Thursday, October 30, 2014

A Cold and Blustery Halloween

FORECAST:

Friday: Mostly sunny during the day with only a slight chance of a passing showers. In the evening, turning colder with gusty winds (possibly up to 20 or 30 mph) and a chance of isolated light showers for trick-or-treaters. High 61, Low 38

Saturday: Sunny. Quite cold. High 50, Low 32

Sunday: Some frost is possible in the morning. Sunny and cold. High 57, Low 30

EXTENDED OUTLOOK:

Monday: Mostly sunny. High 63, Low 36

Tuesday: Partly cloudy. High 69, Low 45

Wednesday: Increasing clouds with a 30% chance of showers/thunderstorms. High 72, Low 50

Thursday: Partly cloudy with a 40% chance of showers. High 68, Low 52

* We "Fall back" an hour Saturday night/Sunday morning as we go back to Standard Time. *

NOTES:

Dr. Tim Coleman has posted a detailed blog about our imminent blast of cold air, which I would recommend reading if you want more details than I have given here.

And the Graduate SKYWARN Class is scheduled for next Tuesday evening at 6:30 p.m. as an online class. If you have never had basic SKYWARN training, then I would strongly suggest using these free resources before signing up for the graduate class. It'll just help you understand the concepts a lot better. Having said that, I very much appreciate the National Weather Service in Birmingham holding these classes, as they provide a free and enjoyable for anyone interested in weather to learn more about the science of severe storms . . . and also about safety and being involved in community safety, that sort of thing. Definitely worth checking out.

DISCUSSION:



So after a pleasant day in the Tennessee Valley, temperatures across the region have fallen into the 50's and even 40's. We are are 47 in Cullman. We had sunny skies today with a High of 63 and a Low of 37. Winds were generally light from the west/northwest. Those temperatures were a little bit lower than forecast. I will take that into account when forecasting the next few days, when we really are going to have some colder air moving in. On the national view, it looks like Fall all the way around. We're getting there, anyhow.


We're actually going to be dealing with two cold fronts here. The second one is the major whammy. The first one looks relatively weak and should be moving through tonight and tomorrow morning. You can see some light showers out ahead of it on the radar and infrared satellite images above, just making it into Western Tennessee and Mississippi.

The second front, with the really cold air, is still draped from the Great Lakes region, through the Midwest, Northern Plains, and all the way back up into Montana and Canada. This one should arrive tomorrow evening for Halloween night and bring a blast of cold air, the coldest this season.


So tomorrow, via the GFS model run above valid at 1 p.m., you can see the cold air starting to blow its way down into our general vicinity. Some light showers are possible, just isolated showers, mainly in the counties of Southern Middle Tennessee. As the night goes on we might see some showers in North Alabama. During the day, we should see mostly sunny skies and temperatures similar to today, but as we get into the evening hours with that front blowing through here, it's going to be cold. And that wind may be anywhere from 10-30 mph gusts. So take that into account when trick-or-treating. It actually wouldn't be impossible for some of the higher elevations of the Tennessee Valley to see a few snow flurries, but even if that were to happen, snow accumulation is not expected in our neck of the woods - NONE. Seems like I saw some buzz on social networks that were trying to overblow that into a serious snow threat. Now up in the Smoky Mountains, yes, they do have a good chance of snow. Around here, maybe a few flurries, probably not even that. You have to be careful . . . don't believe everything you read on the social networks.

On that note, don't believe everything you read on this blog. I finished roughly two years of college focusing on meteorology, but that's it. Other than just learning-by-doing. There are people who know more than I do, obviously, and . . . shop around and make up your own mind. Most of the time when someone is suddenly painting a very scary scenario, it is bogus. Most major weather events will be at least suspected several days in advance. If you find anything that seems "out there", even if I goof up and post such a thing on this blog . . . always look for a second (and third, and maybe more than that, depending on your preferences) opinion. If all else fails, check the National Weather Service, because they are required by the federal government to call things "straight down the middle", to forecast the most likely scenario as best they understand it. You certainly will not find any "hype" with them. And hopefully you won't find it here, either, but if you do, gripe at me a little bit.


Saturday is going to be a cold one. Sunny skies as the front is well clear of our area, but man . . . it keeps trending colder as we get closer to the event. It's looking like we'll be around freezing at daybreak and then only warm up to about 50 degrees or so in the afternoon. In other words, temperatures will be in the 40's most of the day. We might still have a little bit of a northwest breeze too. If you haven't used the heater yet, you definitely will need it tomorrow night and Saturday morning. The winds Friday night will probably lessen the chances of any widespread frost problems. However, those same winds could make it feel like it's more down in the 20's in the early morning!


