February 1-5, 2011 Arctic Blast/Winter Storm Discussion

[srainhoutx]

The 12Z GFS suggests a bit faster arrival of the Arctic boundary, but does not slow down the progression of the U/L (Pacific storm). It is noteworthy that a stronger/slower short wave is lingering to our W and the GFS still suggests some pooling of deep moisture off the S TX Coast and a developing Coastal Low/trough near mid week. Cloud cover is suggested by the GFS to remain rather thick throughout the week.

[txsnowmaker]

The 12Z GFS suggests a bit faster arrival of the Arctic boundary, but does not slow down the progression of the U/L (Pacific storm). It is noteworthy that a stronger/slower short wave is lingering to our W and the GFS still suggests some pooling of deep moisture off the S TX Coast and a developing Coastal Low/trough near mid week. Cloud cover is suggested by the GFS to remain rather thick throughout the week.

Thanks srain. I was noticing the shortwave in the upper air graphics 500 mb chart (12Z GFS) that I think you are referring to. Any reason why it seems to just stay stationary and not move out of the West Texas region around Day 5?

EDIT: Never mind. I see it moving later that day and into Day 6.

[srainhoutx]

And then the GFS suggests this for late week...that's a mighty cold core Upper Low that will travel across the region, if the GFS is correct and is a trend that we've been monitoring closely the past couple of GFS runs...

[Andrew]

And then the GFS suggests this for late week...that's a mighty cold core Upper Low that will travel across the region, if the GFS is correct and is a trend that we've been monitoring closely the past couple of GFS runs...

Gfs offers some possible wintry weather on Sat.

[srainhoutx]

And yet another Arctic Intrusion on the way next Sunday/Monday...

[Andrew]

And yet another Arctic Intrusion on the way next Sunday/Monday...

It never ends! I know you posted that map of the cold front moving through Texas but I wanted to share with the board what Wxman commented on with that map:

The cold front is already pushing south into Texas. It's just north of the D-FW metroplex now. Question is - will it just not move for the next 2 days as it waits for reinforcements? There are some pretty good northerly winds in the cold air.

[TexasMetBlake]

Significat Winter Storm and Significant Uncertainty:

...WINTER STORM OUTLOOK FOR NORTH TEXAS...

AN ARCTIC COLD FRONT WILL MOVE INTO NORTHWEST NORTH TEXAS AFTER
MIDNIGHT MONDAY NIGHT. THE COLD FRONT WILL MOVE THROUGH THE REST OF
NORTH TEXAS BY MIDDAY TUESDAY. TEMPERATURES WILL BEGIN FALLING LATE
MONDAY NIGHT AND CONTINUE FALLING THROUGHOUT THE DAY TUESDAY. MOST OF
NORTH TEXAS IS FORECASTED TO BE BELOW FREEZING BY TUESDAY EVENING.
TEMPERATURES ARE NOT EXPECTED TO WARM ABOVE FREEZING AREA-WIDE UNTIL
FRIDAY.

REGARDING THE TIMING FOR WINTER WEATHER TUESDAY...LOCATIONS ALONG AND
NORTHWEST OF A LINE FROM EASTLAND TO MINERAL WELLS TO BOWIE COULD
SEE A MIX OF FREEZING RAIN AND SLEET BY DAYBREAK TUESDAY. THE WINTRY
MIX TRANSITION LINE IS EXPECTED TO REACH A PARIS...HILLSBORO...
GOLDTHWAITE LINE...INCLUDING THE DALLAS-FORT WORTH METROPLEX...BY
LATE MORNING. BY MID-AFTERNOON...THE TRANSITION LINE WILL LIKELY
REACH AN ATHENS...TO WACO...TO LAMPASAS LINE. A TRANSITION OVER TO
MOSTLY SNOW OR SNOW AND SLEET IS EXPECTED NORTH OF I-20 DURING THE
AFTERNOON. THE WINTRY PRECIPITATION WILL RAPIDLY END FROM WEST TO
EAST DURING AFTERNOON TUESDAY.

