Texas Winter 2013-2014

[Longhornmaniac8]

So this questions goes back a bit to what wxman57 and I were discussing yesterday, but with some new conditions:

Tomorrow, the RAP for the Austin area is showing a very large temperature/dew point spread in the upper/middle atmosphere (which I'm interpreting as unfavorable conditions for precipitation). This is the case all the way until approximately 850 mb, where they suddenly come together (and stay together) all the way to the surface. From the time they come together, they're well below the 0C line, which I thought meant favorable conditions for snow. There is no warm nose present.

What's confusing me is the WWA issued by EWX talks primarily of freezing drizzle/sleet, with snow flurries mentioned only as a possibility. Is there something about the location of the saturation (that is, it's fairly close to the surface...5,000 ft or so) that would inhibit dendritic growth?

I just don't see how the formation of precipitation that falls through a saturated air column below freezing would be conducive to anything other than snow.

Any help here would be much appreciated! We're all trying to learn!

Cheers,
Cameron

Dendritic growth zone, the optimum temperature for them is -10C to -20C. Usually it's higher up in the atmosphere that this occurs (it can happen below but temperatures in your part of the world rarely gets that low near the surface up to 5k ft). You need 100mb+ layer (fairly deep) saturated for the best region to grow these dendrites otherwise the stuff you are seeing is graupel, melted snow, and all that other non uniform stuff, unfinished business.

Ok, so taking that the air column isn't conducive to dendritic growth, I'm still confused what would cause anything to "melt," since the genesis of the precipitation is occurring in a portion of the air column that is below freezing, and falling through air that is below freezing?

Cheers,
Cameron

[somethingfunny]

Those were some odd snowflakes today. Usually we get the big indistinguishable globs of wet snow here in Texas. The first picture here is of a "large snowflake" after it hit my coat... it's just a collection of dry feathery ice crystals. The second image is of some smaller snowflakes, along with another "dry glob", and a short strand of dog hair. The third picture is just a whole bunch of those big dry globs falling around 10am, as opposed to the tiny flakes we had for most of the day.

[SaskatchewanScreamer]

ah now that I wouldn't call a large snowflake...that indeed is a glob.

[Ntxw]

Ok, so taking that the air column isn't conducive to dendritic growth, I'm still confused what would cause anything to "melt," since the genesis of the precipitation is occurring in a portion of the air column that is below freezing, and falling through air that is below freezing?

Cheers,
Cameron

This I don't have a specific answer to. I do know melting doesn't always have to occur when it's above freezing. Dry air also sublimates the snow, perhaps it's leftover stuff that only partially got taken care of by the dry layer and then doesn't have the optimum temperatures near the surface to reform? Maybe a pro met or someone with the study knows more on freezing drizzle.

Great pictures somethingfunny, verifies meteorcane's pointy collection theory! Love those little dendrites at work

[SouthernMet]

fwiw the latest hrrr appears to show more "intense" precip (atleast in west texas) than it showed last night & more snow accumulations right on top of the metro.

[TexasF6]

Can anyone post latest model graphics? CenTex looks good (slightly)for decent precip? Thanks!

[Meteorcane]

Ok, so taking that the air column isn't conducive to dendritic growth, I'm still confused what would cause anything to "melt," since the genesis of the precipitation is occurring in a portion of the air column that is below freezing, and falling through air that is below freezing?

Cheers,
Cameron

One possible reason if the temperature is only marginally below freezing in a shallow layer, is that there are not a lot of "activated" ice nuclei (basically particulate particles) which are required for initial ice crystal formation (except at very cold temperatures). Therefore you may have more supercooled water than actual ice crystals as most ice nuclei won't be activated. That could make it more of a freezing drizzle (because of the shallow saturated layer would not allow droplets to get significant size). Now granted being in a continental near-urban area, there should be decent nuclei concentrations, the questions is will the temperature drop enough to activate them and start the "ice-phase growth process" or will they remain as small supercooled droplets. Also it is possible that if the shortwave is potent enough the associated lift could lift some of the droplets into the sub-freezing layer, which could then cause re-freezing into small ice pellets. Also the latent heat of deposition can warm the layer which might just be enough to get it above freezing if it is marginally below.

All that being said, I think any precipitation that occurs will either be freezing drizzle or flurries, I don't think it is a sleet profile.

[Ntxw]

fwiw the latest hrrr appears to show more "intense" precip (atleast in west texas) than it showed last night & more snow accumulations right on top of the metro.

