The Weather Authority Blog

Looking Ahead & Looking Back

tokerson — Sun, 16 Nov 2008 00:56:00 GMT

Well, it looks like we'll have to wait a little while longer to see our first snow flakes of the season...I didn't see of any reports of flurries today, which honestly isn't surprising since most of the deep moisture pulled away earlier in the day than some forecast models were showing. Even without the flurries, it still felt and looked wintry. Something interesting today....we typically record an overnight low around 5-6 am, just before sunrise, and achieve our high around 2-3 pm. Instead, today our high of 48 degrees was recorded at 12:00 am (midnight), and our low most likely will be recorded at 11:59 pm (still to be determined since I'm typing away at 7 pm). Thankfully, it looks like things will be fairly uneventful this week, with mainly sunny skies in the forecast, and highs bouncing around between the upper 40's and mid 50's.

On a different note...the same system that has brought showers and cold air into our area over the past couple days brought deadly tornadoes to our east. A small town in North Carolina was hit by a tornado just after 4 am this morning, and unfortunately 2 people were killed. This may seem uncommon for November, but it has actually been shown that we experience a secondary peak in severe weather during the fall months...especially November... as warm and cold air masses are frequently colliding. That was no more evident than 3 years ago, when two destructive tornadoes tore through parts of west KY. Areas in Marshall Co. suffered F3 damage, and an F4 tornado ripped through Hopkins Co. For a deeper look at these storms, including damage photos, here's a link to the Paducah National Weather Service's page on the event.....http://www.crh.noaa.gov/pah/?n=nov1505f4

Finally...hearing about the tornado this morning in N.C. was another reminder of just how important it is to have a working weather radio nearby while you are asleep. A large number of the fatalities attributed to tornadoes occur during the overnight hours...fatalities that likely would have been prevented had those folks had a weather radio to alert them to take cover. If you don't have one....be sure to click on the link on our weather page and take advantage of our deal with Reecom Electronics. Hopefully we won't need them for a long time, but when severe weather is a threat, they are invaluable.

Meteorologist Trent Okerson

Wintry Weekend Forecast

tokerson — Thu, 13 Nov 2008 18:15:00 GMT

An already active week of weather will see one more major system pushing through the area on our Friday...with a strong cold front on track to bring more showers for Friday afternoon and evening. Looks like the front will slide through during the afternoon hours, with gusty and mild southwesterly winds ahead of the front, becoming northwesterly behind the front. Showers will begin to enter northwest sections of our area as early as tomorrow morning, and continue to slide southeast as the day progesses....with rainfall totals likely to remain around .25" or less. Temperatures before the front passes through may warm into the lower 60's, but then will plunge back to the 30's by Saturday morning. Saturday will be the day to watch, as things may get a little interesting. On the cold, western side of a closed low, we'll see lots of cold Canadian air blasting in from the northwest, and a good deal of moisture wrapping around the low and keeping our skies cloudy. In fact, with the clouds, most of us will struggle to warm up much past 40 degrees, but with a stiff NW wind...it will feel more like it's in the lower 30's just about all day. What we'll need to watch is just exactly how much moisture remains on the back side of this system...because with such cold air in place, it won't take much to generate some light precip....and with the cold air in place, a few of us may see our first snow flurries of the season. Right now, it looks like the best chance of seeing flurries will be in southern IL, and east of the Lakes in KY. I still am not completely sold on this...but it will be interesting to watch. At least we're just talking flurries right now...won't be long till more substantial winter weather will be possible!

Meteorologist Trent Okerson

Sloppy Week Ahead?

tokerson — Sun, 09 Nov 2008 02:27:00 GMT

Not sure if we have any Guns 'N' Roses fans out there, but their 1992 hit "November Rain" would be an appropriate theme for the week ahead...at least as far as the weather is concerned. A sloppy and cool outlook for the week includes a good chance of rain Monday night into Tuesday, then occasional showers through Thursday and perhaps even Friday...with highs each day only in the 50's.

