Texas Winter 2011-2012...

[Ntxw]

Canadian slows it down and stalls a bit over El Paso also. Probably the warmest of the models but don't have detailed data enough to really tell for sure. It certainly is very very wet this run for a long duration. Trend is not to shear it coming into Texas. Perhaps we can deepen it a little more in future runs!

[Longhornmaniac8]

It seems as though Austin and DFW people are in a similar predicament as far as seeing winter weather is concerned.

In this case, will a slower system out of the SW improve both of our chances?

Though I think I'm getting better at reading the models and such, what are we looking for that would improve wintery precip. chances in Austin and Dallas alike?

[Ntxw]

It seems as though Austin and DFW people are in a similar predicament as far as seeing winter weather is concerned.

In this case, will a slower system out of the SW improve both of our chances?

Though I think I'm getting better at reading the models and such, what are we looking for that would improve wintery precip. chances in Austin and Dallas alike?

A slower system usually means stronger system. More lift and colder aloft for dynamic cooling as the upper wind fields pass overhead. Precipitation will likely last longer too. Dallas/Austin/Houston often times suffer from the 850 warm nose air, western areas of the metroplex as well as the higher parts of the hill country don't have to deal with that problem since there's no 850 level (they are up and air is colder the higher up you go). How cold/dry the air is up in the atmosphere before precip comes in is important as well for dynamic cooling.

Look for dew points before the precip starts, I don't know the exact math but you'd want mid to upper 20s I think before it starts to rain with temps in the upper 30s for good cooling.

[iorange55]

ECMWF continues with the slower/stronger trend tonight. Still looks like it takes the system a little further north than it should.

This could get really interesting if the models are not handling the temps and strength of the system well.

[orangeblood]

ECMWF continues with the slower/stronger trend tonight. Still looks like it takes the system a little further north than it should.

This could get really interesting if the models are not handling the temps and strength of the system well.

IMO, This is the type of system that makes or breaks the legit meteorologists from the model huggers. For the first time in a long time, the NWS is actually taking a proactive approach to forecasting snow before the majority of the models do and I applaud them for that!!! Hopefully we'll see some snow forecast maps sometime tomorrow from our fellow storm2k members???

[Snowshoe]

The NWS of fort worth is gradually increasing the chances of snow Saturday night, so hopefully something happens!

[Turtle]

SHV is onboard with more rain! 50% on Sat. and 80% on Sat Night (36 degrees.. ).

[ndale]

As I thought Austin nws has backed off on their winter precipitation forecast some with warmer temps and the snow line not as close to us as previously predicted. This is a part of their forecast discussion:
WINTRY PRECIPITATION IS LOOKING LESS LIKELY GIVEN THE 00Z MODEL
DATA. WILL HOLD ONTO A MIX OF RAIN AND SNOW ACROSS PORTIONS OF THE
EDWARDS PLATEAU...INCLUDING VAL VERDE COUNTY...LATE FRIDAY NIGHT
INTO EARLY SATURDAY WITH NO ACCUMULATION EXPECTED. WOULD NOT BE
SURPRISED TO SEE THIS PHASED OUT OF THE FORECAST OVER THE NEXT
COUPLE OF CYCLES WITH THE RAIN/SNOW LINE STAYING NORTH OF OUR
AREA.

[Portastorm]

As I thought Austin nws has backed off on their winter precipitation forecast some with warmer temps and the snow line not as close to us as previously predicted. This is a part of their forecast discussion:
WINTRY PRECIPITATION IS LOOKING LESS LIKELY GIVEN THE 00Z MODEL
DATA. WILL HOLD ONTO A MIX OF RAIN AND SNOW ACROSS PORTIONS OF THE
EDWARDS PLATEAU...INCLUDING VAL VERDE COUNTY...LATE FRIDAY NIGHT
INTO EARLY SATURDAY WITH NO ACCUMULATION EXPECTED. WOULD NOT BE
SURPRISED TO SEE THIS PHASED OUT OF THE FORECAST OVER THE NEXT
COUPLE OF CYCLES WITH THE RAIN/SNOW LINE STAYING NORTH OF OUR
AREA.

Once again ... Austinites will have to be content building a coldrainman while their neighbors to the northwest and north enjoy a more frozen variety of precipitation. Not surprised.

[iorange55]

Well, looks like the NAM has gotten a little colder. It also looks like it gets more moisture straight from the gulf, and doesn't seem to have as much moisture to our west. Might mean less precip for far western counties? Also, it's still showing it to be a VERY slow moving storm. It even has flurries trying to fight back over north texas at the 66/69hr timeframe. Finally has it moving out after hr78.

Good signs. Just hope the trend of less and less moisture in our far western counties doesn't continue.

[Portastorm]

Well, looks like the NAM has gotten a little colder. It also looks like it gets more moisture straight from the gulf, and doesn't seem to have as much moisture to our west. Might mean less precip for far western counties? Also, it's still showing it to be a VERY slow moving storm. It even has flurries trying to fight back over north texas at the 66/69hr timeframe.

