December 2017: End Of The Year Weather

[srainhoutx]

I see the 12Z ECMWF came in with some impressive QPF totals of 2 to 3 inch amounts for the end of next week into the Christmas Holiday weekend with some rather chilly air at the surface.

The afternoon Update CPC Day 8-14 Outlook suggests very chilly and wet weather is possible as we head toward the end of December and those Day 11+ Analogs continue to raise an eyebrow.

[harp]

Doesn't look like the cold makes it to SE Louisiana.

[MontgomeryCoWx]

Doesn't look like the cold makes it to SE Louisiana.

It does and will. These are arctic fronts not fall fronts

[MontgomeryCoWx]

Latest Euro buries North Texas in snow and breaks out ice in our area at the end of the run

[davidiowx]

The models consistency is certainly an eye opener. They have been fairly accurate as of late with the Harvey rain totals and then the snow last week. It's quite impressive.

I am curious as to what tomorrow and Sunday is going to bring us? Are we looking at potential for severe weather? Or just rain?

[srainhoutx]

We are starting to see some wording in our local SE Texas AFD that suggests as the weekend ends and we begin next week, eyes turn to potential winter weather worries...

Area Forecast Discussion National Weather Service Houston/Galveston TX
338 PM CST Fri Dec 15 2017

DISCUSSION... Unsettled weather looks to continue through at least the next week (and likely longer) in Southeast Texas, with only brief periods of fairer weather interspersed between more active stretches. Tomorrow night looks to provide some - albeit highly conditional - potential for strong to severe weather on the immediate coast. Additionally, look for a weak front towards mid-week, and finally a more substantial front comes into the picture at the end of the week, but there is low confidence in this timeframe due to significant inconsistency in the guidance both between models and from run to run. How this front behaves will likely set the stage for weather through the Christmas holiday.

NEAR TERM [Through Tonight]... Radar shows most showers have pushed offshore this afternoon, though there may be some light showers or drizzle around Matagorda Bay. However, there`s a good chance that none of these returns are even reaching the ground. Satellite imagery shows overcast skies are beginning to break from north to south, though perhaps too late to allow for much more significant warming this afternoon. Sky cover will be a fairly important consideration overnight as far as overnight temperatures go. At this time things look open enough for the far north to radiate down to the upper 30s to around 40, while the immediate coastline will be hung up around or just above 50, with the rest of the area in the 40s. Rain chances look to be quite low except for a slight chance of showers offshore growing towards dawn.

SHORT TERM [Saturday Through Sunday Night]... Northeast winds early look to veer towards easterly or just south of easterly, aided by the development of a weak surface low off the coast towards Brownsville. Look for that low to quickly scoot up the coast Saturday night, and its precise path may become dreadfully important for the severity of any storms in the late night hours. A low that is able to move onshore and track just inland will allow coastal areas to briefly enter into the warm sector - in a window roughly from 3Z-7Z - which will help surge dewpoints above 66 degrees and create a thermodynamic situation which would allow for storms to become surface-based. This track would also severely back surface winds and create a situation with significant low level shear and a very largely curved hodograph - a perfect situation for transient, low-topped supercells with potential for tornadic waterspouts and even some brief tornadoes very near the coast. The Texas Tech WRF would be a prime example of this scenario.

On the other hand, a track that stays offshore, or even scrapes right on the coastline would limit the potential intrusion of warmer, moister air. The LLJ in this scenario would actually more likely result in a surface layer inversion, and any thunderstorms would become elevated and unable to tap into any low level shear. We`d still see storms, and potentially locally heavy rain - indeed, of the models that follow this scenario, some use convergence on the northeast side of the quickly moving low to generate or at least imply something like a QLCS that could have some briefly torrential rain. On the plus side here, the dynamic wind fields involved should keep everything moving quickly.

While isolated points of street flooding could occur, it seems unlikely that we`d see anything worse than that as we just won`t have time for rain to pile up. With the low clearing out quickly on Sunday, that day should generally be quiet, though perhaps with some lingering shower potential near the coast. But, winds will also very quickly become onshore Sunday night, and begin to pump warmer, high moisture air back in. Because of this, we could see the development of sea fog overnight, and low temperatures across the area look to stay above 50 degrees.