At least over the past few months, most of our weather systems that brought rain chances to our area have involved areas of low pressure moving through the upper Midwest, drawing moisture up from the Gulf...a setup that hasn't exactly produced much in the way of appreciable rainfall (with the exception of a system or two last month). This next system, however, will get organized this weekend over southwest TX, then press eastward near the Gulf Coast. With the low centered to our southwest, this will provide a setup sometimes called "overrunning"....where warm and very moist Gulf air gets pushed up and over a cold, dense airmass. This warm, moist air is forced to cool and condense as it rises, and eventually will produce precipitation. This is a fairly typical cool-season setup, one that usually brings an extended cloudy and showery period....what we are looking at for much of the week ahead. Right now, HPC rainfall forecasts are showing most of us picking up somewhere between 1-2"...with the heavier totals the farther south you go. Here's the latest HPC 5-day precip. forecast:

Meteorologist Trent Okerson

Severe Setup on Thursday?

tokerson — Sun, 02 Nov 2008 23:19:00 GMT

Video Severe Weather Discussion

UPDATE-Wed. Midday--New forecast from the SPC has taken the area completely out of the slight risk for Thu. In fact, latest forecast pushed the slight risk area to the lowest portions of the MS Valley. As I've mentioned in the previous couple posts, the major limiting factor is going to be the lack of any significant instability, which will limit the vertical development of most of the storms that accompany the cold front. As always though, when strong cold fronts blow through this time of year, strong and gusty winds are possible, and will certainly be the case with these storms, even though they may not reach severe levels. This will be a fairly quick frontal passage, so while there may be some heavy downpours, we're only looking at around .25-.50" of rainfall. Still looking at the leading edge of storms pushing into SEMO by Thu. morning, then crossing east of the MS River around midday, and into the Pennyrile region of KY by Thu. evening....then the colder air will push in for the weekend. Be sure to join Jennifer & Kyle tonight at 5,6,9,&10 for the latest information, and check in with John in the morning to find out how the storms may affect your morning commute.

UPDATE-Tue. Night: The SPC has included the entire Local 6 area in a slight risk of severe thunderstorms for Thursday. There are still quite a few uncertainties about this system....first, models are not showing just a whole lot of instability, which could act as a limiting factor in thunderstorm development. Models are, however, still showing a healthy wind field that would support strong thunderstorms if they do develop. A big question is going to be the timing of this system. Still some disagreement between the models on when the system will arrive, but it looks like it will weaken as the day progesses, so an earlier arrival may mean a better chance of storms.....something that will put MO in the crosshairs of the better chances for severe weather. Also, if this system enters our region late morning/early afternoon, that obviously would mean the atmosphere would be at its "juiciest"...so a few isolated storms could possibly form in front of the front. Bottom line...still not looking like the most potent severe weather setup, but a with a strong cold front blowing through, a line of storms is likely to accompany the front, and a few storms may produce some damaging winds and hail. We'll have a better idea of the timing of the system with new model data tomorrow, so be sure to check back then.

--Trent

We've enjoyed a nice run of sunny & 70 degree weather....but that's not exactly the norm for November, and the inevitable clash of warm and cold air masses usually comes with the threat of severe weather....as looks to be the case for later this week. Right now, the forecast models appear to be coming in line with the idea that Thursday will be the day of concern...although the timing of the event is still a little too far out to pinpoint. This isn't unexpected....because November is right at the heart of our "secondary" severe weather season. Here's the setup...

First, remember that we need 3 things for thunderstorms to develop...1) moisture, 2) instability, 3) lift. By Thursday, a strong return flow around the western edge of high pressure in the southeast will be pumping in lots of Gulf moisture....providing the moisture. Also, with temperatures having been running so high lately, plenty of warm, buoyant air at the surface wil be ready to rise....providing instability. And on Thursday, a strong cold front will be approaching from the west, with the colder air clashing with the less-dense warm air providing the lift. Right now, it looks like the most likely scenario for our area would be a squall line advancing though the area ahead of the cold front....and damaging winds would be the main concern if that happens. Nothing is set in stone just yet, and the models are still figuring out the timing of the system, but considering that some of our region's most significant severe weather events of the recent past have occurred in November (see below), we should keep an eye on this storm system.

