February: Tracking Rain/Wintry Mix & Arctic Front

[Paul Robison]

Note: My previous post re: Friday Arctic front contained no drama. BUT: I do want to know if MEX guidance specifies heavy ice or light ice for Friday night/Saturday period at Hobby. I got to do a little flying that day.

[niner21]

Well... Got some racing to do up in Decatur TX next weekend and it's showing some wintry garbage next weekend. Any thoughts on next weekend or are we to far out for that ?

Cold we can do, wet and icy aren't good for road racing.

What kind of race? Bike or run? I have the woodlands marathon next weekend, I am an ultra marathoner, can run in or on anything. If its a run you can surely do it and be fine, bike not so sure.

No, we do auto racing. Rain no es bueno for running around a race track with 65 other idiots like myself.

Please Lord give us sunshine

[srainhoutx]

Not a lot of changes overnight with the current thinking. The only issues is the GFS came in a tad 'colder' at IAH suggesting temperatures may drop to 31/32F early Tuesday morning with light freezing drizzle possible. Look for Winter Weather Advisories to be hoisted later today across portions of SE Texas mainly N and E of Metro Houston. Those with travel plans tomorrow may need to delay your trip by 24-36 hours if your travel plans are to Central/N/NE Texas into Louisiana and locations further E.

[srainhoutx]

Morning briefing from Jeff:

Winter Storm heading for TX.

Increasing threat for ice accumulation over portions of SE TX Monday evening-Tuesday morning.

Surface cool front currently lies along a line from Columbus to BUSH IAH to Cleveland with temperatures falling into the 50’s north of this boundary and rising into the 70’s south of the boundary. Front has shown very little movement this morning and do not expect much more southerly progress for much of today…in fact some of the high resolution guidance actually lifts the front back northward midday. Of bigger importance is the arctic front currently plowing through the panhandle. Temperatures behind this boundary are in the 10’s and this air mass is moving quickly southward and should push across SE TX and off the coast this evening with a much more significant temperature fall.

Strong cold air advection will onset this evening and continue Monday. Temperatures will fall from this evening through the day on Monday. Temperatures Monday morning in the lower 40’s will gradually fall during the day toward the mid 30’s by late afternoon as ice/sleet accumulation develops over north TX on Monday. Model guidance has trended a degree or two colder for Monday night and Tuesday morning which requires the freezing line to be shifted southward bringing more of the area under the threat for freezing drizzle. Additionally, what seemed marginal freezing temperatures yesterday (30-32) are now expected to be closer to 28-30 over our northern counties Tuesday morning and this is certainly into the critical threshold for ice accumulation on bridges and overpasses. Forecast profiles continue to support a very strong warm layer aloft over top of a shallow surface freezing layer (maybe 1000-2000 ft thick). This continues to support a rain/freezing rain P-type…however some of the latest soundings are showing a smaller warm layer aloft from Huntsville to Livingston Tuesday morning and this could support a mixture of freezing rain and sleet over Walker, Polk, Trinity, and San Jacinto Counties.

Freezing Line:
Of course the critical factor is how far south the freezing line progresses into the region. Current indications suggest the freezing line will extend from Columbus to Waller to between Conroe/The Woodlands to Cleveland from late Monday evening through Tuesday morning. This line has been shifted southward about 50 miles since yesterday. Both GFS and NAM guidance do suggest BUSH IAH does fall to 31-32 for a window Tuesday morning and this is possible between roughly 1100pm Monday and 900am Tuesday. Official forecast has IAH falling to 32 Tuesday morning so pockets of freezing temperatures are possible over northern and northwest Harris County overnight Monday into Tuesday morning. Best thinking at the moment is that the north and west portions of Harris County will fall to 32-33 with the rest of the county and metro Houston falling to 33-34. A degree or two could make all the difference between minor ice accumulation in Harris County and no ice at all.

Ice Accumulation:
Forecast models show general lift being maintained Monday night into early Tuesday when critical temperatures will be reached over portions of the area. Liquid QPF amounts range from .05-.10 of an inch in mainly a drizzle or light rain. Ice accumulation will be greatest from Huntsville to Livingston where temperatures will be colder the longest and likely fall into the upper 20’s resulting in effective freezing of the liquid precipitation. Accumulations in this area will likely average .05-.10 of an inch which is just under the .12 of an inch for our local winter storm warning criteria. North of a line from Columbus to Waller to Conroe to Cleveland ice accumulation of .03-.06 of an inch is possible. Temperatures in this area will be in the 30-32 degree range resulting in a less effective freezing process since the falling precipitation will need to be cooled after passing through the warm layer aloft. Bridges and overpasses are also fairly warm from the recent warmth and will take time to cool to freezing so this region has a more conditional ice accumulation threat especially on bridges and overpasses.

