December: New Years Eve Outlook

[srainhoutx]

Gfs has temps in the mid 30's for Houston with plenty of precip. the question is are the models underestimating the cold air due to its shallow nature? just a few degrees can make the difference between an ice storm or just a cold rain.

Don, I have been watching the GEFS (American ensembles) trend colder and colder with each run. It does appear that a secondary storm system may develop next weekend over the Southern Rockies where we may see leeside cyclogensis (surface up to 700mb low pressure) as another short wave dives down into the base of the trough across Arizona and New Mexico. The 168 hour 12Z European model has this feature again today.

12Z GEFS:

12012013 12Z GEFS gfs-ens_T2ma_namer_33.png

12Z Euro:

12012013 12Z Euro f168.gif

[srainhoutx]

On another note looking out into the second week of December, the 12Z Euro does suggest the cold air will remain entrenched across the Western and Central United States extending N into our source Regions of Alaska and the Western 2/3rds of Canada, if that guidance is correct.

[srainhoutx]

Afternoon Update from Jeff concerning the next Arctic Front:

Warm up in progress over the region today as the retreating arctic dome from last week is replaced with increasing warm air advection.

Very cold air mass is building over NW Canada poised to move southward this week.

After a cold end to the month of November, the first week of December will be mild with continuous warm air advection pumping moisture and a Gulf air mass into the region. Surface dewpoints will gradually increase each day through the week reaching the 60’s and possibly approaching 70 by the middle to end of the week. Recent cold air event over the NW Gulf has cooled nearshore water temperatures into the upper 50’s and low 60’s, so dewpoints rising above those levels could result in dense sea fog formation at some point by the middle of the week. Surface temperatures will warm well into the 70’s this week with lows rising into the upper 50’s and eventually the 60’s by Thursday. Rain chances begin to increase on Wednesday and Thursday as moisture deepens.

While we warm, bitter cold air mass will invade the NW US into much of the northern Rockies this week under the influence of a sprawling arctic high pressure dome. Impressive pressure differences are noted along the front range of Colorado by the middle of the week with some suggestion of 30+mb from NW to SE Colorado suggesting a very strong arctic boundary. Temperatures behind this boundary will be very cold for early December with anomalies running upwards of 20-30 degrees below normal for this time of year….this is some impressive cold air for this time of year.

There is little doubt that this cold is coming southward as is so often the case with shallow dense cold arctic air masses. Will see a powerful arctic boundary arrive into the state Thursday and plow off the coast on Friday. Temperatures ahead of the boundary will likely approach 80 on Thursday and Friday (depending on frontal timing) and then tumble behind the front. Rain and showers will accompany the frontal passage and linger in the post frontal cold air. Will easily see temperatures fall a solid 20 degrees with the front and 24-hr temperature differences between Friday and Saturday could be 30-40 degrees. Good potential for much of the area to fall into the 30’s Friday night and stay below 40 into the second week of December for both highs and lows. To complicate matters more, models have been fairly consistent in overrunning the shallow cold dome with plenty of moisture through the weekend resulting in cloudy conditions with periods of drizzle and light rain. Will have to address P-type issues at some point in the next few days as this air mass is colder than the one last week which would support freezing precipitation if surface temperatures are 32 degrees or colder. GFS model continues to hint at shallow surface sub-freezing layer with periods of light rain suggesting freezing rain is possible. Everyone should understand that we are talking 5-6 days out and the chances that the models are correct with the surface air temperature within 1-2 degrees is very unlikely which could make all the difference between ice and a very cold rain. Much uncertainty for next weekend into the second week of December with just how cold the area will get, for how long, and if there will be any winter precipitation.

[Portastorm]

OK, so earlier this afternoon I posted this: "I understand and appreciate the need for Texas-based NWSFOs to cautiously approach forecasts for wintry weather. No need in going "hog wild" five days out when things can (and often do) change. But in the case of my own local office, EWX, I think their take right now on Friday night-Saturday temperatures are going to bust horribly. They're waaaaay too warm. Forecasting a high in the low 40s on Saturday when even the warmest guidance (GFS) shows highs in the low 30s is a bit of a head scratcher.

I'm fairly confident they'll be moving those temps downward with each approaching forecast cycle. But it does create a disconnect when you tell people "get ready for next weekend" and they come back with "oh, I saw the forecast and the temperatures aren't even close to freezing."

