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

[Extremeweatherguy]

NWS FT WORTH TX

ANOTHER SUNNY DAY IS IN STORE...WITH SEASONAL TEMPERATURES.
CLOUDS WILL BE ON THE INCREASE SATURDAY AS THE NEXT STORM SYSTEM
APPROACHES.

THERE IS STILL GOOD AGREEMENT WITH THE INITIAL EVOLUTION OF THE
TROUGH IN THE PACIFIC NORTHWEST DIVING SOUTH...DIGGING INTO THE
DESERT SOUTHWEST...AND SWEEPING TOWARD THE TEXAS/MEXICO BORDER.
BEYOND SATURDAY...THERE IS CONSIDERABLE DISAGREEMENT IN TIMING
AMONG THE MID-RANGE MODELS. GFS REMAINS THE FAST OUTLIER...WITH
THE UKMET ON ITS HEELS. NEW 06Z NAM HAS SPED THINGS UP A BIT...
NOW MORE IN LINE WITH 00Z UKMET. REMAINS IS NOW A BIT FASTER.
DESPITE DISCREPANCIES...ALL FAVOR A QUICK EVENT...AND FEEL
CONFIDENT WITH POPS PRIMARILY SATURDAY NIGHT AND SUNDAY.

LOW TRACK STILL APPEARS TO BE THROUGH CENTRAL TEXAS...NEAR
SOUTHERN EDGE OF CWA. ANY DEVIATION WILL AFFECT THE FORECAST
GREATLY...BUT DECENT MODEL CONTINUITY REMAINS WITH THE STORM
TRACK. ALTHOUGH PROFILES ARE WARMER...ENHANCED LIFT NEAR COLD
CORE WILL PRODUCE SNOW ABOVE THE SFC LAYER. SOME SNOW MAY REACH
THE GROUND ON THE HIGHER TERRAIN OF SW ZONES...BUT WILL CARRY
PRIMARY PRECIP TYPE AS RAIN. SFC TEMPS WILL PRECLUDE ANY SLEET OR
FREEZING RAIN. IMPACT TO TRAVEL SHOULD BE LOW...EVEN WITH
ACCUMULATING SNOWS...AS ROADS WILL BE WARM AND TEMPS SHOULD
PRIMARILY BE ABOVE FREEZING. WITH HOLIDAY TRAVEL ON SUNDAY...WILL
NOTIFY THE PUBLIC WITH THE MENTION OF SNOW...WITHOUT CATEGORICAL
SNOW AMOUNTS OR OTHER DOOM.

NEXT SYSTEM ARRIVES RAPIDLY ON CHRISTMAS DAY. LOOKS FAR LESS
IMPRESSIVE THAN PREVIOUS RUNS...AND STILL FAR TOO DRY FOR ANY
MENTION OF PRECIP.

A FRONT IS PROGGED FOR MIDWEEK...WITH TSRA CHANCES. RAIN CHANCES
MAY LINGER IF EXTENDED MODELS VERIFY...ANOTHER LOW WITH A SOUTHERN
TRACK DAY 6-7.

NO ARCTIC INTRUSIONS IN THE FORESEEABLE FUTURE.

This was written before the 12z run came out. The 12z actually reverses the thinking of some of the "far less impressive runs" and shows a decent cold shot for Christmas day with more moisture. Should be interesting to see what the afternoon AFD looks like.

[Air Force Met]

12z GFS still seems to be showing the potential of snow flurries by the evening of Christmas Day:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _084.shtml

Snow flurries for WHERE exactly? Certainly not SE TX ...given the lower 100mb is above freezing (that's about 2500')

[Furious George]

Looks like Christmas will be cool for SE Texas, but that's about it - it actually will be fairly close to our climatological averages. The 12Z GFS is not encouraging, as seen from the IAH GFS data. Oh well, maybe it's time to look at those 360 hr GFS runs.

http://www.srh.noaa.gov/data/Guidance/G ... KIAH.1.txt

[Yankeegirl]

Jen, I just checked all the winter weather stuff, you are so funny.... I hadnt gotten on this much yesterday since I had to finish playing Santa... I think a little fire will be ok....

[WhiteShirt]

12z GFS still seems to be showing the potential of snow flurries by the evening of Christmas Day:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _084.shtml

Thank you for posting this. Keep us updated, please!

