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El Niño and La Niña Effects on Philadelphia Winters (since 1950)

SNOWFALL BY ENSO STATE
1949-50 THROUGH 2009-2010 WINTER
AVG 21.9
STRONG NINA - 6 WINTERS 15.9
MODERATE NINA - 7 WINTERS 13.8
WEAK NINA - 7 WINTERS 23.1
ENSO NEUTRAL - 22 WINTERS 22
WEAK NINO - 5 WINTERS 28.1
MODERATE NINO - 8 WINTERS 24.3
STRONG NINO - 6 WINTERS 27
NUMBER OF SIGNIFICANT SNOWFALL EVENTS
AT PHL BY ENSO STATE
>/= 6" >/= 10"
STRONG NINA - 6 WINTERS 3 0
MODERATE NINA - 7 WINTERS 1 0
WEAK NINA - 7 WINTERS 4 1
ENSO NEUTRAL - 22 WINTERS 21 8
WEAK NINO - 5 WINTERS 5 3
MODERATE NINO - 8 WINTERS 8 1
STRONG NINO - 6 WINTERS 8 6

Watch/Warning/Advisory Terminology & Criteria

  • 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.
  • 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.
  • 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.
Criteria Maps of Winter Storm Watches, Warnings & Advisories for New Jersey, eastern Pennsylvania, Delaware, eastern Maryland
12-Hour Advisory Snowfall
12-Hour Warning Snowfall
24-Hour Warning Snowfall
Freezing Rain Advisory
Ice Storm Warning
Wind Chill Advisory
Wind Chill Warning

Gradient high wind outlooks, watches, warnings, and wind advisories shall be issued using the following wind speed values
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)

 

 

Snowfall from Past Winters

Seasonal Snowfall Totals from 1979-Present (updated March 2016):

 

Preliminary Top Ten Philadelphia Snow Storms (updated Feb 2016):

Ranking

Value

 

Duration

 

 

1

30.7

 

January 7-8 1996

 

2

28.5

 

February 5-6 2010

 

3

23.2

 

December 19-20 2009

4

22.4

 

January 22-23 2016

 

5

21.3

 

February 11-12 1983

 

6

21

 

December 25-26 1909

7

19.4

 

April 3-4 1915

 

8

18.9

 

February 12-14 1899

 

9

18.7

 

February 15-18 2003

 

10

16.7

 

January 22-24 1935

 

 

 

Winter Weather Awareness and Safety