Texas/New Mexico/Louisiana/Mexico Obs And Discussion Thread Part 5

[Srain]

Afternoon Update from Jeff:

 

Severe thunderstorms possible Sunday afternoon and evening.

 

A strong storm system currently moving through the SW US will eject across TX on Sunday. At the surface strong southerly flow is pumping Gulf moisture northward from the Bay of Campeche, while to the north a strong late season arctic high pressure dome is moving southward down the plains. Impressive cold front will slice across the region late Sunday afternoon returning winter to the area for much of next week.

 

Upper level system currently over the SW US will shear into TX on Sunday with fairly strong dynamics forecasted aloft. Low level jet increases to near 40kts from Matagorda Bay NNE across SE TX by early Sunday afternoon. Increased dewpoints in the mid to upper 60’s and steepening lapse rates support instability values of 1000 to 1500 J/kg of CAPE by mid afternoon. Think mid level warm layer (cap) will hold through at least 1-2pm and then begin to erode from both increasing lift and modest surface heating. GFS and ECMWF develop a line of strong the severe thunderstorms from near Austin ENE toward W LA by mid afternoon as the cap is overcome…however the NAM and some of the other short range guidance holds the cap longer over the region and does not develop as much activity. 0-6km shear values will be on the order 50-60kts across the region and this combined with the expected instability would result in severe thunderstorms.

 

Forecast models that do develop storms show initial mode east of I-35 as supercells with a large hail threat and then quickly transition toward a line with bowing segments which seems likely given the wind energy aloft. Initial supercells could have a slight tornado risk…but think the main threat will be large hail. Storms will move ESE across at least the northern ½ of the region Sunday evening likely becoming increasingly linear. Linear mode favors strong straight line wind damage along the leading edge of the line and in any bowing segments. If a well defined line develops could see a few corridors of wind damage in the region from east of Austin ESE north of US 290 northward toward Huntsville. Will have to watch for the potential for the arctic front to undercut the leading edge of the line and reduce the severe weather threat Sunday evening.

 

Timing continues to look from mid afternoon into mid to late evening. SPC slight risk includes about 75% of the area, but think capping to the SW will be too much to overcome and the main severe threat will be NE of a line from Austin to Columbus to Houston to High Island.

 

Other item is fairly impressive cold air advection with this system and expect cold temperatures Monday-Wednesday. Modified arctic air mass will be fully entrenched by Monday morning with lows in the 30’s across the entire area and possibly upper 20’s northern counties. Will see only modest recovery on Monday as strong north winds continue to transport cold air southward with highs likely in the upper 40’s and low 50’s….a big difference from the highs near 80 on Sunday.

 

SPC Day 2 (Sunday) Severe Weather Outlook:

 

[DFWWeather]

From what little has come out of the weekend shift at the FWD office this afternoon, it looks like latest thinking on ice accumulations is getting dangerously close to Winter Storm Warning criteria for the immediate DFW Metroplex, and certainly there for counties north.

 

Severe weather potential on graphic above is tremendously overdone. Arctic airmass will undercut severe potential except far east/southeast Texas, roughly the area in red.

[Srain]

From what little has come out of the weekend shift at the FWD office this afternoon, it looks like latest thinking on ice accumulations is getting dangerously close to Winter Storm Warning criteria for the immediate DFW Metroplex, and certainly there for counties north.

 

 

Cavanaugh issued a very detailed AFD. I have no clue what you're talking about.

[andyhb]

Severe weather potential on graphic above is tremendously overdone. Arctic airmass will undercut severe potential except far east/southeast Texas, roughly the area in red.

 

What?

 

That's why there's a 30% risk over those areas...

[DFWWeather]

Cavanaugh issued a very detailed AFD. I have no clue what you're talking about.

 Generally, the afternoon update is posted well before it was and all other products had updated except the AFD, and there was no midday update. There is usually always a midday update when an event like this comes. All the other AFD in Texas had already updated their afternoon discussions. So, I was just saying based on what I could glean at the time of my post. That is all I meant.

[DFWWeather]

What?

 

That's why there's a 30% risk over those areas...

