Severe Weather Friday & Saturday...
SW Louisiana Forecast Discussion...Thursday was another beautiful day across the forecast area with highs in the lower 80s once again under Mostly Sunny to Partly Cloudy skies. The quiet weather continues tonight, but our luck could run out on Friday. Tonight skies will be Mostly Clear to Partly Cloudy. A more pronounced onshore flow is present, as high pressure in the mid and upper levels breaks down and moisture surges into all levels of the atmosphere. Temperatures will be quite mild with reading only bottoming out in the low to mid 60s across the area. The much advertised potential severe weather maker continues to trudge Eastward tonight through the Great Plains with another day of tornadoes from Texas to Nebraska. How will this system affect our area, and when? A lengthy breakdown follows...
First, Friday will start off in a rather benign fashion. The day should dawn with generally Partly to Mostly Cloudy skies and the aforementioned mild temperatures. A strong Jet Stream will exist throughout the day, and intensify as daytime heating takes over and creates the usual mixing processes. This will result in strong, gusty winds during the day with winds over 20 mph at times. The persistent onshore flow will continue, and bring in a significant surge of low-level moisture. The high low-level moisture content will play in role in what unfolds Friday afternoon. The potent Pacific storm will move Eastward, and as it does so a very energized atmosphere will create a volatile situation. A short wave (disturbance) will emanate out ahead of the main associated trough. This will be enough of a trigger to spark off some scattered convection especially during the afternoon hours. We should have no problem reaching the convective potential temperature which will be in the lower 80s. Scattered streamer shower activity should develop by late morning to around noon as the deeper moisture moves in. These scattered air mass showers will be quick movers, and rainfall rates will be limited. Not everyone will get in on the rainfall on Friday, however, there is a problem. The atmospheric conditions will be in such a volatile state Friday afternoon as the short wave ejects and interacts with the Jet Stream energy. Thus, the prospects for severe weather should be realized. All forecast models have come into agreement on two rounds of severe weather, and it is the first of which will occur Friday afternoon. All modes of severe weather are possible, however, the greatest risk should be across the Northern half of the forecast area, and into North Louisiana. SW Louisiana is certainly not out of the woods, however, the Gulf is often an inhibiting factor wrt severe weather. This is one reason that the severe risk will be greatest further inland. However, that being said, there is a very strong Jet Stream and good directional shear that is forecast to be in place even along the I-10 corridor. Therefore, severe weather is possible in any given location across the forecast area. The main time frame for said convection will come between noon and 6p.m. As per my Thursday evening analysis, the main severe weather threats with this first round should be large hail and isolated tornadoes. The entire forecast area is highlighted for a slight risk of severe weather as per the SPC forecast, however, a moderate risk for severe weather is currently highlighted over the Northern half of the state. This falls right in line with my current thinking that the best chance for severe weather will be for places such as Shreveport-Bossier City, Ruston, Monroe, and up into Southern Arkansas from around El Dorado over to Monticello, Pine Bluff, and Dumas. Certainly with the presence of a 60-80 kt. Jet Stream over SW Louisiana will be conducive to some of the aforementioned streamer shower to intensify quickly into supercells. These supercells will attain severe characteristics as they move SW to NE across the forecast area. These supercells will have the potential to produce tornadoes across the area, some of which could be long-track tornadoes. Forecasting severe weather is challenging in its own right, but pinpointing exactly who will experience a tornado is near impossible. Just understand, it is very likely that there will be a tornado somewhere in the area Friday. Large hail exceeding golf ball size will also be possible, as well as damaging winds in excess of hurricane force. Activity will peak in the late afternoon, early evening hours before a brief respite occurs across the area in the wake of the emanating short wave. It would be a good idea to review your severe weather plan of action on Friday at your home, school, or business. I urge everyone to keep abreast of the latest weather developments, and I would expect the issuance of a Tornado or Severe Thunderstorm Watch at some point during the day Friday. Again, not everyone will see rain on Friday. It is very much a situation where someone will get severe weather, and someone else just a few miles away won't even get a drop of rain. Rain chances are in the 30-40% range, but they'll be going higher in the next period (Saturday).
Let's quickly review some severe weather safety tips:
-Seek shelter immediately once you hear thunder or see lightning.
-Keep tuned to local TV and/or radio affiliates or other media outlets for the latest weather information.
-If applicable, set your NOAA Weather Radio to alert mode....you can program it for your own parish or county.
