January: Calmer Pattern To End The Month

[Paul Robison]

Two questions:

1. How much icing does it take to break tree limbs and power lines?

2. Will the area get a sufficient coating for these things to happen?

3. Will ERCOT have to initiate rolling outages again?

I count three questions. It would take probably over 1/2" of ice accumulation to cause significant issues with trees/power lines. It is quite unlikely that the greater Houston area will see such accumulations. We're looking at light rain, a little freezing rain (probably under 1/8" accumulations) and a little sleet mixed in. This will probably not be significant enough for any power issues anywhere near Houston.

Latest GFS run has no post-frontal precip across Houston, by the way. It's all to our west on that run. Too soon to be sure about post-frontal precip, but if we get any it should be light.

IN regards to ERCOT, wxman57, I refer to the fact that here in Texas, where electricity is the primary source of heat, the demand for electricity might skyrocket. Won't that cause a real drag on the grid again? That's my worry!

[wxman57]

I don't think the demand for electricity will exceed the Arctic blast from the first week of January.

[Katdaddy]

Wxman57 is correct Paul. The first week of January was much colder than the next Arctic front.

[skidog40]

remember all the rain that will fall will not all dry up before freeze and add freezing rain after. accumulation of precip. is little they say but will be falling on wet ground. NWS just added 50% Thursday night and 50% Friday of wintery mix and lowered temps for katy.

[cisa]

trying not to get too excited as I know what will happen.....it will go another direction or pull and stall some where.

That happens to me too.

[Paul Robison]

remember all the rain that will fall will not all dry up before freeze and add freezing rain after. accumulation of precip. is little they say but will be falling on wet ground. NWS just added 50% Thursday night and 50% Friday of wintery mix and lowered temps for katy.

Have expected accumulations of ice inscreased witih the wintry mix probability?

[mcheer23]

NAM was pretty aggressive with the 00z run.

[Andrew]

NAM was pretty aggressive with the 00z run.

Both Gfs, and NAM where aggressive, but farther west and south with most of the aggressiveness. Interesting to note the hi-res NAM showed abundant moisture across the area (especially around the I-10 corridor) for most of Thursday night into Friday morning. If this scenario came to fruition, there could be some decent issues with travel on Friday morning. This would only be intensified if the p-type stays in the FR, or Sleet range. As for temps, models seem to vary a lot with upper air temps. I feel like with that southerly wind around 800mb, we will see a decent warm nose out of it. The warm nose seems to be shallow in nature and I feel like the models are having difficulties in picking up on this. Luckily we are beginning to get into the higher resolution range for models and this should help to be resolved in the coming day(s).

My personal feeling as of now, is that areas between San Antonio and Houston will see the highest precip totals and best chance for some sort of minor accumulation of precip. I do expect we will see a surprise or two throughout the region but this will be extremely isolated in nature. I do believe with the strong dry air advection at the surface, the farther north and east you go those chances exponentially decrease. A lot of the Global models really have a hard time pushing moisture east and whatever moisture does make it east has to first moisten the lowest couple thousand feet. Dewpoint depression at the surface looks to be about 15 to 20 degrees which will need to be overcome before we really see good precip. Now don't get me wrong, it won't take too much to eat through this, but when PW values range from .5 to .7 in (at best), it does make a difference. Luckily this evaporation should help to cool the surface even more and this is reflected in expected wet bulb temps. I do believe temperatures won't be an issue at the surface for most of the area, and at this point moisture and p-type look to be the biggest issue.

On another note, a special 00z launch will be preformed at KCLL on Friday (AKA Thursday Evening). Hopefully this will spread some light on that pesky warm nose and how much moisture is truly there. I do warn everyone to not get too excited but things do look interesting to say the least. More to come soon!

[Katdaddy]

A very tricky forecast remains for Thursday night through Friday as we draw closer to a possible Winter weather event for a large portion of TX. however I calling a Bear Watch at this point. Freezing rain and sleet remain a concern for Houston metro with light snow potential for the College Station area. Sleet and snow possible across the Hill Country and N portions of S Central TX. Snow and sleet threat will be S and SW of the Dallas-Ft Areas. The NWS does a great job with their AFDs. The Houston-Galveston NWS summarize the upcoming forecast very well:

THIS WILL REMAIN TRICKY AS FORECASTED THICKNESS VALUES ARE NOT ALL IN AGREEMENT. 1000 - 500MB AND 850 TO 700MB THICKNESS VALUES DO NOT INDICATE SNOW. 1000 TO 850MB THICKNESS VALUES DO GET TO 1290 AT KCLL WHICH WOULD INDICATE A CHANCE OF SNOW. A WINTER STORM WATCH OR WINTER WEATHER ADVISORIES MAY BE REQUIRED LATE THURSDAY INTO FRIDAY.

