The 4/5-10/2007 Cold Spell

[donsutherland1]

Recent guidance has been consistent with respect to a cold shot that cold see the biggest anomalies from normal occur over the Middle Atlantic region. The NCEP ensemble mean 500 mb anomalies forecast for April 8, 2007 0z have been as follows:

From 3/31 0z:


From 4/1 0z:


Since 1950, there have been six occasions in which reasonably similar 500 mb patterns have occurred during the 4/1-15 timeframe. The composite 500 mb anomalies were as follows:


The lowest temperature for the cold outbreaks from the composite 500 mb patterns for select cities were as follows:

April 13-15, 1950:
Boston: 34°
Burlington: 27°
Montreal: 27° (-2.8°C)
New York City: 26°
Philadelphia: 24°
Toronto: 16° (-8.9°C)
Washington, DC (DCA): 24°

April 1-4, 1966:
Boston: 34°
Burlington: 25°
Montreal: 26° (-3.3°C)
New York City: 34°
Philadelphia: 31°
Toronto: 21° (-6.1°C)
Washington, DC (DCA): 35°

April 11-14, 1973:
Boston: 31°
Burlington: 17°
Montreal: 16° (-8.9°C)
New York City: 33°
Philadelphia: 29°
Toronto: 18° (-7.8°C)
Washington, DC (DCA): 32°

April 3-6, 1975:
Boston: 32°
Burlington: 26°
Montreal: 26° (-3.3°C)
New York City: 27°
Philadelphia: 26°
Toronto: 15° (-9.4°C)
Washington, DC (DCA): 33°

April 2-6, 1992:
Boston: 33°
Burlington: 29°
Montreal: 25° (-3.9°C)
New York City: 33°
Philadelphia: 30°
Toronto: 24° (-4.5°C)
Washington, DC (DCA): 31°

April 4-6, 2004:
Boston: 30°
Burlington: 19°
Montreal: 16° (-9.0°C)
New York City: 30°
Philadelphia: 31°
Toronto: 20° (-6.6°C)
Washington, DC (DCA): 31°

Taking all the factors—historic, synoptic, and modeled—into consideration, I believe Boston, New York City, Philadelphia, and Washington, DC will all see one or more days with a low temperature of 32° or below. Philadelphia and Washington, DC have a good chance to a low temperature < 30°. Burlington should see a low temperature of 27° or colder and Montreal should have a low temperature of 26° (-3.3°C) or colder. Toronto's coldest temperature will probably come to 23° (-5.0°C) or colder and a low < 20° (-6.7°C) is a possibility.

Finally, at this time, it is still a close call whether a system will move off the Mid-Atlantic coast and head northeastward. If such a situation occurs, odds favor an area running from southern New Jersey across Long Island and then the eastern third of New England to see the most meaningful precipitation. The best chance for some accumulating snow would exist across eastern Connecticut, Rhode Island, eastern Massachusetts and northward. There, the potential might exist for several inches, but such a storm, much less snowfall is not assured at this time.

[Hybridstorm_November2001]

Would appear that your right on the money Don:


EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
100 PM EDT MON APR 02 2007

VALID 12Z THU APR 05 2007 - 12Z MON APR 09 2007

...RECORD COLD SLATED FOR PORTIONS OF THE EAST THIS WEEKEND...

PATTERN DURING MEDIUM RANGE LOOKS LIKE A STABLE ONE...WITH LITTLE
DIFFERENCE BETWEEN MODELS IN BIG PICTURE. DEEP POLAR VORTEX
CENTERED OVER THE ST LAWRENCE VALLEY WILL DOMINATE THE FLOW OVER
THE US...WITH COLD...DRY AIR COVERING MUCH OF THE NATION E OF THE
ROCKIES. L/WV RIDGE WILL BE ANCHORED OVER THE WRN STATES...WITH
S/WV ENERGY LIFTING UP ITS W SIDE DURING THE SECOND HALF OF THE
PD. PREFER ECMWF HANDLING OF THIS DISTURBANCE...ALLOWING LESS EWD
PROGRESSION THAN THE GFS/GEFSMEAN/DGEX SOLUTIONS.

...ERN US...

ANOMALOUS VORTEX OVER THE NORTHEAST WILL FEED COLD DRY AIR INTO
REGION...WITH RECORD LOW TEMPERATURES POSSIBLE FROM THE MID ATL TO
THE GULF STATES OVER THE WEEKEND. TEMPS MAY BE EXTREME ENUF TO
SERIOUSLY AFFECT AGRICULTURE IN THESE REGIONS. SHOWERS OF MOSTLY
SNOW ARE EXPECTED DOWNWIND OF THE GREAT LAKES...WITH THUNDERSTORMS
POSSIBLE WITH PASSAGE OF COLD FRONT THRU THE FL PENINSULA.

CISCO


Source: http://www.hpc.ncep.noaa.gov/discussions/pmdepd.html

[tropicana]

Also, i found this bit of info out on the coming cold spell ...