Sunday morning looks like the coldest by far though. Frost may very well be a problem Sunday morning. Either day, I would take what measures I could to protect any outdoor vegetation. We should start the day below freezing - I'm probably going with 30 degrees, although of course, temperatures will vary from place to place. For Cullman I'm going with 30 degrees, most likely. We should have sunny skies and warm into the upper 50's.

Just by the way, if you have any clocks that are not "automatic", be sure to set them back an hour Saturday night, as we are going from Daylight Savings Time back to Standard Time. Most computers and cell phones do this automatically. The one that always gets me is the car clock. I tend to forget it and then one day go, "Whoa - time sure flies . . ." And only then realize I forgot to set it back.

On Monday as the upper-level ridge continues to the east, our surface center of high pressure should be shifting off into the Atlantic Ocean. And as our next cold front pushes into the Plains, we should remain mostly sunny but warm up a bit. I think Highs will be in at least the lower 60's, and Lows in the morning should be getting back into the upper 30's. So after Saturday and Sunday morning, the major cold is over for a little while.


On Tuesday the front is moving into the Midwest and into Arkansas, Missouri, East Texas. Our winds aloft from the southwest should increase. And that will bring some clouds back. Temperatures should rebound quickly into the 40's in the morning and then warm to probably near 70 in the afternoon. Some clouds will be coming back, but I think we see a little more sun than clouds.


On Wednesday the front is getting into the Mississippi Valley and approaching our area. The timing has kept slowing down from model run to model run over the past several days. I'm not sure if I will introduce low-end rain chances for Wednesday or not. One important thing to note is that the trough associated with this (top graphic) is positively tilted. If you were to draw a line through that "X" in Southwest Texas/bordering Mexico there (and they sort of do, notice the yellow line), it would curve up and to the right. So the deep-layer winds with this system will likely be parallel to the surface front. And despite November traditionally being our secondary severe weather season, this means any severe storms would be very unlikely with this system. Sometimes I feel it's important to tell people what not to worry about. We had an unusually rough October, so I can understand if some people are "gun-shy". This system looks like it would bring only routine rain and thunderstorms.



The European model, at this point, actually does not appear to show any drastic differences in timing of this system. So I will likely put some low-end rain chances in for Wednesday. Temperatures should be 70 or so for Highs and in the lower 50's for Lows. Due to the proximity of the front to our area, shown by the models here, I guess should mention mostly cloudy skies. And rain chances should be about 30-40%.


The front should be pushing through here on Thursday, at the end of this forecast period. It should have some cooler air behind it, but we probably won't feel that until Thursday night/Friday morning to a large degree. So will probably just back temperatures off a little bit for Thursday during the day and continue the chance for showers.

All the tropical activity of interest to us (Gulf/Atlantic) has fizzled out. And usually once we get into November, tropical season is pretty well over. That isn't set in stone, but it's just been my observation that very rarely do the tropics get active much past the month of October.

Our rainfall amounts over the next seven days will probably total only about a quarter-inch. At most I'd say a half-inch in spots. Our rain chances just aren't overwhelming even toward the end of the week. And with so much (typical) uncertain with the models as to the timing of the cold front, it's just hard to predict. The HPC does a great job, seen above. Looks like parts of Texas, Oklahoma, and even Wichita, Kansas could see a decent soaking, between 2-3 inches of rain.

+Matt Graves
@thatweatherdude

Well, that's all I've got for tonight. Hope you stay warm, and I guess I'll see you in the funny papers.

Cold Blast On the Way Tomorrow Night Through the Weekend

FORECAST:

Today: Sunny. Cool. High 65

Friday: Mostly sunny with only a slight chance of an isolated shower or two during the day. Isolated showers are possible in the evening as well, as colder air moves in and winds howl (up to about 20-30 mph, anyway) for trick-or-treaters. High 64, Low 38

Saturday: Sunny. Cold. High 52, Low 34

EXTENDED OUTLOOK:

Sunday: Sunny. High 58, Low 30

Monday: Sunny. High 63, Low 37

Tuesday: Mostly sunny. High 67, Low 44

Wednesday: Partly cloudy. High 70, Low 50

* We "fall back" an hour to Standard Time Saturday night/Sunday morning. *

NOTES:

Here is some climatological information about Fall freezes here in the Tennessee Valley.

And we've got a couple of online SKYWARN classes coming up: The first is this evening at 6:30, a basic class. And then next Tuesday evening at 6:30 is the advanced class.

