SE TX/SW LA Winter WX - 2011-2012

[TexasSam]

Who has the Bear watch graphic?

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
446 AM CST TUE DEC 1 2009

.DISCUSSION...
QUITE A MIXED BAG OF ISSUES WITH THIS UPCOMING PACKAGE. FIRST OFF
WE WILL BE DEALING WITH THE DEEPENING COASTAL LOW PRESSURE SYSTEM
JUST OFF THE LOWER TX COAST. PER THE CURRENT RADAR/OB TRENDS...WE
SHOULD BE IN FOR A RATHER WET DAY AS THE LOW BEGINS TO MOVE NNEWD
UP THE TX COASTLINE. HIGH POPS STILL IN ORDER AS MOISTURE WRAPS A-
ROUND THE LOW AND THE E/NELY WINDS DEVELOPING AHEAD OF IT HELP TO
RAISE TIDAL ISSUES FOR PARTS OF COAST ESPECIALLY DURING HIGH TIDE
TUES AFTN.

THE PASSAGE OF THE COASTAL LOW TODAY WILL THEN BE FOLLOWED BY THE
PASSGE OF THE MAIN UPPER LOW/TROF LATER TONIGHT/EARLY WEDS. THERE-
AFTER WE SHOULD BE DONE WITH POPS (FOR THE TIME BEING) AS ANOTHER
COLD FRONT ALSO PUSHES ACROSS. USUALLY THIS BUILDING RIDGE OF SFC
HIGH PRESSURE IN THE WAKE OF THE FRONT MEANS A QUIETER WX PERIOD.
HOWEVER A MAJOR CHANGE TO THE FCST IS PLANNED FOR THE LATTER PART
OF THE WEEK AS THE SPECTER OF WINTER WX FOR S TX LOOMS. SO AS THE
VERY COLD SFC HIGH BUILDS SWD INTO THE STATE THE UPPER LEVELS ARE
REMAINING ACTIVE. THE LINGERING UPPER LEVEL TROFFINESS ACROSS THE
STATE WILL ALLOW FOR THE SUBSEQUENT DEVELOPMENT/PASSAGE OF YET AN-
OTHER UPPER LEVEL SHORTWAVE OFF THE CNTL ROCKIES ON THU. MOISTURE
SURGING AHEAD OF THIS FEATURE (FROM THE SUBTROPICAL JET) COMBINED
WITH THE VERY COLD SFC TEMPERATURES (A NEARLY 1036MB SFC HIGH) TO
PRESENT THE THREAT OF SOME LIGHT RAIN/SNOW OR MIX OF BOTH FOR FRI.
SO WHILE WE STILL HAVE A LOT OF TIME (AND MODEL RUNS) BETWEEN NOW
AND THEN...A BEAR WATCH IS DEFINITELY IN ORDER. 41

Houston weather!!!
Friday: A chance of rain before noon, then a chance of rain and snow. Cloudy, with a high near 41. Chance of precipitation is 30%.

Friday Night: A chance of rain and snow. Mostly cloudy, with a low around 32. Chance of precipitation is 30%.

[gboudx]

New Orleans met, T Scott Barry is talking about Wintry precip for SELA.

VI. Wintery Weather.

Late this week and going into this weekend, on Friday night the 4th/5th, there are a couple, (2), forecast models that are indicating a chance for some wintery precipitation in Southeast Louisiana. (How would you like that?)

This wintery precipitation, IF this materializes, and continues to be advertised as the 00Z 12/1/2009 GFS shows, will probably come in the form of either sleet or snow, or both, in my estimation, for the southshore. The critical thicknesses are all in the Southeast Louisiana region for late Friday night the 4th & early Saturday morning the 5th. However, the 540 thickness is draped over the northshore parishes of SE Louisiana, late Friday night, on the 102 hr forecast. The 540 thickness line doesn't make it to New Orleans until after the moisture has left, on Saturday morning, daybreak. But you can still get sleet (ice pellets) with a 546 thickness and 0 deg C 850 mb temp. The 1000 - 850 mb & 1000 - 700 mb critical thickness thresholds are upon Lake Pontchartrain late Friday night, too. I won't rule-out any snow flurries at this point since all the thickness lines are close and in the Southeast Louisiana region for late Friday night.