LONG TERM [Monday Through Friday]... As we go into next week, the closed upper low near Mexico`s Pacific coast should start to eject, though there is some difference of opinion as to how much interference/phasing we`ll see with the northern jet as it does so. Beneath that low, a surface low, or at least a trough may develop that will result in upglide from the onshore Gulf flow and result in a new bout of showers. Monday looks pretty solid for some of this rain, while Tuesday is a little more up in the air. The GFS has a pretty solid surge of northwesterly winds Monday night as the upper trough moves quickly by and dries us out very rapidly.

The Euro is a bit more deliberate with the upper low, and though perhaps it has a better defined surface low, a post- frontal northwesterly surge doesn`t look as significant, keeping us from drying out until Tuesday night. Though I would tend towards a slower evolution when it comes to these closed/cutoff lows to our west, I did tamp down PoPs somewhat for Tuesday as the GFS` solution is at least plausible. There will be time to adjust up (or, perhaps down) as we gain greater consensus on this evolution. Despite some deviation here, there is strong consensus in a quick return to onshore flow for the back half of the week. Thursday looks to be relatively drier, but there is a slight chance of a shower. However, potential should increase Friday as lee cyclongenesis over the Oklahoma Panhandle should result in the development of a new low and trailing cold front that is on our doorstep by Friday morning.

Look for showers to develop near the front and persist for some time in the front`s wake. This will set the stage for an unsettled period leading up to Christmas. And while there`s fairly high confidence in that, and generally good confidence that colder air will push into the area, there is significant uncertainty about how that may translate into wintry precipitation. At this point, there is so much inconsistency both between models and between individual runs of the same model, that it`s impossible to state much beyond that it will be colder, there will be periods of precipitation, and some sort of wintry precip is possible (but by no means certain!).

Indeed, just to make things more fun, the GFS doesn`t even bring the 850 front far into our area, if at all, keeping 850 temps well above freezing for all but our northwest. In the words of my esteemed shift partner, this is a "warm and gross rain" scenario. Not so sure I`m convinced about this as reality compared to the Euro, but I put it there to illustrate that in a place where wintry weather hangs on razor thin margins, those margins are totally swamped by range of potential scenarios at this time. Much like in tropical season with potential threats in the extended period, keep calm, make sure you have a plan, and stay tuned.

[sau27]

I have been trying very hard not to get too invested in these model runs yet. One thing that is concerning though is that, as others have said, the models don't always handle the intensity of the cold in these shallow air masses. If the air is indeed colder than projected there is a significant potential for more freezing rain issues than what is already modeled. However like I said I am trying to reserve judgment until at least the beginning of next week.

[MontgomeryCoWx]

Monday should produce a doozy of a AFD from our local offices

[wxman57]

18Z GFS doesn't paint a pretty picture for central to NE Texas and southern Arkansas. Over 3" of freezing rain and sleet - not snow. I'd be very cautious about taking that ECMWF snowfall map at face value. I'm not sure how well it does discriminating between snow and freezing rain/sleet in these situations. I'm not aware of anywhere that I can get an ECMWF sounding as we can with the GFS. We get the full ECMWF package at work, but I don't think we can plot a sounding.

Again, this may more likely be a freezing rain and sleet event - quite a severe ice storm. Central to NE TX and southern Arkansas are under the gun. Not so much of a threat for SE TX this time, it appears. Still a week off, though.

[harp]

One of our local mets has our high temp here in SE La. at 80 next Friday. You know, that real Christmas type feel to the air. Disgusting..... Might be three hot Christmases in a row....

[MontgomeryCoWx]

One of our local mets has our high temp here in SE La. at 80 next Friday. You know, that real Christmas type feel to the air. Disgusting..... Might be three hot Christmases in a row....

It won’t

[jamelyn]

My daughter is supposed to drive here from Lubbock in the 22nd. Wondering if she should leave a day early

[Katdaddy]

The 2017 Weather Year continues onward. Interesting weather days ahead for SE TX and much of TX.

First, this weekend. There is the potential for severe storms and locally heavy rain across S portions of SE TX, especially along the Upper TX Coast. Hoping the warm front remains over the coastal waters and does not move inland. If it does make it inland there will be a low tornado threat in the warm sector. The SPC may be issuing a Marginal risk area tomorrow morning. Locally heavy rains will also be possible, but thankfully storm motion will be quick. I will post an update tomorrow morning.

