Texas winter wx thread#4 - big changes on the way eventually

[double D]

as they dwindle for OK, they increase for TX. It is looking better and better for TX it seems.

Maybe precip. chances but not necessarily snow. Did you read the discussion from Corpus? This isn't exactly the coldest system in the world. I wouldn't give the impression that b/c the low is tracking south that automatically means the chances for snow is looking "better and better" for us. It's irresponsible IMO.

As AFM has needed to state a few too many times now, you have to look at other parameters.

I tend to agree about the temperatures not being that cold. Although I know it doesn't have to be freezing to snow, the 2 meter temperatuers stay well above freezing for 3/4 of the state for the weekend.

That said, there will be a nice little snowpack up north (from current system) and the cold air may not modify as much and temps could be cooler than what the gfs is showing. Just something to think about.

[Portastorm]

The Austin/San Antonio NWSFO office forecasts are out ... not the discussion yet but the forecast is ... here's the interesting part:

SUNDAY NIGHT...MOSTLY CLOUDY. SLIGHT CHANCE OF LIGHT RAIN AND LIGHT SNOW BEFORE MIDNIGHT...THEN A SLIGHT CHANCE OF LIGHT SNOW AFTER MIDNIGHT. LOWS IN THE LOWER 30S.

CHRISTMAS DAY...PARTLY CLOUDY. HIGHS IN THE UPPER 40S.

[double D]

Looking at some of the these AFD's and JB's comments.

Is history going to repeat itself again this Christmas for one particular part of the state???????????

Am I going to have to drive to Corpus to see snow?!?!?!

I think that cctxhurricanewatcher might have to drive up to central Texas this time if that upper low stays on track.

[MiamiensisWx]

Based on synoptic factors favoring fairly low temperatures and some thermal factors at the middle levels over portions of interior Texas, I wouldn't rule out some isolated mixing and light frozen precipitation (with some potential snowfall), but I wouldn't be too aggressive as of now, since other synoptics such as the type of Gulf moisture and gradient factors favor rainfall, as seen here. The location and timing of development of the mid-level low may be critical in determining the extent of the possible frozen precipitation event over portions of Texas and also in determining how much of it reaches the surface. The pace of the movement of the low may also have an impact on the type of precipitation, as well as instability levels, the gradient, and mid-level to surface temperatures. Just my two cents here.

By the way, as an unrelated note this system is likely to enhance some mix and possible isolated snowfall over portions of central Colorado.

[Kludge]

You guys should take a trip down memory lane...

http://www.storm2k.org/phpbb2/viewforum.php?f=22&topicdays=0&start=2150

We all know what happened on Christmas in S.TX that year; it's a real hoot to go back and see what was being posted...and what the AFD's were saying...a week before the event.

Of course our result may and likely will be quite different, but the only real difference I can see from this point is that it doesn't appear that as much cold will be in place at the surface.

Still...isn't it fantastic to at least have the possibility of some Christmas-like weather on Christmas?

[Also, if anyone knows how to find archives of the GFS/Euro/Etc runs from 2 years ago today (or maybe saved them somehow), it would be great examine those from a hindcasting standpoint.][/u]

[cctxhurricanewatcher]

You guys should take a trip down memory lane...

http://www.storm2k.org/phpbb2/viewforum.php?f=22&topicdays=0&start=2150

We all know what happened on Christmas in S.TX that year; it's a real hoot to go back and see what was being posted...and what the AFD's were saying...a week before the event.

Of course our result may and likely will be quite different, but the only real difference I can see from this point is that it doesn't appear that as much cold will be in place at the surface.

Still...isn't it fantastic to at least have the possibility of some Christmas-like weather on Christmas?

[Also, if anyone knows how to find archives of the GFS/Euro/Etc runs from 2 years ago today (or maybe saved them somehow), it would be great examine those from a hindcasting standpoint.][/u]

Thanks for the memories. Reading all of those Winter Storm Warnings and indivdual observations was fun.

[double D]

Hmmm... I like this forecast for Fredericksburg and the Hill Country:

Saturday Night...Cloudy. Rain likely before midnight...Then rain and snow likely after midnight. Lows in the lower 30s. Chance of precipitation 60 percent.
Sunday...Mostly cloudy. Chance of rain and snow in the morning... Then a chance of rain in the afternoon. Highs in the mid 40s. Chance of precipitation 30 percent.

Sunday Night...Mostly cloudy. Slight chance of light rain and light snow before midnight...Then a slight chance of light snow after midnight. Lows in the upper 20s.