Since I'm a firm believer in giving credit when it's due, I have to say "nice job" to the afternoon forecaster at EWX as their afternoon forecast discussion and forecasts have now placed chances of freezing rain in next weekend's forecast and Saturday's high temps are now predicted to be in the mid 30s as compared to the lower 40s as they had this morning. Kinda hard to ignore the overwhelming model support for next weekend. And no doubt that many WFOs will have their hands full in the next week with forecasts.

[wxman57]

I think it would take quite a bit deeper cold air for any snow down to southeast TX next weekend. And if the cold air gets that deep, then the wave that forms in the Gulf may form too far offshore to produce much precip inland. It's too early in the season to think snow in Houston. Most of our snow events come in Jan-Feb, though there have been a couple events in Dec (2004, 2008).

Here' the latest GFS meteogram for Houston. Temps holding in the lower 30s with a wave forming on the front in the Gulf. Such waves produce widespread stratiform precipitation, which should make next weekend pretty miserable across SE TX.

[Heat Miser]

Time to stock up on the firewood.
I know hate is a strong word, but I hate winter.

[wxman57]

Here's a plot of temps from the 18Z (noon) run of the GFS. Quite cold with cold rain next weekend. Maybe a bit of freezing rain and sleet:

[srainhoutx]

That is an impressive 1056mb Arctic High Pressure cell over Eastern Alaska where temps are currently running in the -30 to 40- F range.

[Portastorm]

New GFS- insane wacky fun way out in fantasy land.

Yeah ... once it gets to 10 days out ... oh my goodness. That kind of cold would bring a lot of misery and heartache to many in Texas, especially those who have never experienced such bitterly cold temperatures. A lot of pipe-busting there in that model run.

[srainhoutx]

New GFS- insane wacky fun way out in fantasy land.

Yeah ... once it gets to 10 days out ... oh my goodness. That kind of cold would bring a lot of misery and heartache to many in Texas, especially those who have never experienced such bitterly cold temperatures. A lot of pipe-busting there in that model run.

LOL...Polar Vortex just W of Hudson Bay and a cross Polar flow as Eastern Alaska and the Canadian Prairies reload.

12022013 12Z GFS f288.gif

[MontgomeryCoWx]

LOL, wow.... no words for that run.

[MontgomeryCoWx]

LOL, wow.... no words for that run.

Needs more cowbell, er, moisture...

Yes... yes it does! Anything that would fall I would assume would be snow.

[srainhoutx]

Since the HPC/WPC is somewhat discounting the American models for the coming weekend in favor of the non NCEP guidance, The 12Z Canadian does develop a Coastal Low fairly close to the Middle and Upper Texas Coast next Saturday into Sunday. That time frame is probably the best shot we have of seeing any wintry mischief across the Region if it is going to happen this event.

12022013 12Z CMC f138.gif

12022013 12Z CMC f144.gif

12022013 12Z CMC f150.gif

[vci_guy2003]

So that new GFS run is not for this weekend? it's for later on? I don't hear much about the winter precip for this weekend.

[srainhoutx]

So that new GFS run is not for this weekend? it's for later on? I don't hear much about the winter precip for this weekend.

That long range GFS was for the weekend of the 13th. Everyone is waiting patiently to see just how the up coming weekend unfolds before biting too much on the wintry precip solution just yet. I believe some are a little 'gun shy' after the events just prior to Thanksgiving.

[srainhoutx]

The 12Z Euro does look very wet during the late Saturday into Sunday time frame. That model also suggests a strong surface/700mb low pressure system ejecting out of the Southern Rockies into the Plains with widespread snow across the Plains with temps near and below -20 C. It appears that icing issues may be a concern across portions of the Edwards Plateau/ Northern Hill Country into and W of the Dallas Ft Worth Metroplex.

[vci_guy2003]

Just out of curiousity, what does that model show as far as temps next weekend?

[srainhoutx]

Just out of curiousity, what does that model show as far as temps next weekend?

I know that wxman57 has access to the Euro guidance. Perhaps he can offer some input.

[ticka1]

are we talking about dec 7th weekend or dec 14th weekend!!

[MontgomeryCoWx]

This weekend will be "cool"... next weekend is supposed "arctic anvil" on our heads.