Texas/New Mexico/Louisiana/Mexico Obs And Discussion Thread Part 4

[bubba hotep]

It's hilarious how all models are flip flopping wrt how progressive the trough will be and if it can close a ULL or not.

And 18z GFS brings it back

 

[bubba hotep]

Nice little batch of pea size hail moving through

[Quixotic1]

Nice little batch of pea size hail moving through

nice. something is falling out here. cant tell if its post frontal drizzle or snow flurries with the all the wind. the fropa was more robust than expected, methinks.

edit: plain old rain

[Srain]

The cold front has cleared the coast this morning and the air behind the front is colder than forecasted and over running showers continue from just W of Columbus on NNE to just E of the Dallas areas where sleet and some freezing rain has been reported. It is noteworthy that none of the guidance ‘predicted’ this type event across NE Texas into Oklahoma and Arkansas and it raises an eyebrow as to just how lacking the models continue to be in this current pattern. Temps are a good 30 degrees cooler than yesterday with upper 30’s to mid 40’s reported across Central and the northern areas of SE TX. Hopefully the over running rain showers will diminish as the morning progresses as drier air moves across the eastern half of the  Lone Star State. Across Western Louisiana, rain will be a bit slower to end and further NE in the ArkLaTx Region, freezing rain and sleet may continue into the mid day time frame.

 

Attention then turns to our W as a short wave dives S into Northern Mexico Monday and a positive tilted trough lingers across the region. The guidance is having a very difficult time deciding if a closed core upper low develops or if the trough shears out. A closed core solution would offer the chance of wintry mischief and even the potential of a significant ice storm for portions of Central/N Central and NE Texas into NW Louisiana while a more progressive sheared out trough would limit the best chance of over running precip closer to the Coastal Areas. We will need to closely monitor this potential for Tuesday into Wednesday as the eventual solution could have high impacts for many if a close core low does develop across W Texas.

 

Looking toward next week weekend, a brief warm up appears somewhat likely before all eyes turn to our N during the latter half of the weekend. The Euro is suggesting a very potent Arctic Air mass with a 1058mb Arctic High dropping S into the Plains along the lee side of the Rockies while the GFS is a bit weaker with the high pressure, but has not been consistent and continues to struggle with the evolving pattern. Both global models and their ensembles are suggesting the Polar Vortex will drop well S into the Great Lakes region as heights build across the Pacific into Alaska and a deep trough develops E of the Continental Divide. The European suite of ensembles and operational guidance has been rather consistent in developing a potential Arctic Outbreak early next week, so it will bear watching in the coming days exactly how things unfold. As we can see, the forecast is extremely tricky and has major implication on the sensible weather we can expect this week on into the early next week time frame.

 

[DFWWeather]

Eventhough the ECMWF shows a 1058 mb Arctic high sliding south, the mean trough position is too far east to give Texas anything more than a glancing blow. Even the GFS has broaden the west coast ridge, positioned it a little bit farther east, and thus moved the trough position a bit farther east. We need a McFarland to deliver the goods!

[ams30721us]

Whoa!

 

 

 

 

 

 

 

 

 

12z Euro agrees on this Upper Low staying together a good bit longer. hmmmm

 

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[Srain]

The 12Z Euro continues the trends seen today suggesting a closed core upper low developing across W Texas and sweeping E with the positive tilted trough bringing over running 'precip' and cold air aloft. The 12Z Euro is a bit more progressive with the 5H vort compared to the OP GFS it appears.

[wxmx]

The 0z GFS is, for the first time, showing the possibility of some flurries flying by here the morning of the 16th. The NAM and CMC have been showing this as well on and off. The 12z Euro was close, but didn't. Not holding my breath, but I have noticed the models are a bit colder these last few runs, probably due to the fact that the west coast ridge peaks at over 588dm, with the 582dm contour over the whole W coast up to Vancouver, quite impressive.

[Ed Lizard]

DAL reporting light snow grains, better than nothing, *and* vegetation destroying cold signal of models seems to be fading for SETX.

 

FWD discussing difference in GFS and Euro and how that could affect liquid versus frozen mid week...