[southerngale]

AFM has spoken.



NO SNOW FOR YOU!

[Brent]

12z GFS still seems to be showing the potential of snow flurries by the evening of Christmas Day:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _084.shtml

Snow flurries for WHERE exactly? Certainly not SE TX ...given the lower 100mb is above freezing (that's about 2500')

The voice of reason AGAIN!

[GeneratorPower]

The Snow Nazi.

[Extremeweatherguy]

a met on another weather board I visited said that the model actually was showing snow flurries for at least northern portions of SE Texas. Seems like there may be some disagreement between mets.

At the moment I am just trying to stay hopeful..

[gboudx]

Chance of flurries has been added to our afternoon forecast for Christmas Eve night.

Saturday: Mostly cloudy, with a high near 56. Northeast wind between 5 and 10 mph.

Saturday Night: A 30 percent chance of rain, mainly after 3am. Cloudy, with a low around 39. North northwest wind between 5 and 10 mph.

Sunday: A 20 percent chance of rain. Mostly cloudy, with a high near 51. North northwest wind around 5 mph.

Sunday Night: A slight chance of rain before midnight, then scattered sprinkles and flurries. Mostly cloudy, with a low around 34. Calm wind becoming south southeast between 5 and 10 mph. Chance of precipitation is 20%.

[Johnny]

I saw what he said on that other board EWG. It's a crap shoot but interesting none the less. Keep the faith brother!!

[Extremeweatherguy]

From the Beaumont - Lake Charles afternoon AFD:

THINGS GET A BIT INTERESTING AS WE GET CLOSER TO CHRISTMAS. THE
GSM DRIVES THE SPLIT OFF CLOSED UPPER LOW EVEN FURTHER SOUTH THAN
THE NAM WHICH IMPLIES COOLER TEMPS. NOT READY TO MENTION ANY OF
THE FROZEN VARIETY OF PRECIP...ESPECIALLY WITH THE SECONDARY SURGE
OF COOLER AIR MONDAY NIGHT...HOWEVER GSM THICKNESSES ARE
FAVORABLE FOR SLEET. WILL OPT FOR PRUDENCE AND GO WITH THE NAM
WHICH HAS WARMER VALUES AND SHOULD NOT BE AS INFLUENCED BY THE
DIGGING JET DYNAMICS AS THE GSM. COLD LIGHT RAIN FOR NOW ON
CHRISTMAS EVE. WILL ALSO OPT TO MAINTAIN A PRECIP FREE FCST WITH
THE COOLER WX CHRISTMAS NIGHT WITH NORTHWEST FLOW...NOT GOING WITH
THE MEX WHICH NOW HAS A CHANCE OF RAIN (AND 10% CHANCE OF FROZEN).

hmmm..

[HarlequinBoy]

Well, here we are a few days out and frozen precip over parts of the South still hasn't been ruled out so that's something!

[southerngale]

From the Beaumont - Lake Charles afternoon AFD:

THINGS GET A BIT INTERESTING AS WE GET CLOSER TO CHRISTMAS. THE
GSM DRIVES THE SPLIT OFF CLOSED UPPER LOW EVEN FURTHER SOUTH THAN
THE NAM WHICH IMPLIES COOLER TEMPS. NOT READY TO MENTION ANY OF
THE FROZEN VARIETY OF PRECIP...ESPECIALLY WITH THE SECONDARY SURGE
OF COOLER AIR MONDAY NIGHT...HOWEVER GSM THICKNESSES ARE
FAVORABLE FOR SLEET. WILL OPT FOR PRUDENCE AND GO WITH THE NAM
WHICH HAS WARMER VALUES AND SHOULD NOT BE AS INFLUENCED BY THE
DIGGING JET DYNAMICS AS THE GSM. COLD LIGHT RAIN FOR NOW ON
CHRISTMAS EVE. WILL ALSO OPT TO MAINTAIN A PRECIP FREE FCST WITH
THE COOLER WX CHRISTMAS NIGHT WITH NORTHWEST FLOW...NOT GOING WITH
THE MEX WHICH NOW HAS A CHANCE OF RAIN (AND 10% CHANCE OF FROZEN).

hmmm..

*backs away from the computer slowly*

I will not get sucked into this. I will not get sucked into this. I will not get sucked into this...