-If a tornado warning is issued, take refuge on the lowest floor of your home or office, stay away from windows and doors.
-Protect yourself from flying debris.
-Do not open windows!
-If in your vehicle, abandon it and lay flat in a ditch or culvert and use your hands to cover your head from flying debris. Do not seek shelter under an overpass, and do not try to outrun the tornado.
-Please stay inside during the tornado or thunderstorm for that matter. Yes, pictures are great, but it is not worth risking your life to get photos!
-Call your local law enforcement official or report your severe weather to the NWS in Lake Charles.
-Please send in your pictures of any storm damage (after the storm or if you capture some video or pictures of the storm well in advance) to me @ BestWxMan1980@yahoo.com.
-Feel free to leave me any questions or comments you have right here on the blog or send them to the e-mail provided above.
-Check back during the day Friday for more updates including watch and/or warning information.
Here are some severe weather graphics from the Storm Prediction Center in Norman, OK.
A respite comes Friday evening into the nighttime hours of Friday, however, all eyes will be watching the next round of severe weather unfold out West. The main thrust of this system is a very potent upper level low which will still be back over Texas Friday night, but as it feels influence from the very fast Jet developing over the area it will pick up steam and begin to eject from the base of a Great Plains trough. The energy produced by the Jet Stream and the dynamics of the upper level low will induce a surface low in the Red River Valley Friday. This low will traverse Eastward, and the cold front/dry line will trail from this feature. This will set the stage for the second and final round of adverse weather. This is what will likely bring us a higher threat for severe weather here in the immediate SW Louisiana area, and a moderate risk for severe weather is certainly feasible for areas from Lake Charles eastward for Saturday. The end result will be the development of showers and thunderstorms along and ahead of the boundary over Texas Friday afternoon and evening, with this activity expected to congeal into a squall line or MCS. Soundings and forecast parameters suggest a tornado outbreak will commence across the ARK-LA-TEX region Friday night, and evolve further ESE through the night. While much of the overnight hours of Friday could be quite with just a few scattered showers, as dawn nears on Saturday severe weather possibilities will ramp up once again. Additional Jet Stream may engender a separate surface low over the NW Gulf or just inland over SE Texas. This will trek across SW Louisiana Saturday morning just ahead of the front. Thus, our higher risk for severe weather at that time. A tornado threat will be possible across the entire area, but the greatest tornado risk will be north of I-10 and over into Acadiana. Damaging wind and large hail will be threats as well, although with the amount of wind shear in the atmosphere wind damage seems like the biggest threat. The time frame for which to expect the main thrust of this potential severe weather will be between 6a.m. and noon across the forecast area. SE Texas should experience the advancing MCS around 6a.m. while it should be near the Lake Charles area between 8 and 9a.m. and in the Lafayette vicinity between 10 and 11a.m. This is expected to be a fast mover, and the entire complex should clear the forecast area by noon or shortly thereafter. Once it passes your area, the severe threat is over, and much better weather is to be expected by the latter half of Saturday. I should take a minute to mention rainfall amounts. We do need rain, we don't need the severe weather, but this looks like a situation where we won't get one without the other. 1-2" of rainfall is expected on average for the Friday-Saturday time frame. Certainly with the brief heavy rain expected, some localized street flooding could occur, but overall no flooding problems are expected at least here locally. A more significant flooding problem could occur towards SE Louisiana where heavier rain amounts in excess of 3" are expected in some places. Rain chances for Friday night will remain in the 40% range, but they jump up to the likely category of 80% for Saturday. A mild temperature regime will be in place during this entire event with lows by Saturday morning only around 70. Saturday afternoon temperatures should exceed 80 once again, and it's certainly not out of the realm of possibility that some sunshine may return before the end of the day Saturday as much drier air filters in behind the cold front. I call it a cold front simply because it is that by definition. It won't really do much for us as far as giving us any cooling effects. However, much drier air will filter in and offer up some pleasant weather its wake.