[Srain]

As expected a noisy sub tropical jet and cold surface temps with over running precip has brought sleet across Central (Austin Area) and E Texas this morning as a short wave/jet streak passes. The models are converging on a solution that will bring additional frozen precip for parts of Central/Northern SE TX on N and E for late Tuesday into Wednesday as a potent short wave drops S into Northern Mexico a begins to close off an upper low. Because of the cold core nature of the closed core upper low, additional Winter Weather Advisories are expected and I would not be surprise to see Winter Storm Watches hoisted for a large portion of W Central/SE/NE and E Texas extending E into Louisiana as very cold air aloft is entrained with this upper air feature and borderline freezing surface temps may create travel troubles across much of our Region. Stay Tuned as further guidance updates may bring additional data in this evolving Winter Weather Episode potential. The models have under estimated the events of this morning and I expect that trend to continue into the Mid Week time frame as well.

 

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
510 AM CST MON JAN 14 2013

TXZ163-164-176-177-195>198-141500-
HOUSTON-TRINITY-MADISON-WALKER-BURLESON-BRAZOS-WASHINGTON-GRIMES-
INCLUDING THE CITIES OF...CROCKETT...TRINITY...GROVETON...
MADISONVILLE...HUNTSVILLE...CALDWELL...LAKE SOMERVILLE...
COLLEGE STATION...BRYAN...BRENHAM...NAVASOTA
510 AM CST MON JAN 14 2013

...RAIN MIXED WITH SLEET POSSIBLE THIS MORNING...

POCKETS OF RAIN THIS MORNING MAY BE MIXED WITH SLEET FOR AREAS
NORTH OF A BRENHAM...HUNTSVILLE...LUFKIN LINE. THE RAIN AND SLEET
MIX WILL BE POSSIBLE THROUGH ABOUT 9 AM. TEMPERATURES ARE ABOVE
FREEZING SO THE PRECIPITATION IS NOT EXPECTED TO FREEZE ON
ROADS...BRIDGES AND OVERPASSES. ANY SLEET SHOULD BE SHORT LIVED
AND NO ACCUMULATIONS ARE EXPECTED. CAUTION IS STILL ADVISED ON
AREA ROADS...BRIDGES AND OVERPASSES DUE TO SLICK CONDITIONS.
 

[Srain]

Morning e-mail from Jeff:

 

Cold air mass is firmly entrenched over the area this morning with light rain and drizzle being reported along with some sleet mixing with the rainfall NW of a College Station to Giddings line.
 
Cold front that moved across the area early yesterday is now out over the NW Gulf of Mexico with warm moist SSW flow riding up and over the surface cold dome. Morning soundings from Lake Charles and Corpus show the surface cold dome is only about 2000-3000 feet deep above the surface with warm air (above freezing) extending up to near 13,000 ft. Fort Worth sounding is all below freezing so the front slope is shallow near the coast and then deepens inland falling below freezing just north of our northern row of counties…likely near the 850mb front. Fairly strong shortwave in the SW flow aloft has brought the formation of drizzle and light rainfall to the northern ½ of SE TX this morning. College Station has been reporting a light rain mixed with sleet this morning, but surface temperatures are in the mid 30’s and there will be no accumulation. This short wave will move east of the area by early afternoon ending the rainfall. Clouds may decrease late this afternoon with mostly cloudy to partly cloudy skies tonight.

 

Tuesday-Wednesday:
Models have trended toward the ECMWF solution over the past 24 hours or a stronger and more cut-off upper level storm system for the mid week period. This keeps the cold air locked into place and supports more widespread precipitation Tuesday night-Wednesday. Expect clouds to increase from southwest to northeast on Tuesday as strong lift begins to spread eastward out of MX into TX. Isentropic lifting of a moist Gulf air mass over the surface cold dome will support to develop of drizzle and light rainfall by Tuesday night. NAM model is much more aggressive in developing rainfall across the region while the GFS keeps most of the rainfall near the coast and very light. Other item of interest is the surface temperatures during the overnight and morning hours on Wednesday. Both the NAM and GFS show surface temperatures falling to near freezing (especially north of HWY 105) Wednesday morning, but this is a very shallow layer of potential sub freezing air only about 1000 to 2000 ft thick. Other questions surround the amount of dry air at the surface and the ability of precipitation to reach the ground if the near surface layer is fairly dry. All of this is further complicated by the fact that the dry surface layer can be cooled a few degrees by precipitation falling into this layer. To even further complicate the issue, with the large area of warm air aloft, rain drops falling through this warm layer could offset any near surface evaporative cooling. Would like to see additional model runs help fine tune the freezing line and come into better agreement with both the precipitation placement and amounts before thinking about any freezing rain across the area for Wednesday morning.
 
