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

[CaptinCrunch]

Leading Axis of the front is south of Lubbock (NE winds) and is knocking on Wichita Fall's door.

http://www.weatherforyou.com/maps/temperature.shtml

The Arctic front just busted down the door in Wichita Falls. It's 42 now. Interesting to see how the latest ETA MOS temps did (considering the ETA tends to do a bit better than GFS with these fronts):

06Z ETA MOS Temps for SPS:
06Z -- 59 (actual 61)
09Z -- 58 (actual 60)
12Z -- 57 (actual 59)
14Z -- 56 (actual 42) (interpolated MOS fcst)
15Z -- 56
18Z -- 50
21Z -- 49
00Z -- 42

So ETA MOS temps are already 14F too warm for SPS. It's snowing right across the border in SW Oklahoma now in Lawton with 32 degrees. According to ETA MOS, Lawton is SUPPOSED to be in the mid 40s now.

We're going to see the above blown forecasts over and over again for the next few days. NWS offices will be struggling to keep up with the bitter cold. Dallas probably won't be above freezing for days.

Looking at DFW MOS temps, ETA MOS has DFW above 45 until late Sunday afternoon. Hmm, anyone want to bet me that it won't be below 45 by this afternoon?

As stated in earlier post, forecast and actual FRONPA is about 12 hrs off (earlier) so expect front into D/FW area around 7pm tonight, by then NWS FTW should have included rest of NTX under winter storm warning or Ice storm warning.

Front now thru Guthrie TX, Wichita Falls and Ada OK. Front is right on top of Ardmore OK now.

[jeff]

Arctic front moving through NC TX.



Increasing potential for freezing rain and sleet Monday through Wednesday across SE TX.



Protective measures for plants and pipes should be completed before Sunday.



Significant travel problems expected across the entire state.



Discussion:



Arctic front extends from NE OK to Wichita Falls to NE NM. Temps range from 64 at Dallas to 27 at Amarillo to 0 at Denver. Low teens moving through SW KS at this time should spill into OK and the TX panhandle later today. Frontal boundary is progressing southward faster than models expected…Wonder Why??? Front should clear N TX zones and enter N part of SE TX late Saturday night/early Sunday morning. GFS wants to stall the boundary between Waco and Huntsville for 18-24 hours on Sunday and does not show the front clearing the coast until after sunrise Monday…out the window the GFS goes again. No good reason why the front will stall and given density considerations and intensity of the cold air it is not going to just stop. Front should reach CLL between 600am and 1000am and metro areas between 800am and 100pm and then off the coast by 600pm.



Temps:



Upstream temps are running colder than forecast by the models…anybody surprise this morning?? Will heavily undercut guidance in the post frontal air mass as large snow pack north of TX is allowing for little modification. Freezing line should reach the northern counties early Monday morning and progress southward during the day. Hard to nail down where this line holds up on Monday and this will have major P-type and accumulation issues. By Monday night the freezing line should reach the US 59 corridor and the coast by Tuesday morning. Temps. will remain at or below freezing through Tuesday and into midday Wednesday.



Precip/P-type:



Confidence is growing in prolonged icing/sleet event for SE TX including metro areas.



GFS and other models show overrunning of the arctic boundary starting late Sunday. 850mb to 700mb flow remains out of the S and SW bringing moisture atop the arctic dome at the surface. Surface low pressure looks to form on the arctic boundary off the lower TX coast Monday applying more moisture overhead. Additionally an active sub-tropical jet will bring weak short waves across the region adding the lift.



Problem is the surface temps. will fall to or below freezing resulting in melted snow aloft to become supercooled before striking the ground and then freezing on contact…freezing rain. The result is a sheet of ice or glazing which will coat any object’s surface that is below freezing. Expect freezing rain to onset with the onset of freezing surface temps. Monday morning for our northern counties and then spreading southward during the day. Am tempted to bring icing into Harris County Monday afternoon, but will hold off until Monday night as temps. may hover steady Monday in the mid 30’s and the ice line may stay over Waller and Montgomery counties.