Currently a 1/4" liquid-equivalent is being forecast very late Friday night after midnight up to 6 AM Saturday morning, by your GFS 00Z 12/1/2009 model run. NGP shows between 0.08" to 0.16" for that same time, with a very similar upper air solution of 540 thickness line in SE Louisiana and 850 mb freezing line, as well. So we'll see how this goes. I'll write again on this subject later in the week, if it looks promising. Otherwise, if not, then no more attention will be drawn to this subject matter.

WHO DAT!!!

[PTrackerLA]

The NWS Lake Charles office still isn't impressed as we have a slight chance of rain friday night with lows in the upper 30's and highs in the low 60s saturday. The MOS model numbers are in the low 40s for highs on saturday. I expect a big change in their forecast soon. Regardless of whether we get snow or not December is starting in style!

[JenBayles]

What a crazy weather year. My grandfather was MIC in Kansas City and Albuquerque at the end of his career in the 70's. He'd get a kick out of this year's weather oddities for sure. Extreme heat and drought in the summer, and now... already talking about snow?! I'm not holding my breath for seeing any frozen stuff late this week, but it's always fun to hope while keeping one eye on that football of Lucy's.

[Stormcenter]

NWS out of New Orleans, LA this morning mentions the frozen stuff but is not sold
on it.

DEEP TROUGH WILL DIG SOUTHWARD THROUGH THE END OF THIS WEEK. COLD AIR
ADVECTION WILL CONTINUE AND MID 50S HIGHS WILL PERSIST. GFS SHOWS A
SURFACE LOW DEVELOPING IN THE NORTHERN GULF FRIDAY NIGHT AT THE SAME
TIME THAT THE BASE OF THE TROUGH REACHES THE AREA. THIS SCENARIO IS
TYPICAL OF THE WINTRY PRECIP TYPE...ESP WITH SUCH LOW THICKNESSES.
AT THIS TIME...NOT HOLDING ANY MERIT TO THIS SOLUTION AS IT IS AN
OUTLIAR AMONG OTHERS AND QUITE UNLIKELY FOR THIS TIME OF YEAR. THE
ECMWF SOLUTION LOOKS MUCH MORE APPROPRIATE WITH CONTINUED RIDGING
WELL INTO THE GULF AND THE POTENTIAL FOR A COLD LIGHT RAIN.

[vbhoutex]

If I read the models correctly the NAM seems to be backing off a little, though not totally, while the GFS seems to be getting more bullish with each run. Temps appear to be good for snow, but not for a whole lot of accumulation, especially since the ground is still comparatively warm. Personally, I am impressed with the consistency and length of the runs on this possible snow scenario for our area, but will wait a little bit longer to go "all in". That being said, I have to say I am leaning towards the GFS solutions due to the SFC low building off the coast and the ULL to pass to our North. This combination should cool down the layers from the surface up somewhat making it more likely that our temps may be cold enough for the scenario to unfold. We shall see.

[srainhoutx]

Slight changes in the 12Z GFS. Now has switched to a tad NE with "heavier precip". We shall see, but I expect flip flopping as the models try to grasp the dynamic at play. Just my 0.02 cents worth.

[southerngale]

NWS LCH has rain only in the forecast for SE TX. KBMT Ch.12 in Beaumont is biting on the possibility of snow.

I'll believe it when I see it falling.

Golden Triangle Forecast

UPDATED 11:06 AM

Surface low pressure will move towards Southeast Texas today. This will spread rain into the area from south to north. Areas south of Interstate Ten will see the rain this morning and by later this morning into the afternoon, the rains will spread into the Triangle and then into the Lakes. Once the rain begins, the temperatures will drop so prepare for a cold, wet day.

More rain Wednesday as an upper-level low moves through the area.

Friday, Southeast Texas will see a 50% rain which then should turn over to snow as by evening. Forecast guidance has been adamant on this possible winter weather scenario since yesterday morning. As we all know, much can change and probably will so keep checking back for updates as we continue to refine the forecast.

http://www.kbmt12.com/weather

[PTrackerLA]

It's just amazing we have a chance to break our earliest snowfall ever record (which was just set last December 11th) Friday/Saturday! I have a feeling we may see some flakes mixed in with the rain and not much more but I would be happy with that! We have yet to hit the freezing mark in Lafayette too wouldn't it be something if that happened with a snowfall? NWS Lake Charles has a chance of showers and and low of 32 Friday night, just put in mixed with snow already! Everyone's doing it further west in Texas .

