Christmas Weather Outlook: 2011

FINAL UPDATE: Sat 24 Dec 2011 / 9:20 p.m.

The odds of a white Christmas in Texoma are very low indeed. The cloud-level temperatures aren't cold enough for snow, and the source of cold air aloft which might change that is stalled over west Texas. There could be a few flurries, but no accumulating snow is expected for Texoma.

Oh well...there's always next year...Merry Christmas!

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UPDATE: Fri 23 Dec 2011

The upper low upon which our snow potential hinges is moving slowly, so the window of opportunity now runs Saturday evening into Christmas morning. This precipitation will likely start as light rain before changing to snow overnight Sat-Sun.

There’s nothing new to suggest our chances for a White Christmas have increased; the air aloft is barely cold enough to produce snowflakes, and moisture is not that plentiful, so I’m still offering only a 10% chance you’ll have any snow on the ground Christmas morning:

Some light accumulations of snow are possible along the track of the low's core if surface temperatures can get cold enough Sat night-Sun morning.

The bottom line for most of us will be a cold Christmas Eve and Christmas Day with perhaps a few show flakes, but probably nothing sticking.

Latest Outlook:

Dec 24th:  Light Rain, changinig to light snow late in day/overnight,

Low near 30 / Highs low 40s

Dec 25th: Snow possible A.M. / Decreasing Clouds, Cold, Lows 29-33, Highs 44-48

Hope your Christmas holiday is most excellent!

 

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UPDATE: Thu 22 Dec 2011

Everything points to the mid-level low moving by on Saturday. The speed is slightly slower than in yesterday’s discussion so Christmas Eve looks to be the most likely day for snow. The potential for a significant accumulation is not promising.

It will above freezing during most of the snow potential time, so some of it will melt on the way down and more melts on contact with the warm soil.

For the optimistic soul:

This type of system often generates a narrow path, perhaps 50-75 miles wide, of heavier snow directly under the track of the low’s cold core. “Heavier” in this case would still not be much, perhaps an inch or so.

 

So the long and short of it is:

Snow in the sky is of moderate potential Saturday, but having enough to take a picture of is still looking to be on the low end of hopes.

If you’d like a number, then I’d say there’s a 1 in 10 chance of an accumulating snow in Texoma sometime this weekend. Any accumulations would probably be under an inch.

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UPDATE: Wed 21 Dec 2011

My thinking remains the same as yesterday: light snow possible Fri-Sat. The pattern aloft continues very unstable with two more mid-level lows moving our way over the weekend; the first of these should provide enough lift for rain changing to snow as it heads our way Friday and all snow by Saturday morning.

Part of the circulation from this low may “break off” into a second low and deprive the first system of some energy. This further complicates a messy forecast:

Moisture will be rather limited with northerly winds in place behind Thursday’s cold front. So… as mentioned in my Tuesday blog heavy snow is not expected. Amounts, if any, will generally be in the dusting to less than a half inch range.

What is fairly certain is a cold Christmas weekend.


 

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UPDATE: Tue 20 Dec 2011 / 9:30 p.m. The newest trends still show the upper low core tracking north of Texoma (see discussion below), but closer now compared to the older series from earlier Tuesday and Monday:

This was hinted at in a different model earlier Tuesday, but I generally like to see some agreement among various versions before jumping on a significant change. The trend is moving that direction although we're still a ways off from needing a corn cob pipe for our snowman.

So...the potential for snow to fall as flurries or light snow Friday night/Saturday morning is now moderate, and a light amount of accumulating snow is looking more possible for the NW half of our area. Wednesday will be a very interesting forecast day as this system comes together, and perhaps I can fine-tune the numbers a bit more.

The bottom  line: the potential for finding any snow on the ground in Texoma Saturday morning is still rather low but perhaps in the "slight" category instead of the earlier "very low" range. This will be a fun forecast ride!

Latest Outlook:

Dec 24th:  Light snow or flurries possible A.M. (light accumulations possible), decreasing clouds,  Low near 30 / Highs 40s

Dec 25th: Partly Cloudy, Cold, Lows 22-27, Highs 42-48

A new update will be posted by 6:30 p.m. Wednesday.

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UPDATE: Tue 20 Dec 2011 / 5:15 p.m.

If you’re into “long shots” then here’s one: a slight potential for some snow this weekend, with even longer odds of any accumulating.

Here's the deal: A deep low aloft is diving southward across the western U.S., and the map below shows its expected position to our north Saturday morning (discussion continues below map):

 

  Low tracking to our north means any snow we get would be very light with little accumulation expected.

Very cold air within the core of the low provides both cooling aloft and lifting of the low-level air. This pattern favors snow, BUT, the lower levels will be in the process of drying out behind a Friday morning cold front at the same time.

So what I expect is some snow-flurry activity Friday and possibly into Saturday morning. An accumulating snowfall looks to be unlikely in Texoma, but not impossible. Some snow may stick further north around Tulsa and Oklahoma City closer to the core of the low. The low would have to track a couple hundred miles further south for us to get measurable snowfall, so this bears watching but seems a long shot right now.

What is much more certain: it will be plenty cold this Holiday weekend with highs in the 40s and lows in the 20s. So it will feel like the season, although the chances of it being white for Christmas morning are very low…but not zero.

