Texas Winter 2013-2014

[TeamPlayersBlue]

I find it odd that the NWS still has a 30% chance of winter precip for my area tomorrow morning.

It does? Havent even checked. Took a bit of a break after the alst two storms, work got busy and i needed sleep!

[TheProfessor]

It is still below 30 here. Maybe there will be something to show for the cold tomorrow.

[Portastorm]

Well folks, I more or less blew off this event (Thur-Fri) yesterday thinking at best the Austin area would see a few spots of freezing drizzle and that the event would amount to less than the last two events. But this non-US 12z guidance has me concerned. Surface temps will certainly be at or below freezing for much of the period from early Thursday morning until lunchtime Friday. With these increasing QPF amounts showing up on the Euro and CMC, I'll be very curious to see trends on the NAM/NAM-HIRES/SREF for 18z. This *could* end up being more than what we initially thought.

And I'm not talking about snow or anything nutty like that ... my concern is freezing rain/wintry mix crud.

[Longhornmaniac8]

Porta,

It looked to me like the 850mb levels on the low-res 12z Euro (at the PSU E-Wall page) were well below freezing in our neck of the woods. Could you elaborate why you don't think snow is a possibility here (operating under the assumption there is moisture to work with).

Thanks!

Cheers,
Cameron

[Tireman4]

From HGX: (Humm)

Thursday A chance of rain, freezing rain, and sleet before 9am. Mostly cloudy, with a high near 40. Wind chill values between 20 and 30. Northeast wind 5 to 10 mph. Chance of precipitation is 30%. Little or no ice accumulation expected. Little or no snow accumulation expected.

[TheProfessor]

Well folks, I more or less blew off this event (Thur-Fri) yesterday thinking at best the Austin area would see a few spots of freezing drizzle and that the event would amount to less than the last two events. But this non-US 12z guidance has me concerned. Surface temps will certainly be at or below freezing for much of the period from early Thursday morning until lunchtime Friday. With these increasing QPF amounts showing up on the Euro and CMC, I'll be very curious to see trends on the NAM/NAM-HIRES/SREF for 18z. This *could* end up being more than what we initially thought.

And I'm not talking about snow or anything nutty like that ... my concern is freezing rain/wintry mix crud.

It would be all snow here right? There isn't some random warm nose that no one has mentioned yet, right?

[wxman57]

Well folks, I more or less blew off this event (Thur-Fri) yesterday thinking at best the Austin area would see a few spots of freezing drizzle and that the event would amount to less than the last two events. But this non-US 12z guidance has me concerned. Surface temps will certainly be at or below freezing for much of the period from early Thursday morning until lunchtime Friday. With these increasing QPF amounts showing up on the Euro and CMC, I'll be very curious to see trends on the NAM/NAM-HIRES/SREF for 18z. This *could* end up being more than what we initially thought.

And I'm not talking about snow or anything nutty like that ... my concern is freezing rain/wintry mix crud.

Checking the model soundings for tomorrow, the air (even over Austin) will be well below freezing from the surface to the top of the atmosphere. It would be hard to get freezing rain or sleet with the projected profile. But the big question is whether any precip can be squeezed out of that mid-level cloud deck tomorrow, and then how much of it may reach the ground?

PS: No warm nose from Austin to Dallas-Ft. Worth. Only over SE TX.

[Tireman4]

Well folks, I more or less blew off this event (Thur-Fri) yesterday thinking at best the Austin area would see a few spots of freezing drizzle and that the event would amount to less than the last two events. But this non-US 12z guidance has me concerned. Surface temps will certainly be at or below freezing for much of the period from early Thursday morning until lunchtime Friday. With these increasing QPF amounts showing up on the Euro and CMC, I'll be very curious to see trends on the NAM/NAM-HIRES/SREF for 18z. This *could* end up being more than what we initially thought.

And I'm not talking about snow or anything nutty like that ... my concern is freezing rain/wintry mix crud.

Checking the model soundings for tomorrow, the air (even over Austin) will be well below freezing from the surface to the top of the atmosphere. It would be hard to get freezing rain or sleet with the projected profile. But the big question is whether any precip can be squeezed out of that mid-level cloud deck tomorrow, and then how much of it may reach the ground?

PS: No warm nose from Austin to Dallas-Ft. Worth. Only over SE TX.