[Stormcenter]

It's hard to believe that less then a month ago we were dealing with a hurricane in the GOM! It's amazing how quickly the weather patterns can change.

[Diva]

Please Santa, snow on Friday night would make the lighted Christmas parade in Orange simply perfect!!

[southerngale]

Please Santa, snow on Friday night would make the lighted Christmas parade in Orange simply perfect!!

Are you sure they wouldn't cancel it? You know how everything shuts down when it snows around here.



J/K - that would make it wonderful!

[CYCLONE MIKE]

Well as usual BTR/MSY is last to update major weather changes but have come around with a really good long term forecast. Sounds like it will be cold either way and future forecasts could be even colder. Biggest problem is if a low develops in the gulf as it did today. Plenty of time to not happen, which it probably won't but fun to talk about anyway.

HEADING INTO THE WEEKEND...LARGE DISAGREEMENTS BETWEEN THE GFS AND
EURO MODELS DEVELOP. HOWEVER...THESE DISAGREEMENTS ARE MOSTLY
CONFINED TO THE LOW LEVELS...AND THE DEVELOPMENT OF ANOTHER GULF
LOW HEADING INTO FRIDAY NIGHT AND SATURDAY. IN THE UPPER
LEVELS...BOTH MODELS ARE IN VERY GOOD AGREEMENT THAT A STRONG AND
DEEP UPPER LEVEL TROUGH WILL DIVE THROUGH THE PLAINS STATES AND
INTO THE GULF SOUTH. THE MAIN TROUGH AXIS SHOULD PASS THROUGH THE
AREA FRIDAY NIGHT...ALONG WITH A VERY STRONG FRONTAL BOUNDARY.
BOTH MODELS ARE ALSO IN GOOD AGREEMENT...THAT STRONG COLD AIR
ADVECTION IN THE WAKE OF A COLD FRONT FRONT PROGGED TO SWEEP
THROUGH FRIDAY NIGHT WILL TAKE PLACE. TEMPERATURES WILL DROP BELOW
FREEZING ACROSS THE NORTHERN THIRD OF THE FORECAST AREA FOR FRIDAY
AND SATURDAY NIGHTS. DAYTIME HIGHS WILL BE A GOOD 10 DEGREES BELOW
NORMAL AS THIS DEEP COLD POOL SLIDES THROUGH THE REGION. THE MAIN
DIFFERENCE ARISES WITH THE AMOUNT OF CYCLOGENESIS EXPECTED WITH
THIS APPROACHING TROUGH. THE GFS IS VERY AGRESSIVE AND QUICKLY
SPINS UP ANOTHER DEEP LOW PRESSURE SYSTEM IN THE CENTRAL GULF OF
MEXICO. THIS STRONG LOW WRAPS DEEP TROPICAL MOISTURE UP INTO THE
GULF SOUTH...JUST AS THE COLDER AIR BEGINS TO BLEED INTO THE
REGION. BASED ON THIS FORECAST...SOME TYPE OF WINTER PRECIPITATION
WOULD BE POSSIBLE. HOWEVER...THE ECMWF HAS A MUCH WEAKER LOW FORM
IN THE CENTRAL GULF. MOISTURE IS LIMITED ALONG THE FRONT...AND
EXITS THE REGION WELL BEFORE THE COLDEST AIR MOVES IN. THIS
SCENARIO WOULD KEEP ANY WINTER WEATHER OUT OF THE FORECAST. GIVEN
THE HIGH UNCERTAINTY OF THE SITUATION...HAVE DECIDED TO KEEP THE
ONGOING FORECAST IN PLACE AND WAIT FOR ADDITIONAL GUIDANCE OVER
THE NEXT DAY OR SO.

[PTrackerLA]

Is the 1000-850mb thickness line the correct output to look at in terms of determining if the atmosphere is cold enough to support snow? I sure hope it is as it looks like all of southern LA has a shot at some flakes 84 hrs out!

[srainhoutx]

E-mail from Jeff this evening...

Moderate to heavy rains overspreading the region late this afternoon...main concern is focused on the end of the week.