[stormlover]

We'll we all know models have a hard time with arctic air bec it's so shallow the cold air will be there

[srainhoutx]

Morning Update from Jeff:

Ingredients appear to be coming together to produce a mixture of light winter precipitation across much of the area Thursday night into Friday.

A strong arctic cold front will move southward down the plains today and into TX on Thursday. Temperatures behind this front originate in central Canada and are very cold. While this arctic boundary moves southward, a piece of upper level energy within the mean flow of the upper level trough will break off and develop into an upper level storm system over the SW US on Thursday. This storm system helps to bring a plume of sub-tropical moisture NE from the Pacific as well as some Gulf moisture. This moisture rides back over the top of and into the arctic cold dome over the region by Thursday evening. The overall large scale setup is fairly straight forward….but the details will make all the difference in P-type and accumulation amount.

Temperatures:

Will take the easiest aspect first. Strong cold air advection will onset post front with temperatures quickly falling into the 30’s and 40’s Thursday. Freezing line will advance rapidly southward on Thursday and reach a College Station to Huntsville line likely by sunset and continue to push southward overnight all the way to the coast. Temperatures by Friday morning will range from the mid 20’s north to near 30 at the coast with strong north winds of 15-25mph and gusty pushing wind chills into the teens. Will likely see very little recovery of temperatures on Friday and highs may not get much above freezing if at all with continued cold air advection and clouds/light precipitation which could prolong the threat of winter precipitation into much of Friday.

Precipitation:

Increasing weak large scale ascent and moisture will begin to produce periods of light rain on Thursday as the arctic boundary crosses the area. Suspect a brief break Thursday afternoon before lift increases again on Thursday night into Friday. Large scale models such as the GFS, NAM, and ECMWF show dry attempting to undercut the moisture below the cloud bearing level suggesting that rain falling from the cloud bases will have to saturate the near surface layer before reaching the ground. Current dry layer does not look overly deep and would be overcome with a few hours of precipitation falling. This will however help to “wet bulb” or cool temperatures in the air column toward the dewpoints which will likely play havoc with potential P-types. Overall amounts look greatest over our SW counties around Matagorda Bay and least around Lake Livingston. Do not expect liquid ratio precipitation amounts greater than about .25 of an inch.

P-type:

While surface temperatures will likely be well below freezing, it is what is happening above the surface which determines the type of precipitation that falls at a given location. A freezing surface layer with warmer air aloft results in freezing rain …liquid rain that freezes on contact with the surface forming a glaze of ice. If the warm air aloft is fairly shallow then the snow from aloft will only partially melt through the warm layer and then refreeze into a pellet of ice prior to reaching the surface…sleet. If the column from the surface to aloft is all below freezing then snow is most likely.

Current forecast soundings for Thursday night into Friday show a freezing surface layer up to around 1500 ft deep with a warm layer above that and then freezing aloft. This is pointing toward a freezing rain and sleet mixture across nearly the entire area. These soundings change with time and are different at locations across the area. For example the College Station sounding by Friday morning is nearly all below freezing suggesting more snow than freezing rain. Soundings at IAH and HOU keep a defined warm layer aloft through the period suggesting freezing rain mixed with some sleet.

Best attempt at the moment is:

North of a line from Rockport to Port O Connor to Galveston to High island: rain changing to freezing rain.

North of US 59: freezing rain mixed with periods of sleet

NW of a line from Columbus to Brenham to Huntsville: freezing rain mixed with sleet changing to sleet mixed with snow.

Accumulations:

It is pretty hard to get accumulations correct unless the P-type is right as freezing rain, sleet, and snow all produce different accumulations…start mixing them together and it gets even more challenging. Taking the models QPF models (liquid precip amounts) it appears areas west of I-45 could see upwards of .10 to .20 of liquid. This would equate to 1-2 inches of snow using standard liquid to solid ratios. Sleet amounts would be significantly lower in the ¼ to ½ of an inch range. Freezing rain amounts would be fairly equal to the liquid amount…maybe a little less. Liquid QPF amounts drop off quickly to the NE of Houston as this appears to be where the dry layer below the cloud bases wins out. Would not rule out a trace to .05 of an inch of accumulation in this region, but the main focus will be from Houston to the west and southwest.

Going with the main P-type of freezing rain mixed with sleet for much of the area suggest a possible accumulation of .05 to .15 of an inch of ice and sleet mix which will produce a crusty glaze on elevated objects including bridges and overpasses.

Over the NW counties where more sleet is possible and possibly some snow mix, accumulations may reach ¼ to ½ inch of sleet with possibly a dusting of snow. Would not discount a period of freezing rain and glazing in this region also under a thin layer of sleet/snow which will make bridges and overpasses extremely dangerous.