DISCUSSION:



So here as we approach 6 a.m., we've got clear skies and calm winds in Cullman. It is 38 degrees out there. So don't forget yer booties, eh? Dewpoint temperature is 37, which makes the relative humidity 98%. Barometric pressure is at 30.13 inches and rising.

Oh, and visibility is great - ten miles.

Well, the higher pressure and associated cold air has obviously arrived behind yesterday's cold front.


Today should be a sunny day with a High around 65.


Friday, Halloween, another cold front dives through the area. The main energy with this is going to actually pass to our north and east, where they could even see some light snow. And the front will actually come through in the evening hours. During the day tomorrow, we should be similar to today, just a few more clouds. But tomorrow evening, at trick-or-treating time, it is turning cold and blustery. Winds could gust in the 20-30 mph range. I don't see many good werewolf makeup kits on the shelves anymore, and that is just as well, because the wind could probably blow the fuzz off your face this year.

And a few showers are actually possible tomorrow and tomorrow night, just isolated showers.

The NAM shows just a little bit more moisture in our area than the GFS. It actually wouldn't be impossible for the higher elevations in Northeast Alabama and up across the Tennessee border to see a few snow flurries tomorrow evening.


The system that dives through the Mid-Atlantic region tomorrow night and Saturday is quite apparent here. This is the GFS at 1 p.m. Saturday. We should start the day in the lower to mid 30's and only warm into the lower 50's. Sunny skies.

And then, Daylight Savings Time comes to an end Saturday night/Sunday morning as we "fall back" an hour to Standard Time.

On Sunday with the upper-level ridge to our north, strong high pressure, we should start the day around freezing, or just below freezing, and then warm up to somewhere around 60 degrees, or at least upper 50's. Staying sunny.

On Monday as the ridge starts to slowly move to the east and some of the winds in the region start to turn back west/southwest, we should stay sunny but warm a little bit, at least lower 60's for Highs and upper 30's for Lows.

Tuesday the southwest flow aloft really increases, ahead of our next cold front. We should see Highs in the upper 60's, probably still more sun than clouds, but some clouds coming back.


And on Wednesday it looks like the front may finally be ready to move in here. Still enough uncertainty as to the timing of the front that if I would only say about a 20% chance of showers. So I'm not even going to mention rain chances in the official forecast yet. There hasn't been a lot of consistency between this (the GFS) and the ECMWF, and of course the timing has changed a lot from one model run to the next, over the last few days. Which is nothing unusual, but still . . . playing it conservative here. The one thing that is consistent is that while we will be into our secondary severe weather season (typically November and sometimes lasting into at least early December), there are no signs to indicate this front will produce any kind of severe storms.

In the tropics, still vaguely watching this tropical low centered just northeast of the Virgin Islands. It is expected to turn north/northwest over the next couple days and encounter winds unfavorable for further development.


The Hydrometeorological Prediction Center is suggesting we could see rainfall totals of a half-inch or greater during this forecast period. If that were to happen, almost all of it would be next Wednesday. I personally still think it's too uncertain to make that call yet, but even if so, we could have similar rain amounts if the front was a little slower, arrived on Thursday maybe. If nothing else, it's a good rough estimate.

+Matt Graves
@thatweatherdude

Thanks for reading. See you in the funny papers.

Wednesday, October 29, 2014

A Blast of Cold Air Halloween Night Through the Weekend

FORECAST:

Thursday: Sunny. Cool. High 67, Low 42

Friday: Mostly sunny with only a slight chance of a passing shower in the afternoon or evening. Trick-or-treaters are in for a cold night with gusty, dare-I-say "howling" winds at times. High 65, Low 43

Saturday: Sunny. Cold. High 53, Low 34

EXTENDED OUTLOOK:

Sunday: Sunny. High 60, Low 31

Monday: Mostly sunny. High 68, Low 37

Tuesday: Partly cloudy. High 71, Low 45

Wednesday: Increasing clouds. High 69, Low 52

NOTES:

Here is some climatological information about Fall freezes in the Tennessee Valley.

And there are a couple of online SKYWARN classes coming up: The basic class is tomorrow evening at 6:30, and the advanced class is next Tuesday evening at 6:30.

DISCUSSION:



All right, so we had an interesting day today. Most of us woke up to rain and thunder in the Tennessee Valley. By late morning, it was on its way out. And the clouds cleared out in the afternoon pretty quickly, and we got plenty of sunshine. We were a bit breezy from the North at times behind this cold front. Our High today in Cullman was 66, and our morning Low was 52. Temperatures this evening are in the 60's across the Valley and falling.


Tomorrow, as high pressure and cool air continue filtering into the area, temperatures should be similar to today, with sunny skies. The morning Low should be in the lower 40's, and then mid-to-upper 60's for the High.


