Friday, November 30, 2007

STRONG WINDS FOR THE WEEKEND

The wind speeds will be a little gusty for the weekend. The storm system that will be moving just to our north will create a very strong pressure gradient. A pressure gradient is a change in pressure over a given distance. You can expect wind speeds to be gusting near 30 mph. The good news is that the winds will be gusting out of the southwest and that means warmer temperatures.

Posted by Patrick Crawford at 5:41 PM 0 comments

Thursday, November 29, 2007

F4 TORNADO NOV. 29, 1991


Tornadoes can happen any time of the year for us, though peak season is in the Spring when temperature contrasts between air masses is greatest. Fall brings about similar conditions, just not to the extent of Spring. It was on this day back in 1991 that our neighbors to the north had to contend with a tornado that produced F4 damage. The tornado traveled some ten miles between Nixa and Springfield, producing devastating damage and unfortunately claiming a few lives.

Posted by Ted Zarras at 7:26 AM 0 comments

Wednesday, November 28, 2007

FORT SMITH'S EAST WIND



The Arkansas River Valley is many miles wide in eastern Oklahoma, though becomes narrow to almost a point 100 miles east of Fort Smith. Air, cooling across the Ozark and Boston Mountains to the North as well as Ouachita Mountains to the South, especially at night, funnels into the valley and travels westward, flowing towards the wider opening in the valley and thus creates an easterly wind.

In fact, Fort Smith has an easterly wind direction some 41% of the year and at night it is easterly 50% of the time. Precipitation maximum in a 24 hour period over the calendar year peaks at 10:00 PM, correlating well with the nocturnal easterly wind, which lifts warm moisture -laden air as it flows westward towards Oklahoma. One other unique feature of the easterly wind is that often Fort Smith will drop lower temperature-wise than Fayetteville. This type of a set-up is almost always accompanied by a warm southerly wind aloft which downslopes and warms into Drake field. Such was the case last night with Fort Smith dropping to 38 F and Fayetteville only to 45 F.

Posted by Ted Zarras at 3:47 PM 0 comments

SNOW FOR THE GREAT LAKES

The cold front that will be sweeping through the area later on today is attached to an area of low pressure in the upper Midwest. As this low moves over the great lakes it will create some measurable snowfall. Areas of northern Michigan and northeastern Wisconsin will receive 3-6 inches and surrounding areas will be seeing 1-3 inches. The attached cold front that is moving through our region is very dry and will just give us some strong winds, clouds, and much cooler temperatures. This is a time when our location has really come in handy.

Posted by Patrick Crawford at 7:54 AM 0 comments

Tuesday, November 27, 2007

Windy & Mild Wednesday.......



We're looking for more of a spring-like afternoon for Wednesday thanks to a nice southerly feed. Unseasonably mild highs in the upper 50s and lower 60s are in the forecast.

In addition to increasing temperatures, the winds aloft look to speed up by Wednesday afternoon. Look at the 850 mb map above. Notice how strong the winds are around 5,000 feet. 40 to 50 knt winds aloft are forecasted by the NAM. This is a clue that decent mixing will occur, which will translate into gusty winds at the surface.

Expect winds between 10 to 20 mph with wind gusts over 30 mph across NW AR! Unfortunately, cooler air will work back in behind the front toward the end of the week, with high temperatures only in the low to mid 50s.

Posted by Drew Michaels at 4:04 PM 0 comments

HIGH FIRE DANGER

The Santa Ana winds are returning to the southwest for Tuesday night and Wednesday. An area of high pressure system is setting up over the Great Basin and will create a strong flow out of the east and northeast. As the air flows through the mountains and valleys, it will pick up speed and force the dry air into the southwest. It's this dry and strong wind that is ideal for allowing wild fires to intensify and grow. After what happened just a few months ago, this area is on a major alert for high fire danger. We will keep you posted as this weather scenario unfolds.

Posted by Patrick Crawford at 7:23 AM 0 comments

Monday, November 26, 2007

Clearing Line...........



After several days of clouds and chilly conditions, the sunshine looks to make a return this afternoon. The visible satellite picture shows the clearing line moving into eastern Oklahoma, and the dry air to our west should provide us sunshine and falling dewpoints.

Expect A chilly night with temperatures in the 20s and lower 30s before we warm back up on Tuesday and Wednesday.

Posted by Drew Michaels at 8:12 AM 2 comments

WINTER WEATHER

The wintry mix stayed just to our north for Monday morning. That doesn't mean we didn't get any precipitation to start off the work week. Rain showers moved through the area late last night and early this morning leading to some patchy fog and slick roads. The great news is that this system will be out of our way this afternoon and we could actually see a little bit of afternoon sunshine, especially in northeast Oklahoma.

