Texas/New Mexico/Louisiana/Mexico Obs And Discussion Thread Part 6

[ams30721us]

FWD Discussion:

 

 

 

A SPLIT-FLOW REGIME WILL BE IN PACE ACROSS THE CONUS THIS WEEK.
AN UPPER LEVEL TROUGH IN THE NORTHERN BRANCH WILL DEEPEN ACROSS
THE PLAINS ON TUESDAY. THIS WILL SEND A COLD FRONT BARRELING BACK
TO THE SOUTH AND INTO NORTH TEXAS BY TUESDAY EVENING.
MEANWHILE...THE WEST COAST UPPER LOW WILL BEGIN ITS EASTWARD
ADVANCE TOWARDS NORTH TEXAS IN THE SOUTHERN BRANCH. SCATTERED
SHOWERS AND A FEW STORMS WILL BE POSSIBLE ALONG AND AHEAD OF THE
COLD FRONT TUESDAY AND TUESDAY NIGHT. INSTABILITY WILL BE MARGINAL
AT BEST...SO WE WILL KEEP THUNDER IN THE ISOLATED CATEGORY. MUCH
COLDER AIR WILL SPILL SOUTH INTO THE AREA BEHIND THE FRONT TUESDAY
NIGHT AND WEDNESDAY. THE MOST RECENT GUIDANCE NOW INDICATES SUB-
FREEZING TEMPERATURES AT ALL LOCATIONS FOR WEDNESDAY NIGHT.

ADDITIONAL PRECIPITATION IS EXPECTED WELL BEHIND THE FRONT
WEDNESDAY AND WEDNESDAY NIGHT AS THE SOUTHERN BRANCH TROUGH
APPROACHES FROM THE WEST. TEMPERATURES WILL BECOME PLENTY COLD AT
ALL LOCATIONS FOR RAIN TO MIX AND PERHAPS SWITCH OVER TO SLEET IN
THE COLD AIR LATE WEDNESDAY. THERMAL PROFILES INDICATE THE
POSSIBILITY OF SOME SNOW AS WELL...AND WE HAVE INCLUDED SLEET OR
SNOW FOR ALL COUNTIES WEDNESDAY NIGHT. THE AMOUNT OF AVAILABLE
MOISTURE...STRENGTH OF THE ASCENT ASSOCIATED WITH THE TROUGH...AND
DEPTH OF THE COLD LAYER ARE ALL UNCERTAINTIES...SO WE WILL WATCH
HOW THE SYSTEM EVOLVES OVER THE NEXT FEW DAYS AND FINE-TUNE THE
SPECIFICS AS IT DRAWS NEARER.

[ams30721us]

Austin/San Antonio Discussion:

 

 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
355 AM CST SUN MAR 1 2015

.SHORT TERM (TODAY THROUGH MONDAY)...
LIGHT RAIN/DRIZZLE ACTIVITY WILL CONTINUE TO AFFECT AREAS ALONG
AND EAST OF INTERSTATE 35. ALSO...AREAS OF FOG WILL CONTINUE TO
DEVELOP ACROSS MUCH OF THE AREA THROUGH LATE THIS MORNING. WILL
BE CLOSELY MONITORING THIS SITUATION AS AREAS OF FOG BECOME
WIDESPREAD BY DAWN IN CASE THAT A DENSE FOG ADVISORY IS NEEDED. SO
FAR...NORTHERLY WINDS ARE AVERAGING 6 TO 10 MPH AND EXPECTED TO
REMAIN THAT WAY...LIMITING CIGS AND VBSYS TO LOWER TO THE GROUND.
RAIN CHANCES WILL CONTINUE ACROSS THE EASTERN HALF OF THE AREA
TODAY WITH RELATIVE DRY CONDITIONS OUT WEST. SKIES WILL BE CLOUDY
THROUGHOUT THE DAY WITH HIGHS ONLY IN THE UPPER 40S ACROSS THE
HILL COUNTRY...LOWER TO MID 50S ALONG THE I-35 AND UPPER 50S
ACROSS THE RIO GRANDE PLAINS.

