The blog will be in severe weather mode through Monday.
*Significant Severe Weather Outbreak Possible Monday.*
SW Louisiana Forecast Discussion...The signs of the changing weather are already present on this Sunday evening. It is very humid, unseasonably warm, & windy on the outside as a vigorous Pacific storm makes headway towards this forecast area. Call this the proverbial calm before the storm if you will. Thankfully, this weekend has been dry. Temperatures today reached near the 80 degree threshold, and moisture continued to be pumped in off the Gulf of Mexico via the pronounced return flow that is in place over the area. The deep moisture will remain in place overnight with generally Mostly Cloudy skies prevailing. It will almost seem summerlike overnight as low temperatures only drop to around 70. At the same time, ingredients will begin coming into play to produce some rather robust weather on Monday. Explicit details will follow. First, I can't rule out a few air mass or streamer showers overnight as the moisture levels continue to increase across the area, however, a mid and upper level cap should remain in tact to preclude much in the way of shower activity tonight. The deepening trough will also keep the atmosphere mixed up overnight with South winds in the 10-15 mph range. That should alleviate a fog issue. Expect an eerily quiet start to the day on Monday. The weather should be fine for the morning commute.
While it may seem deceptively quiet as the sun comes up on our Monday, things will be going downhill in a hurry as this Spring storm makes its presence felt on this forecast area. We are still less than a week removed from the previous severe weather event across our area. This time around it appears as though conditions will favor a more widespread event, and a severe weather outbreak that will cover a wider area of our great country. Severe weather is ongoing this Sunday evening in parts of the Great Plains and Mid West. That being said, it is time for me to set up the scenario for you. If you don't read any other part of this discussion, you need to read this section. It will be essential that everyone have a way to keep informed of weather developments through the day Monday. The strong cold front is currently sweeping SE from the Southern Rockies up through the Mid West. It will slide SE tonight and Monday as the associated trough deepens and translate further to the East. This energy from the main Jet Stream will engender surface cyclogenesis as per usual over the Great Plains or Red River Valley. The low will evacuate NE, and the front will continue its SE surge towards the Gulf Coast. Lifting and forcing will dramatically increase after daybreak Monday. Instability and low-level convergence will be on the uptick as well. This will help eliminate all capping that resides on the atmosphere at the time, and as a result showers & thunderstorms will begin to develop in the morning hours.
Unlike our last event, this one will be diurnally driven meaning daytime heating will factor into the equation. Convection initiation should occur between 10 a.m. and noon for most of the area. The front will make excellent headway entering the NW extremities of the forecast area between 17Z and 18Z (12-1p.m. CDT). The deeper moisture pooling over the area suggests that streamer showers will be possible ahead of the front in the morning, and these will have the potential to build up into robust thunderstorms and become discrete supercells. This is where the greatest risk of tornadoes exists. A squall line (MCS or QLCS) will initiate along the cold front tonight, and translate SE just ahead of the boundary Monday. This is what will be approaching the forecast area around lunch time. The juiced up atmosphere will generate the additional convective activity ahead of the squall line. There looks to be a decent amount of wind shear (vorticity) in place for the isolated tornado threat to be realized. However, it should be noted that the greatest vorticity will be just off to our NE from Central LA into NE LA and SE AR and much of Central and Northern MS. This is where the tornado threat will be greater.
The biggest threats from the severe weather here at home should come from large hail and damaging winds, but by no means can I completely rule out some tornadoes. Unlike last time, all modes of severe weather will exist. If you recall, the event from last Tuesday night/Wednesday morning was for the most part strictly a hail event. The differences in atmospheric set up will dictate what type of weather the forecast area experiences. A diagram known as a hodograph is used to determine if there will be a tornado threat or not. This graph basically shows wind direction in the levels of the atmosphere. The more curvature that is indicated, the higher the risk for tornadoes. The LCH hodograph sounding certainly indicates enough curvature for some tornadoes. There is a great deal of energy that needs to be displaced. There is a lot of cold air aloft that will be thrown into the mix, and increasing Jet Stream dynamics will support the damaging wind threat. The sufficient amount of upper level cold air supports the hail threat. In short, all modes of severe weather are possible. Like I said previously, the aspect of convective heating will be in the mix as well.
