Tuesday, February 23, 2010

Winter Storm Warning/WInter Weather Advisory

A winter storm warning is in effect for our southern counties today and a winter weather advisory is in effect for the I-20 corridor. An upper level low pressure will move across the state today causing widespread precipitation to break out. This will likely start out as a rain snow sleet mixture this morning but quickly transition to all snow by the late morning hours. Heavy snow is likely in some areas of East Texas today especially south of the Tyler Longview area. The Image above is the forecast snowfall for East Texas through tonight. Notice the swath of 4 plus inches of snow expected from Palestine to Center. Up to two inches of snow can be expected along the I-20 corridor as well. For our snow lover along the I-30 corridor, we may see a dusting to as much as an inch but it looks as though the majority of the snow will miss our northern counties.

Monday, February 22, 2010

1st Storm Chase of 2010

The first storm chase of the 2010 season ended up providing a little excitement even though our target area was off. Saturday 12Z model runs were pointing to two areas of possible severe thunderstorm development. One was over Louisiana where low clouds and fog would make storm visibility horrible, and the second area was over Central Texas as a dryline was progged to move from Dallas to Waco during peak afternoon heating. We decided to choose the second target based on visibility and an anticipated pooling of moisture out ahead of the dryline. So we decided to head to Corsicana giving us a good north south east and west option depending on where storms developed. Once there a quick look at the new SPC mesoanalysis page, which is amazing, showed instability building in the Fairfield are so we headed south to wait for storm initiation. Once there I found an abandoned house with some very spooky trees and I had to take a shot. You see that at the top of the page. We waited for about 30 minutes and noticed the dewpoint beginning to drop, dry line was mixing through the area. So I took a glance at the NWS in Fort Worth’s Convective Parameters page, which usually performs very well, and noticed the convective interest near Dallas was in the upper 80s, meaning storms were likely to initiate there within the hour. So we raced north.

As we were driving north we noticed storms firing in the Metroplex. The southern storm riding the boundary took on a mini supercellular form. Radar showed 67.5 dbz that never reached higher than 20,000’, as you can see from the volumetric scan.

The next image is the velocity data. The rotation on radar was fairly week but from our vantage point, you could see the updraft tower rotation fairly well.

The reflectivity image shows a small hook on the southwest side of the storm which persisted for about 30 minutes on radar. The view we had of the storm as we approached western Kaufman County was incredible. We were able to see a flanking line, a well defined wall cloud, a tilted updraft, and what appears to be a tornado. In the photo I have it labeled as a tornado look alike but after seeing fellow storm chaser Simon Brewer blog, you can easily see this was a funnel and it was not on the ground. He was much closer to the updraft than I was when my photo was taken.

The storms updraft was quickly undercut by cooler drier air as it moved closer to us. A new updraft began to form on the southeast side of the storm. The photo below is of that rotation updraft with a small funnel trying to develop. Smile Paul!

This updraft was undercut as well and lead to the demise of a very nice mini supercell and left a rainbow coming out of the back of the storm.

New storms were trying to form to our east near Canton but even these storms didn’t have much of a chance as the dry boundary raced east and undercut the storms' development. All in all, not a bad 1st chase day especially for as low of a severe risk we had in Central Texas.

Winter Storm Watch for parts of East Texas

A winter storm watch is in effect a good chunk of Texas including Anderson, Henderson, and Houston Counties in East Texas. An upper level low pressure associated with very cold air aloft will move across the state starting tonight. As this system moves in to East Texas, rain mixed with sleet and snow should start to fall by tomorrow morning. As the precipitation increases, surface temperatures will drop to near freezing by tomorrow afternoon causing snow to accumulate in some areas. Right now it appears the greatest chance of accumulating snowfall will be south of I-20 where some places could receive an inch or two. The greatest snowfall looks to occur from Palestine to Rusk and points south to a Crockett Lufkin line. Isolated amounts could be over 4 inches in these areas. Below is a snow fall accumulation map from the NAM forecast model. This model did very well predicting the East Texas snow 10 days ago 24 hours out so if it is right again, a few places could see as much as 6 inches of snow. It all depends on where the heaviest bands of snow develop which we really won't know until tomorrow, so this snowfall forecast could change.

