for individual locations, and provide the same information as the graphics on this web page, just shown in a different way. All of these values are valid for the same time period as depicted on the graphics.

 

Location Low-End
Amount		 Expected
Amount		 High-End
Amount		 Chance of Seeing More Than
 
Winter Storm Severity Index (WSSI) Winter Storm Outlook (WSO)
Winter Storm Severity Index
Winter Storm Outlook
Local Snow Reports National Snowfall Analysis
National Snow Reports
National Snowfall Analysis
Days 4-7 Winter Weather Outlook
 
Day 4 Winter Weather Outlook Day 5 Winter Weather Outlook
Day 4 Winter Weather Outlook Day 5 Winter Weather Outlook
 
Day 6 Winter Weather Outlook Day 7 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 Week-2 Experimental Heavy Snow Risk
 
CPC Temperature & Precipitation Maps
 

Days 6-10
Temperature  Precipitation
6-10 day temperature 6-10 day precipitation
 
 

Days 8-14
TEMPERATURE  PRECIPITATION
8-14 day temperature 8-14 day precipitation
 
 

Week 3-4

TEMPERATURE

PRECIPITATION
Week 3-4 Temperature Week 3-4 precipitation
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