Significant November Events:

Nov. 6, 2005--Evansville F3 Tornado (23 fatalities) http://www.crh.noaa.gov/pah/?n=evansvilletornado-nov.6,2005

Nov. 15, 2005--Hopkins Co. F4 Tornado (Earlington) & Marshall Co. F3 (Moors Resort) http://www.crh.noaa.gov/pah/?n=nov1505f4

Meteorologist Trent Okerson

Why Leaves Change...

tokerson — Sat, 01 Nov 2008 23:21:00 GMT

Every autumn we revel in the beauty of the fall colors. The mixture of red, purple, orange and yellow is the result of chemical processes that take place in the tree as the seasons change from summer to winter.

During the spring and summer the leaves have served as factories where most of the foods necessary for the tree's growth are manufactured. This food-making process takes place in the leaf in numerous cells containing chlorophyll, which gives the leaf its green color. This extraordinary chemical absorbs from sunlight the energy that is used in transforming carbon dioxide and water to carbohydrates, such as sugars and starch.

Along with the green pigment are yellow to orange pigments, carotenes and xanthophyll pigments which, for example, give the orange color to a carrot. Most of the year these colors are masked by great amounts of green coloring.

Chlorophyll Breaks Down

But in the fall, because of changes in the length of daylight and changes in temperature, the leaves stop their food-making process. The chlorophyll breaks down, the green color disappears, and the yellow to orange colors become visible and give the leaves part of their fall splendor.

At the same time, other chemical changes may occur, which form additional colors through the development of red anthocyanin pigments. Some mixtures give rise to the reddish and purplish fall colors of trees such as dogwoods and sumacs, while others give the sugar maple its brilliant orange.

The autumn foliage of some trees shows only yellow colors. Others, like many oaks, display mostly browns. All these colors are due to the mixing of varying amounts of the chlorophyll residue and other pigments in the leaf during the fall season.

Other Changes Take Place

As the fall colors appear, other changes are taking place. At the point where the stem of the leaf is attached to the tree, a special layer of cells develops and gradually severs the tissues that support the leaf. At the same time, the tree seals the cut, so that when the leaf is finally blown off by the wind or falls from its own weight, it leaves behind a leaf scar.

Most of the broad-leaved trees in the North shed their leaves in the fall. However, the dead brown leaves of the oaks and a few other species may stay on the tree until growth starts again in the spring. In the South, where the winters are mild, some of the broad-leaved trees are evergreen; that is, the leaves stay on the trees during winter and keep their green color.

Only Some Trees Lose Leaves

Most of the conifers -- pines, spruces, firs, hemlocks, cedars, etc. -- are evergreen in both the North and South. The needle- or scale-like leaves remain green or greenish the year round, and individual leaves may stay on for two to four years or more.

Weather Affects Color Intensity

Temperature, light, and water supply have an influence on the degree and the duration of fall color. Low temperatures above freezing will favor anthocyanin formation, producing bright reds in maples. However, early frost will weaken the brilliant red color. Rainy and/or overcast days tend to increase the intensity of fall colors. The best time to enjoy the autumn color would be on a clear, dry and cool (not freezing) day.

Enjoy the color; it only occurs for a brief period each fall.

Courtesy: The Weather Channel

--Meteorologist Trent Okerson

Storm Outlook & Winter Weather

jrukavina — Thu, 30 Oct 2008 20:39:00 GMT

The transition to Fall has been very quick for our region, hardly seeing any frost before our first freeze hit earlier in the week. A swing of warmer weather (could be labeled as Indian Summer) will be with us for about 5-6 days. A stronger storm system will head out of the Central Plains which may give us our first round of severe weather since "Ike".

The computer models have been consistently pushing this storm system further our into the week ahead but are starting to agree on Wed Night into Thursday. Daytime temps will be in the mid 70's. Moisture will be marginal and may be a limiting factor on whether or not we actually get an event. The highest chance of activity has been focused on Missouri. We will update you as we see more model runs over the weekend.

As for WINTER...I know, not yet right!? Well the Old Farmer's Almanac and *** Frymyer have alluded to an earlier winter for the Ohio Valley and Deep South. Both agree on a chance of snow before November and cooler than average temperatures. I have posted below an excerpt from the Old Farmer's Almanac for the Deep South. Keep in mind....the following post is for the Deep South so "north" means Tennessee, Kentucky, and SE Missouri.

