The blog remains in short form until further notice, due to the active weather pattern.
*Possibilities of Frozen Precipitation Increasing for Thursday-Friday.*
SW Louisiana Forecast Discussion...Cold air is firmly entrenched across the forecast area in the wake of last night's cold front. Clouds hung around across the area through the morning, but skies quickly cleared during the late morning hours as strong high pressure built down into the region over the Red River Valley. The system moved quickly, and rainfall totals were limited to around an inch or less. Much colder weather took over in the wake of the front, and this is what was experienced today. High temperatures reached the upper 40s to lower 50s with plenty of sunshine in the afternoon. It felt like the 40s all day with the strong, gusty winds over 20 mph at times. It is going to be a cold night across the forecast area with an area freeze expected with high pressure in control. Winds have relaxed somewhat since this afternoon, but will not go entirely calm due to the orientation of high. This will inhibit maximum radiative potential somewhat, and there will also be some high clouds streaming across the forecast area with a very active Subtropical Jet Stream overhead to help curtail the maximum radiational cooling potential ...this will come into play later on in the forecast period!!! However, the air mass in place is very dry, and skies are clear enough that a freeze will occur. I see no reason to deviate from my forecast from last night with lows expected to be in the mid 20s to near freezing across the forecast area. Wind chill readings will be in low to mid 20s first thing in the morning.
Wednesday will be a dry day, but the high clouds will continue to increase, and by day's end it will certainly be Mostly Cloudy. The clouds will filter the sunshine at times throughout the day as the next big storm system approaches. The typical El Nino storm pattern will repeat itself this go around. The next headache is clearly visible on satellite imagery tonight. There are several components that will come together to bring back the rain chances to the forecast as early as Wednesday night. The first ingredient is already in place, and that is the aforementioned STJ. Another strong cut off upper level low has crashed ashore over Southern California. This will continue to move Eastward over the next couple of days. As it does so, it will energize the STJ, and the occurrence that has taken place many times already this winter will do so once again...Gulf cyclogensis. Wednesday will see the increased cloud cover, but it should remain precip free. Temperatures will struggle to warm up much with the clouds in place. The high clouds will negate the maximum daytime heating potential, just as they curtail the maximum radiational cooling potential at night. That being said, temperatures should fall short of 50, and top out in the mid to upper 40s at best.
The dry weather will carry over into Wednesday night, but it will come to an end overnight. Isentropic lift (overrunning) will commence in the overnight hours as the conglomeration of ingredients takes place. It will overspread the forecast area from West to East overnight, and as it does so light precipitation will break out across the area. Activity should be scattered at first, and this is reflected in the official forecast for this period. However, the precipitation type comes into question here. Temperatures at this time will still be on the cold side with readings falling into the 30s once again. The current air mass in place is very dry, with dew points down into the 10s and 20s. The orientation of the controlling high will not allow for a surface return flow to commence, therefore, moisture levels at the surface will still be very dry as precip begins. The overrunning will create a layer of warm, moist air aloft. This will help to moisten up the boundary layer, and result in light precip to begin reaching the ground eventually. At the onset of the precip, late Wednesday night and Thursday morning evaporative cooling is expected with the dry surface layer. What this means is that as precip falls, it will likely not reach the ground at first (virga). However, at the same time it will result in a moisten up of the boundary layer, which will raise the dew points, but the evaporating precip will also cool off the surface temperature. What this means for precip type from Wednesday night into Thursday morning is some sleet likely will be mixed in with the rain. The precip could in fact begin as sleet depending on what time it commences. Models begin to diverge on the timing of the precip, but certainly with the added energy of the Jet Stream and earlier start time is feasible. Temperatures will bottom out in the lower 30s (near freezing) for Thursday morning, however, due to the light nature of the precip and much of it evaporating initially no icing problems are expected. Winds will become an issue once again as cyclogenesis occurs in the Gulf, and the strong Arctic high only slowly ridges Eastward. NE winds around 15 mph are expected. The forecast will reflect the possibility of light sleet/freezing rain and rain after midnight with better chances occurring right around sunrise.