I haven't looked at the 500mb levels yet in the models but that might mean that the NAM thinks the upper-level system will shear out over the state and, thus, we'll see a stronger surface low reflection in the Gulf. Means more overrunning/precip for eastern half of Texas but that also means the atmosphere profile (air column more saturated by warmer Gulf air) will be warmer, thus ensuring nothing frozen for anyone southeast of a Tyler-Waco-Brady line, methinks.

[iorange55]

I haven't looked at the 500mb levels yet in the models but that might mean that the NAM thinks the upper-level system will shear out over the state and, thus, we'll see a stronger surface low reflection in the Gulf. Means more overrunning/precip for eastern half of Texas but that also means the atmosphere profile (air column more saturated by warmer Gulf air) will be warmer, thus ensuring nothing frozen for anyone southeast of a Tyler-Waco-Brady line, methinks.

I was thinking the same, but it looks like it's still nicely wrapped. I don't see a major difference between the 0z and 12z.

[Portastorm]

Just ran the loop on the 12z NAM at the 500mb level. Rather suspicious-looking vorticity. The model run elongates the vorticity at about 36 hours then brings it together 12 hours later as a rather compact system crossing the state. The 6z NAM kept the vorticity more strung out, like a trough almost. But you're right, it still looks like a healthy ULL. You folks in the Metroplex need that ULL to be a little more south and west for some real wintry magic, should the NAM be close.

[iorange55]

Just ran the loop on the 12z NAM at the 500mb level. Rather suspicious-looking vorticity. The model run elongates the vorticity at about 36 hours then brings it together 12 hours later as a rather compact system crossing the state. The 6z NAM kept the vorticity more strung out, like a trough almost. But you're right, it still looks like a healthy ULL. You folks in the Metroplex need that ULL to be a little more south and west for some real wintry magic, should the NAM be close.

Yeah, I noticed that, very interesting. But, I know! I know the NWS thought the models might be tracking too far north, so hopefully that is still the case.

[wxman57]

Are Austin and Dallas really in the same predicament? Let's take a closer look. First, Dallas.

Here's a GFS-based meteogram for DFW with 2m temp, dew point and 850mb temp plotted. Note that surface temps remain well above freezing through the precip period. However, as the precip ends, the 850mb temp is predicted to finally drop to 32F or lower. This would indicate that any snow that does fall would not stick to the ground.



Now let's take a look at the vertical profile in a little more detail. The graphic below is a GFS model sounding for DFW valid 21Z tomorrow (3pm). Note something interesting. The precipitation (where the red and green lines are close together) occurs in sub-freezing air as the precip is ending. However, below the precip, the air is above freezing from about 6000ft down to the surface. This would suggest that the precip develops/forms as snow and falls through an above-freezing layer down to the surface. Since the sounding is not necessarily taking into consideration cooling due to melting snowflakes/evaporating rain in the above-freezing layer, it is possible that the lower 6000 ft could be a little cooler than the sounding indicates, allowing some snowflakes to reach the ground.

However, I don't think the surface temps will be cold enough to allow any falling snowflakes to hang around long.



Is Austin in the same boat? Not hardly. Look at the meteogram below. Surface and 850mb temps well above freezing through the whole precip event.



What about aloft where the precip forms? Sorry, the predicted vertical profile is above freezing where the precip forms, quite different from Dallas:



Note that the 12Z NAM is quite similar to the GFS profile for Austin. It's actually a bit warmer than the 6Z GFS in the lower 5000 ft during the precip tomorrow. This strongly suggests cold rain with no chance of snow in Austin. Can't completely 100% rule out a stray snowflake there in Austin as the precip ends, but only if all the models are wrong about the upper air profile.

[iorange55]

Thanks for the information wxman57! It's appreciated.

One thing is for sure, the GFS keeps coming in a lot wetter. We just need to work on this cold business a little more. If the models are right about the temperatures and track of the ULL, then here in Dallas we will probably just see a few flakes. Maybe some flurries after Christmas (if NAM is correct.)

However, if the models are wrong (which can happen) then we would be in for some fun.

[Mattie]

I really hate it when the models *might* be right . . . But I'm kind of glad since we have guests coming in from out of town and the travel conditions won't be bad.

[Ntxw]

Great graphics as usual wxman!

The NAM is a bit more generous than the GFS regarding soundings with a smaller layer of surface air above freezing just below 850. Euro is somewhere in between but euro is heavier with the precip.

Temperature at DFW is holding steady at about 38-39 and dewpoint has been dropping a little bit. With such extensive cloud cover I wonder if the 45 predicted will verify

[Brandon8181]

Per National Weather Service Fortworth Forecast for Saturday NIGHT

FOR DALLAS, TEXAS

"60% Rain/Snow Likely" Low of 33 degrees....

Hmmmm

Happy Christmas Eve Eve everyone.

[pwrdog]

Per National Weather Service Fortworth Forecast for Saturday NIGHT

FOR DALLAS, TEXAS

"60% Rain/Snow Likely" Low of 33 degrees....

Hmmmm

Happy Christmas Eve Eve everyone.

That sounds about right... IMHO... The dew points NW of Ft Worth are in the 20's now...

There should be some snow flakes into at least Ft Worth.. How many ??