December 2017: End Of The Year Weather

[redneckweather]

Yes but that low that is supposed to form will keep mostly all the moisture along the coastal counties, correct?

[srainhoutx]

Both the 12Z NAM 3KM and 12KM suggest areas inland across portions of Harris and Montgomery Counties could see an inch or two of snow on grassy surfaces and car tops. Temperatures at 2 meters suggest 36F. Going to be a close call and we'll just have to watch the radar trends as the day wears on into tonight. The forecast had rain ending today, but picking up as the upper air disturbance rolls along E along or just N of I-10.

[srainhoutx]

NWS Fort Worth/Dallas reports snow flurries at their office.

[wxman57]

Yes but that low that is supposed to form will keep mostly all the moisture along the coastal counties, correct?

That's always the dilemma. With coastal lows and snow events, the heavier precip is across coastal counties. However, I think there will be enough moisture this evening that you will see a few flakes. Don't plan on making a snowman.

[DoctorMu]

NAM, Canadian hanging tough. GFS keeps snow SW of the area,,,

[tireman4]

From Travis Herzog...

EW: Latest computer projection even more bullish on snow tonight, especially south of I-10.

WHITE = SNOW
PINK = RAIN/SNOW MIX

Ingredients still have to come together just right, but it's looking more likely that flakes will fly somewhere.

No guarantees, but we're in the game.

[wxman57]

Both the WRF and NAM are coming in colder aloft and with heavier precip. I've seen many such events over my nearly 4 decades as a meteorologist here, but I've rarely seen the models predicting such cold air aloft. Usually they indicate a warm nose (above-freezing layer) between 5000-10,000 feet up that just barely erodes as the precip comes to an end. Not so this time. If the models are correct, we will definitely see snow across a large part of coastal Texas and SE Louisiana. I think it could be heavy enough to accumulate, at least briefly, on cars and grassy areas. It'll be hard for it to accumulate on roadways, as the roads should remain above freezing.

Best time for snow in the Houston area will be from around 7pm to 4am tonight. After 4am or so, the air aloft will become too dry for precip.

[snowman65]

What are the % of precip overnight? 20%,80% ? Thanks

[tireman4]

Just an FYI. As Srain and Wxman 57 have told us in the past, this is still tricky for pro mets all over. It takes all the variables to be just right for this to happen. Many folks ( if this does not happen) will scream bust. Just giving a gentle reminder that it takes all ingredients in the mix to make this happen. There is still a lot of time left. Stay tuned.

[srainhoutx]

Starting to see a bit more activity to our SW in Mexico. Juarez and Monterrey reporting snow. IR loop showing lift increasing as the upper trough and embedded disturbances ride NE across Texas. NWS Corpus states the Cotulla has switched to all snow at this time.

[wxman57]

Just an FYI. As Srain and Wxman 57 have told us in the past, this is still tricky for pro mets all over. It takes all the variables to be just right for this to happen. Many folks ( if this does not happen) will scream bust. Just giving a gentle reminder that it takes all ingredients in the mix to make this happen. There is still a lot of time left. Stay tuned.

The tricky part is getting the vertical temperature profile right. There's always a pocket of warm air aloft that is the big question. I don't see that on any model projections, though. Note that the U of H will be launching a balloon at 18Z. I'll have the data by 1pm-2pm. This will confirm whether the models are correct in showing no warm tongue aloft.

[don]

I'm starting to get more excited about the possibility of snow! lol, it seems like the times that snow verifies here are usually when the models don't sniff it out until the "last minute" like this event. And when the models predict snow for us in the long range is usually when it doesn't pan out... lol

[tireman4]

Just an FYI ( not stating any of these products will be used) for this Winter.

[tireman4]

From Jeff...

Cold and wet today with rain or a rain snow mix possible tonight.

A few reports of sleet this morning in the Jersey Village, Barker, and Sugar Land areas where radar indicated extensive bright banding (high reflectivity from the beam striking the melting snow/sleet aloft). AM soundings show a very deep warm layer at Corpus Christi and nearly 4700 ft above freezing at Lake Charles. Del Rio has falling nearly completely below freezing through the entire column and reports indicate rainfall has changed to snow along the Rio Grande and there is some minor accumulation in progress.

Rain will continue for much of the day as SW flow aloft overruns the cold dense surface dome. A surge of drier air will begin to arrive this evening and gradually decrease precipitation from N to S across the region. As this happens the depth of the sub-freezing layer will gradually increase and this may allow the rain to begin to mix with snow of even change to snow. The big question becomes if there is enough moisture in the air column by the time the profile becomes favorable for snow to reach the surface. The NAM and the HRRR indicate a bit more moisture and more pronounced impulse over the area which results in precipitation continuing past midnight for areas south of I-10 and a better chance for mixed phase. The GFS and TX TECH WRF shows the drier air winning the battle and shutting down the precipitation as the thermal profiles become favorable.

Think the best chances for a rain/snow mix of complete change to snow will be across SC TX into the coastal bend from roughly Matagorda Bay SW toward Laredo where HRRR accumulation runs show amounts of .10 to 1 inch Friday morning. Dynamic cooling looks greatest in this area and reflectivity forecasts show some degree of meso type banding which would support some decent rates if a complete changeover can occur. These higher rates could locally cool the surface temperature toward freezing allowing some accumulation. Could extend the mix area as far NE as Brazoria and Galveston Counties, but moisture becomes a big “if” in these areas. If the NAM is correct this mix would extend up to about I-10 if not to Hwy 105 and accumulations would even be possible over a large portion of SE TX.

Will need to watch trends closely today for even a slight increase in moisture tonight as this would increase the chances for snow across the region. Will also need to take a hard look at surface temperatures today for early Friday morning as sub-freezing temperatures could affect portions of the region (mainly N of HWY 105) and any residual water could freeze on bridges and overpasses.

Forecast confidence is low and there could be changes today.

[DoctorMu]

It's snowing like crazy in Eagle Pass. Wow.

Snow to the SW of Houston seems a certainty. It's all about timing. We have a cold column and warm ground. Does it star wet? Enough precept will cool down the ground...and will the reinforcing cold air and coastal low be timed right? Does the dry air that will filter in spoil the fun? It's too bad peak moisture is timed when temps are likely to be warmest today.

Christmas miracle snow 2004...moisture and cold came together in the late afternoon and evening in HGX and down to Victoria. Man, those snowflakes were FAT!

[DoctorMu]

We've had some graupel in the last hour in CLL, melting on contact.

[redneckweather]

I highly doubt I will see a flake up here just south of Lake Conroe Dam. I've seen this song and dance at least a dozen or so times over the past 18 years and none of them gave me anything. It has actually warmed up outside since daybreak...sitting at 45 degrees. Not happening.

[MontgomeryCoWx]

Two things:

1) It was forecasted to warm up before the reinforcing front hits us this afternoon.

2) I bet your location does see flakes, whether you see them or not. As a matter of fact, I was on 105 this morning and there was some graupel mixing in.

[wxman57]

Note that we have decided on 2 balloon launches today. First will be at 18Z, second near 03Z. They're launched from the University of Houston. Data will be sent to the local NWS office. I'll post it here, too. I'm interested in seeing how well the models are handling the temps aloft.

[Katdaddy]

Lake Charles Morning AFD Update:

Area Forecast Discussion
National Weather Service Lake Charles LA
1008 AM CST Thu Dec 7 2017

.DISCUSSION...
Update the grids through the night with the latest guidance.
Wintry precipitation chances have increased over the past 24 hours
and will be evaluating the latest guidance and make a
determination after coordination on any need to expand the winter
weather advisory.