It's trying to get light snow/flurries to fall tonight before the incoming shortwave, which looks stronger than the one that came through this morning. Question remains how much moisture does it have to work with? The RAP too tries to do this over the metroplex.

[TeamPlayersBlue]

When it snowed in Houston in '93, it didnt stick but those were the biggest flakes ive ever seen. I remember those flakes floating, not falling to the ground. Some called them 'waffles' falling from the sky lol

[orangeblood]

fwiw the latest hrrr appears to show more "intense" precip (atleast in west texas) than it showed last night & more snow accumulations right on top of the metro.

It's trying to get light snow/flurries to fall tonight before the incoming shortwave, which looks stronger than the one that came through this morning. Question remains how much moisture does it have to work with? The RAP too tries to do this over the metroplex.

Precipitable Water values for tomorrow are at or greater than they were this morning

[TheProfessor]

fwiw the latest hrrr appears to show more "intense" precip (atleast in west texas) than it showed last night & more snow accumulations right on top of the metro.

It's trying to get light snow/flurries to fall tonight before the incoming shortwave, which looks stronger than the one that came through this morning. Question remains how much moisture does it have to work with? The RAP too tries to do this over the metroplex.

Precipitable Water values for tomorrow are at or greater than they were this morning

yeah the dew point is about the same or higher than it was last night. The humidity is 83% here. If we have as much moisture as we did this morning, could this system put down more snow than the one today?

[Ntxw]

Precipitable Water values for tomorrow are at or greater than they were this morning

Yep, and looking at how vigorous the precipitation out in California/Arizona is certainly raises an eyebrow or two

[Wntrwthrguy]

Here's to hoping Austin gets a nice surprise tomorrow to raise Porta's spirits and finally end the dreaded 10 year curse.

[South Texas Storms]

Well unfortunately I slept through the wintry precip here this morning. I didn't expect much or else I would've set an alarm to wake up early. One of my friends was up early for it and said it sleeted for about 30 mins and then snowed moderately for about 15 mins. I woke up to a dusting of snow on the ground and not much melted today.

SA woke up to a nice surprise today too. My dad said he got a heavy sleet/graupel shower early this morning. I'm hoping for another surprise tomorrow morning!

[SouthernMet]

fwiw the latest hrrr appears to show more "intense" precip (atleast in west texas) than it showed last night & more snow accumulations right on top of the metro.

It's trying to get light snow/flurries to fall tonight before the incoming shortwave, which looks stronger than the one that came through this morning. Question remains how much moisture does it have to work with? The RAP too tries to do this over the metroplex.

and it's actually a plausible scenario considering what happened this morning.

[Ntxw]

One stat that got overlooked, Waco already broke it's seasonal record for most freezes currently at 53. Most was 51 from 1909/10. They will add quite a few more to it so it will be a fairly large gap between 1 and 2.

Of course Waco's reading site now currently sits in a low lying area that gets cold at night more than surrounding areas and sometimes even North Texas and adjacent Red River counties, but it's still an impressive feat.

[gboudx]

One stat that got overlooked, Waco already broke it's seasonal record for most freezes currently at 53. Most was 51 from 1909/10. They will add quite a few more to it so it will be a fairly large gap between 1 and 2.

Of course Waco's reading site now currently sits in a low lying area that gets cold at night more than surrounding areas and sometimes even North Texas and adjacent Red River counties, but it's still an impressive feat.

I was wondering how they reported so many more than DFW. Did they move their recording site?

[katheria]

what are we up to in dfw? Ntxw

[Ntxw]

I was wondering how they reported so many more than DFW. Did they move their recording site?

I'm not certain when the move was but Waco often sees freezes as early as October and as late as April when DFW doesn't. During cold blasts DFW is colder, but when it's just clear skies and no wind/clouds Waco dives. It sits in a very low area that is recorded, probably near the brazos River basin not certain. Lows there during radiation cooling often is lower than even surrounding DFW counties like Decatur and Graham.

Katheria we are at 43rd, will be 44th in a few hours. 48 is the magic number for guaranteed top 10 tie.

[Portastorm]

Well unfortunately I slept through the wintry precip here this morning. I didn't expect much or else I would've set an alarm to wake up early. One of my friends was up early for it and said it sleeted for about 30 mins and then snowed moderately for about 15 mins. I woke up to a dusting of snow on the ground and not much melted today.

SA woke up to a nice surprise today too. My dad said he got a heavy sleet/graupel shower early this morning. I'm hoping for another surprise tomorrow morning!

You have got to be kidding me??!! Dude, that was YOUR chance. Aye carumba.