National Weather Service United States Department of Commerce

Back-to-Back Pacific Storms to Impact the West Coast; Heavy Snow in the Central Appalachians

Back-to-back powerful Pacific storm systems to impact the Pacific Northwest and northern California through the end of this week with heavy rain, flooding, strong winds, and higher elevation mountain snow. A strong, long-duration atmospheric river will accompany the Pacific storms, bringing excessive rainfall and flash flooding to southwest Oregon and northwest California through the week. Read More >

State College, PA

Weather Forecast Office

Winter Weather Experimental Probabilistic Snow and Ice

Weather.gov > State College, PA > Winter Weather Experimental Probabilistic Snow and Ice
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
 
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"
Ice Accumulation Potential
 

Expected Ice Accumulation - Official NWS Forecast

 
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.
Most Likely Ice Accumulation

What's this?

Most Likely Ice Accumulation

Represents our official ice forecast in inches within the next one to three days. The ice accumulation amounts are provided in ranges.
Ice Accumulation Potential
 

Expected Ice Accumulation - Official NWS Forecast

 
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.
Most Likely Ice Accumulation

What's this?

Most Likely Ice Accumulation

Represents our official ice forecast in inches within the next one to three days. The ice accumulation amounts are provided in ranges.
72 Hour Snowfall / Ice Accumulation Forecasts
72 Hour Snowfall Forecast 72 Hour Ice Accumulation Forecast
72 Hour Snowfall Forecast
72 Hour Ice Accumulation Forecast

 

12 Hour Snowfall / Ice Accumulation Forecasts
12 Hour Snowfall Forecasts (through 72 Hours)
0 to 12 Hours 12 to 24 Hours 24 to 36 Hours 36 to 48 Hours 48 to 60 Hours 60 to 72 Hours
0 to 12 Hour Snow Amount Forecast
12 to 24 Hour Snow Amount Forecast
24 to 36 Hour Snow Amount Forecast
36 to 48 Hour Snow Amount Forecast
48 to 60 Hour Snow Amount Forecast
60 to 72 Hour Snow Amount Forecast

 

12 Hour Ice Accumulation Forecasts (through 72 Hours)
0 to 12 Hours 12 to 24 Hours 24 to 36 Hours 36 to 48 Hours 48 to 60 Hours 60 to 72 Hours
0 to 12 Hour Ice Accumulation Forecast
12 to 24 Hour Ice Accumulation Forecast
24 to 36 Hour Ice Accumulation Forecast
36 to 48 Hour Ice Accumulation Forecast
48 to 60 Hour Ice Accumulation Forecast
60 to 72 Hour Ice Accumulation Forecast

 

Days 4-7 Winter Weather Outlook
 

Days 4-7
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
 
Days 4-7 Precipitation Forecast
 
Days 4-5 Forecast Precipitation Days 6-7 Forecast Precipitation
Days 4-5 Precip Days 6-7 Precip
 
 
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

 

Daily Snow / Ice Reports

Reported Snow/Ice Totals
Text Reported Snow/Ice Totals
Snow/Ice Analysis
Latest snow and ice reports
Text Snow/Rain Reports
Snow analysis

 

National Snowfall Reports/Analysis
National Snow Reports National Snowfall Analysis
National Snow Reports
National Snowfall Analysis

 

From the Middle Atlantic River Forecast Center

24-hr Observed
Observed
Snow Depth
Modeled Snow Water
Equivalent
MARFC Snow Fall Map
MARFC Snow Depth Map
MARFC Snow Water Equivalent Map

 

Average Snowfall (30-Year Average / 1991-2020)
Snow analysis

 

 

** EXPERIMENTAL ** EXPERIMENTAL ** EXPERIMENTAL **

Day 4-7 Winter Weather Outlook

(Winter Liquid Equivalent Exceedance Graphics)
 
Day 4 Day 5 Day 6 Day 7
Day 4 Winter Storm Threat Day 5 Winter Storm Threat Day 6 Winter Storm Threat Day 7 Winter Storm Threat
Winter Storm Threat

 

These images are created using WPC Probability of Exceeding 0.25"
Liquid Equivalent of Snow/Sleet. (Freezing Rain is not included)

** EXPERIMENTAL ** EXPERIMENTAL ** EXPERIMENTAL **
High  High Threat for a Plowable Snow.
   Potential impacts include travel delays and closures. Plan ahead to minimize impact on you and your family.
 
Medium  Moderate Threat for a Plowable Snow.
   Primary threat is disruption to travel.
 
Low  Slight Threat for a Plowable Snow.
   If threat materializes, may cause travel disruptions.
 
None  No significant winter storm threat is currently expected.
   However, light wintry precipitation may still be possible.
 
Precipitation Onset/End Timing
Onset of Wintry Precipitation End Timing of Wintry Precipitation
Winter Precipitation Onset
Winter Precipitation End Time
What's this? What's this?

Precipitation Onset

Most likely time of winter precipitation onset (snow, sleet, freezing rain). Rain is not included here. This information is provided when we issue a Warning or Advisory for expected snow or ice accumulation; typically six to 24 hours in advance. Times are only given for places that are under a Warning or Advisory. They will be blank in areas outside Warnings or Advisories.

Precipitation End Time

Most likely time of winter precipitation ending (snow, sleet, freezing rain). Rain is not included here. This information is provided when we issue a Warning or Advisory for expected snow or ice accumulation; typically six to 24 hours in advance. Times are only given for places that are under a Warning or Advisory. They will be blank in areas outside Warnings or Advisories.

 

 

Weather Type and Coverage Forecast

**Prototype Under Development**
**Not to be relied on for operational decision making**
 

 

 

Detailed information on the Precipitation Type Graphic
can be located here.
 
Winter Storm Outlook (WSO)

 
Winter Storm Outlook (WSO)
for Snow		 Winter Storm Outlook (WSO)
for Ice

 

 
Winter Storm Severity Index (WSSI)

 
Winter Storm Severity Index (WSSI)
Overall Impact

 
Winter Storm Severity Index (WSSI)
Snow Amount		 Winter Storm Severity Index (WSSI)
Ice Accumulation

 
Winter Storm Severity Index (WSSI)
Snow Load		 Winter Storm Severity Index (WSSI)
Flash Freeze

 
Winter Storm Severity Index (WSSI)
Blowing Snow		 Winter Storm Severity Index (WSSI)
Ground Blizzard

 
The purpose of the Winter Storm Severity Index (WSSI) is to provide NWS partners and the general public with an indication of the level of winter precipitation (snow and ice) severity and its potential related societal impacts.

 
Report Snow/Ice to the National Weather Service
REPORT SNOW/ICE AMOUNTS TO US REPORT SNOW/ICE IMPACTS TO US
Text Snow/Rain Reports
Text Snow/Rain Reports

 

 

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to Submit Your Report:

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