FGF Winter Weather Forecasts

Heavy Rainfall to Bring Flooding Threat to California; Heavy Snow in the Sierra

A strong atmospheric river will bring heavy rainfall to California through the holiday week. The heaviest rainfall is expected on Wednesday in the Los Angeles Basin. Flash and urban flooding is possible. A prolonged heavy snowfall is expected in the Sierra Nevada from the atmospheric river, raising concerns for major snow‐load impacts. Travel may be difficult to impossible over the passes. Read More >

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>=18"

Ice Accumulation Potential Experimental - Leave feedback Click here for more information on these products Click here for the NWS Probabilistic Precipitation Portal
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...

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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

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What's this?

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

0 to 6 Hours
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6 to 12 Hours
$>=1\$

12 to 18 Hours
$>=2\$

18 to 24 Hours
$>=4\$

24 to 30 Hours
$>=6\$

30 to 36 Hours
$>=8\$

36 to 42 Hours
$>=12\$

42 to 48 Hours
$>=18\$

0 to 6 Hours
$>=0.1\$

6 to 12 Hours
$>=1\$

12 to 18 Hours
$>=2\$

18 to 24 Hours
$>=4\$

24 to 30 Hours
$>=6\$

30 to 36 Hours
$>=8\$

36 to 42 Hours
$>=12\$

42 to 48 Hours
$>=18\$

0 to 6 Hours
$>=0.1\$

6 to 12 Hours
$>=1\$

12 to 18 Hours
$>=2\$

18 to 24 Hours
$>=4\$

24 to 30 Hours
$>=6\$

30 to 36 Hours
$>=8\$

36 to 42 Hours
$>=12\$

42 to 48 Hours
$>=18\$

0 to 6 Hours
$>=0.1\$

6 to 12 Hours
$>=1\$

12 to 18 Hours
$>=2\$

18 to 24 Hours
$>=4\$

24 to 30 Hours
$>=6\$

30 to 36 Hours
$>=8\$

36 to 42 Hours
$>=12\$

42 to 48 Hours
$>=18\$

0 to 6 Hours
$>=0.1\$

6 to 12 Hours
$>=1\$

12 to 18 Hours
$>=2\$

18 to 24 Hours
$>=4\$

24 to 30 Hours
$>=6\$

30 to 36 Hours
$>=8\$

36 to 42 Hours
$>=12\$

42 to 48 Hours
$>=18\$

0 to 6 Hours
$>=0.1\$

6 to 12 Hours
$>=1\$

12 to 18 Hours
$>=2\$

18 to 24 Hours
$>=4\$

24 to 30 Hours
$>=6\$

30 to 36 Hours
$>=8\$

36 to 42 Hours
$>=12\$

42 to 48 Hours
$>=18\$

Winter Storm Severity Index (WSSI)

Winter Storm Outlook (WSO)

Snow Amount Potential Experimental - Leave feedback Click here for more information on these products Click here for the NWS Probabilistic Precipitation Portal
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.

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

Heavy Rainfall to Bring Flooding Threat to California; Heavy Snow in the Sierra

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Low End Amount – 9 in 10 Chance (90%) of Higher Snowfall

Expected Snowfall - Official NWS Forecast

High End Amount – Only a 1 in 10 Chance (10%) of Higher Snowfall

Percent Chance That Snow Amounts Will Be Greater Than

Snowfall Totals by Location

Low End Amount – 9 in 10 Chance (90%) of Higher Ice Accumulation

Expected Ice Accumulation - Official NWS Forecast

High End Amount – Only a 1 in 10 Chance (10%) of Higher Ice Accumulation

Percent Chance That Ice Accumulation Will Be Greater Than

Ice Accumulation Totals by Location

Selected City Charts
Expected Snowfall - Box and Whisker Plot	Expected Snowfall - Exceedance Bar Plot