TX Winter WX Thread #6 - An Icy and Rough Weekend Ahead

[Portastorm]

The temperature keeps dropping in the Austin and surronding area but the NWS is calling for highs in the 60's? I don't see that happening unless the front is expected to return as a warm front. Very confusing!

I just read that myself, while noting that my camping buddies in Pedernales Falls (Johnson City) experienced FROPA at some point in the wee hours. Hmmmm? Wonder why? All those forecasts telling them no FROPA until Sunday or Sunday night couldn't have been WRONG could they?!

Jen, the good news for your friends is that the bulk of these torrential rains we've had in Austin are in Travis County proper and Pedernales Falls is getting wet but nothing terrible. Here in my part of Austin we are now nearing 3.0 inches of rainfall today.

The bad news is ... they're still probably cold and wet! Then again, some folks like that kind of camping!!

[Air Force Met]

Well at least the Dallas office has finally gotten it about the total accumulation. I couldn't understand why they were calling for .1-.3' yesterday.

Total daytime ice accumulation of 0.2 to 0.4 of an inch possible.

Tonight: Chance of precipitation is 100%. New ice accumulation of 0.4 to 0.6 of an inch possible.

Tomorrow: New ice accumulation of 0.4 to 0.6 of an inch possible.

That's about the 1" to 1 1/2" I was expecting.

[ROCK]

Not that bad tomorrow? I am not going to outside in 40ish (falling temps), wet, and lower 30's wind chill......oh brother.....and I thought ED B, Frank B were bad....

I am covering my plants this afternoon.....no way I am doing it tomorrow....

[jeff]

Threat is increasing for significant ice storm

Potential for crippling ice accumulations.

Discussion:

Front is into SE TX way ahead of forecasted timing and about 18 hours ahead of model data...anybody surprised? Front has passed College Station where the temps. fell to 53 and it is in the 60's at Brenham. Will drive the front to I-10 by early evening and then on off the coast by early Sunday morning with shallow arctic air mass filtering in. Will see highs early on Sunday with temps. falling throughout the day into the 30's under strong NW winds. Freezing line enters our northern counties Sunday afternoon and progresses southward Sunday night likely reaching I-10 Monday midday. Freezing line moves on to the coast by Monday night and this is where things go rapidly downhill.

Precip/P-type:

Winter Storm Watches will likely be issued this afternoon for northern counties and expanded southward on Sunday.

Moist SW flow aloft with several disturbances will overrun the shallow arctic air at the surface producing periods of rain into the cold dome which will range from 1500 to 2500 feet thick. Will onset freezing rain and glazing across the northern tier counties Sunday evening and progress it southward into metro Houston Monday afternoon. Will bring freezing rain all the way to the coast by Tuesday morning with the entire area seeing a freezing rain and sleet mixture Tuesday. May need to consider adding sleet and snow mix for Tuesday night north of I-10 as the cold air deepens, but will hold off and focus on the ice for the time being.

Accumulations:

Prolonged nature of the freezing rain may have very bad results. Accumulations of .25 to .75 of an inch will be common with some locations along I-10 possibly seeing .75 to 1.5 inches of icing. Expect glazing of bridges to begin Sunday evening north and Metro Houston Monday afternoon. Significant ice accumulation on power lines and vegetation will likely result in failures by Tuesday.

Preparations:

Residents should be prepared for an extended period of sub-freezing temps. and very hazardous driving. Stock up on water, gas, and food and be prepared for extended power outages. Plants and pipes should be protected, Public works crews and TXDOT have crews on standby to apply de-icing agent on area freeways and sanding operations. Expect problems to spread from the NW to SE across the county Monday with high freeway connectors being the first problems. BY Tuesday morning ice will likely be everywhere including the freeway main lanes and all side surface streets.

Public Forecast for Harris and Surrounding Counties:

Today: mostly cloudy warm and humid this morning with a 60% chance of showers this afternoon. Highs in the mid to upper 70's then falling into the upper 40's late. S wind shifting to the N and increasing 20-30mph.

