The blog is in short form this update due to the active weather over the next 24 hours. There is also no video blog today as I continue to battle a head cold and still sound raspy. The blog should be back at full capacity tomorrow. Sorry for any inconvenience.
SW Louisiana Forecast Discussion...After the coldest morning of the season so far, some moderation is underway tonight. Tuesday morning's low ranged from the mid 20s to around freezing across the area. It was a beautiful but cool day as expected across the forecast area with a strong high pressure in place. Sunny skies with a few high clouds prevailed during the day, and high temperatures reaching the mid 50s on average. Conditions are changing, even if only briefly, tonight. We have a fast-paced NW flow aloft in place across much of the nation right now. The Jet Stream is dipping down right into Louisiana. An embedded short wave (upper level disturbance) is quickly moving SE out of the Rockies and towards the state tonight. It is currently nearing the Red River Valley, and will push into the ARK-LA-TEX and then into Louisiana overnight. As this cold pocket of dives towards the area, forcing will increase. Precipitation associated with the upper level disturbance (short wave) has broken out over portions of Oklahoma and Kansas tonight. As the embedded short wave travels our way, the adding forcing will engender surface cyclogenesis in the Western Gulf of Mexico. The end result will be the development of a shield of mostly light rain over the area as moisture overspreads the area. The heaviest rain will remain over the coastal waters closer to the surface low. Temperatures are moderating, so only a cold rain is expected across the area. Rain chances will be into the likely category after midnight mostly for locations along and South of I-10. The rain chances will taper off efurther inland, as it should be sporadic thanks to less forcing away from the coastal low.
However, occasional light rain is expected across the forecast area mainly in the early morning hours. A few light showers are possible before midnight as moisture increases, but most of it will wait until the advancing short wave arrives. Rain is expected to be widespread, or at least have the appearance of it on radar. There is still a decent amount of dry air in place at the surface, therefore, most of the rainfall at the onset will evaporate before reaching the ground (virga). As the rain falls, the boundary layer will moisten up, and then the light rain will begin to reach the surface. This virga also leads to a process known as evaporative cooling. That means, that as precipitation falls it cools the surface temperatures until the precip begins to reach the surface. As I said a moment ago, temperatures have moderated somewhat with a very subtle return flow in place. Temperatures will likely be in the upper 30s to lower 40s as the rainfall begins after midnight, and then will fall a few degrees likely into the low to mid 30s across the area. With the developing Gulf low, and weak return flow there is a layer of warm air aloft, but at the same time the approaching upper level disturbance will produce additional cold air aloft, and will help drive the surface temperature down a few more degrees. What does this mean for precip type across the area? You remember last night I mentioned other forms of precip besides rain. My thinking has not changed. This will mostly a rain event for the entire area. However, there is still a small possibility of some snow mixing in with the rain towards daybreak as the system flies by. Any snow that falls will not accumulate, as it will be light in nature. Ground temperatures are relatively warm as well, and this would be a mitigating factor as well. Parts of the state may see some real excitement with upwards of an inch of snow accumulation with this system. Snow is likely to occur in the colder air over the Northern half of the state, and Winter Weather Advisories have been issued from Shreveport over to Monroe for this reason. Rainfall amounts will be light, generally in the 0-10"-0.25" range. If we are to see any snowflakes in the Lake Area, it will most likely occur between 4a.m. and 9a.m. Wednesday, again no accumulations are expected. The only areas of this forecast area that would stand to have any chance of seeing some accumulations would be across Vernon, Rapides, and Avoyelles Parishes where the coldest temperatures will exist, but I stress than even up there it is an iffy proposition. All precipitation will cease by mid-morning Wednesday. It will be a cold morning, but most locations should be above freezing with an average low in the middle 30s across this region.
After perhaps a few backside snow flurries from around sunrise to mid-morning Wednesday, conditions rapidly improve as the upper level system and Gulf low vacate the region. High pressure becomes re-established over the NW Gulf Coast, and skies will rapidly clear out from NW to SE across the area. I expect that the sun will return by the lunch hour in the Lake Area. It will remain on the cool side on the backside of the system with weak CAA in place. Model guidance is too warm for Wednesday given the cloudy and moist start. I have undercut guidance by several degrees, only displaying highs in the low to mid 50s at best across the area. The stage will be set for another cold night, and likely another freeze across the area. High pressure will be firmly entrenched by this time, and very light winds and clear skies will be in place. Overnight lows will range from the mid 20s in the coldest locations to right around freezing at the coast. A heavy frost is likely by Thursday morning. You will want to protect your plants and pets once again. This should not be a freeze that affects the pipes, but it is always better to be safe than sorry. A more significant warming trend will get underway on Thursday after the sub-freezing start. Wall to wall sunshine is on tap, and as the big high moves off to the East, a return flow will commence, thus establishing a warming trend to take to the end of the week. Thursday's maximums will still be below normal with highs falling just shy of the 60 degree mark. Humidity will remain quite low, and it will be a beautiful day.