 

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UPDATE: Mon 19 Dec 2011

Cold air building over Canada will be tumbling through Texoma for Christmas 2011 with conditions very Santa friendly: he won’t be getting hot in that thick red suit! This map shows a large surface high in control for Christmas Weekend:

Of course the million dollar question is “will it snow”?

An intense upper trough passing by (map below) Friday-Saturday could actually wring out a few snow flurries Friday night.....

....but please know very dry low-level air is expected by then.

This means the odds of accumulating snow are extremely low.

Of course if you are wanting a white Christmas you can always hope. A fresh update will be posted Tuesday evening.

 

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UPDATE: Sun 18 Dec 2011

Well...we're within a week now of Christmas morning, and the forecast pattern for the Holiday looks about the same as discussed here since the middle of last week.

There will be a large mid-level trough coming overhead Dec 24th-25th, but surface conditions should be dry with Canadian high pressure in place:

Latest Outlook:
Dec 24th: Partly Cloudy, Lows 30s / Highs 45-50
Dec 25th: Partly Cloudy, Lows 20s / Highs 40s
 
Scroll down for older posts which discuss other aspects of the forecast.
May your Holiday be a most joyous one! - Steve

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 UPDATE: Sat 17 Dec 2011 The models continue to disagree on the mid-level "parade"of troughs as mentioned in earlier posts below. On the other hand, the general pattern and model outputs all suggest a fairly dry and chilly air mass in place for Christmas Eve and Christmas Day.

  GFS and ECMWF models (GFS shown) have good agreement on cold air for Christmas with dry air in place.

So it's likely we could get scattered clouds, but precipitation odds seem even lower now than in yesterday's forecast. Unlike recent rainfall events as upper lows pass, north winds along the Gulf are the primary factor in my dry and cool forecast for Dec 24-25.

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 UPDATE: Fri 16 Dec 2011

The general trend is the same as Thursday’s update (scroll down below the map). A mid-level trough will be passing across the country from west to east on Christmas Eve, and it will provide lifting which may produce some clouds or rain (see 2nd map below).

However, surface high pressure in place (map) means dry low-level air and cool conditions:

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UPDATE: Thu 15 Dec 2011

Forecast doubt expressed in my Wednesday post is re-confirmed today with the latest model guidance, and the current pattern. We continue in a split-flow scenario with occasional cut-off lows (see discussion below). This pattern is notoriously difficult to forecast, especially more than a week out.

The GFS model shows a chance of rain Christmas Eve:

Meanwhile, the ECMWF gives us dry weather for Dec 24th with the trough much further west. The temperature trend seems a little more definite with cool to cold weather Christmas Eve and Christmas Day:

Our unusually stormy December pattern would offer hope for snow from the Dec 23/24th system IF enough cold air were to show up….right now that seems only a remote possibility.

 

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Wed 14 Dec 2011

I may regret this, but I’ve had several requests to do a blog about what weather we might expect in Texoma for Christmas Eve and Christmas Day 2011. So here goes…

Please bear in mind that a specific forecast this far out is of limited use; what I will explore here is the general trend and the range of reasonable possibilities.

Here’s what’s happening:

1. SPLIT FLOW: There’s been a persistent dual-jet pattern for the past few weeks. It contains an active northern jet with many embedded mid-level waves (troughs), and an equally busy southern jet. This pattern generally makes forecasting very difficult. The two streams interact with each other in unpredictable ways and the short wavelength of passing troughs makes timing tough too.

2. CUTOFF LOWS: A split flow regime favors the development of cut-off lows in the southern branch of the jet. A typical set-up starts with a trough diving southward within a core of fast wind (called a jet max) aloft. The jet max helps to “carve” out a low as it drops into the southern jet region. Steering winds weaken around the low, leaving it “cut off” from the faster jet flow and left to poke along quite slowly. 

 

3. COLD AIR: Arctic air masses usually need a “push” to get moving southward, but gravity may allow them to flow all the way to the Gulf Coast without stopping. This is especially true of the colder shots from Canada where the air is especially dense. The lead time on such arctic intrusions rarely exceeds a few days.

If one of these fast-moving waves were to come across a cold surface air mass, then we’d have an opportunity for frozen precipitation.

4. WARM AIR: Recent cold air masses have not moved very deep into the Gulf, which means the cold spells have been rather short. A deep flow of Gulf moisture on top of a cold air mass would make for a wintry mess, while the same flow into a mild storm would possibly bring thunderstorms.

5. PATTERN TIMING: A piece of good forecast news is the rather evenly spaced timing between each wave of 4-5 days. This offers some chance of nailing dry vs. wet days. However, if the wavelengths change the forecast I’m making today will go down like the Titanic.

 

 Q: So, what’s the outlook for Dec 24 and 25th as of right now?

A: The models are showing a “wavy” pattern like the map above shows. Each major wave is running about 4 days apart, and some of them are forming cut-off lows.

The timing puts Dec 24-25 in a dry place between two of them:

            GFS output for 500mb steering winds, valid 12pm Sat 24 Dec 2011, from 12pm 14 Dec model run

Cold high pressure behind a Dec 23rd wave would likely give us subfreezing morning lows and sunny to partly cloudy, cool daytime conditions.

Expect some tinkering to this forecast as we go along…A daily update will be posted. Stay tuned.

Merry Christmas!

Steve LaNore

Chief Meteorologist

KXII-TV

 

 

 

 

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