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December 9, 2009 / Dave Gorham

Long-range outlook for the Deep South Through Christmas Day…Potential Hard Freeze and more Wintry Weather?

ACTIVE WINTER PATTERN FOR THE GULF COAST

 

Much of the longer range weather data we are looking at indicates more surges of very cold air will be building south out of Canada over the next 10 days to two weeks.  Not only will there be a threat of a hard freeze sometime over the next 10 days to two weeks over much of the Deep South and Gulf Coast, but there also may be some wintry precipitation as well thanks in large part to a very active southern storm track.  Of course to get really cold air down to the Gulf Coast temperatures over the source region of Canada need to be at least normal, and at best below normal.  Also a decent snow cover well southward into the U.S. Great Plains is also a big plus considering less modification of any air pouring southward out of Canada would occur.  Let’s take a look at the current conditions followed by the long-range forecast.

 

Current Conditions:

  • Current Snow Depth

Much of the snow across the Plains and Midwest was a result of the large blizzard the roared through that region on the 8th and 9th of December depositing as much as 12-18 inches of snow with snow drifts up to 10 to 20 feet!  Now let’s take a look at the current temperature anomalies across the globe paying particular attention to the source region over Canada.

 

  • Current Temperature Anomalies


Note most of western North America is currently well below normal.  Even parts of central and northern Canada have cooled way off and are currently averaging near to slightly below normal.   Based on the two maps above we have in place the two major ingredients required for a hard freeze on the Gulf Coast.

 

Forecast

  • Temperatures over the Source Region


The map above indicates the source region of western Canada will remain well below normal over the next week meaning there is plenty of cold air poised to move southward if the opportunity is right.

  • Blocking To Continue…Hard Freeze Threat to the Gulf Coast?

All of the computer model ensemble trends continue to advertise a large amount of blocking across the Northern Hemisphere over the next 10 days to 2 weeks (see map below).


As a result more very cold air from Canada will be reloading over the next 1-2 weeks.  In addition since there is already a snowpack down to the northern Texas Panhandle expect less modification with time as future surges of very cold air build southward.  The combination of these factors may result in a hard freeze for the Gulf Coast sometime over the next two weeks.  Confidence in the timing of such an event is very low right now; however, several ingredients are coming together which does favor a very cold weather pattern down to the Gulf Coast. Right now we think the best chance for a hard freeze on the Gulf Coast will be in between the 19th and 25th of December based mainly on ensemble forecasting during that time frame.

 

In addition to the colder air, we continue to see strong evidence in support of a stronger than normal southern storm track over the next two weeks (see map above) resulting from a fairly strong El Nino over the Tropical Pacific.  Moisture associated with the southern storm track could bring a risk of more wintry type of precipitation for parts of the Deep South as well during this time frame, if moisture interacts with the colder air at just the right time.

 

We will have more later on this potential wintry weather for the Gulf Coast over the next week or two.

 

Meteorologist:  Fred Schmude

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