Winter Weather
Winter Weather Products
Climate Prediction Center (CPC)
Current Winter Storm Watches, Warnings and Advisories
Local Products
Other Products
Experimental Products
Wind Chill Information
On November 1, 2001, the National Weather Service (NWS) implemented a replacement Wind Chill Temperature (WCT) index
for the 2001/2002 winter season. The new WCT index:
- uses calculated wind speed at an average height of five feet (typical height of an adult human face) based on
readings from the national standard height of 33 feet (typical height of an anemometer)
- is based on a human face model; incorporates modern heat transfer theory (heat loss from the body to its
surroundings, during cold and breezy/windy days);
- lowers the calm wind threshold to 3 mph;
- uses a consistent standard for skin tissue resistance; and assumes no impact from the sun (i.e. clear night sky).
El Niño and La Niña Effects on Philadelphia Winters
Terminology & Watch/Warning/Advisory Criteria
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Warnings:
A warning is issued to alert the public to imminent dangerous winter weather. Normally a warning is
issued after a winter storm watch has been in effect. A winter storm watch may not precede a warning
if winter weather develops quickly and unexpectedly. A Winter Storm Warning is issued when heavy snow,
significant freezing rain, or heavy sleet is expected to occur. Usually issued 6 to 18 hours in advance
of the winter weather. A Blizzard Warning is issued when sustained or gusty winds of 35 mph or more
are expected to reduce visibility at or below a quarter of a mile due to falling and/or blowing snow
for at least three hours. Wind Chill Warnings are issued when wind chills are expected to be below -24
degrees fahrenheit.
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Watches:
A watch is issued to alert the public to the potential for dangerous winter weather. A Winter Storm Watch
is issued when conditions exist for the possible occurrence of dangerous winter weather such as a
blizzard, heavy snow, significant freezing rain or heavy sleet. Usually issued 12 to 36 hours in advance
of the winter weather.
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Advisories:
A less severe winter weather event will prompt the issuance of an advisory. An advisory is
named specific to the weather event expected and is issued when the event
is expected to be widespread. Travel by foot or vehicle may be dangerous
during an advisory even if the winter weather is not expected to reach
winter storm criteria.
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Gradient high wind outlooks, watches, warnings, and wind advisories shall be issued using the following wind speed values
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Product Type
|
Sustained Wind ( 1 Hr)
|
Any duration gust
|
| High Wind Outlook |
>= 40 MPH (35 KTS) |
>= 58 MPH (50 KTS) |
| High Wind Watch |
>= 40 MPH (35 KTS) |
>= 58 MPH (50 KTS) |
| High Wind Warning |
>= 40 MPH (35 KTS) |
>= 58 MPH (50 KTS) |
| Wind Advisory (land) |
31-39 MPH (27-34 KTS) |
46-57 MPH (40-49 KTS) |
| Wind Advisory for area lakes |
25-30 MPH (22-26 KTS) |
40-45 MPH (35-39 KTS) |
Previous Winters
Seasonal Snowfall Totals (through last winter) for:
Top Snowstorms for Philadelphia (unofficial):
- 30.7" on January 7-8, 1996
- 21.3" on February 11-2, 1983
- 21.0" on December 25-26, 1909
- 19.4" on April 3-4, 1915
- 18.9" on February 12-14, 1899
- 16.7" on January 22-24, 1935
- 15.1" on February 28-March 1, 1941
Storm Archives
Winter Weather Awareness and Safety