Christmas Day...Partly cloudy. Highs in the mid 40s.

[TrekkerCC]

You guys should take a trip down memory lane...

http://www.storm2k.org/phpbb2/viewforum.php?f=22&topicdays=0&start=2150

We all know what happened on Christmas in S.TX that year; it's a real hoot to go back and see what was being posted...and what the AFD's were saying...a week before the event.

Of course our result may and likely will be quite different, but the only real difference I can see from this point is that it doesn't appear that as much cold will be in place at the surface.

Remember, it doesn't have to be arctic cold to make it snow. Just get the whole atmospheric column freezing (or a little below), and you'll have snow. Now, a real arctic cold shot does help, as it is easier to make it snow, and the air coming down is only modified polar air, but in the right conditions, that is enough for snow. For north Texas, the more south the developing low tracks, the less chance for snow (at least up here). 18z GFS is still coming in, so it will be interesting to see how it looks.

[Extremeweatherguy]

truly I would be happy with sleet as well.

I just want some form of winter precip. out of all this mess!

[TrekkerCC]

18z Run is out for GFS:

Here is the relevant panels -- it appears (on the 18z run) that the gulf low develops and tracks northeast in LA/AR area. For at least the North Texas area, it is probably not good. It appears GFS is showing some precip, but this is likely overdone.

96 hours:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _096.shtml

102 hours:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _102.shtml

108 hours:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _108.shtml

114 hours:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _114.shtml

120 hours:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _120.shtml

Relevant piece of FWD's NWS discussion:

IN THE EXTENDED...WEEKEND UPPER LOW POSITION STILL NOT WELL
RESOLVED...BUT MODEL CONSENSUS SEEMS TO BE PUSHING UPPER LOW MORE
TOWARDS SOUTH TEXAS. THIS WOULD MAKE US COLD BUT DRY.

[Extremeweatherguy]

keep in mind though that the GFS usually is too far south at this range. Usually it will shift north a bit with it's lows as the situation gets closer. If it is just a bit further north, then I think a major storm is possible.

[MiamiensisWx]

The breakdown of the surface to mid-level heat ridge near Florida may be critical as well in the timing and potential weak phasing (if it occurs) of this developing low. If the heat ridge over the Bahamas moves eastward quicker and weakens slightly a bit faster, the low may form somewhat further south, depending on the other synoptics at hand. That could affect the precipitation pattern over Texas (in example where it falls, how much reaches the surface, and what the extent may be in particular regions). That's another reason I'm keeping tabs on the 18Z GFS pattern and what the pattern progression may be indicated in the upcoming 0Z run; however, I would watch the synoptics play out on imagery and surface maps (as well as current mid-level to high-level charts) to determine the possible outcomes before resorting to the models.

Hopefully you'll all enjoy the precipitation event! The jet dynamics per the mid-levels at play here should be interesting to watch as it progresses, as that may affect the low formation and synoptics, too.

[double D]

keep in mind though that the GFS usually is too far south at this range. Usually it will shift north a bit with it's lows as the situation gets closer. If it is just a bit further north, then I think a major storm is possible.

Well EWG, if it doesn't pan out for you this time, it looks like sometime around New years you may get another shot of "potential" winter weather as the GFS has been consistent in bringing down some cold air and breaking out some precip.

Has JB sent out an update on what he thinks might happen Christmas weekend?

[aggiecutter]

The AFD out of Shreveport for NE Texas, SW Arkansas, SE Oklahoma, and NW Louisiana:

"LATE THIS WEEKEND...ANOTHER WEATHER SYSTEM...THIS ONE PERHAPS
ACCOMPANIED BY MUCH COLDER AIR...WILL SPREAD ADDITIONAL
PRECIPITATION OVER THE FOUR STATE AREA. SOME WINTRY PRECIPITATION
MAY BE POSSIBLE LATE IN THE WEEKEND...PERHAPS ALONG AND NORTH OF
INTERSTATE 30 AND SPREADING INTO SOUTH CENTRAL ARKANSAS. THE CHANCES
FOR WINTER WEATHER THIS UPCOMING HOLIDAY WEEKEND WILL LIKELY BE
ADJUSTED AS WE GET CLOSER TO THE EVENT."

[Air Force Met]

Well...just a quick summary here for SE TX...it looks way to warm when the first batch of upper level energy comes through and way too dry when the big upper low comes in. In the ealy morning hours of the 26th is when the air column will be coldest and the upper level energy is the best in SE TX...but there is just no moisture to work with. The front is well off shore and dry air is advecting in. There isn't even any appreciable humidity at 700 mb....anywhere in the state.