Drastic improvements follow the severe weather on Saturday afternoon. The cold front and severe weather will be long gone, as it will be over Dixie by that time. We will see an offshore flow develop, and high pressure will be building into the Red River Valley. Clearing skies will take over by Saturday night. Expect temperatures to fall off to near normal late April levels with upper 50s by Sunday morning. The period Sunday-Tuesday should be beautiful and pleasant with high pressure in control at the surface and aloft. A fairly uniform temperature regime is expected as well with lows in the mid 50s to lower 60s each day, and highs hovering around the 80 degree isotherm. A steady state humidifying and warming trend is expected by the middle of the week as high pressure slides off to the East, bringing back the usual onshore flow. Low temperatures will climb back into the low to mid 60s by the end of forecast period, while highs remain in the lower to middle 80s depending on your proximity to the Gulf of Mexico. We will transition from sunny skies at the beginning of the week to a mix of sun and clouds by Thursday as Gulf moisture is ushered back in. A dry forecast is maintained for the time being beyond Saturday. The pattern will be such that it will block any potential storm systems from affecting our area in the Sunday-Thursday time frame. This blocking pattern is exactly what we have been dominated by nearly the entire month of April. Long range models continue to suggest the potential for another significant storm around May 1st. I won't elaborate on that now with so much to be concerned with in the short term, but we'll see how this evolves next week. Stay tuned for more updates on Friday as the severe weather outbreak unfolds!
Be sure to listen to the audio blog for more specifics!
Preliminary Numbers & Zone Forecast:
LCH 66/82 69/83 58/80 0 30 40 80 0 0
LFT 65/83 68/83 60/81 0 30 40 80 0 0
BPT 66/83 70/81 59/82 0 40 50 80 0 0
AEX 61/84 66/80 55/78 0 40 60 90 0 0
POE 61/83 67/80 56/78 0 40 60 90 0 0
ARA 66/83 71/81 61/81 0 30 40 80 0 0
Overnight...Mostly Cloudy. Low 66. SE wind 10 mph.
Friday...Partly to Mostly Cloudy & Windy with a 30% chance of showers & thunderstorms. Some severe storms with damaging winds, large hail, & isolated tornadoes possible. High 82. SSE wind 20-25 mph and gusty.
Friday Night...Mostly Cloudy with a 40% chance of showers & thunderstorms. Some severe storms w/ tornadoes, damaging winds, & large hail possible towards morning. Low 69. SSE wind 15-20 mph and gusty.
Saturday...Cloudy & Windy with showers & thunderstorms likely during the morning. Severe storms & locally heavy rainfall possible. Rain ending by noon with drastic improving in the afternoon. Clouds decreasing in the afternoon. High 83. SSW wind 20-25 mph and gusty. Chance of rain 80% in the morning. Rainfall amounts up to 2" possible.
Saturday Night..Mostly Clear & Cooler. Low 58. WNW wind 10 mph.
Sunday...Sunny. High 80. West wind 10 mph.
Drew's 7 Day Outlook
Friday
4-23-10
High: 82
Rain: 30%
Wind: SSE 20-25
Saturday
4-24-10
Low: 69
High: 83
Rain: 80%
Wind: SSW 20-25
Sunday
4-25-10
Low: 58
High: 80
Rain: 0%
Wind: W 10
Monday
4-26-10
Low: 56
High: 78
Rain: 0%
Wind: WNW 10
Tuesday
4-27-10
Low: 58
High: 80
Rain: 0%
Wind: WSW 10-15
Wednesday
4-28-10
Low: 61
High: 83
Rain: 0%
Wind: SSW 10-15
Thursday
4-29-10
Low: 65
High: 85
Rain: 10%
Wind: SSE 15-20
...Marine Forecast...
Tonight...Southeast winds 15 to 20 knots. Seas 2 to 3 feet building to 2 to 4 feet after midnight.
Friday...South winds 15 to 20 knots. Seas 2 to 4 feet subsiding to 2 to 3 feet in the afternoon. A slight chance of showers and thunderstorms.
Friday Night...South winds 15 to 20 knots. Seas 3 to 4 feet. A slight chance of thunderstorms in the evening. A chance of showers. A chance of thunderstorms after midnight.
Saturday...South winds 15 to 25 knots becoming southwest 15 to 20 knots in the afternoon. Seas 3 to 4 feet subsiding to 2 to 3 feet in the afternoon. A chance of showers and thunderstorms.
Saturday Night...Southwest winds 10 to 15 knots. Seas 2 to 3 feet subsiding to 1 to 2 feet after midnight.
Sunday...Northwest winds 10 to 15 knots. Seas 1 to 3 feet.
Have a Great Friday & Check Back for More on the Severe Storm Situation Later Today! God Bless!
-DM-
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