Texas Fall-2015

[Brent]

Cavanaugh just wrote this for FWD:

SATURDAY AND SUNDAY...FOR THOSE WATCHING RAW MODEL OUTPUT THIS FAR
OUT...IT IS EASY TO NOTICE THAT TEMPERATURES IN FORECAST SOUNDINGS
DROP BELOW FREEZING WHILE STILL INDICATING GOOD CHANCES FOR
PRECIPITATION DURING THE DAY ON SATURDAY. THINK THAT OUR CHANCES
OF FROZEN PRECIPITATION ARE NOT QUITE AS GOOD AS RAW MODEL
GUIDANCE IS ADVERTISING BECAUSE OF THE PROGGED POSITION OF THE
UPPER TROUGH ON THE DYNAMIC TROPOPAUSE MAPS DURING THIS TIME. THE
DYNAMIC TROPOPAUSE MAPS KEEP THE UPPER LEVEL POTENTIAL VORTICITY
RESERVOIR OVER THE CENTRAL PLAINS. WHILE SHALLOW COLD AIR CAN
CERTAINLY "OUT RUN" THE POTENTIAL VORTICITY RESERVOIR ALOFT...DEEP
COLD AIR WILL REMAIN TIED TO THIS RESERVOIR. THE DYNAMIC
TROPOPAUSE HELPS DETERMINE THE DEPTH OF THE TROPOSPHERE...WHICH IS
MINIMIZED UNDER THE PV RESERVOIR ALOFT. A LOW THICKNESS
TROPOSPHERE DIRECTLY CORRELATES TO A COLDER AIRMASS ON
AVERAGE...MEANING THAT COLD AIR WILL GENERALLY REMAIN TIED TO THIS
FEATURE ALOFT. WITH NORTH CENTRAL TEXAS REMAINING SOUTH OF THIS
RESERVOIR ALOFT...THINK THAT THE POTENTIAL FOR US TO RECEIVE DEEP
COLD AIR IS LOW...MAKING A COLD RAIN MORE LIKELY THAN A FROZEN
PRECIPITATION EVENT AT THIS TIME. WILL KEEP A CLOSE EYE ON THIS
SYSTEM IN THE COMING DAYS.

[weatherdude1108]

Cavanaugh just wrote this for FWD:

SATURDAY AND SUNDAY...FOR THOSE WATCHING RAW MODEL OUTPUT THIS FAR
OUT...IT IS EASY TO NOTICE THAT TEMPERATURES IN FORECAST SOUNDINGS
DROP BELOW FREEZING WHILE STILL INDICATING GOOD CHANCES FOR
PRECIPITATION DURING THE DAY ON SATURDAY. THINK THAT OUR CHANCES
OF FROZEN PRECIPITATION ARE NOT QUITE AS GOOD AS RAW MODEL
GUIDANCE IS ADVERTISING BECAUSE OF THE PROGGED POSITION OF THE
UPPER TROUGH ON THE DYNAMIC TROPOPAUSE MAPS DURING THIS TIME. THE
DYNAMIC TROPOPAUSE MAPS KEEP THE UPPER LEVEL POTENTIAL VORTICITY
RESERVOIR OVER THE CENTRAL PLAINS. WHILE SHALLOW COLD AIR CAN
CERTAINLY "OUT RUN" THE POTENTIAL VORTICITY RESERVOIR ALOFT...DEEP
COLD AIR WILL REMAIN TIED TO THIS RESERVOIR. THE DYNAMIC
TROPOPAUSE HELPS DETERMINE THE DEPTH OF THE TROPOSPHERE...WHICH IS
MINIMIZED UNDER THE PV RESERVOIR ALOFT. A LOW THICKNESS
TROPOSPHERE DIRECTLY CORRELATES TO A COLDER AIRMASS ON
AVERAGE...MEANING THAT COLD AIR WILL GENERALLY REMAIN TIED TO THIS
FEATURE ALOFT. WITH NORTH CENTRAL TEXAS REMAINING SOUTH OF THIS
RESERVOIR ALOFT...THINK THAT THE POTENTIAL FOR US TO RECEIVE DEEP
COLD AIR IS LOW...MAKING A COLD RAIN MORE LIKELY THAN A FROZEN
PRECIPITATION EVENT AT THIS TIME. WILL KEEP A CLOSE EYE ON THIS
SYSTEM IN THE COMING DAYS.

That is a good explanation! I haven't heard of a PV reservoir. Interesting! Weather is so fascinating! That Cavanaugh is awesome!

[TheProfessor]

I like this statement.

[Ralph's Weather]

I understand what he is saying, the deep cold will struggle to make it all the way into Texas. I could see a very shallow area of sub-freezing temps over N TX though the rain may bring down enough warmth to combat the density of the cold. It is a very complicated situation.

[Brent]

I understand what he is saying, the deep cold will struggle to make it all the way into Texas. I could see a very shallow area of sub-freezing temps over N TX though the rain may bring down enough warmth to combat the density of the cold. It is a very complicated situation.

I'm a little confused because wouldn't deep cold equal more snow than ice? which has never really been modeled here anyway? There is a good point about warmth preventing ice in shallow cold though. We saw that a couple times last year.

[TeamPlayersBlue]

Excellent explanation.

[SouthernMet]

Here we go folks...

[TheProfessor]

I understand what he is saying, the deep cold will struggle to make it all the way into Texas. I could see a very shallow area of sub-freezing temps over N TX though the rain may bring down enough warmth to combat the density of the cold. It is a very complicated situation.

I'm a little confused because wouldn't deep cold equal more snow than ice? which has never really been modeled here anyway? There is a good point about warmth preventing ice in shallow cold though. We saw that a couple times last year.

It depends on how deep the cold is for snow and how cold the shallow cold is for ice instead of rain. if the Temperatures are in the mid 20s while preciptation is still falling, then it likely would end up freezing on surfaces and causing a mess, if it's closer to 32 like last year then it would probably stay rain all the rain. It would depend on when the precip is falling too. night vs day.

[TheProfessor]

I think the 18z GFS has Thunder sleet for North Texas

[TheProfessor]

and my flight would still be canceled in the world of the 18z GFS as it doesn't have it going above 20 degrees the following Sunday.

[TheProfessor]

looks like the 18z GFS run drops another 1-2 inches of liquid QPF while it has temps below freezing.

[Brent]

Here we go folks...

Is this really snow?

[TheProfessor]

Here we go folks...

Is this really snow?

Twisterdata.com is a lot slower that tropicaltidbits but once hour 198 comes out you can go to that website for GFS and click on a map for the DFW area, it will take you to a skew-t for that time, if there is no, or very little warmnose then that would indicate snow.

[Brent]

[Ntxw]

A good way to broadbrush is if 850s are below 0C along with the surface. 5k ft below freezing is roughly good enough for SN. Not perfect but good generalization

[Ralph's Weather]

I expected the GFS to flip back to holding the -EPO ridge, but that is some crazy cold (not sure I believe it with precip falling).

[Brent]

Okay then...

[Brent]

HIGHS next Sunday

[Ralph's Weather]

Okay then...

And according to this run most of what falls over NW N TX would be snow.

[JayDT]

Im rooting for the models! I need some winter weather to really get me in the holiday spirit, lol.