The strong to severe squall line will migrate into the forecast area Monday afternoon feeding off of the extremely moist Gulf air mass in place. The greatest risk for severe weather in the forecast area will occur from around noon to 6p.m. Monday. The cold front will quickly push into the coastal waters by sunset. The severe weather threat will end with passage of the front. Rainfall will be heavy at times especially along and just ahead of the front, however, the fast upper level flow and Jet Stream in place will keep the storms moving. This will reduce rainfall amounts, however, 1-2" of rainfall is still expected across the area. The rainfall is much needed, but will not be enough to completely alleviate the drought situation. Of course, there is no way to specifically pinpoint who will get what form of severe weather. Any one location stands an equal chance of getting hit with these adverse weather conditions. I fully expect a Tornado Watch to be issued for the forecast area during the course of the day on Monday. I would surmise that the Lake Charles area will be at greatest risk for severe weather between 2p.m. and 6p.m. It will continue to be unseasonably warm & humid in the pre-frontal environment. High temperatures will flirt with the 80 degree mark ahead of the front Monday. A strong onshore flow will prevail as well until frontal passage in the afternoon. Rainfall comes to an end with much drier and cooler air filtering in Monday evening. A strong offshore flow will ensue as well.
The rest of the forecast period will be much quieter. High pressure will quickly build in behind the departing cold front. All of the storminess and rainfall comes to an end Monday night with a much cooler and drier air mass moving in. Strong CAA will also prevail in the wake of the front. Skies will clear out setting us up for a beautiful couple of days. Clear, breezy, and unseasonably cool temperatures are in store for Tuesday. By sunrise, temperatures will be in the mid 40s on average with the coldest locations reaching closer to 40. It will feel much colder than that given the gusty North winds, and the fact that it has been so warm lately. You will want to grab a jacket or sweater as you head out the door first thing Tuesday morning. Afternoon highs will likely fall just short of the 70 degree mark with generally mid to upper 60s across the area. The same general conditions will be present for Wednesday. Wall to wall sunshine is expected, and it will start out on the cool side of 50 once again with mid to upper 40s. Afternoon highs will be a bit warmer with readings back into the lower 70s for most. The very dry air mass will remain in place as the high pressure sticks around. CAA will cease, and the surface high will begin to slide Eastward late in the day. This will bring back the return flow of Gulf air by day's end, but it will be of little consequence as far as weather conditions are concerned at that time.
The remainder of the forecast period will be highlighted by a return of warm & humid conditions. The return flow will quickly become more pronounced on Thursday as the surface high slides over the SE U.S. On its Western periphery, we will see a well established return flow. The deep moisture will begin to flow back over the area. Temperatures will reflect this as well. The wall to wall sunshine will be replaced by a generally Partly Cloudy sky. There could be a little bit of morning low cloudiness and patchy fog, but a dry pattern is expected with the main storm track remaining locked in place well to our North. High temperatures will return to near 80 by Thursday with morning lows in the mid 50s north to mid 60s closer to the coast. The April warm up will continue for Friday & the upcoming weekend with essentially the same atmospheric conditions in place. Low temperatures Friday will be in the mid 60s or so while afternoon highs eclipse the 80 degree mark. Patchy fog and/or early morning low cloudiness will be prevalent, but that will burn off by mid-morning and be replaced by a general mix of sun and clouds. The warmest weather of the season is expected for the upcoming weekend with highs creeping up into the mid 80s, with upper 80s in inland locations. This will occur as upper level ridging strengthens. Morning lows will be close to 70, almost more like summer than the second week of April. This is one of those weeks when the phrase "if you don't like the weather, wait 5 minutes it'll change" applies. The predominant onshore flow will keep the high humidity in place as well. No mention of rain is expected again until around the first part of next week, but models are still differing on those solutions so we'll see how that evolves once we get past Monday's episode. Stay tuned!