Now, on to next weekend. Still a long way out, but model consistency has been ongoing all week with different types, amounts, and coverage of Winter precipitation across a large portion of TX. I would love to see snow again, but do not want another significant ice storm with long term power outages similar to a hurricane. Yes, that is extreme and many areas could end up with messy, cold rain if the cold air above the surface is shallow but enough consistency to take note.

The take away is to be more weather aware through next week, especially with much travel ongoing as we approach Christmas. The Houston-Galveston NWS AFD end their discussion very well this afternoon:

Much like in tropical season with potential threats in the extended period, keep calm, make
sure you have a plan, and stay tuned.

[wxman57]

My daughter is supposed to drive here from Lubbock in the 22nd. Wondering if she should leave a day early

If it was my daughter, I'd strongly recommend driving on Thursday vs. Friday. She may run into heavy freezing rain in central Texas Friday afternoon.

[wxman57]

One of our local mets has our high temp here in SE La. at 80 next Friday. You know, that real Christmas type feel to the air. Disgusting..... Might be three hot Christmases in a row....

It won’t

One thing this Christmas won't be is hot. Now, temperatures may approach the upper 70s on Thursday, but the temperature may hold in the 30s next Friday through Christmas - not just for lows, for highs, too.

[sau27]

00z GFS coming in with a nasty ice storm for C. Texas again. Like I said before, if the overrunning trend keeps up and the GFS is underestimating the cold at the surface this could be even more interesting. I am interested to see the NAM's solution on this once we get into it's range as it did so well with the last event.

[Texaspirate11]

Its been a while since I posted - I have been busy with Hurricane Harvey/disability issues
With the past snowfall & upcoming potential for an arctic blast - many are still living in tents
while its "exciting" to see what may happen - it will be more suffering for many who are still displaced.

I think the usual culprits will see the heavy"wintry" stuff - CTexas up through DFW - DFW usually gets the bad stuff
(wont mention the Cowboys )
It's gonna be an interesting week indeed.

[TexasMetBlake]

Looking at the 00z/06z GFS and the Saturday 00z Euro, it's definitely going to get cold but as the event draws closer, I think the warm nose will be pretty stout and difficult to overcome. The 00z Euro brings the front in around 12z Friday (compared to 18z on the previous 12z and between 18 and 20z with the GFS) and keeps surface temps above freezing (but still very cold -- low 40s from Friday-Tuesday AM).

Friday's 12z Euro was definitely more in favor of frozen precip here locally but overnight guidance has shifted back to all rain. The Euro is colder than the GFS but only by a few degrees. Nothing dramatic.

What about the opportunity to wetbulb? Looking at the 06z GFS, there isn't much, if any, room to wetbulb as we stay saturated from 650-700 mb to the surface. Temps and dewpoints stay within a few degrees of each other (mid 40s). I also went and looked back at the 00z GFS and while it's colder than the 06z run, the Td's are comparable to the temperature leaving little wiggle room for evaporative cooling.

The freezing level is also hanging out around that same level (650-700 mb) and stays parked around 650 mb until after the precip is ending. This could change with subsequent runs but right now, looking like a miserable, wet/cold holiday weekend.

For those that are mad at me for putting an end to our winter storm, there is still plenty of time for all this to change in our favor. Anecdotally speaking, these arctic fronts usually come in quicker and colder than forecast. We'll see what happens. Even if we DO get wintry precip, it still an ice event as the depth of the cold air just isn't there.

Central Texas however could be in for quite the ice storm. We'll see.

[Andrew]

Yea looking like only rain here. Even if we do get to below freezing at the surface with such a potent warm nose everything would most likely come down as rain. Opposite setup of the other week where above the surface was all below freezing. Looking more and more likely that the Christmas eve/23rd time frame is going to be cold with rain with temps struggling to get out of the 40s. Now if moisture can stick around longer until Christmas or after, another reinforcing shot of cold air could make things more interesting. Keep an eye out though, especially the further north you are. Looks like it could be difficult for traveling, especially to the DFW area.

[WeatherDuck]

Central Texas however could be in for quite the ice storm. We'll see.

I live in Taylor, TX. About 30 miles NE of Austin.

In the next few days, could some preparations for an ice storm be warranted?