The blog is in short form for the rest of the week with a potential severe weather outbreak looming for Saturday.
SW Louisiana Forecast Discussion...Another quiet April evening is ongoing across the forecast area in the wake of another pretty April day. Skies were Mostly Sunny during the morning, and Partly Cloudy during the afternoon with sporadic fairweather cumulus dotting the landscape on Wednesday. This continued dry spell was as a result of mid and upper level ridging, and a blocking surface high to our East. An onshore flow continued across the area providing some low-level moisture. The temperature forecast verified quite nicely with lows in the mid 50s, and highs right around the 80 degree mark. Quiet weather continues tonight with clear skies and pleasant temperatures expected once again. Some patchy fog could develop late tonight, but this shouldn't be a major issue by any means. Overnight lows will be near seasonable values in the upper 50s to right around 60.
While it's quiet here, a strong Pacific storm system is getting revved up out to our West. Severe weather is occurring for the second straight night in parts of the Texas Panhandle, and this could perhaps be a harbinger of things to come around these parts later on. The blocking pattern will hold for one more day on Thursday, thus the active weather associated with this potent Pacific storm should remain well removed from our area. We will see a continuance of the dry late April pattern on Thursday. Skies will range from Mostly Sunny to Partly Cloudy once again with a continued steady onshore flow. Winds will increase a bit in response to the pressure differential due to the Western storm. Afternoon highs will meet or exceed the 80 degree mark. Thursday night will be another quiet time frame, but some subtle changes will take place. A break down in the upper level ridge will occur as some Jet Stream energy from Northern Mexico flows into the region behind the slow to depart blocking high. This will result in deeper low-level moisture, and an increase in cloud cover across the area. Temperatures will be mild as well with lows in the mid 60s. This is several degrees above normal.
Changes take place more significantly Friday. This, as the Pacific storm moves our direction as the blocking high to our East finally breaks down. A strong low-level Jet will develop in advance of the system, and this will create windy conditions across the forecast area. The day will start quietly with just some clouds, mild temperatures, and increasing clouds. At this same time, storms will likely be ongoing over parts of Texas stretching up through the heart of Tornado Alley. A significant severe weather outbreak is expected in this area on Friday. The advancement of the front will weaken the proverbial cap on our atmosphere, and generate enough forcing combined with daytime heating and sufficient low-level moisture to result in the formation of some scattered showers and thunderstorms for the afternoon hours on Friday. This is really much change in my thinking from last night, except I will add the possibility of severe weather to the mix for Friday. There will be plenty of instability in place, and the expected development of a surface low over the Red River Valley will place the entire area in the right-front quadrant of the Jet Stream. This is an area where severe weather often occurs. The convective potential temperature should be reached on Friday, and this will result in the development of the aforementioned scattered activity during the afternoon. A fast Jet Stream over the area will cause rapid movement of activity, but the scattered activity will have the chance to reach severe limits as it moves NE across the area, and feeds off of the available Jet Stream energy. The environment that is expected to be in place will favor all modes of severe weather, however, I still believe the highest risk for severe activity on Friday will be to our N and W in closer proximity to the surface low and trailing cold front. Isolated tornadoes, damaging wind, and large hail are possible really anywhere in the forecast area, but it is hard to be specific about who will get what. Friday will be warm and windy with highs in the lower 80s and winds over 20 mph at times with the presence of the strong Jet Stream across the area.
The chance for adverse weather will continue for the Friday night-Saturday period as the front draws near. It is Saturday during the day when the highest risk of severe weather will occur across the forecast area. This will be along and just ahead of the cold front. The cold front is progged to move into SE Texas between daybreak and mid-morning and into SW Louisiana from the late morning hours through early afternoon. IT is a set up for Saturday that favors the evolution of an MCS. This squall line will likely form Friday during the day across Texas and transition Eastward through the night Friday and move through the forecast area Saturday between 12Z and 18Z (7a.m.-1p.m.) The risk of scattered convection (potentially severe) will continue ahead of the squall line. This poses problems for Friday night as this is the worst possible time for severe weather to occur, since most of us will be sleeping. You know I'll be up round the clock if need be. The environment for Friday afternoon and Friday night is one that will be conducive to supercells while an environment transformation will occur as the front nears on Saturday to one that will suggest an MCS. Along with the severe weather threat, a heavy rainfall threat will exist as well with 1-2" of rainfall expected for this event. However, we can use the rain, so flooding problems should not arise. The driving force with this system is a potent upper level component which will bring the hail threat in response to the associated cold pocket of air aloft. It is the Jet Stream dynamics that will lead to the aforementioned tornado and wind damage threat. The tornado threat will be less with the MCS on Saturday morning, but tornadoes can certainly occur within the squall line as well. Oft times though, it is wind damage that becomes the more common severe weather mode with an MCS. There is still a lot of forecasting that has to be done to evaluate the exact risk of severe weather, but the bottom line is that the chances for our first true severe weather outbreak of the Spring are increasing. One limiting factor for us is as always the Gulf of Mexico. The greatest threat for dangerous weather should be well inland across Central and North Louisiana, but South Louisiana is by no means out of the woods. Further re-assessment and even more specificity will be cited on Thursday. The front clears the area Saturday afternoon, and rapidly improving conditions will be in the offing at that time. It is vital that you stay informed about the potential weather situation for Saturday due to timing uncertainties, and potential impact on any plans you may have in the Friday-Saturday time frame. Saturday's temperature regime will certainly be supportive of severe weather will unseasonable morning lows in the upper 60s to around 70, while afternoon highs top out near 80 because of the rain. Rain chances are in the likely category, and could very well end up maxing out based on tonight's model data. It is essential to have a severe weather plan of action in place, and also have your NOAA Weather Radio set to alert mode just in case. If you don't have a weather radio, make sure you have some way of getting the latest watches and warnings so you will be aware of rapidly changing weather conditions. This is most crucial at night.