RAIN CHANCES WILL BE INCREASING TONIGHT INTO MONDAY AS UPPER LEVEL
MOISTURE ARRIVES FROM THE SOUTHWEST. OVERNIGHT LOWS ARE EXPECTED
TO DROP TO THE UPPER 30S ACROSS THE HILL COUNTY AND 40S ELSEWHERE.
A COOL MONDAY IS IN STORE WITH MOSTLY CLOUDY SKIES AND CHANCES OF
RAIN MAINLY ALONG AND EAST OF HIGHWAY 281.

&&

.LONG TERM (MONDAY NIGHT THROUGH SATURDAY)...
BIG CHANGES ARE ON THE WAY FOR THE MIDDLE OF THE WEEK AS A PACIFIC
FRONT MEETS AN ARCTIC FRONT LATE TUESDAY INTO WEDNESDAY. ON TOP OF
THIS SCENARIO...UPPER LEVEL FLOW SUPPORTS THUNDERSTORM ACTIVITY
AND EVEN HEAVY DOWNPOURS OVER PARTS OF THE AREA. MOST MODELS BRING
THE ARCTIC FRONT AROUND 12Z-15Z WEDNESDAY TIME FRAME ACROSS THE
HILL COUNTRY WITH THE EXCEPTION OF THE NAM SOLUTION...WHICH IS
DELAYED BY ABOUT 6 HOURS. AFTER GETTING SOME GOOD RAIN-RATES OVER
THE AREA ON WEDNESDAY(POSSIBLY 1 TO 2 INCHES IN SOME
PLACES)...ANOTHER COLD AIRMASS WILL SPREAD SOUTHWARD IN THE WAKE
OF THE ARCTIC FRONT. BY THE TIME THE COLD AIRMASS ARRIVES ACROSS
THE AREA...MOST OF THE PRECIPITATION HAS PUSHED TO THE SOUTH.
HOWEVER...THERE IS A CHANCE FOR ANOTHER WINTER PRECIPITATION TYPE
EVENT ACROSS THE HILL COUNTRY IN A FORM OF LIGHT SNOW. AREA
FORECAST SOUNDINGS ACROSS THE SOUTHERN EDWARDS PLATEAU AND HILL
COUNTRY SUPPORT THE FORMATION OF LIGHT SNOW WEDNESDAY EVENING INTO
THURSDAY MORNING ALONG AND NORTH OF A PANDALE TO BOURNE TO
GEORGETOWN LINE. SNOW ACCUMULATIONS SHOULD BE VERY LIGHT WITH NO
IMPACTS EXPECTED AT THIS TIME. NOTE...JUST HAVE IN BACK OF YOUR
MIND THAT RAIN IS EXPECTED EARLIER IN THE DAY AND TEMPERATURES ARE
FORECAST TO DROP QUICKLY WEDNESDAY AFTERNOON/EARLY EVENING BEFORE
RAIN TRANSITION TO SNOW...AND THIS CAN POSE TRAVEL IMPACTS ACROSS
THE HILL COUNTRY. STAY TUNED FOR MORE DETAILS ON THIS NEW WEATHER
SCENARIO AND CHALLENGING WEATHER PACKAGE IN DAYS TO COME.

