Snowfall Scarce Following February 50s; Washington Snow Rare Immediately After Warm Temperatures

The weather-wise are all a-Twitter over the prospect of snowfall in the Washington, DC region on Sunday, but the situation is giving forecasters fits. There's a good reason for that, since warm-February snows, while not impossible, are rare.

Since official records were kept at or near the current location at National Airport beginning in 1930, there have been only 8 instances in which 2" or more of snow fell in the calendar day following a day with temperatures of 50° or higher. With today's high of 54° and a similar reading expected tomorrow, there is a considerable climatological obstacle to overcome. In fact, there have been only 5 cases in which a 2"+ snowfall followed a day with a high above 53°.

The most recent instance of significant snow following 50°+ temperatures was on Feb. 22, 2001, when 2.8" of snow followed a previous day's high of 57°. That was preceded by a 3.6" snowfall on the same date in 1986, following a temperature of 56°.

The full list of February 2"+ snowfalls on the day after 50°+ temperatures is:

Date     Snowfall Temperature
2/16/1937 5.6       52
2/14/1940 2.5       53
2/17/1945 2.6       60
2/11/1955 2.5       63
2/17/1967 5.7       63
2/8/1974  4.0       50
2/22/1986 3.6       56
2/22/2001 2.8       57 

Image (click to enlarge) Washington, DC 2"+ snowfalls on the day following temperatures of 50° or higher, CapitalClimate chart from National Weather Service data, background image © Kevin Ambrose (www.weatherbook.com)

Washington's Warmest Winters: 2012 in Fifth Place, Fourth Feasible

PM Update, February 14: With today's high of 56° and low of 37° exceeding the 24-hour forecast by 8° and 5° respectively, the winter average temperature to date is holding at 42.7°.

Original post:
With a little over 2 weeks left in meteorological winter, Washington's current seasonal average temperature of 42.7° is now ahead of 1998 as the 5th warmest winter in records dating back to 1871. A projection of the final winter average based on the forecast temperatures for tomorrow through February 20 and climatological averages through the rest of the month would give a result of 42.5°, enough to still tie with 1998. If the temperature averages at least 3.7° above climatology for the 21st through the 29th, that would be enough to push the winter average to a tie with 1950 as the 4th warmest. Given that the month to date is averaging 4.6° above average so far, and the 8-14 day forecast indicates a nearly 50% chance of above-average temperatures (vs. a climatological expectation of 33%), this seems to be a feasible result.

The monthly averages and departures from climatology for the winter so far:

December 45.0° (+5.3°)
January  40.7° (+4.7°)
February 42.7° (+4.6°) 

Image (click to enlarge): Washington's 10 warmest winters vs. 2011-12 average to date and projected through end of February, CapitalClimate chart from National Weather Service data

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SnowFail 2011-12 Update: Midwest Snow Running Nearly 40% Below Average

The Northeast and Mid Atlantic are not the only regions with significant snow deficits at the end of the third quarter of winter 2011-12. National Weather Service reports indicate that the Midwest is averaging 40% below the normal snowfall season-to-date. Of the 43 major reporting locations in Minnesota, Wisconsin, Michigan, Iowa, Illinois, Indiana, Ohio, Missouri, and Kentucky, only Ft. Wayne, Indiana has had more snow than the climatological average, by a mere 2.2", or about 11%.

The largest deficit in absolute terms is at Sault Ste. Marie MI, where the current total of 55" is over 3 feet less than the normal amount to date of just over 91". The map of snow depth on the ground for central and northern Michigan as of February 4 shows deficits of 2 feet or more in the Upper Peninsula. Temperatures at Sault Ste. Marie have been well above normal for all 3 winter months (December +3.8°, January +6.0°, February to date +13.1°).

Percentage-wise, the less than 1" at Kansas City MO is 94% below average. The weighted average deficit across all reporting stations is 39%.

The stations shown in the charts are:

DLH Duluth MN
MSP Minneapolis MN
STC St. Cloud MN
RST Rochester MN
LSE La Crosse WI
EAU Eau Claire WI
MSN Madison WI
AUW Wausau WI
GRB Green Bay WI
ANJ Sault Ste. Marie MI
APN  Alpena MI
HTL Houghton Lake MI
MQT Marquette MI
DTW Detroit MI
FNT Flint MI
GRR Grand Rapids MI
LAN Lansing MI
MKG Muskegon MI
ALO Waterloo IA
DSM Des Moines IA
MCW Mason City IA
SUX Sioux City IA
DBQ Dubuque IA
MLI Moline IL
ORD Chicago IL
RFD Rockford IL
PIA Peoria IL
IND Indianapolis IN
FWA Ft. Wayne IN
CMH Columbus OH
CAK Akron OH
MFD Mansfield OH
TOL Toledo OH
YNG Youngstown OH
DAY Dayton OH
CLE Cleveland OH
COU Columbia MO
STL St. Louis MO
MCI Kansas City MO
BWG Bowling Green KY
LEX Lexington KY
SDF Louisville KY
JKL Jackson KY  

Images (click to enlarge): Total winter snowfall to date vs. average, snowfall deficit in inches, and snowfall percentage deficit; all data from December 1, 2011 through February 7, 2012 from National Weather Service, charts by CapitalClimate; Michigan snow depth on ground departure from average, February 4, 2012, from National Weather Service

2011-12 Northeast/Mid Atlantic Snow Drought: Deficit Near 60%

With 3 weeks left in February, the winter of 2011-12 enters its fourth quarter with a major snow deficit in much of the U.S. In sharp contrast with last season, Northeast and Mid Atlantic winter snowfall to date is averaging nearly 60% below the climatological mean.

