The blog remains in severe weather (winter weather) mode until further notice. That means the impetus will on the discussion & the actual forecast with many sections omitted. The video is an essential part of the blog in this situation, so look for the latest one just below here. Be sure to scroll down for the text form, and stay tuned throughout the night for further updates. There's no sleeping when the weather is active you know. One other note here before I begin, send me your pictures of the winter storm, but be very careful. I will post your pictures on the blog, and give you proper accolades.
SW Louisiana Forecast Discussion...The expected winter storm is materializing tonight. It started in the mid-late morning hours with periods of freezing rain and sleet across the area. Temperatures didn't move much, and we only made it to 33 today. That, of course, was enough to change the freezing rain to plain ole rain, but this will change tonight as temperatures drop back below freezing. The two key synoptic features creating thus precipitation are still in play. Of course, we have the entrenched Arctic air at the surface. Isentropic lift (overrunning) continues ahead of the now forming surface low and the advancing upper level feature over Texas. The low will migrate slowly NE through the night, and upper level disturbance will move Eastward, and these systems will conglomerate to consolidate moisture over the area. This overrunning moisture will lead to widespread precipitation spreading across the area overnight. The main part of this storm will come after midnight through much of the day on Friday. The forecast I laid out for you last night remains right on track. Of course, there are still questions that are present here even now that we are in the short form. The biggest questions are what will be the dominant p-type and how much will accumulate? The answer to the first question is more cut and dry, that will depend upon your location in the forecast area. The second question is not as simple to answer, but it is safe to say we will all see accumulations and all have ramifications. I will break down what I believe we'll happen as far as accumulations in a moment.
First, the periodic precipitation will slowly transition to widespread precipitation overnight as the aforementioned synoptic scale features come into play. At present, we are in a lull after a good round of sleet earlier this evening, but to the West of Houston snow is beginning to form as lifting and forcing increases. The overrunning moisture will cause widespread precipitation to stream inland from the Gulf of Mexico from SW to NE across the forecast area, and from the West in Texas. Most of the precipitation will be on the light side, but with sufficient lifting and forcing in place as well as some instability there could be periods of moderate to occasionally heavy precipitation. The atmospheric profile still suggest there is a warm tongue of air above the surface as generated by SW winds aloft. This warm tongue will likely result in the majority of the precipitation falling in the form of sleet and freezing rain. There will be a chance for some snow as well, but the best chances of this will be over the NW portion of the forecast area and roughly along a line from near Houston to Leesville to Monroe. Snow is possible over immediate SW Louisiana and SE Texas, but accumulations will be limited and this may not occur until after sunrise Friday. 1-3" of snow is possible towards Toledo Bend to Leesville. Further south, we might see up to an inch of snow if we are lucky. Our biggest issue will be the ice and sleet. Significant accumulations of freezing rain and sleet are expected. The warm layer of air above the surface will remain in place if models are correct. Temperatures between 925 and 850 mb. are above freezing, so as the precip falls as snow it will melt when it hits this layer. The parcel of air may cool overnight as the widespread precipitation falls, and allow the warm layer to shrink in size towards morning. Thus, sleet seems the most likely p-type for the Lake Area. Up to 1" of sleet accumulation is possible, but average amounts will be around 1/2". That is more than sufficient enough to lead to very serious and dangerous driving conditions. Sleet would not be as bad with regards to downed trees and power lines, but you can pretty much forget about trying to navigate Friday morning. The greatest risk for significant freezing rain accumulations and ice accretions will be over Acadiana. The warm layer of air is thicker over that region, so the predominant p-type will be in the form of freezing rain mixed with some sleet. Ice accumulations will be around 1/4" on average with potential for up to 1/2" where the precipitation is a little heavier. That is more than sufficient enough to create a coating of ice on the power lines and trees, and lead to widespread power outages along with the very dangerous driving conditions realized in this region as well.
The timing is a bit more certain after observing the radar and satellite trends downstream. The periods of sleet and freezing rain mixed with some snow will continue through midnight, and then between 2 and 4a.m. the widespread wintry precipitation should begin as forcing continues to increase along the NW Gulf Coast. The shield of frozen precipitation will continue into a good portion of the day on Friday. This should be at least through noon, but if the system travels a bit slower than expected we could see precip last until the mid to late afternoon hours. The bottom line is that no matter when the precip ends, the Friday morning commute will be a nightmare. It is recommended you stay home. All schools are closed Friday, and I am sure many businesses have followed suit. It would be the smart thing to do. The window of opportunity to see any snow will be between 9a.m. and 3p.m. Friday as the precip begins winding down. The atmospheric column will likely cool on the backside of the Gulf low. The low and upper level disturbance will propagate Eastward through the day, and precipitation will gradually taper in the afternoon. Chances of precipitation are maxed out for tonight and tomorrow with gradual improvement. Temperatures will remain cold with lows in the upper 20s to around 30 tonight, and highs only close to freezing Friday. A stiff offshore flow will continue since the surface low will remain offshore leaving us in the cold sector. NNE winds 15-20 mph will be commonplace for tonight and tomorrow. Wind chills will remain in the 10s and 20s through Friday. A Winter Storm Warning is in effect for all parishes and counties along and North of I-10 corridor, while a Winter Weather Advisory is in effect for the coastal parishes. It is in effect until Noon Friday, but understand this event may last longer than that. Once the main event begins, determining the end of the precipitation will become easier as we can base it off of satellite and radar trends.