Speaking of Houston, will they do soundings at UH for tomorrow?

[Portastorm]

Porta,

It looked to me like the 850mb levels on the low-res 12z Euro (at the PSU E-Wall page) were well below freezing in our neck of the woods. Could you elaborate why you don't think snow is a possibility here (operating under the assumption there is moisture to work with).

Thanks!

Cheers,
Cameron

I looked at a Skew-T from the 12z GFS for Austin tomorrow at 1 p.m. and saw a 10-degree Celsius nose from 700mb to 850mb. I poked around a few other times and looked at the Skew-T's and still saw that warm nose. Granted, it's not as deep as what we saw for the event on the 24th ... so this could be more sleet and less freezing rain. These kinds of determinations are well beyond my understanding of meteorology though, to be honest.

I see that wxman57 posted about this already. Perhaps he can explain to me (and all of us) how I'm not interpreting the Skew-T accurately. Like I said ... Skew-T's are not in my wheelhouse.



Uploaded with ImageShack.us

[wxman57]

On that Skew-T, what you want to look for is the 0C line that runs diagonally from about the center of the graphic (at the bottom) to just above the "400mb" line. The red line is the predicted temperature at each level, the green is the dew point temperature. When those two are close together (within 5C) that indicates clouds and/or precip.

In the graphic above, only a tiny bit of the red (temperatures) line touches the 0C line at the time of the plot. But note that the red and green lines are not very close together for most of the plot, indicating dry air at noon tomorrow. Look at the 12Z plot instead. Note that the red and green lines are fairly close together from about the 730mb level to just above the 500mb level (using the scale on the left). This indicates clouds and/or precip between about 9000 and 20000 ft. But below 9000 ft (730mb) the lines are farther apart, indicating drier air in the lower 9000 ft.

[Portastorm]

On that Skew-T, what you want to look for is the 0C line that runs diagonally from about the center of the graphic (at the bottom) to just above the "400mb" line. The red line is the predicted temperature at each level, the green is the dew point temperature. When those two are close together (within 5C) that indicates clouds and/or precip.

In the graphic above, only a tiny bit of the red (temperatures) line touches the 0C line at the time of the plot.

Oh .... now I get it!

See, I knew you could educate me. And hopefully some here who don't know how to read Skew-T's. And you're doing all of this on Weatherperson's Day!! What a good guy. I guess we better get you some 90 degree temps now.

[Portastorm]

Yeah, here's the 12z plot for tomorrow for Austin. A little more red line/green line connection than the 18z plot.



Uploaded with ImageShack.us

[Longhornmaniac8]

On that Skew-T, what you want to look for is the 0C line that runs diagonally from about the center of the graphic (at the bottom) to just above the "400mb" line. The red line is the predicted temperature at each level, the green is the dew point temperature. When those two are close together (within 5C) that indicates clouds and/or precip.

In the graphic above, only a tiny bit of the red (temperatures) line touches the 0C line at the time of the plot. But note that the red and green lines are not very close together for most of the plot, indicating dry air at noon tomorrow. Look at the 12Z plot instead. Note that the red and green lines are fairly close together from about the 730mb level to just above the 500mb level (using the scale on the left). This indicates clouds and/or precip between about 9000 and 20000 ft. But below 9000 ft (730mb) the lines are farther apart, indicating drier air in the lower 9000 ft.

http://www.twisterdata.com/data/tmp/scr ... .5000W.png

I see that there is very dry air above 700 mb, but does the entire air column need to be moist for precipitation to happen? I wouldn't think so (at least dry air aloft I wouldn't think would inhibit precipitation if there is moisture in the lower levels). By my interpretation, that Skew-T shows fairly moist air (close temp/dew point spread) from 400 to 725 mb or so, and then slightly dryer air below that. I don't have a good grasp for how big a gap that actually is below 725.

Am I interpreting that correctly? And would the spread shown produce enough moisture for anything other than virga?

Cheers,
Cameron

Edit: I keep changing the numbers as I look at it more.

[TheProfessor]

Post one for dfw please.

[Portastorm]

Just issued ...


URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE FORT WORTH TX
249 PM CST WED FEB 5 2014

TXZ091-100-101-115-116-129-060500-
/O.NEW.KFWD.WW.Y.0004.140206T0900Z-140206T2000Z/
/O.CON.KFWD.WC.Y.0002.140206T0900Z-140206T1800Z/
MONTAGUE-YOUNG-JACK-STEPHENS-PALO PINTO-EASTLAND-
INCLUDING THE CITIES OF...BOWIE...NOCONA...GRAHAM...OLNEY...
JACKSBORO...BRECKENRIDGE...MINERAL WELLS...CISCO...EASTLAND...
RANGER...GORMAN
249 PM CST WED FEB 5 2014

...WINTER WEATHER ADVISORY IN EFFECT FROM 3 AM TO 2 PM CST
THURSDAY...
...WIND CHILL ADVISORY REMAINS IN EFFECT FROM 3 AM TO NOON CST
THURSDAY...

THE NATIONAL WEATHER SERVICE IN FORT WORTH HAS ISSUED A WINTER
WEATHER ADVISORY FOR SNOW...WHICH IS IN EFFECT FROM 3 AM TO 2 PM CST
THURSDAY.

* TIMING...LIGHT TO MODERATE SNOW IS EXPECTED TO DEVELOP LATE
TONIGHT INTO EARLY THURSDAY MORNING ACROSS PARTS OF NORTH TEXAS.
THE BULK OF THE SNOW SHOULD COME DOWN BETWEEN 5 AM AND NOON.

* MAIN IMPACT...SNOWFALL ACCUMULATIONS WILL GENERALLY RANGE
BETWEEN 1 AND 2 INCHES WEST OF AN EASTLAND TO JACKSBORO TO BOWIE
LINE THROUGH MIDDAY THURSDAY. SNOWFALL IS EXPECTED TO BE LIGHT
AND POWDERY...AND TEMPERATURES WILL BE SUFFICIENTLY COLD FOR ANY
SNOW TO STICK TO AREA ROADS. TRAVEL MAY BECOME HAZARDOUS ACROSS
WESTERN PORTIONS OF NORTH TEXAS DURING THE DAY THURSDAY.

* WIND CHILL VALUES...WIND CHILL VALUES OF 0 TO MINUS 5 DEGREES
ARE EXPECTED LATE TONIGHT INTO EARLY THURSDAY MORNING.

* OTHER IMPACTS...TEMPERATURES WILL FALL INTO THE LOWER TEENS
FOR LOWS TONIGHT INTO THURSDAY MORNING. TEMPERATURES THIS COLD
CAN CAUSE EXPOSED PIPES TO BURST. TAKE PRECAUTIONS TO PROTECT
OUTDOOR PIPES.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WINTER WEATHER ADVISORY MEANS THAT PERIODS OF WINTER
PRECIPITATION MAY CAUSE TRAVEL DIFFICULTIES. BE PREPARED FOR
SLIPPERY ROADS AND PLAN ON SOME TRAVEL DELAYS.

A WIND CHILL ADVISORY MEANS THAT VERY COLD AIR AND STRONG WINDS
WILL COMBINE TO GENERATE LOW WIND CHILLS. PROLONGED EXPOSURE TO
THE COLD MAY RESULT IN FROSTBITE AND LEAD TO HYPOTHERMIA IF
PRECAUTIONS ARE NOT TAKEN. IF YOU MUST VENTURE OUTDOORS...WEAR A
HAT AND GLOVES. REMEMBER TO BRING YOUR PETS INDOORS AND PROTECT
ANY EXPOSED METAL PIPES.


&&

$$

TXZ092>094-102>104-117-130-060500-
/O.CON.KFWD.WC.Y.0002.140206T0900Z-140206T1800Z/
COOKE-GRAYSON-FANNIN-WISE-DENTON-COLLIN-PARKER-ERATH-
INCLUDING THE CITIES OF...GAINESVILLE...SHERMAN...DENISON...
BONHAM...DECATUR...BRIDGEPORT...DENTON...LEWISVILLE...
FLOWER MOUND...THE COLONY...PLANO...WEATHERFORD...BRIAR...
STEPHENVILLE...DUBLIN
249 PM CST WED FEB 5 2014

...WIND CHILL ADVISORY REMAINS IN EFFECT FROM 3 AM TO NOON CST
THURSDAY...