 

Yes, but I can almost guarantee no severe weather anywhere from the Metroplex northward and that graphic seems to indicate otherwise, and the FWD AFD pretty much agrees with me. I think there is a tendency to over do severe potential sometimes. And this is a good example. The 5 percent line or maybe 10 percent should be where the 30% line is, in my opinion. To me that graphic is overdone, so I find it rather ridiculous to have a 5% chance of severe storms into Oklahoma. Ice is going to be much more of a concern from the Metroplex northward into southeast Oklahoma into Arkansas. I do agree with the potential for convection as outlined in general in the green shaded area on the first graphic.

[David Reimer]

 Generally, the afternoon update is posted well before it was and all other products had updated except the AFD, and there was no midday update. There is usually always a midday update when an event like this comes. All the other AFD in Texas had already updated their afternoon discussions. So, I was just saying based on what I could glean at the time of my post. That is all I meant.

 

That would be because the crew was busy updating the EM briefing, considering any sort of geographical changes to the advisory, along with writing a very detailed update. Oh, not to mention recording the public video update. Plenty was going on that you simply didn't know about. By the way, the "weekend" crew actually has most of the good forecasters on shift. Quit your bi***ing. Dennis usually issues his AFD around or just after 4 PM because he takes the time to write a detailed explanation of the forecast and the decisions that go into it. 

 

The five percent line is for the potential of elevated hail storms later tonight. That is a valid concern with this setup. For tomorrow's severe potential I do agree it seems to be overdone a bit with the front undercutting most attempts at surface based convection pretty quickly. However, if one cell does manage to go up it could certainly warrant that risk. Better to be safe than sorry. 

[andyhb]

Yes, but I can almost guarantee no severe weather anywhere from the Metroplex northward and that graphic seems to indicate otherwise, and the FWD AFD pretty much agrees with me. I think there is a tendency to over do severe potential sometimes. And this is a good example. The 5 percent line or maybe 10 percent should be where the 30% line is, in my opinion. To me that graphic is overdone, so I find it rather ridiculous to have a 5% chance of severe storms into Oklahoma. Ice is going to be much more of a concern from the Metroplex northward into southeast Oklahoma into Arkansas. I do agree with the potential for convection as outlined in general in the green shaded area on the first graphic.

 

Based on what?

 

Also, there's no such thing as a 10% risk in the D2 or 3 outlook.

[DFWWeather]

That would be because the crew was busy updating the EM briefing, considering any sort of geographical changes to the advisory, along with writing a very detailed update. Oh, not to mention recording the public video update. Plenty was going on that you simply didn't know about. By the way, the "weekend" crew actually has most of the good forecasters on shift. Quit your bi***ing. Dennis usually issues his AFD around or just after 4 PM because he takes the time to write a detailed explanation of the forecast and the decisions that go into it. 

 

The five percent line is for the potential of elevated hail storms later tonight. That is a valid concern with this setup. For tomorrow's severe potential I do agree it seems to be overdone a bit with the front undercutting most attempts at surface based convection pretty quickly. However, if one cell does manage to go up it could certainly warrant that risk. Better to be safe than sorry. 

I wasn't meaning to sound snippy, at the time of my post there was not AFD update, and hadn't been one since early morning. A lot had changed in model world since then, and quite frankly, I was very surprised their wasn't a midday update. My quote was not meant to be taken negatively.

[Quixotic1]

Christmas 2012. Juicy surface with an approaching arctic front with lagging SW. That was a humdinger both winter and severe-wise. Don't think it is an exact fit but close enough to peak interest.

[DFWWeather]

Based on what?

 

Also, there's no such thing as a 10% risk in the D2 or 3 outlook.

Sorry, I meant 15% risk, but you get the idea of what I am saying.

 

Based on the fact that I have lived here for 35 years and know a little bit about the weather.

 

For tomorrow, I agree with a general threat of convection, I don't agree with the extent of the severe weather threat. That is over done.

 

I do think the public in general has gotten to where they don't heed severe weather warnings anymore because its gotten to where every thunderstorm event is a severe weather event and every storm is severe, at least here in Texas. In reality that just isn't the case. And more often that not it isn't the case. Like tomorrow. I think we cry wolf on severe weather much too often.  Forecasters in this area play that card a little too often. In my opinion, we shouldn't even consider it a severe storm until winds reach at least 70 mph or greater, golfball sized hail or larger, very heavy rainfall, and/or one that can produce a tornado.