The warm up is enhanced on Friday with a more pronounced Southerly flow. Conditions seem like they may be primed for a foggy start. The return flow will send the warmer Gulf air inbound towards the cooler air over land, and thus poses the recipe for fog. I don't believe it will be a very dense fog for Friday morning since there will be a lot of low-level dry air that needs to be displaced first, but certainly some patches of fog are to be expected. Morning low temperatures will still be on the cool side, and a jacket will likely be required as you head out the door on Friday. Temperatures will range from the mid 30s in the coldest locations to the mid 40s along the coast and over in SE Texas. After any fog dissipates, a generally Mostly Sunny to Partly Cloudy day is expected. Low level moisture will increase through the day as the onshore flow intensifies ahead of our next weather maker. Afternoon highs will likely be close to normal levels reaching the mid 60s for most locations. It will feel warmer than that since it's been so cold this week. The benign weather continues for Friday night into Saturday to start the weekend. It may be a very foggy start to the second full weekend in December. A significant amount of low-level moisture will be in place by Saturday morning, and much milder conditions temperaturewise will co-exist. The stage will be set for a dense fog across the area. Further revisions to this portion of the forecast are likely in the coming days. Saturday will be the warmest day of this forecast period. Under Partly Cloudy and windy conditions, high temperatures across the forecast area will reach the lower 70s. This comes after morning lows in the low to mid 50s across the area.
Another Arctic cold front will be approaching during the day Saturday, and as it does so rain chances will return to the forecast. A strong cap will be in place through Saturday morning, but as the strong front approaches in the afternoon, lifting and forcing will increase such that rain chances shall return to the forecast. This doesn't appear to be a widespread or significant rain event by any means, but there will certainly be more than enough low-level moisture in place, and marginal instability for some shower and thunderstorm activity to develop during the afternoon and evening hours on Saturday in the pre-frontal environment. There should be sufficient dynamics for some thunderstorms ahead of the front Saturday evening and Saturday night, but no severe weather is anticipated in our part of the world at this time. However, there will be the possibility of some severe weather off to our NE closer to the better dynamics. I can't rule out a renegade severe storm around here, but we will fine tune this as the front draws near. It is a bit early to pinpoint exact timing of said boundary, but it should be before midnight Sunday. The shower and thunderstorm activity should quickly come to an end once the front screams through the area into the coastal waters. The transition from a strong onshore flow to a strong offshore flow will take place rather quickly. In the post-frontal environment temperatures will plummet thanks to strong CAA behind the Arctic front. Temperatures will fall from the low to mid 70s Saturday afternoon to the upper 30s to lower 40s by Sunday morning. Wind chills readings will likely be in the 20s for all locations by sunrise Sunday with a strong Northerly wind in place. Skies will clear out quickly as well in the wake of the front. Sunday we will face the reality of December once again as highs struggle to reach the 50s across the board, and I believe many locations stay in the 40s with CAA offsetting daytime heating.
The coldest air of the season takes over for Sunday night into Monday as winds begin to decouple, and crystal clear skies remain in place. A large area of Arctic high pressure will be sliding down the base of the Rockies, and have a firm grip on much of the nation by that time. This means that it will be a very cold period. Expect lows to fall well down into the 20s, and a hard freeze is expected area wide for Monday morning. The coldest locations could conceivably wind up in the upper 10s, it remains to be seen, but either way you slice the bread, it will be very cold to start the new work week. Model guidance currently suggest upper 20s for Monday morning, but you have to keep in mind that at this stage of the game the models trend towards climo at the latter stages. That being said, I am undercutting guidance and reflecting mid 20s for the time being. We could approach record lows for Monday. Again, this is something that will need further assessment in the days ahead. It will certainly be a dry cold this time around, with no mention of any embedded NW flow disturbance. Sunny skies are expected for Monday with the Arctic high pressure in place. Expect a maximum to reach the mid 40s at best. The very cold conditions will continue for Monday night into Tuesday with the large Arctic anti-cyclone in our vicinity. Temperatures will once again drop well down into the 20s for the morning low with crystal clear skies. Afternoon highs on Tuesday will approach 50 as a slow moderation of the air mass begins. Just beyond this forecast period, modifying of temperatures and a dry weather regime will be in the fold. It is likely that a return flow will be established by the middle of next week allowing temperatures to approach more seasonable levels by the latter half of the week. In a drought stricken year, we desperately need rainfall, and this colder and drier than usual pattern doesn't help. We will take whatever we can get at this stage of the game. The long range models continue to support the idea of more cold blasts into the latter half of this month. It is too early to speculate on what kind of weather we will have for Christmas. Stay tuned!