Posted by Patrick Crawford at 7:27 AM 0 comments

Sunday, November 25, 2007

24 Hours... CLEARING OUT!




Just a little pocket of cold air remains in a semi cut-off area of Low pressure to our WSW. This Low is in what is known as "spin-down" stage. Cold air is no longer advecting (horizontally moving) into the system, and adding to it's strength. It is filling in and becoming mixed with surrounding air. This process can take up to 5 days or so and the Low will be long gone by then.

But, for the time being, the system has been quite stubborn in going over to an all rain event! Note Abilene's temperature in the observations (32F) and the snowy scene. As this system passes over our area tomorrow morning, we may see a little bit of a wintry mix and even some light snow. NE OK and possibly NW Benton county stand the best chance as the Low looks to track just south of I-44, though please use caution on all area-wide bridges and overpasses tomorrow morning. There could be isolated slick spots. Be sure to check in with Patrick tomorrow morning for any travel issues or concerns. By tomorrow afternoon we should see breaks of sun and Tuesday looks to be a fine day with ample sunshine and highs in the mid 50s... at this point, the gem of the week!




Posted by Ted Zarras at 4:09 PM 0 comments

SUNDAY AM UPDATE


Throughout the day, we are predominantly looking at a cold rain. Temperatures may not break 40 degrees north of I-40. Just along the leading edge of precipitation this morning though, there have been pockets of sleet and possibly a little freezing rain. The ground is still relatively warm so slick spots will likely not be an issue, but with limited visibility and wet roads it would be wise to just take it easy if your traveling today.

As we clear out tomorrow morning, enough cold air on the western side of the Low may give us a brief period of wintry precipitation. Tune in tonight at 5:30 and 10:00 PM for the latest information and any impending travel concerns for your commute to work on Monday morning.

Posted by Ted Zarras at 6:22 AM 0 comments

Saturday, November 24, 2007

POSSIBLE WINTRY WEATHER


Check out the two model soundings for Fort Smith and Fayetteville at 6:00 AM on Sunday. The numbers on the bottom in yellow are temperatures in Celsius and they are "skewed" to the right up the chart, hence therefore the name "Skew-T chart", which is what the diagrams are typically called.

Of particular note is how close the the red line (temperature) and dashed black line (dew point) are to zero degrees at the bottom of the chart (surface). The temperature profile actually warms aloft and is not below freezing until roughly 10,000 feet, but at the surface all it takes is a shallow layer of air below freezing to create a glaze, especially on bridges and overpasses.

We'll be updating current conditions at 7:00 AM Sunday and will alert you to any travel issues or concerns.

Posted by Ted Zarras at 9:46 PM 0 comments

Friday, November 23, 2007

Are you saturated, or dry?



An upper level storm system to our west is providing the necessary lift for decent snowfall accumulations across western Oklahoma and Kansas tonight. We're even starting to see radar returns move into our area; however, the lower atmosphere is way too dry, so anything that does fall aloft would likely evaporate before reaching the surface. Dewpoints are still in the teens, which represents the dry nature of the atmosphere at least at the surface.

Take a look at these 0Z soundings from Little Rock and Amarillo. Notice ow different they look.





Amarillo has a clearly defined saturated layer between 800 and 700 mb. That's a great layer for snowmaking. Several inches of snow fell across the panhandle of Oklahoma, and you can see why by looking at the sounding. Conversely, look at Little Rock, now that's a stout dry layer of air. That's way too dry for any precipitation to fall.

Posted by Drew Michaels at 8:19 PM 0 comments

CHILLY!




With a 1035mb High stamped almost directly on top of us, the clouds cleared out, the wind went calm and temperatures plummeted! Tahlequah, OK takes the honors of the coldest spot this morning... 12F. Yikes! Even Fayatteville bottomed out in the lower teens with a chilly 14F. Elsewhere, upper teens and lower 20s were common.

In the immediate future, our eyes will be on a system to the west which looks to bring the threat of some wintry weather, possibly in the form of sleet and freezing rain for a few hours on early Sunday morning. If we're clear for long enough Saturday night, we'll cool and that will leave a shallow layer of cold air to intercept the precipitation from the system. Depending on the depth of this layer,we could be looking at possibly a little light snow at the onset, but more likely some sleet going over to freezing rain before switching over to just a cold rain as the atmosphere warms up above freezing. This is tricky forecasting... we'll be monitoring developments closely as well adjusting the timing as the system gets closer. Be sure to catch the latest with Drew tonight at 6 and 10 PM.