Not so lucky Monday night through Wednesday. Freezing line should progress southward to the coast with freezing rain and icing all locations. Cold air begins to deepen with time and sleet will become mixed with the freezing rain forming a bumpy crusted layer on objects. Some hints that snow may also mix in Tuesday night into Wednesday morning N of I-10.



Accumulations:



Too soon to really discuss accumulation potential as we are still 72 hours out. Feel areas along and N of I-10 may see accumulations of ¼ to ½ of an inch which will weigh heavily on trees and power lines. Locations along and S of I-10 may see accumulations of 1/10th to 1/4th on an inch. Accumulation amounts heavily depend on the onset time of the freezing rain and the duration. Expect bridges and overpasses to ice over by Tuesday morning and secondary side streets and freeway main lanes to become ice covered and slippery by Tuesday night and Wednesday morning. Warm ground temps. may help melt some of the ice and sleet however how much is questionable and depends on the surface temp. Accumulation amounts will be fine tuned as the event draws near. Expect Winter Storm Watch or Ice Storm Watch to be posted Sunday morning for portions of SE TX and be adjusted and redefined Monday to include much of the area.



Preparation:



Public works crews will load dump trucks with crushed chatrock/limestone mixture and equip with spreaders today. TXDOT crews are on stand by to deploy anti-ice chemical to freeway overpasses and bridges this weekend before the event is underway…however expected pre-frontal rains may negate this effort and wash the chemical off the freeway before it dries. Sanding operations will begin once ice is reported on any roadway surface...however significant travel problems are likely if the current forecast holds…and travel may be nearly impossible Tuesday and Wednesday.



Icing may become enough to break tree limbs and down power lines and residents should be prepared to power outages and lack of heating. Trees at most risk are pines, evergreens, and those with any foliage still left. A large size Oak Tree with 1.0 inch of ice loads nearly 1 ton of weight on the tree.



Exposed outside pipes should be wrapped and covered to protect against freezing. Plants should be covered and braced as ice accumulation on larger covering surfaces may result in the entire plant being destroyed.



As with all winter weather events there will be fluctuations in the forecast up until the event starts. P-type and accumulation amounts will change over the next 2-3 days as we get closer to the event and it becomes better defined. Confidence is always low in SE TX when dealing with winter weather.



Public Forecast for Harris and Surrounding Counties:



Today through Saturday night: cloudy with a 40% chance of showers. Warm with lows in the 60’s and highs in the mid 70’s. S wind 10-15mph



Sunday: cloudy with a 70% chance of showers and thunderstorms. Turning much colder. Highs in the morning in the low 70’s with temps falling into the upper 30’s during the afternoon. S wind shifting to the north and increasing 20-30mph.



Sunday night: cloudy and cold with a 40% chance of light rain. Lows in the mid 30’s. NW winds 15-25mph and gusty.



Monday: cloudy and very cold with near steady temps. from 32 to 35. A 40% chance of light rain possibly freezing rain. Minor accumulation is possible.



Monday Night: Cloudy with freezing rain and sleet. Lows from 28-32. Chance of precipitation is 60%. Ice accumulation is likely.



Tuesday: Cloudy and very cold with a 60% chance of mixed precipitation. Near steady temps. from 29-33. Ice/sleet accumulation is likely.



Tuesday night: cloudy and cold with a 50% chance of mixed precipitation. Near steady temps. from 28-31. Ice/sleet accumulation is likely.



Wednesday: cloudy and cold with a 40% chance of morning sleet. Temps. near steady through noon around 30 then rising into the mid 30’s by afternoon. Morning sleet accumulation possible.



Thursday: cloudy and continued cold. Lows near 30 and highs in the low 40’s.