The whole system will wind down Friday afternoon and evening with some lingering snow flurries possible until the evening hours. Skies will clear our rapidly Friday night into Saturday as much drier air moves into the region with high pressure re-established in the wake of the winter storm. With temperatures remaining at or near freezing Friday, most of what falls during the storm will remain on the ground. Temperatures will plummet with clear skies, light winds and snow and ice on the ground. Anything that melts, will re-freeze and black ice will become an issue as well for Friday night into Saturday with another hard freeze in place. Lows for Saturday morning will range from the upper 10s to lower 20s across the area as the Arctic air remains in place at least for a little while longer. The weekend is shaping up nicely. We come out of the deep freeze Saturday, all of the snow and ice will melt during the day Saturday as temperatures climb well above the freezing mark. We should reach the mid 40s for maximums Saturday. That will feel warm compared to where we have been since Tuesday afternoon. The Arctic air mass modification process continues for the entire weekend. Lows will be near freezing for Sunday morning with a light freeze realized along and North of I-10. Super Bowl Sunday should be a very nice day with plenty of sunshine after the chilly start. It will be warmer still in the afternoon with highs in the upper 50s to around 60. A return flow sets up in the afternoon. Winds off the Gulf will return in advance of our next cold front.
This next front arrives on Monday, and moisture will be limited. There will a chance of showers as some lifting is created by the front. Just enough displace the moisture that will be in place Monday morning. The exact timing of the front is still in question, and quite frankly I haven't spent much time looking at the specifics here since all our eggs are in the winter weather basket right now. However, it looks like models show a faster solution and suggest the front will arrive overnight Sunday into the early morning hours of Monday. A slight chance of showers is expected, but this will in no way be a big rain event. The temporary warm up will be halted, as CAA takes place again on Monday. Highs will struggle to get out of the 40s. This front will have Arctic teleconnections. Skies should clear out quickly behind the front. High pressure is in place for Tuesday, and it should be a day with cold sunshine. Morning temperatures will be in the hard freeze category again with low to mid 20s expected while highs reach the mid 40s. A very, fast progressive pattern with a NW flow aloft in place will send another surge of Arctic air Southward. This should arrive behind another cold front on Wednesday. It is too early to say for sure, but this front has the potential to be even stronger than the one that ushered in the current air mass. Some clouds will increase ahead of this front, but again very little in the way of rainfall is expected as the front slides through Wednesday. A small chance of rain is noted for this time frame. Afternoon highs may reach the low 50s with WAA in place, but the brief period of warm air intrusion will be halted dramatically as this front plows on through. Temperatures will plummet Wednesday night into the mid 20s. Clouds will remain in place as models suggest the possibly of a low forming in the wake of the front. Models are still clinging to the idea of the potential for additional winter weather. Right now, they suggest this will be in the Wednesday night-Thursday time frame. Right now, I don't reflect this idea, but I will keep it cloudy in the Wednesday night-Thursday morning time frame with very cold temperatures. The coldest morning of the season, and perhaps in many years comes up on next Friday just beyond this forecast period. We could see lows in the 10s over a widespread area of the forecast area. Again, we'll hone in on all of this after we get this Winter Storm out of the way. Stay tuned for more information & stay home!
Preliminary Numbers & Zone Forecast:
LCH 29/33 21/46 30/58 100 100 20 0 0 0
LFT 29/34 22/45 30/57 100 100 30 0 0 0
BPT 28/33 23/47 32/60 100 100 20 0 0 0
AEX 25/30 18/43 27/56 80 80 30 0 0 0
POE 25/30 19/44 27/56 80 80 20 0 0 0
ARA 30/35 22/45 30/58 100 100 30 0 0 0
*Winter Storm Warning in effect until Noon Friday.*
Tonight...Cloudy, Windy, & Very Cold with sleet, freezing rain, & snow likely. Total combined accumulations up to 1". Ice accumulations up to 1/4" possible. Low 29. NNE wind 15-20 mph and gusty. Chance of precipitation 100%.
Friday...Cloudy, Windy, & Very Cold with the winter storm continuing. Sleet, snow, & freezing rain likely. Accumulations of sleet and snow up to an inch. Ice accumulations between 1/4 and 1/2 of an inch. Precipitation ending during the afternoon. High 33. NNE wind 10-15 mph. Chance of precipitation 100%. Wind chills readings 15-25.
Friday Night...Mostly Cloudy with a 20% chance of snow early on, then skies clearing overnight. A hard freeze is expected. Low 21. North wind 10 mph.
Saturday...Sunny & Warmer. High 46. NE wind 10 mph.
Saturday Night...Clear & Not Quite as Cold. Low 31. North wind 5 mph.
Sunday...Mostly Sunny & Warmer. High 58. ESE wind 5-10 mph.
Drew's 7 Day Outlook
Friday
2-4-11
Low: 29
High: 33
Precip: 100%
Wind: NNE 15-20
W.C.: 15-20
Saturday
2-5-11
Low: 21
High: 46
Precip: 10%
Wind: E 5-10
W.C.: 20-30
Sunday
2-6-11
Super Bowl
Low: 30
High: 58
Precip: 0%
Wind: SE 5-10
Monday
2-7-11
Low: 38
High: 50
Rain: 30%
Wind: SSW/NNW 15-20
W.C.: 25-40
Tuesday
2-8-11
Low: 24
High: 44
Precip: 0%
Wind: NNW 15-20
W.C.: 15-30
Wednesday
2-9-11
Low: 31
High: 47
Precip: 20%
Wind: NNE/NNW 15-20
W.C.: 20-35
Thursday
2-10-11
Low: 22
High: 36
Rain: 30%
Wind: NNW 15-20
W.C.: 10-25
Stay tuned for more details on this potentially dangerous winter storm!
Good night & God bless!
-DM-
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