If should be clearly noted that precipitation amounts look to be on the light side…while not expecting heavy icing…it
only takes a very small amount of ice on roadways to cause major problems.

Uncertainty:

Still a lot of uncertainty with respect to the P-type and accumulations across the region and likely this will continue up to the start of the event. Appears that the area will see enough of both cold and moisture at the same time to potentially cause some problems on bridges and overpasses across much of the area. Do not expect enough ice accumulation to result in any large scale power outages. Forecast changes are likely over the next 24 hours both to P-types and accumulation amounts.

A Winter Storm Watch will likely be needed for parts of the area by late today or early Thursday.    

[Heat Miser]

You just don't see the local NWS write anything like this very often.

A Winter Storm Watch or winter weather advisories may be required late Thursday
into Friday.

[cristina6871]

I see where the stations are being somewhat conservative with how cold it may get - is there a possibility it could be colder than they are predicting?

[stormlover]

of course they are because its a tough forecast, but arctic air is really shallow and its hard for models to pick up on it so yes I would say it will be 3-5 degrees colder than what ur guys are saying.

[srainhoutx]

You just don't see the local NWS write anything like this very often.

A Winter Storm Watch or winter weather advisories may be required late Thursday
into Friday.

No, you don't Heat Miser. I have to give the forecasters a lot of credit to temper what we all were seeing via the various data and model guidance over the past week and wait until we actually have come into the time frame that more reliable data became available before even mentioning the need for possibly having to issue Watches or Advisories. It's tough to get wintry weather of any sort down here and it doesn't happen very often. We often see many a bust when wintry weather is boldly forecasted days ahead and even sometime being a little too conservative and catching folks off guard as we witnessed late in November. What is worrisome when looking at the various data, charts, computer models and satellite imagery are the signals of moisture over the Eastern Pacific near Baja festering and being pulled across Mexico toward Texas and a trough/upper air disturbance arriving after the cold air is in place as well as the growing chances of a Coastal trough/low down near Brownsville/Corpus Christi are the classic recipe needed for a Central and Coastal Texas Winter Weather Event. After many years of watching Texas weather events unfold, those ingredients all have to come together just at the right time to produce a winter weather event in our part of the world. Today would be a good day to let those that may not be so 'weather wise' know of the potential so they don't wake Friday morning and start that commute only to start slip sliding away, as the old song says.

[srainhoutx]

The 12Z NAM is getting into range where that shorter term model can begin to pick up on subtle features such as banding/higher reflectivity solutions and such. The 12Z version of the NAM is suggesting a Coastal trough/low near the Lower Texas Coast, brighter banding features N of the Coastal trough where heavier precipitation may develop and temperatures cold enough to support wintry weather. We will see.

[redneckweather]

Interesting setup. The trend looks to give my area the shaft once again like in 2004 when the moisture had too much dry air to overcome resulting in nothing but a cold dry wind while areas south of me got some solid snow accumulations. I'm hoping to see one solid big snowflake and I will call it a WIN.

I'm liking the direction the NAM is taking. Is it showing some good snow accumulations around Austin? Boy howdy, that will really get Portastorm all worked up!!! lol

[djmike]

I know theres a lot of chatter about what the Houston metro area will possibly see, but as of right now, what do you guys see for the Beaumont area? Anyone have any graphics that cover our area? Thanks!

[srainhoutx]

I know theres a lot of chatter about what the Houston metro area will possibly see, but as of right now, what do you guys see for the Beaumont area? Anyone have any graphics that cover our area? Thanks!

You guys in far SE Texas and SW Louisiana are not out of the woods for this event, Mike. We will be covering everywhere from the Rio Grande Valley to Central/SE/E Texas as well as all our folks in the Beaumont/Lake Charles area all the way to New Orleans.

LCH snippet:

THE UNCERTAINTY CONTINUES ON
THE AMOUNT OF MOISTURE POOLING ACROSS THE SFC TROF ACROSS THE NW
GULF...AND HOW FAR NORTH THIS MOISTURE MAY REACH DURING THIS
PERIOD. THUS WILL CONTINUE ONLY 20% CHANCE OF -SN/IP MAINLY ALONG
AND N OF I-10...WITH MAINLY IP MIXED WITH RA/FZRA FROM ROUGHLY
I-10 TO THE COAST THRU LATE FRI MORNING. WITH THE CAA CONTINUING
FRI AND CLOUD COVER...TEMPS NOT EXPECTED TO GET MUCH HIGHER THAN
THE MID/UPPER 30S.

[srainhoutx]

The 09Z SPC SREF ensembles continues to suggest wintry weather is certainly a possibility across much of our Region.