As confirmed by all major weather models, it is no April Fool's Joke that since the upcoming cold snap will be prolonged and December was so mild, there is a possibility that the Easter holiday weekend across the Great Lakes, Southern Ontario and Northeast United States could be just as cold, if not colder, than this past Christmas.
Temperatures should show a gradual but painfully slow recovery by mid-week of the following week.

It is noteworthy that since 1937, only 2 Aprils have ever been completely snow-free in the Toronto region, back in April 1941 and more recently, in April 1998.

While such a prolonged cold snap is rare this time of year, it is not unheard of.

Despite the chill, we are unlikely to break any records in Toronto as regards low temperatures.
The coldest April temperature on record in Toronto is MINUS 17.2C ( 2F) set back on April 7, 1972.
That brutal 1972 cold snap kept temperatures zero Celsius (32F) and below( in the daytime) for 4 consecutive days (Apr 5-8 1972).
April 6 1972 fell to minus 11.7C (11F) and April 8 1972 fell to minus 13.3C (8F). In addition, April 9 1972 had a low of -9.4C (15F) Those four *1972* records stand unchallenged to this day, 35 years later.

-justin-

[Hybridstorm_November2001]

Where is Global Warming when we need it LOL!

[Category 5]

It dropped 21 degrees in 1 hour here.

[Ptarmigan]

I heard the forecast for Easter is going to be cooler than normal.

[Tstormwatcher]

We have a freeze watch up for our area on Friday morning and we will probably have it for Saturday and Sunday morning as well. All my flowers are coming up too.

[aOl]

WHAT is going on?! Down here on the Gulf coast NWS says 50% chance of snow on Sunday! This is for Mobile, Pensacola, and most of the forecast area. It makes no sense to me with a predicted high of 54 that day and a low of 33 for the morning hours... WTF?!

The forecast discussion does not mention it at all. How could they have made such an error for the whole forecast area? It seems like it couldn't have been an error since the POPs vary for different areas. Go to Mobile NWS and see for yourself!

[JonathanBelles]

Whats wrong with the NWS? all of the 7-days are calm winds and no picture

[Hybridstorm_November2001]

We are having a raging near blizzard (heavy snow and wind, just not cold enough for an official designation), right now here in most of New Brunswick and Maine. Damn this sucks as a way to start the Easter/Passover Weekend!

[HarlequinBoy]

WHAT is going on?! Down here on the Gulf coast NWS says 50% chance of snow on Sunday! This is for Mobile, Pensacola, and most of the forecast area. It makes no sense to me with a predicted high of 54 that day and a low of 33 for the morning hours... WTF?!

The forecast discussion does not mention it at all. How could they have made such an error for the whole forecast area? It seems like it couldn't have been an error since the POPs vary for different areas. Go to Mobile NWS and see for yourself!

DISCUSSION: A MAJOR FAILURE IN THE GRIDDED FORECAST DATABASE THIS
MORNING HAS ADDED A VERY SIGNIFICANT WORKLOAD AND MAJOR DELAYS IN
THE FORECAST PRODUCTION. WE ARE RUNNING SIGNIFICANTLY LATE ON ALL
PRODUCTS THIS MORNING. THE LONG TERM FORECASTER EXPECTS TO HAVE THE
ZONE FORECASTS DONE BY 545 AM AND THE GRIDS REBUILT BY 6 AM. THE
FIRE PRODUCTS WILL BE SIGNIFICANTLY DELAYED TODAY.

That was in their AFD. Maybe that had something to do with it?

Haha, otherwise I have no clue.

[Janie2006]

I can't access the NWS website right now. They must be having some significant problems with it.

[donsutherland1]

So far, the magnitude of the cold is living up to expectations.

Some highlights through this morning:

Lowest Temperatures:
Boston: 28°, 4/6 (first subfreezing April low since 4/6/2004 and coldest April reading since 28°, 4/1/2003)
New York City: 31° (first subfreezing April low since 4/6/2004 and coldest April reading since 31°, 4/6/2004)
Philadelphia: 31° (first subfreezing April low since 4/5/2004 and coldest April reading since 31°, 4/5/2004)
Pittsburgh: 24° (coldest April reading since 24°, 4/5/2004)
Toronto: Preliminary: 19°F/-7°C (coldest April reading since 17°/-8.4°C, 4/6/2003)

Lowest Maximum Temperatures:
Boston: 45°, 4/5 (coldest April maximum reading since 42°, 4/5/2004)
New York City: 44°, 4/5 (coldest April maximum reading since 43°, 4/5/2004)
Philadelphia: 45°, 4/5 (coldest April maximum reading since 42°, 4/9/2003)
Pittsburgh: 31°, 4/5 (coldest April maximum reading since 31°, 4/8/1972)
Toronto: 28°/-2.1°C, 4/5 (coldest April maximum reading since 27°/-3.0°C, 4/4/2003)

[wx247]

We had some snowflakes today!!! I was even under a Snow Advisory yesterday evening. It is the latest snow on record since I believe 1953 for this area. Lows tonight will be around 15. Brr!!!!