[bubba hotep]

That would be because the crew was busy updating the EM briefing, considering any sort of geographical changes to the advisory, along with writing a very detailed update. Oh, not to mention recording the public video update. Plenty was going on that you simply didn't know about. By the way, the "weekend" crew actually has most of the good forecasters on shift. Quit your bi***ing. Dennis usually issues his AFD around or just after 4 PM because he takes the time to write a detailed explanation of the forecast and the decisions that go into it. 

 

The five percent line is for the potential of elevated hail storms later tonight. That is a valid concern with this setup. For tomorrow's severe potential I do agree it seems to be overdone a bit with the front undercutting most attempts at surface based convection pretty quickly. However, if one cell does manage to go up it could certainly warrant that risk. Better to be safe than sorry. 

 

[bubba hotep]

I wasn't meaning to sound snippy, at the time of my post there was not AFD update, and hadn't been one since early morning. A lot had changed in model world since then, and quite frankly, I was very surprised their wasn't a midday update. My quote was not meant to be taken negatively.

 

I totally got what you were saying, people seemed a little testy around here this afternoon

 

A couple of things that jumped out at me from the “infamously timed” afternoon AFD:

 

TO OUR NORTH...21Z SURFACE OBSERVATIONS ACROSS SOUTHERN KANSAS AND

NORTHERN OKLAHOMA RANGED FROM THE LOWER TEENS TO THE MIDDLE 20S.

COMPARING THESE TEMPERATURES TO THE MORNING NAM 21Z FORECAST FOR

SURFACE TEMPERATURES INDICATED THAT THE NAM WAS RUNNING 8 TO 10

DEGREES TOO WARM WITH AIR ASSOCIATED WITH THE ARCTIC FRONT.

UNFORTUNATELY THE NAM IS THE COLDEST OF THE POPULAR OPERATIONAL

FORECAST MODELS...

 

...AND IF IT LOOKS LIKE WE WILL

GET COLDER SIGNIFICANTLY FASTER...WE MAY HAVE TO UPGRADE SOME

PORTIONS OF THE ADVISORY INTO A WINTER STORM WARNING BEFORE SUNDAY

MORNING.

[DFWWeather]

I totally got what you were saying, people seemed a little testy around here this afternoon

 

A couple of things that jumped out at me from the “infamously timed” afternoon AFD:

 

TO OUR NORTH...21Z SURFACE OBSERVATIONS ACROSS SOUTHERN KANSAS AND

NORTHERN OKLAHOMA RANGED FROM THE LOWER TEENS TO THE MIDDLE 20S.

COMPARING THESE TEMPERATURES TO THE MORNING NAM 21Z FORECAST FOR

SURFACE TEMPERATURES INDICATED THAT THE NAM WAS RUNNING 8 TO 10

DEGREES TOO WARM WITH AIR ASSOCIATED WITH THE ARCTIC FRONT.

UNFORTUNATELY THE NAM IS THE COLDEST OF THE POPULAR OPERATIONAL

FORECAST MODELS...

 

...AND IF IT LOOKS LIKE WE WILL

GET COLDER SIGNIFICANTLY FASTER...WE MAY HAVE TO UPGRADE SOME

PORTIONS OF THE ADVISORY INTO A WINTER STORM WARNING BEFORE SUNDAY

MORNING.

 

This from the aviation discussion also seemed a bit concerning:

 

THERE WILL CONTINUE TO BE THE POSSIBILITY OF ISOLATED

THUNDERSTORMS INTO THE AFTERNOON AND IF THIS

HAPPENS...PRECIPITATION AMOUNTS WILL END UP BEING HEAVIER THAN

THE CURRENT FORECAST.

 

As far as Warning criteria, I already think Denton, Collin, Wise counties are there pretty much from a forecast standpoint. Northern portions of the Metroplex are also very borderline, but if we get convective bands of sleet going, then it will be interesting for sure. This would be especially true if the NAM is too warm on temperatures.

[bubba hotep]

This from the aviation discussion also seemed a bit concerning:

 

THERE WILL CONTINUE TO BE THE POSSIBILITY OF ISOLATED

THUNDERSTORMS INTO THE AFTERNOON AND IF THIS

HAPPENS...PRECIPITATION AMOUNTS WILL END UP BEING HEAVIER THAN

THE CURRENT FORECAST.