There is a HUGE dry slot at 850...with dewpoints in the -20C range...and as low as -25C at 12Z (at 800 mb). The atmosphere is saturated above 650 MB...with the upper low...but the air is so dry anything that would fall would:
1) Evaporate and
2) Melt...as there appears to be a 100 mb thick layer above freezing above the sfc.

Bottom line is the second upper level impulse coming through is the best chance and it is slim. If the models are right...winter precip has the best chance on the morning of the 26th...and it may be a flurry or two in some thick virga in the area of greatest upper level vertical motion. The cold front is going to be all the way into the caribbean and south of the BoC...so no coastal low or anything like that is possible.

When the moisture is present...with the low at the sfc...it will be too warm. There is an outside chance of something in east Texas just as the system moves out...but I wouldn't bet on it. When the cold air moves in...it will be too dry.

[MiamiensisWx]

Well...just a quick summary here for SE TX...it looks way to warm when the first batch of upper level energy comes through and way too dry when the big upper low comes in. In the ealy morning hours of the 26th is when the air column will be coldest and the upper level energy is the best in SE TX...but there is just no moisture to work with. The front is well off shore and dry air is advecting in. There isn't even any appreciable humidity at 700 mb....anywhere in the state.

There is a HUGE dry slot at 850...with dewpoints in the -20C range...and as low as -25C at 12Z (at 800 mb). The atmosphere is saturated above 650 MB...with the upper low...but the air is so dry anything that would fall would:
1) Evaporate and
2) Melt...as there appears to be a 100 mb thick layer above freezing above the sfc.

Bottom line is the second upper level impulse coming through is the best chance and it is slim. If the models are right...winter precip has the best chance on the morning of the 26th...and it may be a flurry or two in some thick virga in the area of greatest upper level vertical motion. The cold front is going to be all the way into the caribbean and south of the BoC...so no coastal low or anything like that is possible.

When the moisture is present...with the low at the sfc...it will be too warm. There is an outside chance of something in east Texas just as the system moves out...but I wouldn't bet on it. When the cold air moves in...it will be too dry.

I tend to agree, and while I believe mid-level moisture and input and output may be sufficient for precipitation, mid-level drier air synoptics may prevent a more widespread mix or frozen precipitation event. Either way, the amounts don't appear to be very significant in most areas.

By the way, I see you've returned, Nelson. Welcome back!

[Furious George]

Thanks for the update AFM. I guess it is hard for SE Texas to get that moist air / cold air combo, so it's back to reality. Though it does seem like some models (GFS in particular) want to keep reinforcing some cold air post Christmas. I'm still hoping the hill country will see something out of this though.

[Air Force Met]

Thanks for the update AFM. I guess it is hard for SE Texas to get that moist air / cold air combo, so it's back to reality. Though it does seem like some models (GFS in particular) want to keep reinforcing some cold air post Christmas. I'm still hoping the hill country will see something out of this though.

It is very hard. It's not unusual for us to be cold enough...but most times it is too dry for anything to happen. It takes a lot for the air to get that cold down here and in order for it to happen...it usually takes a nice strong polar front or an arctic front. Those are usually very dry airmasses and the moisture gets advected out with the front.

[Kelarie]

From Austin/San Antonio

ALTHOUGH CONFIDENCE IS SOMEWHAT LOW ON OUR SNOW FORECAST ..CONFIDENCE IS HIGH ON OUR TEMPERATURE FORECAST. LOOK FOR ABOVE NORMAL TEMPERATURES TO CONTINUE THROUGH FOMORROW...WITH TWO DAYS OF NEAR NORMAL TEMPERATURES FOLLOWED BY WELL BELOW NORMAL TEMPERATURES BEGINNING SATURDAY NIGHT AND LASTING THROUGH AT LEAST CHRISTMAS DAY.

[Opal storm]

From Austin/San Antonio

ALTHOUGH CONFIDENCE IS SOMEWHAT LOW ON OUR SNOW FORECAST ..CONFIDENCE IS HIGH ON OUR TEMPERATURE FORECAST. LOOK FOR ABOVE NORMAL TEMPERATURES TO CONTINUE THROUGH FOMORROW...WITH TWO DAYS OF NEAR NORMAL TEMPERATURES FOLLOWED BY WELL BELOW NORMAL TEMPERATURES BEGINNING SATURDAY NIGHT AND LASTING THROUGH AT LEAST CHRISTMAS DAY.

Fomorrow?