* WIND CHILL VALUES...WIND CHILL VALUES OF 0 TO MINUS 3 DEGREES
ARE EXPECTED LATE TONIGHT THROUGH THURSDAY MORNING FOR LOCATIONS
ALONG AND NORTH OF A CISCO TO WEATHERFORD TO MCKINNEY TO BONHAM
LINE.

* OTHER IMPACTS...TEMPERATURES WILL FALL INTO THE LOWER TEENS
FOR LOWS TONIGHT INTO THURSDAY MORNING. TEMPERATURES THIS COLD
CAN CAUSE EXPOSED PIPES TO BURST. TAKE PRECAUTIONS TO PROTECT
OUTDOOR PIPES.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WIND CHILL ADVISORY MEANS THAT VERY COLD AIR AND STRONG WINDS
WILL COMBINE TO GENERATE LOW WIND CHILLS. PROLONGED EXPOSURE TO
THE COLD MAY RESULT IN FROSTBITE AND LEAD TO HYPOTHERMIA IF
PRECAUTIONS ARE NOT TAKEN. IF YOU MUST VENTURE OUTDOORS...WEAR A
HAT AND GLOVES. REMEMBER TO BRING YOUR PETS INDOORS AND PROTECT
ANY EXPOSED METAL PIPES.

&&

[GRAYSONCO.WX]

FW NWS Issued Winter Weather Advisory for these counties: MONTAGUE-YOUNG-JACK-STEPHENS-PALO PINTO-EASTLAND.

[GRAYSONCO.WX]

Just issued ...


URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE FORT WORTH TX
249 PM CST WED FEB 5 2014

TXZ091-100-101-115-116-129-060500-
/O.NEW.KFWD.WW.Y.0004.140206T0900Z-140206T2000Z/
/O.CON.KFWD.WC.Y.0002.140206T0900Z-140206T1800Z/
MONTAGUE-YOUNG-JACK-STEPHENS-PALO PINTO-EASTLAND-
INCLUDING THE CITIES OF...BOWIE...NOCONA...GRAHAM...OLNEY...
JACKSBORO...BRECKENRIDGE...MINERAL WELLS...CISCO...EASTLAND...
RANGER...GORMAN
249 PM CST WED FEB 5 2014

...WINTER WEATHER ADVISORY IN EFFECT FROM 3 AM TO 2 PM CST
THURSDAY...
...WIND CHILL ADVISORY REMAINS IN EFFECT FROM 3 AM TO NOON CST
THURSDAY...

THE NATIONAL WEATHER SERVICE IN FORT WORTH HAS ISSUED A WINTER
WEATHER ADVISORY FOR SNOW...WHICH IS IN EFFECT FROM 3 AM TO 2 PM CST
THURSDAY.

* TIMING...LIGHT TO MODERATE SNOW IS EXPECTED TO DEVELOP LATE
TONIGHT INTO EARLY THURSDAY MORNING ACROSS PARTS OF NORTH TEXAS.
THE BULK OF THE SNOW SHOULD COME DOWN BETWEEN 5 AM AND NOON.

* MAIN IMPACT...SNOWFALL ACCUMULATIONS WILL GENERALLY RANGE
BETWEEN 1 AND 2 INCHES WEST OF AN EASTLAND TO JACKSBORO TO BOWIE
LINE THROUGH MIDDAY THURSDAY. SNOWFALL IS EXPECTED TO BE LIGHT
AND POWDERY...AND TEMPERATURES WILL BE SUFFICIENTLY COLD FOR ANY
SNOW TO STICK TO AREA ROADS. TRAVEL MAY BECOME HAZARDOUS ACROSS
WESTERN PORTIONS OF NORTH TEXAS DURING THE DAY THURSDAY.

* WIND CHILL VALUES...WIND CHILL VALUES OF 0 TO MINUS 5 DEGREES
ARE EXPECTED LATE TONIGHT INTO EARLY THURSDAY MORNING.

* OTHER IMPACTS...TEMPERATURES WILL FALL INTO THE LOWER TEENS
FOR LOWS TONIGHT INTO THURSDAY MORNING. TEMPERATURES THIS COLD
CAN CAUSE EXPOSED PIPES TO BURST. TAKE PRECAUTIONS TO PROTECT
OUTDOOR PIPES.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WINTER WEATHER ADVISORY MEANS THAT PERIODS OF WINTER
PRECIPITATION MAY CAUSE TRAVEL DIFFICULTIES. BE PREPARED FOR
SLIPPERY ROADS AND PLAN ON SOME TRAVEL DELAYS.