Tonight: cloudy and turning much colder with a 60% chance of rain. Temps. falling into the low 40's. N winds 20-30mph.

Sunday: cloudy and cold with temps. falling into the mid 30's. A 60% chance of rain. N winds 15-25mph

Sunday night: cloudy and cold temps. steady in the low to mid 30's. A 60% chance of rain.

Monday: cloudy and very cold with temps. falling into the upper 20's and low 30's. A 60% chance of rain changing to freezing rain possibly mixed with sleet. Accumulation of 1/10th the 1/4th of an inch possible.

Monday Night: Winter Storm Conditions, Cloudy with near steady temps. in the upper 20's to near 30. A 60% chance of freezing rain and sleet. Additional ice accumulations of 1/4th to 1/2 an inch.

Tuesday: Winter Storm Conditions, Cloudy with near steady temps. in the upper 20's to lower 30's. A 60% chance of freezing rain and sleet. Additional ice accumulation of 1/4th to 1/2 an inch.

Tuesday night: Winter Storm Conditions, Cloudy with near steady temps. in the upper 20's. A 60% chance of freezing rain and sleet early changing to sleet and snow after midnight. Additional accumulation of ice of 1/10 to 1/4th an inch. Accumulation of sleet or snow may reach 1.0 inch.

Wednesday: Cloudy with a 30% chance of morning sleet and snow. Temps. nearly steady in the low 30's. Additional accumulation of ice or sleet less than 1/0th of an inch.

Next update this afternoon.

[Johnny]

I can do a heck of alot better job than Mario can any day of the week. Isn't that pathetic?

[JenBayles]

Not that bad tomorrow? I am not going to outside in 40ish (falling temps), wet, and lower 30's wind chill......oh brother.....and I thought ED B, Frank B were bad....

I am covering my plants this afternoon.....no way I am doing it tomorrow....

Same here - IMHO, everyone in the Houston metro should finish prep today, and the earlier the better.

[JenBayles]

I can do a heck of alot better job than Mario can any day of the week. Isn't that pathetic?

I feel like I'm in the Twilight Zone watching these OCMs. They all look so shocked and confused when the front is actually knocking on their doorsteps, but stubbornly go with what the computers tell them to say. Don't know whether to laugh or cry! At any rate, they're finally coming on board... a day late and a few degrees short, but JEEZ!

[double D]

According to the latest 6z gfs, we might have to go through the same thing next weekend (if i'm looking at it right).

[Extremeweatherguy]

yeah, these on air mets have been pretty bad lately. The only ones I can truly say are doing somewhat "ok" are David Paul (KHOU)<<he's been actually doing "good", David Tillman (ABC13) and a few of the mets I saw on CW39. Other than that though...Channel 2 is pretty much a joke (still calling for 40 on Monday) and Mario Gomez on Channel 11 is not worth watching either.

[wxman57]

Taking a look at the front this morning, I see a VERY SHALLOW layer of modified Arctic air south of College Station and just south of Austin. I've plotted some model soundings using RUC to demonstrate how shallow the cold air really is.

First, here's College Station:
http://myweb.cableone.net/nolasue/cll.gif

Since most of you won't understand that chart, I'll explain. The cold air over College Station is maybe 1000 ft deep. Above that level, the wind is from the south at 35-45 mph and the temperature is in the 16C range (low 60s or so). Freezing level aloft near 11,500 ft.

Over in Austin:
http://myweb.cableone.net/nolasue/aus.gif

The cold air in Austin is maybe 1500-2000 ft thick with temperatures in the low 60s just above that level and south winds 30-45 mph. Freezing level aloft just above 11,500 ft.

Farther north in Waco:
http://myweb.cableone.net/nolasue/act.gif

In Waco, the cold air is a bit deeper, maybe 2000-2500 ft. Temps just above the frontal boundary are near 60 with a S-SSW wind of 35-45 mph in the warm air. Freezing level aloft near 11,500 ft.

