November Weather Discussion. Rollercoaster Pattern.

[wxman57]

Wxman57's meteogram is still going to kill all the beautiful lush banana plant foliage.


Not going to shoot the messenger, he's the play by play announcer at the Texans game, not the head coach, but cold without school cancelling winter precip is just depressing.

Maybe not. It really takes temps into the mid to upper 20s to impact Banana plants. I have some bananas in my backyard that are nearly a foot in diameter and up into the power lines. I know they can take a light freeze easily.

[wxman57]

srain mentioned Great Falls, MT, so I thought it might be fun to look at the latest GFS projection for temps there this week. -19F for Wednesday morning but a rapid "warm-up" Thu-Fri. Looking at Great Falls' past Novembers, last year, the lowest measured there in November was 21F. In Nov 2008, the lowest was 18F. Yesterday's low was -13F. Today's low was -3F. Their normal low/high for today is 21/39. So the air is definitely colder than normal, but normal there, like here, is an average of extremes this time of year. It's not the same as Houston being 30F below normal in July, for example.



Let's look at temps up in Canada all the way to the Arctic Circle. Not particularly cold. A number of reports of -10 to -20, but we'd have to adjust these downward for elevation in many cases. You could probably call this seasonable cold in Alberta/Saskatchewan.



Snow cover extends down through Montana and South Dakota. There is plenty of relatively warm ground between here and there, allowing for more modification of the cold air than we'd see later in a fall/winter when the snow cover might extend down to Kansas or even Oklahoma.



What does it all mean for us? Some unseasonably cold air arriving on Thanksgiving Day. If the front arrives after sunrise, then we could see the temperature fall from the mid 70s to the mid 50s in just an hour after frontal passage. Down to the upper 40s about 2-3 hours after frontal passage. It'll be a very sharp cool-down. No freeze here Friday, as it will be cloudy. Perhaps 40-43F at IAH Friday morning. IAH could be close to freezing on Saturday morning. Maybe 32-34 in west and southwest parts of the city. Certainly a frost across much of Houston. South side of the city will be in the mid 30s.

Rapid warm-up after Saturday morning, but watch out for a colder cold front around the 30th or 1st.

[redneckweather]

Oh shoot, my commment was tongue in cheek wxman...nothing more, nothing less. I sure do appreciate the detailed analysis. I actually like the idea of the cold front hitting around 11 am or so on Thanksgiving Day in my parts. It doesn't get any better than a good cold blasting through our neighborhood on Thanksgiving Day!

[srainhoutx]

For what it's worth, the 12Z GFS appears to be a bit faster with the front by about 6 hours. Also there is some post frontal moisture on this run as well with a shortwave that is lagging back to our W .

[wxman57]

For what it's worth, the 12Z GFS appears to be a bit faster with the front by about 6 hours. Also there is some post frontal moisture on this run as well with a shortwave that is lagging back to our W .

srain, I plotted the 12Z GFS meteogram and it looks slower with the front by about 4 hrs, bringing it in between 3pm and 4pm rather than 11am. 12Z Euro appears to indicate a late afternoon arrival on Thursday. Canadian is even slower - Thursday night. What are you looking at that makes it appear to come in faster?

Here's the latest meteogram for IAH from the 12Z GFS.

[srainhoutx]

For what it's worth, the 12Z GFS appears to be a bit faster with the front by about 6 hours. Also there is some post frontal moisture on this run as well with a shortwave that is lagging back to our W .

srain, I plotted the 12Z GFS meteogram and it looks slower with the front by about 4 hrs, bringing it in between 3pm and 4pm rather than 11am. 12Z Euro appears to indicate a late afternoon arrival on Thursday. Canadian is even slower - Thursday night. What are you looking at that makes it appear to come in faster?

I was running it through your meteogram file, but I admit I was a bit busy at that time and may well have read it wrong. Too much multi tasking this Monday morning getting ready for a short week.

[srainhoutx]

Just a quick update on some early discussion coming out this afternoon. Both Little Rock and Shreveport are hinting at some possible wintry mix before the moisture ends for those that may be traveling Thanksgiving evening/Friday morning up in NE TX, N LA, and AR.

Shreveport...

MUCH OF THE RAINWITH THIS SYSTEM IS EXPECTED TO BE POST FRONTAL. IN THE
MEANTIME...MUCH COLDER TEMPERATURES WILL BE MOVING INTO THE REGION
FROM THE NORTHWEST BEHIND THE FRONT...POSSIBLY ALLOWING SOME
LOCATIONS TO DROP TO FREEZING THURSDAY NIGHT. THIS WILL HAVE TO BE
WATCHED CLOSELY OVER THE NEXT FEW MODEL RUNS. CURRENTLY IT LOOKS AS
IF THE PRECIP WILL MOVE OUT OF THE AREAS THAT ARE EXPECTED TO FREEZE
BEFORE TEMPERATURES FALL. HOWEVER...THIS WILL NEED TO BE WATCHED
THE NEXT COUPLE OF DAYS AS IT WILL ALL DEPEND ON TIMING.