Friday, February 19, 2010

Another Significant Snow on the Way?

This could go down as one of the snowiest winters on record if the solution mid and long range forecast data suggests comes true. Right now we know a strong cold front will move through Sunday bringing us a chance of thunderstorms, some of which could reach severe limits, followed by cooler air next week. For quite sometime now all indications were the air mass behind the front would not be all that cold but continue to give East Texas below normal temperatures. But all that is beginning to change over the past 12 hours. New forecast data suggest a much colder week is in store for East Texas and an area of low pressure will once again develop to our south in the strong subtropical jet.

So what does all this point to? The chance of another significant snow across East Texas. Now remember, what I am showing you is the forecast trend, not an official forecast. However, if this trend continue over the next day or two, look for snow to be put back in our forecast.

Above is the forecast sounding for Tyler at noon on Tuesday afternoon of next week. This sounding screams heavy wet snow, like we saw last week. The forecast sounding 6 hours before and 6 hours after look about the same. This would give us a prolonged period of heavy wet snow, again only if this scenario pans out. A few things that peek my interest looking at this sounding. First, the atmosphere is at saturation from the surface to 300mb, basically this time of the year the stratosphere. This would allow for very heavy precipitation to fall. Also you can see the temperature of the atmosphere remains below freezing except the last 300' or so near the surface, much like last week. This means the snow will be very wet. Finally there is some upper level instability in this sounding. This means there could be some lightning in the clouds giving us, yes, thundersnow.

Below is the forecast for the accumulation of snowfall up to 120 hours out, or Tuesday afternoon. You can see that through the Dallas area, another significant snowfall is shown with over 10" in a few places.

The next image shows the snowfall farther east into East Texas. Again this only goes out to 120 hours when the heaviest snow begins to fall. If you interpolate the data it looks as though another swath of 4"-6" is possible across the northern half of East Texas.

Again a lot can and probably will change between now and this event. However, long range forecast data performed very well on last weeks snow event, even under forecast the snow amounts. This is in no way is an offical forecast for the area but, if this trend continues parts of East Texas could get more snow making this the snowiest winter on record.

Tuesday, February 16, 2010

4th Greatest Snowfall in Longview Last Week

Thanks to the National Weather Service Fort Worth

Last week's snowfall across East Texas produced an amazing amount of snow across the area. Notice the snowfall map above that parts of East Texas saw a foot of snow near Canton and points west. We already looked at the way this storm stacks up historically in Tyler. So now let's look at this storm historically in Longview. It looks as though this snow will also go down as the 4th greatest snowfall in Longview as well. Longview kept much better records with no gaps of missing years of data. The top five snowfall events for Longview are as followed:

#1 Dec 21st, 1929 14"
#2 Dec 15-16th, 1983 8.5"
#3 Jan 13th, 1982 8.25"
#4 Feb 11-12th, 2010 7.0"
#5 Feb 1-2nd, 1985 6.0"

4th Greatest Snowfall in Tyler Last Week

Last week's snowfall across East Texas produced snowfall amounts many areas have not seen in over 20 years. So I thought I would dig through the record books to see how this snow compared to some of the greatest snowfalls in East Texas history. The official records for Tyler go back to 1883. However, there are a few holes in the data. The winter months are missing from 1883 through 1889. Also, the years 1906-1939and 1951-1954 are missing entirely. So my findings cannot be 100% accurate but from the data available, last week's snow will go down as the 3rd greatest snowfall off all time. Here is a list of the 5 greatest snowfalls in Tyler on record:

#1 Jan 14th, 1982 8.0"
#2 Jan 30th, 1949 7.5"
#3 Feb 11-12th, 2010 6.0"
#4 Jan 14th , 1944 6.0"
#5 Feb 1-2nd 1985 5.5"

Looking through the missing data years at other East Teas locations I found on December 21st, 1929 a strong snow storm covered most of East Texas with 10 to 16 inches of snow including 14 inches in Longview. So I have a hard time believing that Tyler did not receive at least 10 inches of snow during this event which would make last week's snow the 4th greatest of all time. There of course were other snow events during the missing data years but by judging what occurred around Tyler, I feel pretty confident these events did not eclipse the 6 inch mark. This snow event will also go down as the greatest amount of snow for the month of February in Tyler.