Preliminary Numbers & Zone Forecast:
LCH 71/80 45/67 46/72 20 80 20 0 0 0
CAM 75/78 50/70 51/68 20 80 20 0 0 0
LFT 71/81 46/68 45/72 20 80 20 0 0 0
ARA 72/80 47/69 47/71 20 80 20 0 0 0
BPT 71/79 45/69 47/73 30 80 20 0 0 0
AEX 67/77 40/65 41/69 30 80 20 0 0 0
POE 67/77 41/65 42/70 30 80 20 0 0 0
Tonight...Mostly Cloudy with a 20% chance of showers after midnight. Continued unseasonably warm & humid. Low 71. SSE wind 10-15 mph.
Monday...Cloudy, Warm, & Windy with showers & thunderstorms likely. Severe weather & heavy rainfall w/ damaging wind, large hail, & isolated tornadoes possible. Rainfall amounts 1-2" & the greatest risk for severe weather will come between noon and 6p.m. High 80. SSE wind 20-30 mph and gusty, becoming SSW in the afternoon. Chance of rain 80%.
Monday Night...Cloudy w/ a 20% chance of rain early. Skies clearing overnight. Much cooler & windy. Low 45. NNW wind 20 mph and gusty.
Tuesday...Sunny. High 68. NNW wind 10-15 mph.
Tuesday Night...Clear & Cool. Low 46. Light North wind.
Wednesday...Sunny. High 72. NE wind 5-10 mph.
Monday 4/4/11 Daily Planner
6a.m.
Weather: Mostly Cloudy & Warm
Temp: 71
Rain: 20%
Wind: SSE 12
9a.m.
Weather: Mostly Cloudy
Scattered Showers & Storms Firing Up
Temp: 74
Rain: 40%
Wind: SSE 19
Noon
Weather: T-Storms Likely
Severe Weather Outbreak Beginning
Temp: 77
Rain: 80%
Wind: SSE 24
3p.m.
Weather: T-Storms
Cold Front Approaching Lake Charles
Temp: 80
Rain: 80%
Wind: SSW 28
6p.m.
Weather: Cloudy
Rain Ending from West to East, Turning Much Cooler
Temp: 64
Rain: 60%
Wind: NNW 24
9p.m.
Weather: Clearing & Much Cooler
Temp: 58
Rain: 20%
Wind: NNW 17
Drew's 7 Day Outlook
Monday
4-4-11
Low: 71
High: 80
Rain: 80%
Wind: SSE/NNW 20-30
Tuesday
4-5-11
Low: 45
High: 67
Rain: 0%
Wind: NNW 10-15
Wednesday
4-6-11
Low: 46
High: 72
Rain: 0%
Wind: NE 5-10
Thursday
4-7-11
Low: 57
High: 80
Rain: 0%
Wind: SSE 10-15
Friday
4-8-11
Low: 66
High: 82
Rain: 0%
Wind: SSE 10-15
Saturday
4-9-11
Low: 69
High: 84
Rain: 0%
Wind: SSE 15-20
Sunday
4-10-11
Low: 71
High: 83
Rain: 0%
Wind: SSE 15-20
...Marine Forecast...
*Gale Watch in effect from Monday night through late Tuesday night.*
*Small Craft Advisory through Monday morning.*
Tonight...South winds 20 knots and gusty. Seas 2 to 4 feet building to 3 to 5 feet after midnight.
Monday...South winds 15 to 20 knots shifting northwest 25 knots in the afternoon. Seas 3 to 5 feet. A chance of showers and thunderstorms in the late morning and early afternoon. Showers and thunderstorms likely late in the afternoon. Some thunderstorms may be severe.
Monday Night...North winds 30 knots and gusty. Seas 4 to 6 feet. Showers and thunderstorms likely early in the evening...then a chance of showers and thunderstorms late in the evening. Some thunderstorms may be severe.
Tuesday...North winds 25 knots becoming northeast 10 to 15 knots in the afternoon. Seas 3 to 5 feet subsiding to 2 to 4 feet in the afternoon.
Tuesday Night...Northeast winds 5 to 10 knots becoming southeast after midnight. Seas 1 to 2 feet.
Wednesday...South winds 10 to 15 knots. Seas 1 to 3 feet building to 2 to 3 feet in the afternoon.
Stay tuned for more updates on the impinging severe weather! Have a great Monday & God bless!
-DM-
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