 

As far as Warning criteria, I already think Denton, Collin, Wise counties are there pretty much from a forecast standpoint. Northern portions of the Metroplex are also very borderline, but if we get convective bands of sleet going, then it will be interesting for sure. This would be especially true if the NAM is too warm on temperatures.

 

I haven't really had a chance to look at things in any kind of detail today but just a quick glance here and there has me thinking Collin (IMBY) and points N and E will get upgraded.  I might change my tune after a couple of beers and the 00z models but it should make for an enjoyable evening model gazing.

[David Reimer]

FWD is upgrading Fannin, Lamar, Delta, Hunt, and Hopkins counties to a Winter Storm Warning.

[bubba hotep]

FWD is upgrading Fannin, Lamar, Delta, Hunt, and Hopkins counties to a Winter Storm Warning.

 

Not surprising after looking at the 00z NAM.  Pretty tight gradient from DFW out to Paris, wouldn’t take much of a west shift to get things really nasty across much of DFW.

[David Reimer]

Not surprising after looking at the 00z NAM.  Pretty tight gradient from DFW out to Paris, wouldn’t take much of a west shift to get things really nasty across much of DFW.

 

That concern is shared by myself as well. 

[DFWWeather]

Not surprising after looking at the 00z NAM.  Pretty tight gradient from DFW out to Paris, wouldn’t take much of a west shift to get things really nasty across much of DFW.

 

Cold front moving south much faster than expected. FWD is speeding up arrival of cold front from 3 am to midnight for DFW and starting frozen precip a couple hours earlier. Things appear to be going down hill.

[bubba hotep]

Christmas 2012. Juicy surface with an approaching arctic front with lagging SW. That was a humdinger both winter and severe-wise. Don't think it is an exact fit but close enough to peak interest.

 

That was such an awesome event with thunder all night long and then the rapid transition to heavy snow during the late morning.  I would put that right up there with any event that I experienced while living in DC.  The all night thunder and lightning really made for an unique event.

 

We really haven’t had an overperformer this winter… maybe this one will be it?

[DFWWeather]

Latest update from FWD talks about possibly expanding the Winter Storm Warning into the DFW Metroplex and south and east along the I-35 corridor.

[Quixotic1]

That was such an awesome event with thunder all night long and then the rapid transition to heavy snow during the late morning. I would put that right up there with any event that I experienced while living in DC. The all night thunder and lightning really made for an unique event.

We really haven’t had an overperformer this winter… maybe this one will be it?

We are due. With the exception of the early December event, we have underperformed. Judging by what FWD is saying, North and east of the metroplex has a better shot. Weenie mode ready to be engaged.

[bubba hotep]

From FWD:

 

THE NAM...TX TECH WRF...RAP...AND OUR LOCAL WRF ALL HAVE
REASONABLE PRECIPITATION TRENDS TOMORROW AND AM LEANING TOWARDS
THEIR SOLUTIONS. THEY HAVE PRECIP OCCURRING ALONG AND BEHIND THE
FRONT IN THE EARLY MORNING HOURS WITH A LITTLE LULL IN THE
ACTIVITY DURING THE LATE MORNING HOURS AND AROUND MIDDAY

 

Too bad we don't have the traffic that some of the other Regions have b/c that would be prime time weenie suicide time

 

ISOLATED THUNDERSTORMS COULD ALSO
OCCUR AND SOUNDINGS INDICATE THUNDERSLEET MAY OCCUR IN THE
AFTERNOON HOURS.

 

:weenie:

[bubba hotep]

Front has cleared Denton and is crashing into the metroplex

 

ETA: Looks to have cleared the line from Frisco across to MBY but DFW still reporting S winds.

[1900hurricane]

Even with the severe weather threat looking as marginal as it is at the moment, I'll still probably make the short drive into the Brazos River floodplain to intercept something. I did this a few times last spring for some of the cold fronts and it was pretty cool. Great visibilities too.

[Quixotic1]

Even with the severe weather threat looking as marginal as it is at the moment, I'll still probably make the short drive into the Brazos River floodplain to intercept something. I did this a few times last spring for some of the cold fronts and it was pretty cool. Great visibilities too.