Dallas:
http://myweb.cableone.net/nolasue/dfw.gif

In Dallas, the cold air is still deeper, maybe 2500-3000 ft thick with upper 50s above that. Freezing level aloft is in the 11,000 ft range. So lots of warm air above the surface near-freezing layer. This will limit precip to freezing rain and sleet. No snow.

Now let's look in Oklahoma City where the cold air is much deeper:
http://myweb.cableone.net/nolasue/okc.gif

The graphic indicates that the cold air is about 6000 ft thick with a sub-freezing layer from the surface to 4000 ft. That's enough for snow. Above that cold layer is a warm pocket with temps in the upper 40s for a bit then dropping back to freezing aloft at about 10,500 ft.

So the cold air is VERY shallow on the leading edge of the front now. With a very warm ground ahead of it, the leading edge of cold air should steadily modify today. I think the boundary will reach central Houston by this evening, but I don't think the temps will immediately fall into the 30s behind the front as they did up north. Upper 40s to low 50s more likely post-frontal at least for a while in Houston.

Maybe mid 40s or so tomorrow morning and then a slow, steady drop toward mid to late afternoon Sunday when the secondary surge of Arctic air arrives. After that, it's low-mid 30s through at least Wednesday morning. Good chance of freezing rain here from Monday afternoon through Wednesday morning. Freezing rain amounts will be greatest around I-10 corridor and just north of there, decreasing south of I-10 -- particularly around Galveston Bay.

[Portastorm]

We've got high-water rescues occuring now in downtown Austin!!

If any of you know Austin's roads ... Mopac is closed in the northern part of the city due to flooding, along with a bunch of other problems.

OK ... resume Ice Storm 2007 discussion.

[JenBayles]

Whoa - Mopac is closed?! What a snarl that must be generating!

[JenBayles]

wxman57, many thanks for that post, graphics and particularly, the explanation. You answered several questions at once for me.

[Air Force Met]

Taking a look at the front this morning, I see a VERY SHALLOW layer of modified Arctic air south of College Station and just south of Austin. I've plotted some model soundings using RUC to demonstrate how shallow the cold air really is.

Here are some satellite soundings that show how shallow the air is...

http://www.orbit.nesdis.noaa.gov/smcd/o ... l/hlr.html

http://www.orbit.nesdis.noaa.gov/smcd/o ... l/dfw.html

[wxman57]

Taking a look at the front this morning, I see a VERY SHALLOW layer of modified Arctic air south of College Station and just south of Austin. I've plotted some model soundings using RUC to demonstrate how shallow the cold air really is.

Here are some satellite soundings that show how shallow the air is...

http://www.orbit.nesdis.noaa.gov/smcd/o ... l/hlr.html

http://www.orbit.nesdis.noaa.gov/smcd/o ... l/dfw.html

Thanks, AFM. Didn't know those soundings existed. I wonder how accurate they are through thick cloud cover?

[TrekkerCC]

Taking a look at the front this morning, I see a VERY SHALLOW layer of modified Arctic air south of College Station and just south of Austin. I've plotted some model soundings using RUC to demonstrate how shallow the cold air really is.

Here are some satellite soundings that show how shallow the air is...

http://www.orbit.nesdis.noaa.gov/smcd/o ... l/hlr.html

http://www.orbit.nesdis.noaa.gov/smcd/o ... l/dfw.html

Thanks, AFM. Didn't know those soundings existed. I wonder how accurate they are through thick cloud cover?

I'll let AF_Met answer about how accurate they are. From what I read, the GOES soundings use model (AVN/GFS) to derive a first estimate, then use GOES information to update the profile. Usually, from what I remember from the reading, the usual thing that is changed from the "model" sounding is the moisture profile. Also, GOES soundings will not be produced in conditions of total cloudiness. That's about the limit of my knowledge.

[Air Force Met]

Taking a look at the front this morning, I see a VERY SHALLOW layer of modified Arctic air south of College Station and just south of Austin. I've plotted some model soundings using RUC to demonstrate how shallow the cold air really is.