ADDITIONALLY...GUSTY NORTH WINDS WILL COMBINE WITH THE COLD
TEMPERATURES TO PRODUCE WIND CHILLS IN THE TEENS AND 20S BY TUESDAY
AFTERNOON. WIND CHILLS WEDNESDAY MORNING WILL FALL INTO THE SINGLE
DIGITS TO BELOW ZERO OVER THE NORTHWEST HALF OF NORTH TEXAS.

SIGNIFICANT UNCERTAINTY REMAINS REGARDING TIMING...TYPES OF WINTER
PRECIPITATION...AND ACCUMULATION AMOUNTS ON TUESDAY. HOWEVER...
CURRENT FORECAST DATA INDICATES AREAS OF SIGNIFICANT ICE...SLEET OR
SNOW ACCUMULATIONS ARE POSSIBLE. THE AMOUNT OF ICE AND SNOW
ACCUMULATIONS WILL DEPEND ON HOW FAST TEMPERATURES DROP BELOW
FREEZING AND HOW FAST THE PRECIPITATION MOVES OFF TO THE EAST
TUESDAY AFTERNOON.

THE DETAILS AND POTENTIAL IMPACTS OF THIS WINTER WEATHER EVENT ARE
STILL BEING DETERMINED AND WILL BE BETTER RESOLVED DURING THE NEXT FEW
OF DAYS. A WINTER STORM WATCH WILL LIKELY BE ISSUED FOR PART OF
NORTH TEXAS IN THE NEXT 24 HOURS.

[srainhoutx]

Oh my...

[biggerbyte]

Ditch the models for forecasting purposes this week if you want to remain sane.

We are still waiting to see how much cold air will come this far south, and how quickly. As srain pointed out, we could have frontal passage a bit swifter. In the short term, forget about precip. of the frozen kind. Long term holds some possibilities as we also watch for possible additional pushes of cold air. Again, as srain mentioned, this is an evolving situation with many possibilities that could change on a dime. It will be a daily evaluation. Welcome to winter, s.e. Texas.

In the meantime...

As things look today, there is cold air coming. Teens to twenties for many in our area as the middle of the week comes around. Highs look to be thirties and forties, with some northern areas struggling with the freezing mark. Freezes along the coast a possibility. Now, some folks have already seen teens before this event, so we'll see later how impressed they get. As a matter of fact, we'll see if anyone gets impressed if we decide on Monday and Monday night that this is going to come in like a lamb. Really, the best accurate forecasts will be seen up in the day on Monday. I suspect the way things look today will hold true another day.

[txsnowmaker]

Sure am liking the trends late week...

[Ptarmigan]

Interesting that another cold front comes next week. I saw this forecast from NWS Houston.

Code: Select all

Tuesday Night: Mostly cloudy and blustery, with a low around 31.

Wednesday: Mostly cloudy, with a high near 42. 

Wednesday Night: Mostly cloudy, with a low around 26. 

Thursday: Mostly cloudy, with a high near 45. 

[b]Thursday Night: Partly cloudy, with a low around 23. [/b]

Friday: Sunny, with a high near 51. 

Friday Night: Mostly clear, with a low around 30. 

Saturday: Sunny, with a high near 59.

[wxman57]

And then the GFS suggests this for late week...that's a mighty cold core Upper Low that will travel across the region, if the GFS is correct and is a trend that we've been monitoring closely the past couple of GFS runs...

Gfs offers some possible wintry weather on Sat.

Note that the GFS is somewhat similar to the EC and UKMET in developing a frontal wave well offshore. Both the EC and GFS indicate only a trace of moisture near the coast (less than .05") Friday night. That's not much moisture. The low would have to form a good bit farther north and west for us to have a shot at any significant frozen precip here (as per the 12Z Canadian). I doubt we'll see anything, but can't rule it out absolutely.

[txsnowmaker]

And then the GFS suggests this for late week...that's a mighty cold core Upper Low that will travel across the region, if the GFS is correct and is a trend that we've been monitoring closely the past couple of GFS runs...

Gfs offers some possible wintry weather on Sat.