[ams30721us]

And...to not leave out a bit of mention for our SE TX friends:

 

 

 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
352 AM CST SUN MAR 1 2015

.DISCUSSION...
AREAS OF LIGHT RAIN CONTINUE TO DEVELOP EARLY THIS MORNING ACROSS
SOUTHEAST TEXAS AND ADJACENT COASTAL WATERS AND MOVE OFF TO THE NORTH
AND NORTHEAST. ANTICIPATE ONLY SUBTLE CHANGES IN THE WEATHER PATTERN
OVER THE NEXT COUPLE OF DAYS...RESULTING IN PERIODS OF MAINLY LIGHT
RAIN OR RAIN SHOWERS ALONG WITH AREAS OF FOG. SOME OF THE FOG COULD
BECOME DENSE...AND DENSE FOG ADVISORIES MIGHT BE NEEDED. MIGHT EVEN
SEE A THUNDERSTORM OR TWO...BUT THE GREATEST RISK AREA FOR THAT IS
EXPECTED TO BE OFF TO OUR NORTH AND NORTHEAST. WITH THIS FORECAST
PACKAGE...HAVE CONTINUED YESTERDAY`S TREND OF SLIGHTLY LOWERING
TEMPERATURES. A SIGNIFICANT WARM UP IS STILL IN STORE FOR THE AREA
ON TUESDAY AS SOUTH WINDS FINALLY RETURN AND STRENGTHEN AHEAD OF THE
AREA`S NEXT COLD FRONT. IT STILL LOOKS LIKE THIS STRONG FRONT WILL
MOVE THROUGH SOUTHEAST TEXAS ON WEDNESDAY WITH TEMPERATURES FALLING
BEHIND THE BOUNDARY. A TIGHT PRESSURE GRADIENT BEHIND THE FRONT WILL
BRING BREEZY/WINDY CONDITIONS TO THE AREA...AND WOULD NOT BE SURPRISED
IF WE END UP NEEDING A WIND ADVISORY WEDNESDAY NIGHT ON INTO THURSDAY
MORNING. CONDITIONS STILL LOOK FAVORABLE FOR POSSIBLE FROZEN PRECIP
UP NORTH WEDNESDAY NIGHT THROUGH THURSDAY MORNING. THERE IS A LOT OF
TIME FOR THIS FORECAST TO CHANGE...SO STAY TUNED. 42

[vwgrrc]

6z GFS shows even earlier transition of p type

[bubba hotep]

[vwgrrc]

A special wx statement today?

[bubba hotep]

Really strong agreement b/w the 00z Euro, EPS, & Control... 

[Srain]

The 12Z GFS continues the trend seen yesterday via the Euro of a slower ejection of the upper air disturbance over Northern Mexico after the Arctic front arrives Tuesday night into Wednesday. This next front appears to have a punch with it and with upper energy associated with the upper trough hanging back to our West and SW, over running precipitation appears to be gaining some strength Wednesday night into at least early Thursday.

 

 

 

[Quixotic1]

Would be cool to see the guys south of here get an awesome event.

[vwgrrc]

Would be cool to see the guys south of here get an awesome event.

dfw is so close to something huge...

[bubba hotep]

12z Euro switches up how it handles the energy coming out of the SW and that results if pretty big changes across Texas.  It looks like Arkansas is pretty locked in but Texas will be much more at risk of coming up short.  Probably lots of changes coming in future model runs with all the energy spinning around out West. 

[1900hurricane]

Would be cool to see the guys south of here get an awesome event.

 

I'll happily take it, but after this, I'm ready for spring and chase season (maybe someday...).

[ams30721us]

[vwgrrc]

I'll happily take it, but after this, I'm ready for spring and chase season (maybe someday...).

probably not that south to college station lol...

[vwgrrc]

why it's so different from GFS snowfalls

[RIsnow]

All that matters now is that there is a storm. All models have been atrocious 3+ days out, so I wouldn't worry.

[1900hurricane]

probably not that south to college station lol...

 

Why not? HGX is already giving us a chance with a 70% chance of a wintry mix for Wednesday night (with thunder possible too). It very well may end up just being rain down here, but don't you think it's too early to rule anything out yet, particularly with National Weather Service meteorologists already highlighting the potential?

[Portastorm]

Wednesday night into Thursday is looking like the best shot at a decent winter storm in two years for Austin. If today's 12z GFS verified it would be one nasty storm for us.

[vwgrrc]

Is the cold air tending slower? We may have a later transition to froze precipitation.