Awesome isn't it to have a high vantage point? I used to do the same thing on a hill just east of Eagle Mountain lake. A little frightening at times.

[1900hurricane]

Awesome isn't it to have a high vantage point? I used to do the same thing on a hill just east of Eagle Mountain lake. A little frightening at times.

 

There really isn't a high point to sit atop, but everything is so flat and (more importantly) treeless that you can see everything for quite a while around.

[1900hurricane]

I feel like I just went back in time to March and April 2013.

 

 

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1149 PM CST SAT MAR 01 2014

VALID 021200Z - 031200Z

...THERE IS A SLGT RISK OF SVR TSTMS FOR ERN TX TO THE LOWER MS
VALLEY...

...SYNOPSIS...
SHORTWAVE TROUGH OVER THE LOWER CO VALLEY WILL EJECT EWD...REACHING
THE LOWER MS VALLEY/MID-SOUTH BY EARLY MON. ROBUST COLD FRONT OVER N
TX WILL MOVE SEWD ACROSS THE WRN GULF TO CNTRL GULF COAST...AS AN
EXPANSIVE ANTICYCLONE BUILDS OVER THE GREAT PLAINS.

...ERN TX TO LOWER MS VALLEY...
DESPITE MID-LEVEL HEIGHT FALLS/DCVA DOWNSTREAM OF THE APPROACHING
SHORTWAVE TROUGH...CYCLOGENESIS SHOULD BE NIL ALONG THE PROGRESSIVE
COLD FRONT. THIS SUGGESTS STRONG FORCING FOR ASCENT WILL PRIMARILY
REMAIN ALONG/N OF THE FRONT...YIELDING A LARGELY ANAFRONTAL
CONVECTIVE SCENARIO. LOW-LEVEL MOISTURE RETURN BENEATH AN EML WILL
REMAIN CONFINED FROM THE WRN GULF OWING TO LOW PW VALUES OVER THE
ERN GULF. THIS SHOULD EFFECTIVELY LIMIT THE ERN EXTENT OF SURFACE
DEW POINTS AOA 60 DEG F TO THE CNTRL GULF COAST.

SCATTERED ELEVATED CONVECTION SHOULD BE ONGOING OVER PARTS OF THE
OZARK PLATEAU AT 12Z. POST-FRONTAL CONVECTION WILL INCREASE IN
COVERAGE THROUGH THE MORNING AND AFTERNOON WITH SWWD EXTENT...AS
FORCING FOR ASCENT STRENGTHENS. INITIALLY STEEP MID-LEVEL LAPSE
RATES AND STRONG SPEED SHEAR WITHIN THE CLOUD-BEARING LAYER SHOULD
FAVOR ISOLATED SEVERE HAIL.

SURFACE-BASED PARCELS ALONG THE FRONT MAY REMAIN CAPPED THROUGH PEAK
HEATING OWING TO A PRONOUNCED EML AND PERSISTENT SWLY FLOW. BY
EVENING...AN OVERSPREADING MID-LEVEL JET SHOULD YIELD SOME
SHARPENING OF THE FRONT AS IT IMPINGES ON THE PLUME OF RICHEST
LOW-LEVEL MOISTURE. INHIBITION SHOULD SUFFICIENTLY WEAKEN FOR
SURFACE-BASED STORMS FROM FAR SERN TX INTO LA. THIS CONVECTION
SHOULD GROW INTO A BROKEN BAND AMIDST 700 MB WINDS AOA 40 KT.
LOW/MID-LEVEL SHEAR WILL BE SUFFICIENT FOR SHORT-LINE SEGMENTS AND
EMBEDDED SUPERCELL STRUCTURES CAPABLE OF ISOLATED DAMAGING WINDS AND
A TORNADO. HOWEVER...GIVEN THE UNDERCUTTING NATURE OF THE FRONT
ALONG WITH LOWER MEAN MIXING RATIOS WITH ERN EXTENT...OVERALL SEVERE
RISK SHOULD BE TEMPERED IN COVERAGE/INTENSITY.

..GRAMS/ROGERS.. 03/02/2014

[andyhb]

I feel like I just went back in time to March and April 2013.

 

[1900hurricane]

The front is really barreling south this morning, and the gradient is from crazyland! Temps in the 70s ahead, but only in the 20s behind!