Winter will be much colder than normal, with temperatures one to two degrees below normal, on average. The coldest periods will occur in mid-December, early and late January, and mid-February. Precipitation will be below normal in the north but well above normal in the south. Snowfall will be above normal in the north, with the snowiest periods in late December and early January. Elsewhere, snowfall will be below normal.

Frost Above Freezing???

tokerson — Wed, 29 Oct 2008 17:33:00 GMT

This time of year a common question we hear is, "How can you say there is going to be frost if the temperature is not going to drop to 32 degrees?" This is a good question...and the answer is a little bit tricky. Here it is:

Part of the answer involves understanding how "official" temperatures are reported. The description of surface temperatures is a little misleading because "surface temperatures" are actually measured at a height of 4 to 6 feet above ground, and the thermometers are placed inside boxes called Stevenson screens, which gives us a shaded temperature (important for summer) and a temperature not directly influenced by snow, ice, wind, etc. (important for winter).

On a clear night with calm winds, all of the heat the ground collected from the sun during the afternoon is radiated away from the ground at night, causing the true surface temperature to become much cooler than the "surface temperature" we report. And since this cold air is more dense, it remains at the surface. With this setup, on most clear, calm nights, we experience something called a temperature inversion, where the temperature increases slightly as we move upward from the ground. The exception to this is when our winds remain active at night...this works to "mix" the colder air and the ground with the warmer air that escapes upward....which keeps our temperatures more uniform from the ground up.

Another very small factor is something called evapotranspiration. This is the natural process of plants giving off oxygen and moisture through their stomata (pores). As plants release moisture into dry air, a tiny bit of evaporation may occur, and air always cools down slightly during evaporation due to the absorption of latent heat by the water molecules from the surrounding atmosphere.

So...in brief...frost can form at above freezing temperatures because the true surface temperature is usually colder than the "surface temperature" that we report.

Meteorologist Trent Okerson

Breezy & Frosty Forecast!

tokerson — Sun, 26 Oct 2008 01:15:00 GMT

A strong cold front and area of cold Canadian high pressure will invade the region on Sunday afternoon, with gusty northwest winds bringing in the coldest airmass of the fall. This will bring possibly freezing temperatures to the area as soon as early Monday morning...and prior to that, strong and gusty northwest winds that may help to bring down a few of the remaining loose limbs left behind from Ike on Sunday afternoon and evening.

As for the prospects of frost.....a reminder of what the necessary conditions are for frost formation....1) Clear skies are needed for radiational cooling....where the heat of the afternoon sunshine is lost to space. 2) Temperatures near or below 32 degrees. 3) Very light or calm winds.....as strong winds help keep the atmosphere mixed, which helps keep around some of the heat of the day, and stirs up the molecules that would cause the frost to form and settle on plants and other objects. The winds over the next few nights will be the key as to whether we see frost or not. As of now, here's the chilly outlook:

Sunday Night--We'll have clear skies and temperatures will fall to near freezing, but only for an hour or two...plus we'll have a persistant NW wind, so frost is unlikely, except for in areas that are sheltered from the wind.

Monday Night--Clear skies again and lows falling to around or just below freezing, but winds again are likely to be strong enough to prevent widespread frost except for in sheltered areas. However, if the center of the high creeps a little closer than expected, then winds may die off enough for some patchy frost....so precautions may not be a bad idea just in case.

Tuesday Night--With the high centered close to the region, clear skies will be in place, lows may fall as low as the upper 20's, and winds will likely subside. This will be our most significant chance of frost...in fact, widespread frost is likely, and a hard/killing freeze is quite possible for a good portion of the area.

By the second half of the week, our temperatures will begin to moderate and may actually be a degree or two above average by next weekend. Meanwhile, as we get ready for this cold snap, don't forget to bring in your potted plants, cover those that you can't bring in, and be sure to remember your pets as well by providing them with some extra straw to stay warm. Also, now would be a good time to check your air filters in your home heating unit, as well as take some time to seal up any drafty spots around your doors and windows to make your home more energy efficient. Stay warm!