By definition, Saturday's system is a cold front, but it really won't do much for us as far as cooling us off. Certainly, though much drier air will take over in the wake of the front beginning Saturday night. Skies will clear as high pressure over the Rockies builds in, and this will set the stage for a beautiful second half of the weekend on Sunday. Not only Sunday, but much of the rest of the forecast period will be nice with the high pressure slow to pull away. Temperatures will not be far from normal, and some mornings in the Sunday-Wednesday time frame will stand to be quite pleasant. Highs will remain at or just above normal for each day. Morning lows should be in the mid 50s to lower 60s. This is essentially the norm for late April. No chance of rain is mentioned for the Sunday-Wednesday time frame with very little in the way of any clouds expected until Tuesday or Wednesday when a deeper low-level return flow will allow for higher dew points and humidity to return with the surface high oriented over the SE U.S. at that time. In the long range, it looks like another strong system could move in just in time for month's end with the chance for some severe storms carrying over into the first weekend of May.
Preliminary Numbers & Zone Forecast:
LCH 60/81 64/83 67/82 0 0 0 30 40 70
LFT 59/82 63/84 67/83 0 0 0 30 40 70
BPT 61/83 66/82 68/83 0 0 0 40 50 70
AEX 55/81 60/82 64/80 0 0 0 30 60 80
POE 56/81 61/82 65/81 0 0 0 30 60 80
ARA 62/82 65/83 68/82 0 0 0 30 40 70
Overnight...Mostly Clear. Low 60. Light SE wind.
Thursday...Partly Cloudy. High 81. SSE wind 10-15 mph.
Thursday Night...Partly Cloudy. Low 64. SSE wind 10 mph.
Friday...Mostly Cloudy with a 30% chance of showers & thunderstorms. Some storms could reach severe limits with isolated tornadoes, large hail, & damaging winds in the afternoon. Windy. High 83. SSE wind 20-25 mph and gusty.
Friday Night...Cloudy & Windy with a 40% chance of showers & thunderstorms. Some storms could reach severe limits. Low 67. SSE wind 20 mph and gusty.
Saturday...Cloudy & Windy with showers & thunderstorms likely. Locally heavy rainfall & severe weather possible. All modes of severe weather possible. High 82. SSE wind 20-25 mph and gusty, becoming SW at 15-25 mph and gusty in the afternoon. Chance of rain 70%.
Thursday 4/22/10 Daily Planner
6a.m.
Weather: Clear
Temp: 60
Rain: 0%
Wind: SE 4
9a.m.
Weather: Mostly Sunny
Temp: 70
Rain: 0%
Wind: SSE 11
Noon
Weather: Partly Cloudy
Temp: 75
Rain: 0%
Wind: SSE 14
3p.m.
Weather: Partly Cloudy
Temp: 81
Rain: 0%
Wind: SSE 15
6p.m.
Weather: Partly Cloudy
Temp: 79
Rain: 0%
Wind: SSE 12
9p.m.
Weather: Partly Cloudy
Temp: 74
Rain: 0%
Wind: SSE 7
Drew's 7 Day Outlook
Thursday
4-22-10
Low: 60
High: 81
Rain: 0%
Wind: SSE 10-15
Friday
4-23-10
Low: 64
High: 83
Rain: 30%
Wind: SSE 20-25
Saturday
4-24-10
Low: 67
High: 82
Rain: 70%
Wind: SSE/SSW 15-25
Sunday
4-25-10
Low: 60
High: 82
Rain: 0%
Wind: W 10-15
Monday
4-26-10
Low: 58
High: 82
Rain: 0%
Tuesday
4-27-10
Low: 58
High: 81
Rain: 0%
Wind: WSW 10
Wednesday
4-28-10
Low: 60
High: 83
Rain: 0%
Wind: SSE 10-15
...Marine Forecast...
Tonight...South winds 5 to 10 knots. Seas 1 to 2 feet.
Thursday...South winds 10 to 15 knots. Seas 1 to 2 feet building to 2 to 3 feet in the afternoon.
Thursday Night...Southeast winds 15 to 20 knots. Seas 3 to 4 feet.
Friday...South winds 15 to 20 knots. Seas 3 to 5 feet building to 5 to 7 feet in the afternoon. A slight chance of showers and thunderstorms.
Friday Night...South winds 15 to 20 knots. Seas 5 to 7 feet. A chance of showers and thunderstorms.
Saturday...Southwest winds 15 to 20 knots. Seas 3 to 5 feet. A chance of showers and thunderstorms.
Have a Great Thursday and God Bless!
-DM-
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