Decision Support Matrix:

Burleson, Madison, Walker, Trinity, San Jacinto, Polk:

Ice Accumulation: .05-.10 of an inch

Timing: 600pm Monday-1000am Tuesday

Temperatures: 28-30 degrees

Winds: NNE 10-15mph

Confidence: high



Transportation: prepare for anti-ice operations

Education: delays and cancellations possible

Aviation: anti-ice operations likely

Power: isolated outages possible

Brazos, Grimes, Washington, Montgomery, Waller, northern Liberty:

Ice Accumulation: .03-.06 of an inch

Timing: 1000pm Monday-1000am Tuesday

Temperatures: 30-32 degrees

Winds: NNE 10-15mph

Confidence: moderate



Transportation: standby for anti-ice operations

Education: delays and cancellations possible

Aviation: anti-ice operations likely

Power: isolated outages possible

Austin, Colorado, north Harris, central Liberty:

Ice Accumulation: patchy ice accumulation possible

Timing: 1100pm Monday-900am Tuesday

Temperatures: 31-33 degrees

Winds: NNE 10-15mph

Confidence: low to moderate



Transportation: monitor trends/standby equipment and personnel

Education: delays possible

Aviation: anti-ice operations possible at Hooks and IAH

Power: None

Fort Bend, southern Harris, Wharton, Jackson, Matagorda, Brazoria, Galveston, Chambers:

Ice Accumulation: None expected at this time

Timing: N/A

Temperatures: 33-35 degrees

Winds: NNE 14-18mph

Confidence: moderate



Transportation: None

Education: None

Aviation: None

Power: None

Will update again this evening.

[srainhoutx]

HGX issues Freezing Rain Advisories basically N of Austin, Waller, Harris, and Chambers Counties.

[ticka1]

come south!!!!

[jasons2k]

Snow is fun but I don't get why anyone would wish for ice. It's dangerous. All it does is jack-up the roads and cause misery. Plus with the spring bloom in progress it's just bad timing.

[Heat Miser]

Snow is fun but I don't get why anyone would wish for ice. It's dangerous. All it does is jack-up the roads and cause misery. Plus with the spring bloom in progress it's just bad timing.

Couldn't agree more. Anyone who's been in that stuff knows it's just dangerous and damaging. Snow, or nothing.

[sambucol]

come south!!!!

Yes!!!! Come south!!!

[srainhoutx]

The cold front is pushing south quickly now as a strong 1048+mb Arctic High has dropped into the Northern Plains. Temperatures as well as strong gusty N to NE winds are building in behind the front. Temperatures will fall through the 50's and 40's tonight into the 30's tomorrow. There likely will not be much of any warming tomorrow as cold air in the teens across Kansas and the Panhandle filters S. It was a nice Spring like day across Houston with a high of 78F at IAH.

[Andrew]

Models have severely underestimated the timing and intensity of the colder air dropping south to our west. Lubbock is already sitting at 21 degrees which is a good 5+ degrees colder than most of the guidance. The key will be how fast and strong can that air shift east before precipitation dies off. Also remember the shallowness of this cold air will be key as a lot of the warm air above can be dragged down with precipitation (especially if it gets heavy). That could limit overall frozen precipitation.

[BlueJay]

I agree srain, we did have a pretty good weekend.
Temps are really falling kind of fast. From a high of 73F temp has fallen down to 60F and feels chilly outside. It is very dark and gloomy.
Not looking forward to this next week to much. (SAD!)

[BlueJay]

Thanks for the update Andrew.
I guess I will bring in the plants and cover the most vulnerable.
Sigh.....

[tireman4]

It is 68 here. Slowly cooling down. Bagging my run today. Going to do 21 miles and run tomorrow in the cold. Now that will rock.

[tireman4]

Please have a weather eye to your local media outlets, the NWS and here. Andrew made a great point and this is an ever changing upcoming event.

[srainhoutx]

Evening briefing from Jeff:

Winter Storm heading for much of TX

NWS has issued a Freezing Rain Advisory for ice accumulations of .03-.07 of an inch from 600pm Monday until 900am Tuesday for the following counties: Burleson, Madison, Houston, Brazos, Washington, Grimes, Walker, Montgomery, Trinity, Polk, San Jacinto, and Liberty.

Arctic cold front plowing southward across TX this afternoon with 78 at BUSH IAH and 19 in Amarillo to 21 in Lubbock. Temperature in Lubbock is running about 3-4 degrees colder than what model guidance suggested and temperatures over N TX including DFW are running about 3 degrees colder at this time than expected. In fact numerous reports of light to moderate sleet is already being reported across N TX about 3-5 hours earlier than expected. General model consensus continues to indicate surface freezing line making good progress into the area late Monday afternoon and evening off the sleet and ice covered land of N TX. Forecast soundings show strong warm air advection above the surface cold dome with temperatures nearing 50 degrees a couple thousand feet above the surface. This will limit P-type to rain or freezing rain across the region and make the most critical forecast element the surface air temperature.