There has been a few changes in the guidance today with respect to the Friday event. 12Z GFS and NAM are slightly drier, but still produce a good bit of QPF over the region. Also, temperatures have been warmed slightly on the air column which now brings the Matagorda Bay region out of the snow area and focuses the majority of the frozen precip. along and N of US 59. GFS sounding profiles are above freezing through about 3000 ft Friday morning and then with strong cold air advection during the day fall to freezing or below through nearly the entire column by 600pm. Moisture is pulled into the column in the 700-500mb level with fairly dry layers noted below at KIAH. Dewpoint and air temperatures are fairly close together so not a lot of room for wet bulb cooling with this air mass. Dynamics with the short wave looks impressive and the strong lift may help to overcome a lack of good moisture. There is much uncertainty with the following aspects.

1) Track and timing of the short wave and dynamics. A slower track will allow for more cooling, while moisture may become less and shunted eastward.

2) Cooling of the above freezing levels during the day Friday. Strong CAA is noted with 850mb 0C line pressing toward downtown Houston by early afternoon with -2C 850mb temperatures overspreading our N counties.

3) Degree of moisture and level of the moisture. Soundings support good mid level moisture but a fairly large dry sub layer. This suggest precip. aloft may have a hard time reaching the ground and it may take a good bit of virga to moisten the low levels.

With all this said...will start to lean toward the stronger solution as both the GFS and NAM show this. Will not dabble in any QPF or accumulation amounts at this time as it is very uncertain. Will note a rain/snow line across SE TX midday Friday spreading toward the coast during the afternoon hours including metro Houston. Will also increase precip. chances in the 40-50% range with a frozen mix changing to snow from NW to SE during the day.

This period remains highly uncertain with extremely low forecast confidence. Significant changes will be possible over the next 24-36 hours. Will need to start to consider advisories/watches by early Thursday if model trends hold for another 24 hours as enough accumulation looks possible to cause some serious travel issues by Friday afternoon across portions of SE TX.

[wxman57]

Is the 1000-850mb thickness line the correct output to look at in terms of determining if the atmosphere is cold enough to support snow? I sure hope it is as it looks like all of southern LA has a shot at some flakes 84 hrs out!

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 8_084m.gif

One major caveat about using these graphics - you're looking at features that are not necessarily at the same time as one-another. For example, the green precipitation area is NOT valid for the time of the chart, it's valid for the previous 6 hours. So the green over SE TX on that map may have moved east of us by the time that map is valid. As an example, take a look at the map valid 6 hours later (12Z Sat), below. Note that NO precip is indicated to be falling anywhere near SE TX between 06Z-12Z Sat. The 12Z map indicates that by 06Z Saturday the precip area has moved all the way to central LA. It's a difficult concept for some to grasp, but you always have to look closely at the maps 6hrs before and after a time to really get a feel for whether there will be precip at that mid point map.

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 8_090m.gif

The thickness lines are valid at the time of the map, and they're certainly low enough for snow. The thickness favors snow all afternoon/evening on Friday. So anything falling Friday afternoon/evening will most likely be snow.

[srainhoutx]

Hope everyone dreamed of snow last night. Couple of thoughts this morning. Things are still looking good for us in SE TX. The ECMWF showed some improvement regarding moisture in the 00Z run last night. Although it wasn't much, but a tad more than the 12Z run of yesterday showed (0.10 QPF the best I can tell). Other guidance continued the trend as well. My gut feeling is that the colder air will arrive a bit earlier than guidance is suggesting (Thursaday night into Friday morning for Coastal areas) and the our Upper disturbance (shortwave) will dig a tad further SW into N MX to near a Del Rio line and swing across S Central TX and move ENE across SE TX in the late in afternoon on Friday through the night into Saturday morning. It is interesting to see the HPC is showing a 4 inch area for Austin and the Hill Country for Friday during the day. The idea of a Coastal Low/trough across S TX is still on the table. With the cold air in place and over running moisture developing to our SW late Friday afternoon and increasing across our area Friday evening. As everyone has stated, timimg is everything with these events and the bust factor is high, but all in all things are looking rather good for snowwfall for most of SE TX. No speculation from me concerning amounts or storm totals. I'll leave that to the "pros", but I'm still liking the trends. More "hints" today as we see more guidance and data from Upper Air samples. Stay Tuned.

[PTrackerLA]

So if there is any precip still around by the time the 0 degree thickness moves offshore we could have snow falling all the way to the coast? Sounds great to me!

[JenBayles]

Question: How many times will Charlie Brown spin in the air this time when Lucy pulls the football?

[vbhoutex]

Question: How many times will Charlie Brown spin in the air this time when Lucy pulls the football?