Extended:
Main upper level system should progress east of the area on Thursday with decreasing clouds and slowly warming temperatures. Cloudy and cold conditions will be replaced with partly cloudy and warmer conditions. Highs will warm from the 40’s today-Wednesday into the 50’s Thursday-Sunday. Long range forecast models have been suggesting a surge of very cold arctic air deep into the US for the week of the 21st. While the pattern seems to support a cold air outbreak into the US, the trajectory of the incoming cold air is aimed more toward the MS valley and eastern US with a glancing blow expected for the southern plains. Will follow this line of thinking and support a strong cold frontal passage early next week, but keep the brunt of the arctic air NE of TX.

[Srain]

The 12Z 4km WRF/NMM (NAM) continue to raise an eyebrow for wintry weather across a large portion of our Region as the positive tilted trough and 500mb upper low closes off and becomes cold cored.

 

[Srain]

MESOSCALE DISCUSSION 0032
   NWS STORM PREDICTION CENTER NORMAN OK
   0846 AM CST MON JAN 14 2013
  
   AREAS AFFECTED...NERN TX...NRN LA...SRN AR...W-CNTRL/NWRN MS
  
   CONCERNING...FREEZING RAIN
  
   VALID 141446Z - 141845Z
  
   SUMMARY...FREEZING RAINFALL RATES UP TO 0.02 IN/HR /PERHAPS HIGHER
   BENEATH CONVECTIVELY ENHANCED SHOWERS/ ARE FORECAST TO OCCUR THROUGH
   18Z FROM PORTIONS OF NERN TX E-NEWD ACROSS NRN LA/SRN AR INTO
   W-CNTRL/NWRN MS. AFTER 18Z...SURFACE TEMPERATURES ARE FORECAST TO
   WARM ABOVE FREEZING...BRINGING THE FREEZING RAIN THREAT TO AN END.
  
   DISCUSSION...COMBINATION OF A WEAK UPPER IMPULSE MOVING NEWD ACROSS
   NRN TX AND SUBSEQUENT STRENGTHENING OF LOW-LEVEL FRONTOGENESIS IS
   AIDING IN A SHIELD OF PRECIPITATION EXPANDING OUT OF NERN TX INTO
   SRN AR/NRN LA. THE 12Z RAOBS FROM KSHV AND KFWD ALSO INDICATE WEAK
   MUCAPE VALUES ROOTED FROM 750-600 MB...WHICH WILL FAVOR LOCALLY
   ENHANCED PRECIPITATION RATES EMBEDDED WITHIN THE BROADER SHIELD OF
   RAIN. SURFACE FREEZING AND WET-BULB ZERO LINES EXTEND FROM NERN TX
   NEWD INTO EXTREME NERN LA...WHILE ABOVE FREEZING LAYER IN THE
   950-700 MB LAYER EXISTS ABOVE THE SUB-FREEZING SURFACE AIRMASS. THIS
   THERMAL STRATIFICATION WILL FAVOR FREEZING RAINFALL THROUGH
   18Z...WITH RATES OF 0.02 IN/HR POSSIBLE /PERHAPS LOCALLY HIGHER WITH
   CONVECTIVELY ENHANCED SHOWERS/. SHORT-TERM MODEL GUIDANCE INDICATES
   THE SURFACE AIRMASS WILL WARM ABOVE FREEZING AFTER 18Z...WHICH WOULD
   BRING THE FREEZING RAIN THREAT TO AN END.
  
   ..GARNER.. 01/14/2013
  
  
   ATTN...WFO...MEG...JAN...LZK...SHV...
 

[ams30721us]

http://imageshack.us/photo/my-images/20/12znamsolution.jpg/'>

 

[Srain]

While the GFS is somewhat slower to close off the 500mb upper low and a tad slower or less progressive than the WRF/NMM (NAM) suggested. That model (GFS) is suggesting a wave of surface low pressure develops along Coastal Texas and very cold air aloft slowly treks E across Central Texas. The GFS is drier at the 700mb level, but as we have seen the models are not handling features too well with the noisy sub tropical jet and embedded short wave activity.