Posted by Ted Zarras at 5:50 AM 0 comments

Thursday, November 22, 2007

Pesky Forecasted Cut-Off Low

Ted Zarras says it best, "a cut off low, is a weatherman's woe!" We're back in that situation toward the end of the weekend. Look at the NAM's progression of this cut-off feature.



This picture above shows the trough getting pinched of from the main upper level flow.



The cut off low develops late Saturday night into Sunday morning. Now the fun forecasting begins.



At this point the cut-off feature will move over us on Sunday creating a decent chance for cold rain; however, cold air will wrap around the low for Monday morning, and that could spell a wintry mix for the morning commute. This is all subject to change, and we'll watch it closely.

Posted by Drew Michaels at 3:57 PM 0 comments

Wednesday, November 21, 2007

TEMPERATURE DROP



Temperatures overnight and into the morning hours remained incredibly mild for most of us. This is also when we collectively reached our highs. From the morning onward, though we dropped into the 50s and then the 40s and now even 30s are showing up. Our lows for today will be the last observations taken tonight.

The maps highlight an average 30 degree drop or so from midnight through 4:00 PM today. By the end of the day some locations will be near 40 degrees lower than “this morning’s” highs!

Posted by Ted Zarras at 3:27 PM 0 comments

Tuesday, November 20, 2007

ACTIVE PERIOD AHEAD


g Troughs

g Jetstream

Our weather is turning active indeed as we plow into the late fall and early winter months. Globally, we presently have seven distinct long waves circumventing the northern hemisphere, inferring an active weather pattern. The dashed yellow lines represent the troughs and the green wavy arrow circling the globe is the *mean jetstream flow. (*meaning the "avg." flow, though sometimes the jetstream can pack a punch; in that case the jetstream would be the mean mean jetstream!)

It's looking like we've got three troughs to contend with over the course of the next week. In the picture, they are just off to the west, off the west coast and lastly south of Alaska. The first will bring the most significant cool down we've seen so far this year. A short wave diving into the first trough looks to merge with the second and possibly bring in some wintry precipitation over the course of this weekend. The scenario would be a cold air mass in place with warm and humid air pushing in from the south with a southern tracking Low, overrunning the cold. These type of set-ups are famous for snow to sleet to freezing rain to ultimately rain events as cold air gets eroded. The last trough looks to move in next Tue./ Wed... We'll get through the first two before talking about next week

Fine-tuning still needs to be done with the weekend forecast, though confidence is high that we will get cold so, remember to dress in layers and wear a hat. About 30% of body heat escapes from an uncovered head.

Posted by Ted Zarras at 4:17 PM 0 comments

Gulf Stratus Blanket




Gulf stratus can be a forecaster's nightmare across eastern Oklahoma and western Arkansas. You can easily bust on high temperatures if you don't take in account the thick stratus. Gulf stratus is really just a low level cloud deck around 1500 feet above the surface. This is a low deck that can bury temperatures if you don't get any breaks in the deck.

Typically, we see stratus off the gulf when 850 mb RH is over 80%, and your southerly winds are stronger than 35 knts. A pressure gradient ahead of a cold front will usually draw that moisture straight from the gulf. The RUC analysis this morning shows the winds at 850 mb around 35 knts.



Fortunately, the RUC erodes the 850 mb RH throughout the afternoon, and we should see sunshine later on today.

Posted by Drew Michaels at 8:02 AM 0 comments

TRAVEL WEATHER

I am planning on doing some traveling for Wednesday. I am heading to Illinois for Thanksgiving and I will driving all day Wednesday. I might be running into some rainy weather for my trip and that could add some time to my travel. Airports could also see a few delays for Wednesday and Thursday. I have attached a couple of links of some websites where you can look for travel conditions all across the U.S.! Have a great Thanksgiving and please stay safe with all your traveling.



AIRPORT DELAYS

ROAD CONDITIONS

Posted by Patrick Crawford at 6:37 AM 0 comments

Monday, November 19, 2007

THANKSGIVING CHANGES...YOU MIGHT NOT LIKE THESE CHANGES

We have been getting spoiled with our temperatures lately. Highs have been well above average for the month of November. We now could be experiencing below average temperatures for the rest of the month. A very strong cold front will sweep through the region for Wednesday. It will bring a chance for showers and some very strong winds. We could see some snow flurries for NW Arkansas on the backside of this system for Thursday morning. The big difference that we would like to point out about this cold spell, when we compare it to other cold spells this season, is that it will be lasting much longer. We are not seeing any warming trends in the extended forecast. That means cold temperatures will be with us for the entire Thanksgiving weekend!