[Air Force Met]

a met on another weather board I visited said that the model actually was showing snow flurries for at least northern portions of SE Texas. Seems like there may be some disagreement between mets.

At the moment I am just trying to stay hopeful..

Actually...the GFS is showing nothing of the sort. Looking at a vertical profile at 18Z on the 25th...the temp profile all the way up at Waco is still too warm for snow. The sfc temp is 3-4C (which could be off...)...and the freezing level is at 2000'. It's at 3000' where SE TX would "start" with a sfc temp of near 5C...this is WAY too warm for snow.

By 21Z...the freezing level is down to 3000' all the way to Conroe area...but the 4C temps are sitting at 1000'. This is also the area where the model is showing the moisture. So...there are no flurries going to be falling through 3000' of above freezing air...1000' of which is above 4C.

By 00Z...the freezing level is about 3000' over the entire area...but the moisture is gone. RH's are below 50% everywhere. Still too warm for snow....and also dry.

On several different cross-sections...from GLS-CLL/GLS-SAT/GLS-ACT/GLS-LFK...the lowest I find the freezing level is 3K feet and that is after the moisture passes. When the moisture is present...it is in the 4K - 5K foot range.

I don't know who the MET was...but if he says the GFS is showing flurries...he is likely making the same mistake that some on here make...and that is glancing at the thickness and the 850MB temps. As I have said over and over again (much to your dislike ) it is morethan looking at those two things. Snow can't make it if the air column is above freezing for more than 1500-2000' thick and even less than that if the warm layer is above 3C. It melts.

Most times...we get a shallow cold layer with a warm layer aloft that melts the snow. That is not what is occuring here. It is a normal temp profile...colder aloft and warmer at the sfc. No real inversion. So...sleet isn't even much of a possibility...especially since the WBZ will be higher this time around.

[southerngale]

AFM, it was Dan Meador on the KHOU board. This is exactly what he said:

Interesting change on the 12z GFS. It's the second system moving in on Christmas Day that (according to the GFS) may bring a chance of snow flurries (especially northern sections of southeast Texas.) The only real negative will be the surface temperatures, as they will be marginal at best.

The 12z NAM is in total disagreement and has the precipitation long gone as does the ECMWF, however there is some support from the 12z Canadian.

http://www.nco.ncep.noaa.gov/pmb/nwprod ... p_084m.gif

Now we watch if the GFS will change its forecast or if other models begin to agree.

[Air Force Met]

*backs away from the computer slowly*

I will not get sucked into this. I will not get sucked into this. I will not get sucked into this...

Sleet is not totally out of the question in some area...on the very backside of the upper low as it moves out and the dry air mixes in...but it is very low (and I agree...it is about a 10-20% chance...and that is CHANCE...not 20% of the area will see sleet COVERAGE).

Snow flurries on the other hand...well...here's my advice...

On the 25th...when you walk outside and it is drizzling on you...grab a hot air balloon...inflate...go up 3000-5000 feet...and there you will find SNOW!

That is all.

[southerngale]

[Air Force Met]

AFM, it was Dan Meador on the KHOU board. This is exactly what he said:

Interesting change on the 12z GFS. It's the second system moving in on Christmas Day that (according to the GFS) may bring a chance of snow flurries (especially northern sections of southeast Texas.) The only real negative will be the surface temperatures, as they will be marginal at best.

The 12z NAM is in total disagreement and has the precipitation long gone as does the ECMWF, however there is some support from the 12z Canadian.

http://www.nco.ncep.noaa.gov/pmb/nwprod ... p_084m.gif

Now we watch if the GFS will change its forecast or if other models begin to agree.

I don't get that....the only real negative? It is the negative...and when it comes to snow (whether precip will be snow or not...not whether there will be precip or not)...you have to have all positives. It's physically impossible for the air column to support snow...IF (here is the caution flag) it is as warm as the model is saying. S I've said before...thickness really isn't a positive...since it is just an indicator of what the temp of the air column is. It's s all about temps...and if the temps are above freezing for the final 3-5K feet of that flurries life...it will become drizzle....and since the sfc RH's are already high and don't dry out until after the precip passes...there isn't a lot of evap cooling to cool the column off.

[Brent]

On the 25th...when you walk outside and it is drizzling on you...grab a hot air balloon...inflate...go up 3000-5000 feet...and there you will find SNOW!

That is all.

Oh that was funny. I can just see extreme doing that.