National Weather Service reports through February 6 show that stations from northern Maine to central North Carolina have all seen snowfall amounts below normal. In absolute terms, the deficit amounts range from 2.8" at Caribou, Maine to over 41" at Syracuse, New York. Percentage-wise, Caribou is only 5.3% below normal, while the southern locations in Virginia and North Carolina are at 100%, with no measurable snow reported.

The 3 major reporting locations in the Washington, DC region are all over 80% below normal, with Baltimore's BWI at nearly 90%.

The stations shown in the charts are:

CAR Caribou ME 
BGR Bangor ME         
BTV Burlington VT     
PWM Portland ME     
CON Concord NH      
ALB Albany NY       
BGM Binghamton NY   
SYR Syracuse NY     
BOS Boston MA       
ORH Worcester MA    
PVD Providence RI     
BDL Hartford CT       
BDR Bridgeport CT     
NYC Central Park NY   
EWR Newark NJ         
AVP Scranton PA       
ACY Atlantic City NJ  
PHL Philadelphia PA   
ABE Allentown PA      
ILG Wilmington DE     
BWI Baltimore MD      
DCA Washington DC     
IAD Dulles VA         
RIC Richmond VA       
ORF Norfolk VA        
RDU Raleigh NC          

Images (click to enlarge): Total winter snowfall to date vs. average, snowfall deficit in inches, and snowfall percentage deficit; all data from December 1, 2011 through February 6, 2012 from National Weather Service; charts by CapitalClimate

Out-of-Season Downpour in Key West Sets New All-Time February Daily Rainfall Record; 9th Wettest February in 1 Day

The National Weather Service reports that the 4.34" of rainfall at Key West, Florida on February 5 is a new all-time daily rainfall record for the month of February. It also put this month into the position of 9th wettest February in climate records extending back to 1871. The 0.22" of precipitation as of 4 pm today moves the month up to 8th place, barely behind the 4.63" just 2 years ago.

The wettest February at Key West was in 1872, when 7.19" was recorded. Three of the wettest Februaries at Key West have now occurred in the last 15 years (1998, 2010, and 2012).

Key West also set a daily precipitation record by a wide margin on October 17, when the 6.91" smashed the previous record of 4.08" in 1910.

From the National Weather Service:

RAINFALL ON SUNDAY FEBRUARY 5TH TOTALED 4.34 INCHES AT KEY WEST   
INTERNATIONAL AIRPORT. THIS BROKE THE PREVIOUS RECORD OF 2.89   
INCHES...WHICH WAS SET IN 1872. IN FACT...THIS WILL ALSO GO DOWN AS   
THE WETTEST FEBRUARY DAY IN HISTORY. THE PREVIOUS RECORD OF 4.04   
INCHES WAS SET ON FEBRUARY 28TH...1954.   

..24-HOUR RAINFALL TOTALS...IN INCHES...FOR AVAILABLE STATIONS  
  
KEY WEST INT'L AIRPORT                                        4.34  
KEY WEST WFO                                                  3.79  
KEY LARGO NORTH--HANDAR                                       2.74  
BIG COPPITT KEY--COCORAHS                                     2.26  
CUDJOE KEY--COCORAHS                                          1.68  
CURRY HAMMOCK--COOP                                           1.50  
BIG PINE KEY--HANDAR                                          1.26  
CUDJOE KEY                                                    1.08  
MARATHON AIRPORT                                              1.03   

Image (click to enlarge): Radar-estimated rainfall for the Key West, Florida region, February 5, 2012, from wunderground.com

Denver Breaks All-Time February 1-Day and 3-Day Snowfall Records

The National Weather Service reports that the heavy snowfall through this morning at Denver has set new 1-day and 3-day records for February:

12.5 INCHES OF SNOW FELL AT DENVER INTERNATIONAL AIRPORT ON FEBRUARY
3RD 2012. THIS ESTABLISHES A NEW SNOWFALL RECORD FOR THE DATE. THE
OLD RECORD WAS 7.5 INCHES SET BACK IN 1932. THE 12.5 INCHES THAT
FELL ALSO ESTABLISHED A DAILY SNOWFALL RECORD FOR THE MONTH OF
FEBRUARY. THE PREVIOUS DAILY SNOWFALL RECORD FOR FEBRUARY WAS 9.5
INCHES ON FEBRUARY 22ND 1909 AND FEBRUARY 19TH 1953.

IN ADDITION...FROM THE EVENING OF THE 2ND THROUGH THE MORNING OF THE
4TH...15.9 INCHES OF SNOW FELL AT DENVER INTERNATIONAL AIRPORT. THIS
ESTABLISHES A NEW THREE DAY SNOWFALL TOTAL FOR THE MONTH OF
FEBRUARY. THE OLD RECORD OF 14.1 INCHES OCCURRED BACK IN 1912. 

Denver climate history began in 1872. The average temperature for the first 3 days of February at Denver is 2.5° above normal. Since Denver generally has its heaviest late-season snows in March, this could be considered an early spring storm.

Preliminary reports from the National Climatic Data Center show 27 daily snowfall records set on February 3, nearly all in Colorado.

Image (click to enlarge): Snowfall totals in the Denver region, February 2-4, 2012, from National Weather Service