Posted by Patrick Crawford at 7:13 AM 0 comments

Saturday, November 17, 2007

GFS RUN TO RUN




One thing that is nice to see when fine-tuning the timing of a forecast is run to run consistency of model information. The closer the solutions are to each other on a consistent basis implies that the model has a good handle on the solution. The two maps (12Z and 18Z runs) represent the position of a healthy Low that will pass through the central part of the country this week and although they appear identical, on close inspection, subtleties can be picked out. Notice the precipitation (green) that dips into NE OK and NW AR on both maps (feature shows great consitency). This precipitation is coupled with thickness values less than 540 decameters; one of the "critical thicknesses" looked at to decide where it will rain or snow. Thicknesses are the vertical distance between two isobaric surfaces (pressure levels) and when they are below a particular critical value for a layer of atmosphere, the average temperature within that layer is below freezing. In regards to the precip. in our area, although light, it would be snow! There are many "critical thicknesses" to consider though. Check out the table below.

Critical Thickness Rain/Snow Line
1000-500 mb / 5400m
1000-700 mb / 2840m
1000-850 mb / 1300m
850-700 mb / 1540m
850-500 mb / 4100m
700-500 mb / 2560m

The map below shows the thicknesses for 6:00 AM on Thursday morning. In this case nearly all critical thickness values are just south of parts of NW AR and NE OK. "If", and it's a BIG IF... the present model solutions hold true... we will see some Flurry activity late Wednesday night and into Thursday morning as the Low pulls out. A lot could and will likely change between now and then, but there's nothing wrong with a little wish-casting.

Let it snow, Let it snow, Let it snow!


Posted by Ted Zarras at 11:59 PM 0 comments

Forecasting 101: 700 mb Clearing Trough



As an operational forecaster, it becomes very helpful to remember common rules when putting together a forecast, and one of these rules deals with the position of the 700 mb trough.

If you know when the 700 mb trough will swing through, you'll have a better idea of when the weather will clear out. Take a look at the picture above. This picture deals with our Thanksgiving forecast later this week. Notice the position of the 700 mb trough in relation to our area.

Subsidence, or sinking air at the mid levels of the atmosphere, becomes responsible for the weather clearing up. The picture is for midnight heading into Thanksgiving morning. Looks like Thanksgiving will be cold, but dry, thanks to the speed of our next system.

Posted by Drew Michaels at 7:50 PM 0 comments

Friday, November 16, 2007

THANKSGIVING TRAVEL WEATHER

The travel weather for the Thanksgiving holiday could be a little messy. A strong upper level trough will dig into the central and southern plains by Wednesday. This system looks to produce some interesting precipitation. Parts of Colorado, Kansas, Nebraska, and Iowa could see accumulating snow. Areas of Texas, Kansas, Oklahoma, Missouri, and Northwest Arkansas will have a chance for a mix of rain, sleet, ice, and even snow. While the Mississippi River Valley will get rain. Conditions could be dangerous for the busiest travel day of the entire year. Keep it tuned to 40/29 TV and 40/29tv.com for the very latest weather forecasts that will impact your holiday plans.

Posted by Patrick Crawford at 6:16 AM 0 comments

Thursday, November 15, 2007

Turkey Day Cold Snap........Flurries?



Look at the 850 temperatures for Thanksgiving day! Yikes! This impressive cold snap is on the way, and this cool down may only yield highs in the upper 30s and lower 40s for the holiday. Of course, that's if this scenario plays out, but we have noticed a faster more progressive solution over the last 24 hours.



Now, this is an interesting picture, notice the dark blue shades on the map across NE OK and NW AR. This color denotes high relative humidity values at 850 over 80%, which may contribute to light snow or flurries across portions of NE OK and NW AR. Temperatures are cold enough, so we'll have to wait and see if the moisture's deep enough. At this point, I feel confident to mention flurries or light snow. Regardless, it's going to get very cold!

Posted by Drew Michaels at 8:16 PM 0 comments

THE SUN FROM SPACE


Here's a neat picture of the sun from space. Without the Earth's atmosphere, refracting and scattering the light spectrum, the sun appears white, with the entire light spectrum unimpeded.

Posted by Ted Zarras at 2:36 PM 0 comments

Wednesday, November 14, 2007

TORNADO STATISTICS


With a little over a month left in the year the number of reported tornadoes, 1271, is already above the 30 year average of 1045, though below the 1819 tornado reports of 2004. There have been 79 fatalities due to tornadoes this year, which is up above the 30-year average of 69 per year, though still far below deaths due to floods. Floods remain the most deadly weather related phenomenon.