Current indications is that the freezing line will extend southward along and north of a line from Columbus to Waller to Conroe to Cleveland overnight Monday into early Tuesday with light freezing rain and freezing drizzle along and north of this line. Elevated objects such as trees, power lines, and bridges/overpasses will likely accumulate a thin glaze of ice potentially resulting in hazardous travel in the advisory counties.

Freezing line could move a little bit more southward than currently expected and impact Austin, Waller, and north/west Harris (Katy to Jersey Village to Kingwood). Current thinking is that these areas may just touch 32 for a few hours with some patchy ice possible. Only 1-2 degrees of additional cooling will make a big difference in this area between ice and no ice…so temperature trends will need very close monitoring on Monday, but this could also be offset by the current warm ground temperatures and warm bridge/overpass temperatures. Not very confident at exactly what temperature ice may form on bridges and overpasses given the recent warmth…experience last year suggested temperatures needed to fall into the 29-30 degree range…but that was also with pre-treatment solution applied.

Freezing Rain/ice accumulation (>.01 of an inch) threat probabilities:

http://www.hpc.ncep.noaa.gov/pwpf/wwd_a ... babilities

Decision Support Matrix:

Burleson, Houston, Madison, Walker, Trinity, San Jacinto, Polk:

Ice Accumulation: .03-.07 of an inch

Timing: 600pm Monday-1000am Tuesday

Temperatures: 28-30 degrees

Winds: NNE 10-15mph

Confidence: high



Transportation: anti-ice operations likely

Education: delays and cancellations possible

Aviation: anti-ice operations likely

Power: isolated outages possible

Brazos, Grimes, Washington, Montgomery, Waller, northern Liberty:

Ice Accumulation: .03-.05 of an inch

Timing: 1000pm Monday-1000am Tuesday

Temperatures: 30-32 degrees

Winds: NNE 10-15mph

Confidence: moderate



Transportation: prepare for anti-ice operations

Education: delays and cancellations possible

Aviation: anti-ice operations likely

Power: isolated outages possible

Austin, Colorado, north Harris (Katy-Jersey Village-Kingwood), central Liberty:

Ice Accumulation: patchy ice accumulation possible

Timing: 1100pm Monday-900am Tuesday

Temperatures: 31-33 degrees

Winds: NNE 10-15mph

Confidence: moderate



Transportation: monitor trends/standby equipment and personnel

Education: delays possible

Aviation: anti-ice operations possible at Hooks and IAH

Power: None

Fort Bend, southern Harris, Wharton, Jackson, Matagorda, Brazoria, Galveston, Chambers:

Ice Accumulation: None expected at this time

Timing: N/A

Temperatures: 33-35 degrees

Winds: NNE 14-18mph

Confidence: moderate



Transportation: None

Education: None

Aviation: None

Power: None

[Ptarmigan]

Models have severely underestimated the timing and intensity of the colder air dropping south to our west. Lubbock is already sitting at 21 degrees which is a good 5+ degrees colder than most of the guidance. The key will be how fast and strong can that air shift east before precipitation dies off. Also remember the shallowness of this cold air will be key as a lot of the warm air above can be dragged down with precipitation (especially if it gets heavy). That could limit overall frozen precipitation.

They have not handled it well this winter.

[srainhoutx]

Tropical convention developed fairly rapidly this afternoon SW of the Baja Peninsula. That moisture is being picked up and spreading NE with the strong upper low generating rainfall across Southern California this evening for the Oscar Ceremonies in Hollywood. The sub tropical jet is becoming very noisy and that trend may continue into Wednesday before the upper trough finally passes Wednesday night.

[jeff]

Currently 44 at CLL. 18Z GFS did not have CLL reaching 43 until 09Z Monday morning. It was forecasting a 00Z temperature of 51 (off by 7 degrees).

12Z NAM was forecasting a 00Z temp of 51 also and CLL not reaching 44 until 12Z Mon. OUCH.

[srainhoutx]

Currently 44 at CLL. 18Z GFS did not have CLL reaching 43 until 09Z Monday morning. It was forecasting a 00Z temperature of 51 (off by 7 degrees).

12Z NAM was forecasting a 00Z temp of 51 also and CLL not reaching 44 until 12Z Mon. OUCH.

That raises an eyebrow further S into Austin, Waller and the Northern half of Harris County for tomorrow afternoon. It seems that freezing line keeps creeping further S with every new guidance update.