[wxmx]

It's trending a little slower in the GFS, but it's more in line with other guidance (Ukie, Euro and GGEM). Also it's warmer, but that's a bias I have noticed in the GFS, trend warmer inside 120 hours, just to go colder the last 24-36 hours. Euro and apparently the UK (can't really see the temps for the Ukie) are currently colder than the GFS. The GGEM is always colder, but is getting in line with the european guidance.

 

It's interesting that my best shot to get my first freezing temp is in March, in an overall below normal winter.

[bubba hotep]

21z SREF is pretty uninspiring, generally about an inch of snow area wide but it is skewed by a few heavy members.  It looks like most of the frozen is sleet or snow and not much freezing rain.  So an inch of snow on top of some sleet with temps falling into the 20s could cause some issues. 

 

ETA: Also, the 12z Euro EPS backed off things a good bit, it has been running more aggressive than the operational up until this run.  It wasn't so much as a cutback in amounts on the individual members as there appears to be just more members that whiff. A good number of the members that deliver are more impressive than the operational. 

[jm1220]

Looking like Thursday might be an "ice day" from work in Austin if these trends continue. I'm not a fan of ice-I saw more than enough of that up north. And this cold/cloudy/foggy weather is getting real old, fast. 

 

Hopefully the models trend drier down here when the arctic front comes, seems like that could be a possibility.

[bubba hotep]

00z GFS is a step back towards a significant event for Texas when compared to 18z but not as impressive as 12z. It is probably a good compromise at this point and could be more impressive if the cold air moves in faster than anticipated. 

[David Reimer]

The 0Z runs of the GFS and ECMWF both show a winter weather event on Wednesday from the Permian Basin into the Concho Valley, Big Country, North Texas, and Northeast Texas. They also indicate the wintry mischief could extend pretty far south into Central Texas and the Brazos Valley. I suspect we'll see Winter Storm Outlooks issued this morning and if trends continue we could see our first Winter Storm Watches issued this afternoon. 

 

Here's the 0Z GFS precipitation type output. 

[Srain]

Morning briefing from Jeff:

 

Cloudy, cool, and damp sums up the weather across the area this morning…and for much of this week.

 

Coastal surface trough continues to plague the area with fog and drizzle north of the trough and much warmer spring like temperatures south of the boundary. This feature pushed inland yesterday allowing Pearland and Angleton to reach the upper 70’s while Sugar Land remained in the 50’s and College Station in the mid 40’s. Overnight this trough axis and pushed back southward into the coastal waters with north winds in place across the entire region and temperatures running in the 40’s and lower 50’s. Not expecting much warm up today under drizzle, fog, and cloud cover. Warm air advection over top of the surface cold dome will keep the dreary weather locked in place all day.

 

Big changes transpire on Tuesday…for the best day of the week weather wise! Coastal warm front will rapidly surge inland flooding the area with mild air. Dewpoints and temperatures will sharply rise with the frontal passage with dewpoints pushing into the upper 60’s and temperatures the mid and upper 70’s. Warm dewpoints over the cold nearshore waters will likely result in dense sea fog formation. Drizzle and showers will move out of the area with the warm frontal passage and skies may even scatter out south of the warm front and north of the coastal sea fog bank.

 

Even bigger changes arrive on Wednesday. Another strong arctic cold front will plow across the region Wednesday afternoon resulting in rapidly falling temperatures. High temperatures in the 70’s will fall quickly into the 40’s and 30’s by evening. Freezing line will quickly advance into the region Wednesday night. Air mass ahead of the front will be moist, but likely capped off by warm mid level temperatures. Not expecting much in the way of severe weather given the warm sector air mass will likely have widespread cloud cover and little heating. Rain chances certainly increase with the frontal passage and continue into the post frontal air mass…which leads to the next concern.