Little Rock...

SHOWERS AND THUNDERSTORMS WILL AGAIN BE EXPECTED THURSDAY AND
THURSDAY NIGHT MAY EVEN BE COLD ENOUGH IN THE NORTH FOR A LIGHT
WINTRY MIX OF PRECIPITATION. TIMING OF THE PRECIPITATION WITH THE
ARRIVAL OF THE COLD AIR WILL BE KEY IN GETTING WINTRY PRECIPITATION.

[wxman57]

18Z GFS puts FROPA between 5pm-6pm Thursday. If it's that late, I may be able to get in a bike ride before the pre-frontal rain/storms hit in the afternoon.

[helloitsb]

18Z GFS puts FROPA between 5pm-6pm Thursday. If it's that late, I may be able to get in a bike ride before the pre-frontal rain/storms hit in the afternoon.

Not to take anything away from your bike ride but I hope it moves in earlier than that! What kind of Thanksgiving is an 80 degree Thanksgiving (and don't even say the last 10 )

[skidog38]

Wednesday night the front moves in. Snow Thanksgiving night. thats my forecast.

[helloitsb]

Wednesday night the front moves in. Snow Thanksgiving night. thats my forecast.

ha! thats a pretty big forecast! You are talking about SE Texas?

[skidog38]

Wednesday night the front moves in. Snow Thanksgiving night. thats my forecast.

ha! thats a pretty big forecast! You are talking about SE Texas?

yes

[helloitsb]

Wednesday night the front moves in. Snow Thanksgiving night. thats my forecast.

ha! thats a pretty big forecast! You are talking about SE Texas?

yes

Well here is to hoping that it happens

[Ptarmigan]

This should be a rather interesting Thanksgiving. Warm and stormy. Now, how often does that happen?

[Mr. T]

The 0z GFS suggests we could be stuck in the 40s all day friday with overcast skies and showers.

Ugh

I'm going to ren fest on friday, and that's not going to be fun. Of course it can't be like today; Today was perfect.

[helloitsb]

Just a question, what are the differences between the 0z 6z 12z and 18z models, I know they all show different things so I want to know why they have 4 different types.

[Mr. T]

Just a question, what are the differences between the 0z 6z 12z and 18z models, I know they all show different things so I want to know why they have 4 different types.

The numbers are the different times the model runs in zulu time

Of course, the model will vary from run to run

[wxman57]

Just a question, what are the differences between the 0z 6z 12z and 18z models, I know they all show different things so I want to know why they have 4 different types.

It's not 4 different types of models, it's 4 runs of the same model (or models), each with different initialization data. There are upper air soundings taken twice a day at stations around the world (12Z and 00Z). These data make it into the 12Z and 00Z model runs. Some additional data may make their way into the intermediate 18Z and 06Z runs.

The European model is only run twice a day (12Z and 00Z). They take a lot more time verifying data before the data go into the model. That makes the process longer, so they can only run the model twice a day.

Yes, the same model will very often forecast something completely different each 6 hour period. That's particularly true the farther out that the model is looking. Just a small change in the input data (variables) can have a big impact on the long-range forecast.

[helloitsb]

OOO! Ok Wxman! I was looking at the GFS for the cold front in December and the 18z is showing up to be a lot more different so I was just wondering.

[wxman57]

18Z GFS puts FROPA between 5pm-6pm Thursday. If it's that late, I may be able to get in a bike ride before the pre-frontal rain/storms hit in the afternoon.

Not to take anything away from your bike ride but I hope it moves in earlier than that! What kind of Thanksgiving is an 80 degree Thanksgiving (and don't even say the last 10 )

Probably only 77-78 degrees, the clouds and rain should hold the high down below 80. That is, unless a squall line develops and we get some SSW-SW flow ahead of it mid afternoon. Could top 80 if that happens. The front could arrive earlier. We won't be more sure of the time until Wednesday afternoon most likely.

As for snow? Uh, maybe in a freezer, but not outside this Thu/Fri. The temperature aloft Thursday evening is forecast to be well into the 60s 5000 feet up, and well above freezing throughout the moisture layer all the way to 12,000-13,000 ft up. By Friday morning, the freezing level will still be over 10,000 ft up and temps at 5,000 ft over 50F. Can't get anything frozen out of that, sorry.