Friday, February 12, 2010

The Biggest Snow in Nearly 20 Years

Widespread snowfall covered East Texas this morning. Amounts were mostly around 6 inches but a few areas received as much as 10 inches, Lindale for instance. I will be putting together a photo log of this event and create a snowfall map so everyone can see what an amazing event this really was.

Wednesday, February 10, 2010

Winter Storm Watch Issued

The image above from the National Weather Service Shreveport

A winter storm watch is in effect for our central and eastern counties tomorrow afternoon through Friday morning. Widespread snowfall amount of two plus inches can be expected. A few heavy bands of snow could develop along and south of I-20 producing local amounts between 3 and 5 inches, possibly as high as 6 inches in localized areas. Most of the snow will accumulate on elevated and grassy surfaces but during periods of heavy snow, slushy roads will develop. Overnight Thursday night we will see some snow develop on roadways.

Snow Looking More Likely.

I must admit this winter weather scenario for Thursday and Thursday night has been one if not the most challenging forecast I have had to deal with. Right now it looks as though snow will fall across most of East Texas tomorrow and could accumulated in some areas, maybe as much as two inches along the I-20 corridor east of Tyler. But it could be worse.

Our official forecast for snowfall accumulations as of 9:00AM Wednesday is for around an inch of snow to accumulate on grassy surfaces along a line from Athens to Bullard to Carthage and points north. Along the I-20 corridor East of Tyler there could be as much as 2 inches. But as I write this new forecast data is coming into the office trending a bigger snow event, like was advertised on Monday.

What makes this forecast so difficult is the fact the temperature I the atmosphere straddles the freezing line from the surface to about 7000 feet. Usually we see in a situation like this, a warm nose of air around 5000 feet that melts the snow on the way to the surface. With this system we do not see that however, there are places where the temperature around 5000 feet does go above freezing. In these areas snow would melt and only rain would reach the ground. The problem is locating where this will occur and even if it does, heavy precipitation could cool this warm nose of air back to the freezing point and then we are back to snow.

Now if this warm nose of air never makes it up to the I-20 corridor, which some forecast models are showing now, nothing but snow will fall from Athens to Carthage north and this would cause a large increase in snow accumulation. In fact, looking at the latest snowfall accumulation chart, a swath of 4 to 5 inches in being shown across the I-20 corridor. I look for winter storm watches to be issued later today for parts of East Texas after looking at the latest data. Again, a lot could happen between now and the event but it is looking more like snow will occur.

Monday, February 8, 2010

Rain Today, Snow Possible Later This Week

A strong storm system will develop today across central Texas bringing a good chance of showers and thunderstorms today. Some of the storms could produce small hail thanks to the cold mid level temperatures today. The farther south you move today, the better chance of seeing a strong storm or two. A warm front will move into the extreme southern counties of East Texas today, from Crockett to Lufkin. Along and south of this line I can’t rule out an isolated severe storm however, most of the severe weather should remain well to our south.

Later this afternoon and into this evening, a strong cold front will usher in much colder air. Right now it appears most of the moisture will be out of the area as the cold air moves in however, there is a chance a few snow flurries could develop tonight mainly from I-20 north. This will set the stage for a possible winter storm starting as early as Wednesday night through Friday morning.

An area of low pressure will begin to develop across southwest Texas Wednesday afternoon. Right now it appears this low will track to the east remaining well to the south of East Texas. This will give most of East Texas a chance at seeing some snow develop. As moisture moves over the cold dome of air at the surface, light rain and sleet should develop across the area towards Late Wednesday night. This will help cool the atmospheric column allowing snow to reach the surface by Thursday morning. Right now forecast models are showing the potential of a prolonged light to moderate snow event. The meteogram below shows a detailed forecast with timeline of what could happen if the low pressure remains on its forecast track (remember, the timeline starts to the right and then moves left).