Meteorologist Trent Okerson

Rain Moves In...1-2 Inches Possible

jrukavina — Thu, 23 Oct 2008 00:46:00 GMT

An active weather pattern has unfolded bringing a descent chance of rain for all. Weather computer models have come into agreement on timing and intensity of the storm system. The GFS, NAM, ECMWF, and RPM bring locally heavy rain and a few thunderstorms as we move into the day on Thursday. Greater chances for rain stick West of the Mississippi until noon then slowly migrate eastward during the afternoon and evening. Friday looks to be fairly wet as well with periods of rain, mainly before noon.

The computer models also suggest at least 1, possibly 2 inches of rain with locally higher amounts. Flash flooding should not become a widespread issue. To avoid additional water logging in your own yard, be sure to keep drains clear of leaves and twigs from previous storms.

Once the cold front passes the region Friday, wrap around moisture will give us lingering showers Friday night and Saturday before gradually clearing on Sunday. Unseasonably cool weather will be with us for the next 7 days. Several reinforcing shots of cool air will be moving through keeping daytime highs in the upper 50's and lower 60's.

If your community receives high amounts of rain, send a quick email along with any photos you might want to share with other viewers. Send to storms@wpsdlocal6.com.

Chief Meteorologist Jennifer Rukavina

RAINFALL FORECAST FROM THURSDAY-SATURDAY

Weather Changes Mean Fall Returns

kmounce — Wed, 15 Oct 2008 01:24:00 GMT

Summer is trying to hold on, but it will certainly feel more like fall by the end of the week. A slow moving weather system will be responsible for the changes. It will bring a chance for rain across the region, but totals look to stay under a half inch (at best). We sure could use a little more rain. After an early October system brought widespread rainfall, we've been very dry. This has caused some counties to issue a burn ban...needing at least one inch of rain in 24 hours to cancel it.

While we may only get a little relief from the dry weather, the system promises to bring much cooler air. By Thursday, high temperatures will fall into the upper 60s to near 70. Our average high for this time of year is in the lower 70s. The weekend is also looking dry and cool. Great weather (except for those looking for rain) for any outdoor plans you might have.

Meteorologist Kyle Mounce

Rain!!!....Burn Bans Lifted

tokerson — Wed, 08 Oct 2008 18:21:00 GMT

A gloomy day is never a lot of fun....but it was really really good to see a nice soaking rain yesterday, especially since most of the rain fell in the locations that needed it the most. Many folks in KY & TN picked up anywhere from 1/2 inch to close to 2 inches.....good enough to start greening up some of my grass! That said, areas that have been so far behind with their rainfall totals over the past 60-90 days are still running 2-3 inches below normal. It's better though that we make up that deficit gradually, and as we head into our rainy season, that shouldn't be a problem.

With yesterday's rain over W KY, most of the counties that were under burn bans have had those lifted. At last check, only Crittenden Co. was still listed under a burn ban, having only picked up 0.6" of rain (usually 1" in 24 hours is required to lift the ban). Keep in mind that Oct. 1-Dec. 15 is considered Forest Fire Hazard Season, and that you are only allowed to burn between the hours of 6PM & 6AM (when humidities are higher and winds are lighter), and you cannot burn within 150 feet of woods and brushlands.

Off topic.....

Look for a new blog post that I am going to start on weather history. I enjoy looking back to see what wild weather events happened in the past from day to day, so I thought maybe I could share a few on here from time to time. Here's one for today:

1871 - Prolonged drought and dessicating winds led to the great Chicago fire, the Peshtigo horror, and the Michigan fire holocaust. Fire destroyed more than seventeen thousand buildings killing more than 200 persons in the city of Chicago, while a fire consumed the town of Peshtigo WI killing more than 1100 persons. In Wisconsin, a million acres of land were burned, and in Michigan, 2.5 million acres were burned killing 200 persons. "Tornadoes of fire" generated by intense heat caused houses to explode in fire, and burned to death scores of persons seeking refuge in open fields. (Source: weatherforyou.com)

Laughing at myself....

If you watched midday today, you may have noticed a slip of the tongue on my part when I said that the humidity level was at "93 miles per hour". That must be some really fast moving fog! Not sure if that would be considered "YouTube" material, but the crew sure did give me a hard time about it.....just have to laugh at that one.