Preliminary Numbers & Zone Forecast:
LCH 35/51 29/56 39/64 60 30 0 0 0 0
LFT 34/50 28/55 38/63 60 30 0 0 0 0
BPT 39/53 30/57 42/66 70 30 0 0 0 0
AEX 32/47 25/52 35/61 60 30 0 0 0 0
POE 32/47 25/52 35/62 60 30 0 0 0 0
ARA 34/52 29/55 40/64 70 30 0 0 0 0
Tonight...Cloudy and Not Quite as Cold with rain likely. Rain could possibly mix with light snow towards daybreak. No snow accumulations expected. Low 35. East wind 5-10 mph becoming NW at 10 mph after midnight. Chance of rain 70%, chance of snow less than 20%.
Wednesday...Cloudy with a 30% chance of light rain possibly mixed with light snow early. No accumulation of snow. Precipitation ending quickly, and becoming Sunny by afternoon. High 51. NNW wind 10-15 mph.
Wednesday Night...Clear and Cold w/ a freeze. Low 29. North wind 5-10 mph.
Thursday...Sunny. High 56. NE wind 5-10 mph becoming SE during the afternoon.
Thursday Night...Clear and Not as Cold w/ some Patchy Fog after midnight. Low 39. Light SE wind.
Friday...Patchy Early Morning Fog otherwise Mostly Sunny to Partly Cloudy. Warmer. High 63. SSE wind 10 mph.
Wednesday 12/8/10 Daily Planner
6a.m.
Weather: Light Rain & Cold w/ a Few Snowflakes Possible
Temp: 35
Rain: 60%
Wind: NNW 10
W.C.: 28
9a.m.
Weather: Mostly Cloudy...Perhaps a Leftover Snow Flurry
Temp: 38
Rain: 20%
Wind: NNW 12
W.C.: 32
Noon
Weather: Mostly Sunny
Temp: 47
Rain: 0%
Wind: N 14
W.C.: 41
3p.m.
Weather: Sunny
Temp: 51
Rain: 0%
Wind: N 12
6p.m.
Weather: Clear
Temp: 46
Rain: 0%
Wind: N 6
W.C.: 42
9p.m.
Weather: Clear
Temp: 40
Rain: 0%
Wind: N 3
W.C.: 38
Drew's 7 Day Outlook
Wednesday
12-8-10
Low: 35
High: 51
Rain: 30% AM (A Few Flurries)
Wind: NNW 10-15
W.C..: 25-40
Thursday
12-9-10
Low: 29
High: 56
Rain: 0%
Wind: NE/SE 5-10
W.C.: 25-40
Friday
12-10-10
Low: 39
High: 63
Rain: 0%
Wind: SSE 10
Saturday
12-11-10
Low: 54
High: 71
Rain: 40%
Wind: SSE 15-20
Sunday
12-12-10
Low: 38
High: 47
Rain: 0%
Wind: NNW 15-20
W.C.: 25-35
Monday
12-13-10
Low: 26
High: 45
Rain: 0%
Wind: N 10
W.C.: 15-30
Tuesday
12-14-10
Low: 24
High: 47
Rain: 0%
Wind: NE 5-10
W.C.: 20-35
...Marine Forecast...
Tonight...East winds 5 to 10 knots becoming northeast at 20 knots and gusty after midnight. Seas building to around 3 feet after midnight. A chance of rain.
Wednesday...Northeast winds 20 knots and gusty decreasing to 10 to 15 knots in the afternoon. Seas around 3 feet. A chance of rain in the morning.
Wednesday Night...Northeast winds 10 to 15 knots. Seas 1 to 2 feet.
Thursday...East winds 10 to 15 knots becoming southeast in the afternoon. Seas 1 to 2 feet.
Thursday Night...South winds 10 to 15 knots. Seas 1 to 2 feet.
Friday...South winds 5 to 10 knots. Seas 1 to 2 feet.
Good night! Have a great Wednesday & God Bless!
-DM-
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