[aggiecutter]

The air mass is quite a bit colder than a lot of the local mets were anticipating. Currently, there are -20degree temps in the northern plains and the teens are about to enter northern Oklahoma and the Texas panhandle. Looking at the latest moisture feed makes me think that the northern third of Texas has the potential to have a devastating ice storm, particularly if the freezing temps get into the eastern part of North Texas, which at this time is starting to look more likely, where there is a lot of foliage.

Current Temperatures:
http://twister.sbs.ohio-state.edu/surface/ustemp.gif

[rlltex]

One of ou rlocal stations in Beaumont has been sticking to ABOVE freezing lows for all of next week. This am she said it was because the ground is to warm to allow temps to drop that low. Could some of you guys give me a better take on that?

[aggiecutter]

Look like this pattern is locked in for atleast the next couple weeks. For those in Austin, the Omega Block will spare ya'll any winter weather and cold.

Ensemble 850's: The hits keep coming:
http://www.cdc.noaa.gov/map/images/ens/ ... times.html

[Portastorm]

Look like this pattern is locked in for atleast the next couple weeks. For those in Austin, the Omega Block will spare ya'll any winter weather and cold.

Ensemble 850's: The hits keep coming:
http://www.cdc.noaa.gov/map/images/ens/ ... times.html

Don't make me come up there, aggiecutter!!

[cctxhurricanewatcher]

One of ou rlocal stations in Beaumont has been sticking to ABOVE freezing lows for all of next week. This am she said it was because the ground is to warm to allow temps to drop that low. Could some of you guys give me a better take on that?

Well when we had our snow back in 2004 down here in the Coastal Bend, some said that no way would it stick. If stuck around for two days after it fell. Ground temps can drop pretty quick if the cold is sustained and this spell has the markings to be one.

[wxman57]

One of ou rlocal stations in Beaumont has been sticking to ABOVE freezing lows for all of next week. This am she said it was because the ground is to warm to allow temps to drop that low. Could some of you guys give me a better take on that?

Well when we had our snow back in 2004 down here in the Coastal Bend, some said that no way would it stick. If stuck around for two days after it fell. Ground temps can drop pretty quick if the cold is sustained and this spell has the markings to be one.

Before snow can stick, it has to fall. It's highly questionable as to whether this very thin layer of sub-freezing Arctic air will support snow. Right above the Arctic air the temperature will be well above freezing, so any snow falling from above would melt in the warm layer above 1000-2000 ft.

[cctxhurricanewatcher]

One of ou rlocal stations in Beaumont has been sticking to ABOVE freezing lows for all of next week. This am she said it was because the ground is to warm to allow temps to drop that low. Could some of you guys give me a better take on that?

Well when we had our snow back in 2004 down here in the Coastal Bend, some said that no way would it stick. If stuck around for two days after it fell. Ground temps can drop pretty quick if the cold is sustained and this spell has the markings to be one.

Before snow can stick, it has to fall. It's highly questionable as to whether this very thin layer of sub-freezing Arctic air will support snow. Right above the Arctic air the temperature will be well above freezing, so any snow falling from above would melt in the warm layer above 1000-2000 ft.

Oh, I know that. I was just responding to his comment about what his area TV met said about it staying above freezing because the ground is to warm. Seems like that TV met ( if he is even a Met at all) will bust on that call.

[Portastorm]

I suspect we will be seeing many more notes from NWS Texas offices like this one in the next 24 hrs:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN ANGELO TX
904 AM CST FRI JAN 12 2007

.UPDATE...
DESPITE A LOT OF UNCERTAINITY HAVE EXTENDED WINTER STORM WATCH TO
THE SOUTH TO INCLUDE STERLING...COKE...RUNNELS ...COLEMAN AND
BROWN COUNTIES. THESE COUNTIES ARE ON THE BORDER OF WHERE THE
FREESING DRIZZLE AND FREEZING RAIN IS EXPECTED TO OCCUR.

[Tireman4]

Our local met from KHOU, David Paul really looks worried about this situation. I have noticed that temperatures are colder than the models forecasted. I do realize that GFS has a terrible time with cold air, but this event COULD be really bad. My question is, when the precipitation comes out of the clouds, is it a crap shoot as to whether it will be sleet or freezing rain, or is there a scientific way to know?