 

Wednesday night/Thursday morning:

Strong arctic front will have moved into the Gulf of Mexico by Wednesday evening with strong cold air advection driving temperatures into the 30’s over much of the area. Strong winds will likely require wind advisories for at least the coastal counties with gust possibly up to 40mph which will drive wind chills into the 10’s and 20’s. Rain chances will linger behind the front as moisture overruns the surface arctic dome. Surface freezing line will move into the area Wednesday evening and likely reach as far south as a Brenham to Cleveland line (sound familiar). Light rain may change over to light freezing rain early Thursday across the northern 1/3^rd of the area. Forecast soundings show mainly a freezing rain P-type, but might suggest some sleet mixed in also especially from College Station to Huntsville. Right now it appears the freezing line will remain north of Harris County and the precipitation will remain liquid. This air mass is certainly very cold and adjustments will likely be needed over the next few days.

 

Thursday-Sunday:

Yet another storm approaches from the SW US with the cold air locked in place. Temperature should warm safely above freezing, but it will continue to be cold and miserable with increasing chances for widespread drizzle, fog, and rain. Lows will range from the 30’s to highs only in the 40’s Thursday and Friday. In fact many locations may see highs only in the 30’s on Thursday. The late week forecast will likely have some additional adjustments in the coming days as the latest GFS has backed off greatly on the amount of rain in the weekend time period.  

 

 

 

[Roy]

I am glad it looks like at least DFW will get into a drier pattern for a bit after Wednesday's system. We are having a house built and need to have it done by early April for locked in closing rate etc., so this last week slowed things down a bit. At least now we are finally a little above average in precip since Dec. 1. Slightly.

 

Wednesday looks interesting....will see if they will start issuing watches today.

[aggiegeog]

Looking at the recent GFS runs it appears to show too little post-frontal precip considering SW flow and an approaching shortwave. Hopefully the RGEM will give a better idea, but we will have to wait until tomorrow to get within its range.

[DFWWeather]

The models overall have been trending drier and warmer with this event for DFW. Especially the GFS from Sunday, when it had surface temps at 15°F and nearly 3/4 to an inch liquid pumping into system. Now we are 28°F to 32°F at the surface on most models. These look very marginal to me. These temperatures at DFW are really not cold enough for a solid sheet of ice on roadways (or high-impact event), more just a slushy mess. Bridges and overpasses will be different of course. If QPF continues to dwindle, this may just be a minor headache event.

 

Edit: 12z ECMWF down to 0.08 of an inch liquid equivalent frozen with low temps of 31°F at DFW Wednesday night.

[bubba hotep]

The models overall have been trending drier and warmer with this event for DFW. Especially the GFS from Sunday, when it had surface temps at 15°F. Now we are 28°F to 32°F at the surface on most models. These look very marginal to me. These temperatures at DFW are really not cold enough for a solid sheet of ice on roadways (or high-impact event), more just a slushy mess. Bridges and overpasses will be different of course. If QPF continues to dwindle, this may just be a minor headache event.

Edit: 12z ECMWF down to 0.08 of an inch liquid equivalent frozen with low temps of 31°F at DFW Wednesday night.

It is a tricky setup with the upper low opening up and sending a pulse of energy off to the NE. It looks like the 12z Euro increased qpf across parts of N. Texas but it mostly falls with temps above freezing. Overall, 12z runs were pretty uninspiring for those of us looking for one last shot of winter weather. I could see things changing pretty drastically with some minor timing differences but the trends have not been encouraging today. 18z has been the trend starter for us lately anyway!

ETA: I'm tossing this run since it shows less snow for me and a storm in Gulf...

[vwgrrc]

It is a tricky setup with the upper low opening up and sending a pulse of energy off to the NE. It looks like the 12z Euro increased qpf across parts of N. Texas but it mostly falls with temps above freezing. Overall, 12z runs were pretty uninspiring for those of us looking for one last shot of winter weather. I could see things changing pretty drastically with some minor timing differences but the trends have not been encouraging today. 18z has been the trend starter for us lately anyway!

is it possible models couldn't handle the shallow cold air?