You can clearly see there is nearly a 36 hour period of snow (forecast is for Tyler). This could lead to a significant snowfall for parts of East Texas if this verifies. The latest accumulated snowfall forecast puts a swath of three to five inches of snow across parts of East Texas (See Below).

As with all winter weather forecast here in East Texas, a lot could and probably will change before this system develops. If the low pressure tracks farther north, then most of East Texas will see rain. A little farther south and much of East Texas will see snow. I will say this however. This system has been advertised for many days now and continues to show a significant threat of winter weather across parts of East Texas. Usually as we approach a winter weather event, forecast models trend farther north and warmer with systems. This system has trended colder and farther south. Stay tuned as we fine tune the forecast as more details become available.

Wednesday, February 3, 2010

Old Man Winter on his way Back!

Next week it looks as though old man winter will make another visit to East Texas, and much of the eastern half of the Nation. There will also be two opportunities for winter weather next week as a couple of storm systems move through with cold air in place.

A strong arctic high pressure is building across the Canadian Prairies and will begin to move south this weekend. This will send a strong cold front racing towards East Texas either late Sunday or Monday giving us a chance of rain as this front moves through. An area of low pressure is forecast to develop somewhere along this front. If this low forms to our west, it will move south of East Texas along the Gulf coast as the cold air rushes in. If, and this is a big if, this happens, East Texas would be under the gun for a major snowstorm. Timing is always an issue here when it comes to winter forecasting. Usually the moisture is gone by the time the cold air moves in however, it is interesting that forecast models are beginning to show the cold air reaching East Texas before the moisture moves out. The image below is a meteogram from the 06Z GFS forecast model (the time line goes from right to left, opposite from what you would normally read).

The meteogram shows a strong front moving through dropping temperatures around Midnight Monday followed by a 12 hour period of snow, some of which would be heavy. Now let me stress this is just a trend. I am not forecasting a big snow storm early next week, right now I am just mentioning rain followed by cold weather but, it is very interesting to see these latest forecast model trends.

The next opportunity of winter weather would be late next week as the arctic high move east and an over running precipitation event takes shape. Warmer air from the Gulf could be forced over the cold dome of air at the surface causing clouds and precipitation to develop. With surface temperatures at or below normal and temperatures above freeing aloft, sleet and freezing rain would be the main threats with this event. The following two images are forecast maps for Friday evening. Notice the temperatures are in the upper 20s and low 30s with around 0.25” precipitation falling. This could produce a significant amount if ice accumulation.

Again this is a long way out. What I have covered are forecast trends, not an official forecast. I am very confident that a significant cold air mass will move into East Texas next week. If this air mass while moisture is in place, we will see a winter event. But in most cases, the moisture is gone when the cold air moves in making significant winter weather events very rare across East Texas. Stay tuned, more to come.

Tuesday, February 2, 2010

One of the Coldest Arctic Outbreaks 59 Years Ago Today

On February 1st, 1951, A strong arctic high pressure moved south out of the Canadian Prairies and by the morning of the second, set up over East Texas. This produced some of the coldest temperatures in history including the coldest temperature ever in Lufkin. Along this front precipitation broke out and a large band of snow developed from Central Texas through the northern Gulf States. Dozens of record lows were set across the country the morning of the 2nd including a few of the following:

Lufkin, TX -2°F
Tyler, TX 2°F
Longveiw, TX 3°F
Texarkana, TX -3°F
Shreveport, LA 2°F
Lake Charles, LA 13°F
Beaumont, TX 13°F
College Station, TX 5°F
Memphis, TN -11°F
Tupelo, MS -1°F
Jonesboro, AR -3°F
Greenville, MS -2°F
Tuscaloosa, AL 5°F
Huntsville, AL 3°F
Muscle Shoals, AL 1°F
Nashville, TN -13°F