[wxmx]

Timing and trajectory of the ULL are critic to know where the heaviest snowfall will be. Right now it looks like NW LA will be the jackpot winner in our region, with some chances for C and NE TX and a little for NE MX.

[DoctorMu]

NOAA and the models really underestimated the subtropical jet today and the low temps, and it could be a player later in the week. Surprise possible

[wxmx]

NOAA and the models really underestimated the subtropical jet today and the low temps, and it could be a player later in the week. Surprise possible

Yep, if precipitation can overcome the dry surface air, there is a lot of room for evaporational cooling and wintry precipitation. Models are very dry, with the NAM being one of the wettest. The models are trending stronger with the ammount of energy at the base of the trough/ULL.

[ams30721us]

12z Canadian

 

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[Srain]

The 12Z Euro continues the trends suggested by the other global and shorter range operational guidance but is a bit progressive or faster in moving the 500mb low across Texas. It is noteworthy that the Euro does suggest a bit more moisture and colder surface temps across Louisiana. The Euro also develops a wave of low pressure along the Texas Coast and moves that surface low ENE toward Southern Louisiana.

[Srain]

For our neighbors in New Mexico, light snow continues to fall from S of ABQ on N to the Taos Area and on E in the Eastern Plains of that State:

[wxmx]

18z models are more progressive, colder but drier.

[DoctorMu]

18z models are more progressive, colder but drier.

 

A chance of freezing rain now in the NOAA forecast and discussion for CLL for the next 36 hrs with very light accumulation.

[Srain]

Light drizzle and rain has developed across E Central TX this morning but surface temps are above freezing and only a few isolated spots in the Hill Country on NE to the Waco area may have a chance of seeing some light freezing drizzle or very light sleet. Travel issues appear to not be a problem. Winter Weather Advisories are in affect for NE Texas N of Lufkin with Ice Storm Warnings for portions of Southern Arkansas and Northern Louisiana.

Later this evening into the overnight hour of early Wednesday would be the best chance of seeing any freezing precip mainly N of HWY 105 in Montgomery County as some colder surface temps filter S as the positive tilt trough begins to move E from W Texas. Early morning water vapor imagery is showing increased moisture over Northern Mexico with a stronger short wave that may arrive as the colder air moves in tonight. We'll see what the trends today bring regarding that potential. NWS San Antonio/Austin as well as Houston/Galveston continue to keep a chance of light freezing drizzle and even some light sleet potential in the forecast, but uncertainty remains the theme this morning.

It does appear that we'll finally see an end to the moisture chances as the trough finally moves E into the Lower Mississippi/Tennessee Valley and hopefully some peaks of the sun for the weekend.

As for the next cold front. Depending on which model is more correct, either a glancing blow of modified Canadian air via the GFS or a stronger surge via the Euro will arrive late Monday into Tuesday.

[Srain]

Update:

Wintry precip has developed rapidly across the Dallas/Ft Worth area and Winter Weather Advisories have been extended further W in N Central Texas. Also of note is College Station is reporting light freezing rain this hour. Ground temps are borderline, so travel issues there do not appear to be a problem at this time. For the Dallas area, travel impacts do appear to be an issue and light accumulations of freezing rain/sleet and light snow may affect that region throughout the morning hours. NWS FWD is concerned that the positive tilted trough may attempt to close off an upper low and may even become negative tilted even though none of the guidance suggests this happening. We will need to monitor trends today for such a scenario in case the models are in fact clueless and have under estimated the strength of the approaching short wave currently over NE Mexico as. Water Vapor Imagery is suggesting.

[DoctorMu]

Mixed wintry precip and light SNOW in CLL

[bubba hotep]

Unexpected Thunder Snow FTW!!

[DoctorMu]

snow at DFW. Accumulation possible

[bubba hotep]

We've passed a dusting and it is really coming down with more thunder

ETA: really coming down now, everything is white and starting to cover sidewalks

ETA2: roads turning white, this is legit

[Srain]

IP/RN in NW Harris County.