Note that the GFS is somewhat similar to the EC and UKMET in developing a frontal wave well offshore. Both the EC and GFS indicate only a trace of moisture near the coast (less than .05") Friday night. That's not much moisture. The low would have to form a good bit farther north and west for us to have a shot at any significant frozen precip here. I doubt we'll see anything, but can't rule it out absolutely.

What about the piece of energy showing up in West Texas? Also, can you share your thoughts on the latest Canadian run?

[ticka1]

Oh my...

Explain the Oh My!!!!!

[TexasMetBlake]

Oh my...

Explain the Oh My!!!!!

Canadian showing a deep disturbane traversing the area while the deep cold air is in place. Another arctic boundary for the weekend perhaps.

[wxman57]

What about the piece of energy showing up in West Texas? Also, can you share your thoughts on the latest Canadian run?

I edited my previous post to mention the Canadian's forecast of a low forming much closer to the TX coast on Friday. However, with the low closer to the coast, there's much greater warm advection aloft. The Canadian, while it shows much more precip, has our lower levels well above freezing with the 850mb freeze line from NW of Dallas to west of SAT/AUS. So it's not forecasting snow in SE TX on Friday/Saturday. Could be a thin layer of sub-freezing surface air that could lead to some freezing rain, probably north of Houston, though.

Check out the dark black 850mb (5000ft) freezing line on the lower right panel. It's Well to our north and west.

[Ptarmigan]

Note that the GFS is somewhat similar to the EC and UKMET in developing a frontal wave well offshore. Both the EC and GFS indicate only a trace of moisture near the coast (less than .05") Friday night. That's not much moisture. The low would have to form a good bit farther north and west for us to have a shot at any significant frozen precip here. I doubt we'll see anything, but can't rule it out absolutely.

If it was to rain, the temperature at the surface would be 32°F, while at 5,000 feet (850 mb) it would be 29°F, and at 18,000 feet (500 mb), it would be 7°F. That should allow some snow to fall. Usually when it snows, it is not that cold.

The average ratio of snow in Houston is 7:1, which is 7 inches of snow equals 1 inches of rain, which is wet snow. The highest ratio is 12:1, which happened in January 1973 (12.7:1) and December 1989 (12.1:1).

Here is snow events where more than a trace fell in KIAH.

Code: Select all

KIAH	01/11/73	2	0.58	3.448276
KIAH	02/09/73	1.4	0.11	12.727273
KIAH	02/17/73	1.4	0.51	2.745098
KIAH	01/19/78	0.4	0.38	1.052632
KIAH	02/02/80	1.4	0.22	6.363636
KIAH	01/02/85	0.4	0.04	10
KIAH	02/01/85	0.3	0.03	10
KIAH	12/22/89	1.7	0.14	12.142857
KIAH	02/01/94	0.1	0.01	10
KIAH	12/10/08	1.4	0.31	4.516129
KIAH	12/04/09	1	0.22	4.545455

[txsnowmaker]

What about the piece of energy showing up in West Texas? Also, can you share your thoughts on the latest Canadian run?

I edited my previous post to mention the Canadian's forecast of a low forming much closer to the TX coast on Friday. However, with the low closer to the coast, there's much greater warm advection aloft. The Canadian, while it shows much more precip, has our lower levels well above freezing with the 850mb freeze line from NW of Dallas to west of SAT/AUS. So it's not forecasting snow in SE TX on Friday/Saturday. Could be a thin layer of sub-freezing surface air that could lead to some freezing rain, probably north of Houston, though.

Check out the dark black 850mb (5000ft) freezing line on the lower right panel. It's Well to our north and west.


Alright. Thank you for keeping my "hopes" in check, wxman.

[srainhoutx]

Also notice that the Canadian never shows 850's below freezing after the front passes SE TX on Tuesday. Not likely, IMO.

[wxman57]

Also notice that the Canadian never shows 850's below freezing after the front passes SE TX on Tuesday. Not likely, IMO.

That is true, so what to trust? Sometimes with really cold and thin Arctic air the surface temperature can be quite a bit colder than the 850 mb temperature.