[donsutherland1]

Verification:

The ensemble guidance picked up quite well on the severe shot of cold that culminated with a number of all-time minimum and cold maximum readings for April. Even then, the ensemble guidance underdid the magnitude of the trough that produced the historic outbreak of cold and unseasonable snow across Texas and also the Southeast and lower Mid-Atlantic region. At the same time, the flow of cold air brought incredible late-season lake effect snows across parts of Michigan and western New York State.

Ensemble Forecasts:

From 3/31 0z:


From 4/1 0z:


Actual 500 mb Anomalies for 4/8 0z:


My 4/2 Temperature Discussions:

Taking all the factors—historic, synoptic, and modeled—into consideration, I believe Boston, New York City, Philadelphia, and Washington, DC will all see one or more days with a low temperature of 32° or below. Philadelphia and Washington, DC have a good chance to a low temperature < 30°. Burlington should see a low temperature of 27° or colder and Montreal should have a low temperature of 26° (-3.3°C) or colder. Toronto's coldest temperature will probably come to 23° (-5.0°C) or colder and a low < 20° (-6.7°C) is a possibility…

The historic years noted earlier also showed the potential for the lowest temperature to reach well into the 20s at Pittsburgh (Median: 23°; Mean: 25°) and below freezing at Raleigh (Median: 27.5°; Mean: 28°). So, based on this data and the latest guidance, I believe Pittsburgh will likely see its coldest reading at or below 25° and Raleigh (RDU) will likely see its coldest reading come at 30° or below.

Coldest Readings:
Boston: 28°, 4/6 (coldest since 4/1/2003 when the temperature fell to 28°)
Burlington: 23°, 4/7 (coldest since 4/9/2006 when the temperature fell to 23°)
Montreal: 23°F/-5.2°C, 4/7 (coldest since 4/8/2006 when the temperature fell to 22°F/-5.5°C)
New York City: 30°, 4/8 (coldest since 4/5/2004 when the temperature fell to 29°)
Philadelphia: 30°, 4/9 (coldest since 4/1/2003 when the temperature fell to 30°)
Pittsburgh: 23°, 4/7 (coldest since 4/7/2002 when the temperature fell to 22°)
Raleigh: 27°, 4/8 (coldest since 4/7/2002 when the temperature fell to 27°)
Toronto: 19°F/-7.2°C (coldest since 4/6/2003 when the temperature fell to 17°F/-8.4°C)
Washington, DC (DCA): 29°, 4/8 (coldest since 4/10/1997 when the temperature fell to 28°)

Coldest High Temperatures:
Boston: 39°, 4/6 (coldest since 4/9/2003 when the high reached 37°)
Burlington: 33°, 4/6 (coldest since 4/5/2004 when the high reached 28°)
Montreal: 32°F/-0.1°C, 4/6 (coldest since 4/7/2003 when the high reached 30°F/-1.0°C)
New York City: 41°, 4/8 (coldest since 4/9/2003 when the high reached 39°)
Philadelphia: 41°, 4/7 (coldest since 4/8/2003 when the high reached 38°)
Pittsburgh: 30°, 4/7 (coldest since 4/13/1950 when the high reached 28°)
Raleigh: 48°, 4/7 (coldest since 4/13/2005 when the high reached 47°)
Toronto: 28°F/-2.2°C, 4/6 (coldest since 4/4/2003 when the high reached 27°F/-3.0°C)
Washington, DC (DCA): 41°, 4/7 (coldest since 4/8/2003 when the high reached 41°)

Additional Temperature Highlights:

All-time low temperatures for April:
Asheville, NC: 20°, 4/7
Brownsville, TX: 39°, 4/8 (tied record)
Charlotte, NC: 21°, 4/8
Jacksonville, FL: 31°, 4/8 (latest freeze on record)
Savannah, GA: 28°, 4/8

All-time low maximum temperatures for April:
Abilene, TX: 36°, 4/7
London, KY: 36°, 4/8
Lubbock, TX: 31°, 4/7
San Angelo, TX: 38°, 4/7

Brownsville Climate Summary for 4/8:


Jacksonville Climate Summary for 4/8:


My 4/2 Snowfall Discussion:

…it is still a close call whether a system will move off the Mid-Atlantic coast and head northeastward. If such a situation occurs, odds favor an area running from southern New Jersey across Long Island and then the eastern third of New England to see the most meaningful precipitation. The best chance for some accumulating snow would exist across eastern Connecticut, Rhode Island, eastern Massachusetts and northward. There, the potential might exist for several inches, but such a storm, much less snowfall is not assured at this time.

The storm developed but it tracked farther to the south than I had thought. As a result, its meaningful snows fell across North Carolina, West Virginia, and Virginia. Consequently, Richmond and Norfolk saw a rare accumulation of snow in April.

[cctxhurricanewatcher]

Hey Don,

IF this would have hit us in the Dec to February time frame, how much colder would it have been considering things like snow pack, lack of sun, etc in the plains?

[donsutherland1]

Cctxhurricanewatcher,

One can only imagine what it might have been like. I believe the event would likely have been a historic cold and snow event for Texas with some pretty sizable accumulations of snow.