Friday, Halloween, gets interesting. A second cold front will be moving through the area as an Alberta Clipper system dives through the Mid-Atlantic states Friday into Saturday. Notice how some of the moisture is getting close to our Tennessee counties, and in the northern part of Tennessee, that moisture is along the "freeze-line". That trend may need to be monitored, "just in case".

The NAM is showing the moisture extending all the way down into North Alabama at 1 p.m. The freeze line is a little farther north via the NAM, but as we get into the evening, it dips into our area, along with the moisture. For now this is an outlier, and it's just something to watch. You don't go with one model run that shows a strange scenario for a forecast; you look at overall trends. But Ms. Jill Gilardi made an interesting post this morning speculating on light snow in the higher elevations of Northeast Alabama and up into the Cumberland Plateau in Tennessee. Even she said, it would be actually hard for anything to stick, it would be confined to the higher elevations, and it would be light. That sounds like "flurries" to me. Now, further north into Eastern Tennessee, there certainly is a chance of light snow, or at least a mix of rain and snow. At the moment, for the Tennessee Valley though (North Alabama and bordering Tennessee counties), I think we just have a chance for flurries Friday night mixed in with some light rain, for our higher elevations in Northeast Alabama and up into the Cumberland Plateau. Even a "dusting" of accumulation strikes me as very unlikely in those areas. Anyway, just something fun to look at . . .

Around here, we should be mostly sunny during the day Friday but have some chances for isolated showers in the afternoon and evening. The wind is going to pick up in the evening as the colder air blows in behind this second front (our first front came through today), possibly getting up in the 20-30 mph range. So trick-or-treaters will want to dress warmly.


We're not really concerned with snow in the Tennessee Valley though; that was just a wild idea I decided to explore, mostly to show that it probably has no validity in our neck of the woods, and illustrate that while individual model runs that show something "strange" are fun to consider . . . it isn't a good idea to get too hung up on them.

The big story is just the cold air. Saturday morning we should start in the lower-to-mid-30's. And we should only warm into the lower 50's. (Have you noticed how that High temperature keeps being adjusted downward with every forecast?) And this is despite ample sunshine. The strong northwest flow aloft behind this cold front is going to do a number on us.

By the way, remember to set your clocks back by one hour Saturday night, as we are going back to Standard Time overnight Saturday into Sunday. Considering Sunday's cold morning, you'll probably be glad to stay in bed just a little longer, especially if your place is in the least bit drafty.


Sunday morning should be the coldest so far this season. The high pressure center should move directly to our North before sunrise, and during a few hours, we could see a freeze. Potential for widespread frost is also a given, here. That threat should go away after sunrise, but in the few hours before sunrise, we're likely to see a frost or even a freeze. Low temperatures will probably be at least down to freezing, maybe a couple of degrees lower than that. And then we warm to about 60 or so during the day - nice, sunny day, just a very cold start to it.

On Monday an upper-level ridge moves through the Ohio Valley to our North. A trough and associated cold front are moving into the Plains. We should stay sunny and warm well into the 60's. The morning Low should be well above freezing as well, mid to upper 30's.

Ahead of this trough and front, our winds aloft turn back to the southwest on Tuesday. We should start to see some clouds returning and temperatures warming to about 70.


Then on Wednesday, that cold front may finally be knocking on our door. At this point, the most I might mention in the official forecast is a very low-end chance for showers and thunderstorms. I also want to emphasize that although we will be into our Fall severe weather season (typically the month of November, sometimes lasts into at least part of December though), there is nothing here to indicate severe weather potential.


The ECMWF has been consistently less aggressive in bringing that front on in here, so probably for next Wednesday I'll just put "increasing clouds" in the forecast. The timing is probably too unclear just yet to actually introduce rain chances. If I was putting rain chances in there, they'd be about 20%. And when that's seven days out, I don't even mention it in a forecast. Only you discussion-readers get that treat. Heh.



Quick look at the tropics . . . we do have a tropical low just north of the Leeward Islands. It is currently moving northwest and might develop a little more, but after a couple of days is expected to turn north, when conditions for development are much less favorable. I might keep a casual eye on it if I was in any of those islands very close to it, or up in Bermuda, just to be on the safe side. But it poses no threat to the mainland, and it probably won't be a really big deal for anyone.

And although our rain chances are marginal for this forecast period, the HPC is outlooking a chance for up to a quarter-inch of rainfall for most of us and close to half an inch for most of Southern Middle Tennessee and far Northwest Alabama.

+Matt Graves
@thatweatherdude

Thanks for reading. See you in the funny papers.