The upper level low will move across Texas only slowly Thursday, and while that is ongoing the Gulf low will be tracking Eastward over the coastal waters. This coastal storm will again provide for rough conditions offshore. The overrunning effect will be maximized at this time, therefore precip chances are maxed out at this time in response to the movement of this latest El Nino storm. The morning hours mainly from around 6-10a.m. will continue the possibility of some frozen precip mostly in the form of sleet. The atmospheric sounding doesn't support snow at this time for any location in the forecast area except maybe the extreme Northern fringe. A significant snowstorm may occur for North Louisiana, where all the precip associated with this system may fall as snow. The I-20 corridor seems like a prime spot for significant accumulations. Back home, no accumulation of sleet is expected due to the very light nature of the precip and the slowly eroding drier layer of air at the surface. The aforementioned features will create plenty of lift across the area. All precip should become liquid before noon, but it will continue through the day and as isentropic lift continues to strengthen in the afternoon, rainfall will become heavier with 1-2" of rain expected on Thursday. Regardless of if we have any frozen precip or not on Thursday, it will be a very raw day. The forecast area will remain on the cold side of the system as the low tracks through the Gulf. Model guidance continues to be way too warm for maximums on day 2 (Thursday), and I will undercut them by several degrees. The highs may be more than 20 degrees below normal for mid February. We will struggle to reach 40 Thursday, and the winds will produce a wind chill well down in the 20s. Rain should be the primary precip for the majority of the daylight hours on Thursday, but heading into Thursday night things will most likely change again...
Rain could be heavy at times Thursday evening and Thursday night as the low makes its closest approach to the forecast area, this is the surface low mind you. The upper level will still be back over Texas at this time. An additional 1-2" of rain is expected during this time, but after midnight as the surface low moves Eastward, and the upper level low approaches much of the area North of I-10 will transition from rain to snow as temperatures drop into the lower 30s once again, and some colder air on the back side of the low in the upper levels filters in slowly. Further South, a mix of rain and snow is expected down to the coast after midnight as the low tracks through the Gulf passing a good 100-200 miles offshore. The eventual track of the low will determine exactly what kind of precipitation the forecast area will see. Right now, I suspect the surface low should track from off the Lower Texas coast to 100-200 miles offshore of Louisiana, to the NE Gulf. This track is an average of the forecast models. Models diverge on the exact track of the low with some bringing it closer to the coast, and some keeping it even further offshore. A track closer to the coast would lessen our frozen precip chances in this case because of the warm air created by the low, but a track further over the Gulf would pull down colder air, thus in turn increasing the frozen precip chances heading into Friday morning. At this time, the most likely time frame to see snow across the forecast area, and perhaps a significant winter storm somewhere in close proximity will be this time frame from the overnight hours on Thursday through noon Friday. The current forecast track of the low suggests that a band of heavy snow will occur somewhere in the forecast area, likely north of I-10 between the Hwy. 190 and Hwy. 84 corridor. I believe that area will see the greatest chance of seeing several inches of snow, with lighter amounts on either side of that zone. I will be more specific about possible accumulations in the forecast area tomorrow if it still is trending towards snow/sleet possibilities. For now, I suspect that most of the forecast area will see some sleet and snow, but accumulations will be limited due to wet grounds and marginal surface temperatures.
Getting back to the snow potential for late Thursday and Friday...the low tracking through the Gulf is a favorable set up, and I believe there will certainly be a deformation zone (convergence). It is more often than not these deformation zones that lead to heavy snowfall. Meteorology is an imperfect science, and there is no skill in predicting where the heaviest snow amounts will be this far out when we have a system that is hard to detect by our upper air networks at this stage of the game. So, hopefully we'll have a more clear cut solution on Wednesday. The set up with this system is somewhat similar to the snow event back in December, but there are some differences. The biggest difference lies in the atmospheric profile, and some synoptic scale features that factor into snowfall forecasting. Temperatures will be marginal in a layer just above the surface as a warm tongue of air resides in response to the ongoing isentropic lift. This layer around 850 mb. (5,000 ft) is forecast to be above freezing, thus melting the snow as it falls, however, it is a shallow layer, and with the cold surface temperatures the precip will have time to transition back to a frozen form of either sleet or snow. Temperatures at the surface should be just above freezing for much of the area with the exception of areas along and North of Hwy. 190, and this will likely result in melting on contact with the ground. However, with plenty of lift and moisture being overthrown by the low heavier precip is still possible Friday morning, and if this occurs then some snow accumulations will be likely mainly on grass and elevated surfaces. Precipitation should wind down Friday afternoon, but will likely change back to mix or all rain depending on how much warming occurs during the day. There certainly won't be much warming as the cold air remains in place with the clouds and precipitation in a continuous state as well. I doubt we get out of the 30s on Friday, and I will forecast upper 30s at best. Coldest locations across the forecast area will likely barely make it above freezing, and thus they stand a better chance of real snow. Once again, I stress that forecasting snow is by far the most difficult task in all of meteorology, and there is still a lot of question marks at this point. I strongly urge you to stay tuned over the next couple of days, and by all means please don't get your hopes up just because I've mentioned the "s" word. This is a very borderline situation between a significant winter storm, and just a plain ole cold rain for the duration of the event. Here's my best guess right now...snow will fall, but only light accumulations are expected Friday morning with less than an inch along and South of Hwy. 190 and 1-2" North of the Hwy. 190 corridor. Locations closer to Alexandria could see over 2", but I will re-evaluate tomorrow as I said. The upper level low will evacuate the region Friday afternoon, thus ending all precip liquid and frozen. The cold temperatures will remain, though it should be above freezing allowing for any snow or sleet to melt. Gusty winds will continue as well creating brutal wind chills in the 10s at times.