Meteorologist Trent Okerson

Update on Severe Weather Threat Tue-Wed

jrukavina — Mon, 06 Oct 2008 23:57:00 GMT

Update on rain potential and severe weather threat...The Storm Prediction Center has yet to outline our area for a great potential for severe weather. They do, however, mention in their Monday afternoon discussion that they will be closely watching our region and that they may eventually upgrade to a slight risk. Any threat of severe weather will likely come in the form of strong winds and hail.

As for the rain, things still look like they are coming together where most of us are set to get as much as 1-2 inches of rain. We may see some dry time on Tuesday afternoon. If any sunshine breaks through then our chances for a few strong to severe storms will be higher. Showers and storms look to last on and off until Wednesday night, then wind down with lingering cloud cover on Thursday.

Review safety with your family, especially kids....they love to have an assigned responsibility when it comes to the important things. (ie. have them grab the flashlight, check the weather radio, make a checklist) Keep these things in mind when reviewing your plan..

Have a safe place to go when a severe weather alert is issued for your county/community.
Check and replace old batteries in your weather alert radio and make sure it is programmed correctly.
Keep copies of your insurance card, and contact list in a specific spot or with you in your safe place.
Designate items to cover and protect your head from flying debris. (blankets, mattress, helmet)
Keep flashlight, bottled water, extra batteries, AM/FM radio, emergency contact info all with you in your safe place.
Designate a place for everyone/family to meet in the case of separation

Sat. AM Fog

tokerson — Sat, 04 Oct 2008 23:20:00 GMT

We've hit the time of year where it is a common occurrence to experience something called "evaporation fog". This is when dense fog forms over and near bodies of water when the air temperatures dip into those chilly 40's. Water heats up and cools down much slower than the air and ground, and so the waters are still much warmer, which promotes rapid evaporation into the cool dry air, causing fog development. That occurred on our Sat. morning, and the Paducah National Weather Service captured some interesting satellite images that showed the dense fog, especially along portions of the Ohio & Mississippi Rivers.

Meteorologist Trent Okerson

Severe Weather - Fall Season Arrives

jrukavina — Wed, 01 Oct 2008 00:22:00 GMT

A peak in severe weather is typical during the Spring and the Fall season. Our Spring was quiet compared to the average but does not indicate how our Fall severe weather season will play out. The arrival of fall has been felt with cool Canadian air and dry conditions. The first sign of severe weather may be on the horizon with the arrival of a strong storm system indicated by the models to arrive by the start of the next workweek.

The early run of the GFSX shows a deep cut-off low making its way through the Red River Valley in Texas/Oklahoma. We may actually just get some beneficial rain from this system but if the models trend this system a bit more north, we will be in the warm sector and have a threat of severe weather. The moisture returns along with a highly sheared environment (turning of winds with height).

This being said, take the time this week or over the next weekend to review severe weather safety. Our region is notorious for outbreaks of severe weather in October and November. For a check of the Top 5 Severe Weather Events for Our Region, click here.

Have a safe place to go when a severe weather alert is issued for your county/community.
Check and replace old batteries in your weather alert radio and make sure it is programmed correctly.
Keep copies of your insurance card, and contact list in a specific spot or with you in your safe place.
Designate items to cover and protect your head from flying debris. (blankets, mattress, helmet)
Keep flashlight, bottled water, extra batteries, AM/FM radio, emergency contact info all with you in your safe place.
Designate a place for everyone/family to meet in the case of separation

Chief Meteorologist Jennifer Rukavina

Fall is here! So, what can we expect?

kmounce — Tue, 23 Sep 2008 01:26:00 GMT

Ah, it's that time of year again...the time when you get all the football you can handle, the days get a little cooler, and leaves start falling everywhere. Yes, fall has arrived! (Even if the high temperatures still feel like summer). The big question lately has centered around what we can expect for the new season. It is a good question, especially since fall is a season of change. For those looking for the answers of weather this fall, the Climate Prediction Center has some insight. Below, I have included their forecast for October-December. While they are interesting to look at, take it with a grain of salt. These are expected trends, but nothing is set in stone.

Explaining the graphics

Both the temperature and precipitation outlooks call for equal chances across our region. This means that our chances of getting above average temps/precip are the same as getting below average temps/precip.

One thing is for sure. The days are getting shorter. On average, we're losing about 3 minutes of daylight each day!

Meteorologist Kyle Mounce