Fort Smith had a significant Tornado pass through on January 11, 1898. The storm crossed Garrison Ave., devastating many businesses and residences. Unfortunately the tornado hit at 11:15 PM. There is a fascinating account of the storm that was put into booklet form and sold with pictures of the devastation it produced. Here's a link to an online reprint. http://www.fortsmithhistory.com/archive/July2007/Tornado1898text.html

Posted by Ted Zarras at 3:34 PM 0 comments

Will Thanksgiving Be A Turkey?

Hmmm, the long range models are painting a very interesting picture for Thanksgiving, so does that mean the chance for a little winter weather? We're still a week out, but this system definitely bears watching. The last several computer model runs have been consistent with dropping a cold air mass across the central United States for Wednesday.

These are 850 mb temperatures for Thanksgiving morning. Notice the freezing line that sits right along I-44. Now look at the second graphic. This is the computer model depiction of where the precipitation will fall. Our viewing area sits very close to the freezing line, but that could mean that some winter precipitation has the chance to fall just to the northwest of our area. The GFS is notorious for being way too cold with temperatures, so I'm not ready to believe in this scenario quite yet. Keep checking back for more blog entries. The weather team would love to hear your thoughts, so sign up and post your comments!



Posted by Drew Michaels at 3:17 PM 0 comments

STORMS STAY SOUTH

The cold front sweeping through the area today will give us much cooler temperatures, strong wind gusts, and shower chances. The good new is that the stronger storms will take place well to our south. That is where the strong upper level winds, the surface cold front, and the warm and humid air out of the Gulf of Mexico will all come together at the same time. This front will still leave it's mark with us, allowing our temperatures to drop 15°-25° from the previous days highs and lows. A noticeable change from the warmth we have been seeing all week.

Posted by Patrick Crawford at 6:40 AM 0 comments

Tuesday, November 13, 2007

Here Comes the Falling Temperatures....



The cold front that's coming for Wednesday remains to our north tonight, but we're still expecting a windy change by Wednesday afternoon. Here's the latest on the 850 mb temperatures for Thursday. Look at how they drop! What a difference as the temperatures cool to around 0 Celsius.

A decent pressure gradient will also follow the front as cold air advection takes place. Strong winds are slated for Wednesday afternoon and evening. Wind gusts close to 30 mph are possible. The breezy winds will relax for Friday morning as we expect lows in the 20s and 30s.

Posted by Drew Michaels at 7:08 PM 0 comments

DRY NO MORE?

Remember how we started off the month of October? The record rainfall in a 24 hour period...ring any bells? Well, since that huge start our weather has been rather quiet. A few showers or thunderstorms here and there, but no big rainfall totals. Here is a forecast from the climate prediction center from November 20-26 for precipitation. Notice that we fall into the above average category. The interesting part about this forecast is that it's two weeks out...meaning that Thanksgiving falls into this prediction. We could see some precipitation while we are eating our turkey and stuffing.

Posted by Patrick Crawford at 7:18 AM 0 comments

Monday, November 12, 2007

Cooler Changes Are Coming........




Fall is just going to have to wait a little bit longer. 850 air aloft will continue to boast unseasonably warm temperatures at the surface, but those changes are on the way. The picture below shows 850 mb air between 15 and 17 degrees Celsius for Tuesday afternoon. Highs in the 70s!




Look what happens on Wednesday.....yikes! The warm bubble will burst, and Thursday and Friday will feature much cooler afternoons. By Thursday look at how the 850 air drops!

Posted by Drew Michaels at 8:26 PM 0 comments

A GOOD CHANCE FOR RAIN

A short wave is moving through the area today out ahead of a cold front. One characteristic of a short waves is that they can provide lots of lift. Lift is ideal for generating showers and thunderstorms. Here is a look at Monday afternoon's rain chances. Some areas will see stronger storms than others.

Posted by Patrick Crawford at 6:18 AM 0 comments

Sunday, November 11, 2007

A Beautiful Weekend Retreat








The thick low level stratus may have held down high temperatures on Saturday; however, the clouds provided a wonderful opportunity to experience the fall colors.

I spent the majority of the weekend in Subiaco, AR on a retreat with the Catholic Campus Ministry at UAFS, and I wanted to share some photos with you from the trip. The trees were simply breathtaking. The photos were taken on the grounds at the Subiaco Abbey. If you have never traveled there, you must make it a point of interest along Hwy 22. Make sure you ask one of the Benedictine monks for a tour!



The picture below is a cooperative weather station that the National Weather Service maintains. My wife Adrienne snapped the picture.



de

Posted by Drew Michaels at 3:06 PM 0 comments