Here are some satellite soundings that show how shallow the air is...

http://www.orbit.nesdis.noaa.gov/smcd/o ... l/hlr.html

http://www.orbit.nesdis.noaa.gov/smcd/o ... l/dfw.html

Thanks, AFM. Didn't know those soundings existed. I wonder how accurate they are through thick cloud cover?

They are very accurate. If the cloud cover is too thick...you won't be able to get a sounding and the link will be red.

Here is the main page:
http://www.orbit.nesdis.noaa.gov/smcd/o ... whome.html

I use them all the time...especially during the spring and summer for severe weather. The other sounding fields are here:

http://www.orbit.nesdis.noaa.gov/smcd/o ... ields.html

This gives you a good broad-brush of the CAPE and LI (Etc) over a wide area. Again...excellent during spring/suumer for severe.

[aggiecutter]

The front still hasnt passed through Texarkana. It is still about 10 miles to the west, moving eastward at 5. Texarkana should have frontal passage within the next couple hours. 30 miles west of here, Temperatures are already in the upper 30's.

I just checked the local observation for Dallas, and they are still above freezing at 34 with a dewpoint of 32. I also checked Denton, which is just up the road, and they are at 31 with a dewpoint of 28, so the colder, drier air is steadily diving southward.

Dallas should be to the freezing point by noon. I dont think the freezing line reaches the Texarkana area until sometime tomorrow morning. That might sound like good news, but the models are still predicting another couple inches of precip after that period into late Monday.

I think the significant icing will be north and west of a Pine Bluff, Arkansas, Shreveport, LA, College Station, Tx to Austin, Tx line. IMO, SE of that line temperatures are problematic as far as winter precip are concerned, atleast significant winter weather.

[Air Force Met]

Taking a look at the front this morning, I see a VERY SHALLOW layer of modified Arctic air south of College Station and just south of Austin. I've plotted some model soundings using RUC to demonstrate how shallow the cold air really is.

Here are some satellite soundings that show how shallow the air is...

http://www.orbit.nesdis.noaa.gov/smcd/o ... l/hlr.html

http://www.orbit.nesdis.noaa.gov/smcd/o ... l/dfw.html

Thanks, AFM. Didn't know those soundings existed. I wonder how accurate they are through thick cloud cover?

I'll let AF_Met answer about how accurate they are. From what I read, the GOES soundings use model (AVN/GFS) to derive a first estimate, then use GOES information to update the profile. Usually, from what I remember from the reading, the usual thing that is changed from the "model" sounding is the moisture profile. Also, GOES soundings will not be produced in conditions of total cloudiness. That's about the limit of my knowledge.

That's correct. And if there is going to be something messed up...it will be the moisture profile. The temp profile is usually fairly close. Sometimes the moisture profile can be off...which is why they give you the model data and the sensor data.

It also will have a hard tie handling extreme inversions...which can be the case with arctic air.

I use them with skew-t data. They work better when the atmosphere is "normal."

[Extremeweatherguy]

The front still hasnt passed through Texarkana. It is still about 10 miles to the west, moving eastward at 5. Texarkana should have frontal passage within the next couple hours. 30 miles west of here, Temperatures are already in the upper 30's.

I just checked the local observation for Dallas, and they are still above freezing at 34 with a dewpoint of 32. I also checked Denton, which is just up the road, and they are at 31 with a dewpoint of 28, so the colder, drier air is steadily diving southward.

Dallas should be to the freezing point by noon. I dont think the freezing line reaches the Texarkana area until sometime tomorrow morning. That might sound like good news, but the models are still predicting another couple inches of precip after that period into late Monday.

I think the significant icing will be north and west of a Pine Bluff, Arkansas, Shreveport, LA, College Station, Tx to Austin, Tx line. IMO, SE of that line temperatures are problematic as far as winter precip are concerned, atleast significant winter weather.

I don't know about that. If Jeff is right, then many in the Houston area could be looking at 1/4" to 3/4" of ice and a few places could see 1"+ along and near I-10. That would be significant indeed if it were to play out.