[Portastorm]

Our local met from KHOU, David Paul really looks worried about this situation. I have noticed that temperatures are colder than the models forecasted. I do realize that GFS has a terrible time with cold air, but this event COULD be really bad. My question is, when the precipitation comes out of the clouds, is it a crap shoot as to whether it will be sleet or freezing rain, or is there a scientific way to know?

Well Tireman4, he SHOULD be worried. If we indeed get a surface low development in the western GOM after 72 hrs ... that will sling a ton of moisture on top of the shallow arctic air ... after some overrunning has already occurred.

[JenBayles]

My question is, when the precipitation comes out of the clouds, is it a crap shoot as to whether it will be sleet or freezing rain, or is there a scientific way to know?

From Jeff's post above:

Problem is the surface temps. will fall to or below freezing resulting in melted snow aloft to become supercooled before striking the ground and then freezing on contact…freezing rain.

My understanding is you have to look at temps at various levels of the atmosphere. Snow falls into a warmer layer, melts, recrystalizes in the cold surface layer and refreezes either into sleet or freezing rain. I'm certain one of our more knowledgeable members can give a far better explanation.

[gboudx]

The DFW NWS didn't seem all that concerned for this area in the morning AFD. I get the impression some folks here think that will bust. I haven't been able to really pay too much attention yet, so I'm curious about why we might go from no SWS to an Ice Storm Warning.

[wxman57]

New ETA MOS for DFW has temps in the 27-31 range next 2 days with high chance of precip. So much for the 40s Sat/Sun. Last Dallas AFD had 37-40 for Saturday. Probably won't be that warm all day. I've been watching these Arctic fronts "surprise" the local NWS offices for 2 1/2 decades and am always amazed that they never see it coming. Must be a new crop of forecasters every year or two who have to learn all over again what an Arctic front can do.

[Portastorm]

New ETA MOS for DFW has temps in the 27-31 range next 2 days with high chance of precip. So much for the 40s Sat/Sun. Last Dallas AFD had 37-40 for Saturday. Probably won't be that warm all day. I've been watching these Arctic fronts "surprise" the local NWS offices for 2 1/2 decades and am always amazed that they never see it coming. Must be a new crop of forecasters every year or two who have to learn all over again what an Arctic front can do.

Us weather weenies wonder the same thing, Wxman57!

To their credit, Amarillo NWS and Lubbock NWS have been all over this event so far and done well. Maybe they should do a day seminar for their Texas colleagues in other parts!!

[double D]

NWS Amarillo thought that the temperature would fall to 26 by 5pm, but they are already at 22 degrees (much faster than they thought) I wonder if it will drop even more. This cold air was handled poorly by the models.

[wxman57]

The DFW NWS didn't seem all that concerned for this area in the morning AFD. I get the impression some folks here think that will bust. I haven't been able to really pay too much attention yet, so I'm curious about why we might go from no SWS to an Ice Storm Warning.

I did some front mocement calculations. Between 00Z and 12Z it moved 10.6 kts. From 9Z-13Z it moved about the same in the direction of Dallas. At 8am CDT it was 88 miles from Dallas, that puts it into central Dallas around 4pm this afternoon. Within 2 hours after FROPA, the temperature will be in the upper 30s and falling. Probably below freeezing in Dallas before midnight. With precip likely the next few days, you'll be in a warning soon.

[cajungal]

I know this discussion has mainly been about Texas. Should residents in SE Louisiana expect similar conditions? Our local news (New Orleans) has been giving a high of 48 degrees and lows around 35 for Tuesday. Not even below freezing for lows. But, with rain. It sounds like a miserable, nasty day to be out and cold, but not brutally cold.

[gboudx]

Thanks wxman57. Guess I'll make a trip to Lowe's during lunch to get a few things to protect the plants and faucets.