A WIND CHILL ADVISORY MEANS THAT VERY COLD AIR AND STRONG WINDS
WILL COMBINE TO GENERATE LOW WIND CHILLS. PROLONGED EXPOSURE TO
THE COLD MAY RESULT IN FROSTBITE AND LEAD TO HYPOTHERMIA IF
PRECAUTIONS ARE NOT TAKEN. IF YOU MUST VENTURE OUTDOORS...WEAR A
HAT AND GLOVES. REMEMBER TO BRING YOUR PETS INDOORS AND PROTECT
ANY EXPOSED METAL PIPES.


&&

$$

TXZ092>094-102>104-117-130-060500-
/O.CON.KFWD.WC.Y.0002.140206T0900Z-140206T1800Z/
COOKE-GRAYSON-FANNIN-WISE-DENTON-COLLIN-PARKER-ERATH-
INCLUDING THE CITIES OF...GAINESVILLE...SHERMAN...DENISON...
BONHAM...DECATUR...BRIDGEPORT...DENTON...LEWISVILLE...
FLOWER MOUND...THE COLONY...PLANO...WEATHERFORD...BRIAR...
STEPHENVILLE...DUBLIN
249 PM CST WED FEB 5 2014

...WIND CHILL ADVISORY REMAINS IN EFFECT FROM 3 AM TO NOON CST
THURSDAY...

* WIND CHILL VALUES...WIND CHILL VALUES OF 0 TO MINUS 3 DEGREES
ARE EXPECTED LATE TONIGHT THROUGH THURSDAY MORNING FOR LOCATIONS
ALONG AND NORTH OF A CISCO TO WEATHERFORD TO MCKINNEY TO BONHAM
LINE.

* OTHER IMPACTS...TEMPERATURES WILL FALL INTO THE LOWER TEENS
FOR LOWS TONIGHT INTO THURSDAY MORNING. TEMPERATURES THIS COLD
CAN CAUSE EXPOSED PIPES TO BURST. TAKE PRECAUTIONS TO PROTECT
OUTDOOR PIPES.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WIND CHILL ADVISORY MEANS THAT VERY COLD AIR AND STRONG WINDS
WILL COMBINE TO GENERATE LOW WIND CHILLS. PROLONGED EXPOSURE TO
THE COLD MAY RESULT IN FROSTBITE AND LEAD TO HYPOTHERMIA IF
PRECAUTIONS ARE NOT TAKEN. IF YOU MUST VENTURE OUTDOORS...WEAR A
HAT AND GLOVES. REMEMBER TO BRING YOUR PETS INDOORS AND PROTECT
ANY EXPOSED METAL PIPES.

&&

You beat me to it

[Longhornmaniac8]

Post one for dfw please.

[Ntxw]

its a snow profile porta, remember the chart is diagonal, it will be all below freezing. Quite a good snowmaking profile if there was sufficient moisture, powder.

DFW is high ratio snow, again with sufficient moisture

[wxman57]

I see that there is very dry air above 700 mb, but does the entire air column need to be moist for precipitation to happen? I wouldn't think so (at least dry air aloft I wouldn't think would inhibit precipitation if there is moisture in the lower levels). By my interpretation, that Skew-T shows fairly moist air (close temp/dew point spread) from 400 to 725 mb or so, and then slightly dryer air below that. I don't have a good grasp for how big a gap that actually is below 725.

Am I interpreting that correctly? And would the spread shown produce enough moisture for anything other than virga?

Cheers,
Cameron

Edit: I keep changing the numbers as I look at it more.

No, precip can develop in an area where the red and green lines are close together for only a few thousand feet. What's important is that the region where the two lines are close together is close to the surface. The gap below 725(mb) is not huge, but it doesn't indicate much clouds or precip in the lower levels. That would mean that any precip falling from above, say, 725mb would likely evaporate (sublimate) and moisten up the lower levels before it would reach the ground. Evaporating or sublimating precip would also have the effect of cooling the lower levels, as it takes heat to evaporate rain or sublimate ice.

A better sounding for significant snow would have the two lines nearly touching down to maybe 900mb (or lower).