Conditions improve for Friday night, but it will be cold. This is good news with a plethora of Mardi Gras parades and events slated to kickoff the long festive weekend. Skies will clear Friday night as high pressure builds in behind the departing low. This will result in another freeze for most locations. Low clouds will hang around through the evening with a slow clearing overnight, otherwise we would easily see 20s for Saturday morning. This could certainly still change depending on how things evolve with the frozen precip. Winds will stay up as well, limiting cooling, but also producing wind chills in the 10s to lower 20s by morning. You will certainly need to bundle up if you heading out to some Mardi Gras parades, but at least you can leave the umbrella in the car. For now, I will forecast a low close to 30. Saturday looks great, but cold with highs only warming to the mid 40s as the Arctic air remains in place. It will slowly moderate beginning Saturday night into Sunday morning. 30s are expected once again with another light freeze in the offing. Much of the long Mardi Gras weekend looks dry, all of it looks cold! The fly in the ointment comes in late Sunday into Monday as another embedded disturbance in this ever persistent El Nino storm track moves across. It will be much weaker than its predecessor. Clouds will increase on Sunday (Valentine's Day), but much of the day will remain dry for parades and such. Highs should reach the lower 50s Sunday. A rain chance is introduced Sunday night as this disturbance moves in. The air mass should moderate enough that it will be rain. Rain chances will be small at this time for this period, and it should be a quick mover. Lows for the Sunday night and Monday morning time frame should be somewhere in the mid to upper 30s. The disturbance moves on out Monday (Lundi Gras), and does bring another cold front through the area. Clouds may hang around for much of the day Monday, and it will be windy as well with the usual pressure anomalies taking place. Monday's highs will be held down into the 40s because of the clouds and CAA behind the short wave and cold front. For Mardi Gras day itself, it looks Sunny with high pressure in place across the Bayou State. What could perhaps be the biggest Mardi Gras ever as we continue to celebrate the Saints, looks like one of the coldest in some time as well. A significant freeze is in the offing as more Arctic air spews into the forecast area. It could be as cold as the mid 20s across portions of the forecast area, with readings right around freezing at the coast. The mid-February sun will try to offset CAA across the area, but temperatures will only reach the mid 40s at best. The cold weather will continue beyond the forecast period through Ash Wednesday and beyond. The active Subtropical Jet Stream will continue as well, so we could very well have much below normal temperatures and above normal precipitation through the entire month of February. Stay tuned for all the latest on the frozen precip possibilities!
Preliminary Numbers & Zone Forecast:
LCH 28/47 32/38 33/39 0 0 30 100 100 80
LFT 27/48 32/39 33/38 0 0 30 100 100 80
BPT 29/47 33/40 34/41 0 0 40 100 100 70
AEX 25/46 28/36 30/36 0 0 30 100 100 80
POE 25/46 29/37 30/37 0 0 30 100 100 80
ARA 29/48 32/41 34/42 0 0 30 100 100 80
Tonight...Clear and Cold. Low 28. North wind 10 mph. Wind chill around 20 by sunrise.
Wednesday...Mostly Sunny early, Increasing Cloudiness through the day. Mostly Cloudy by evening. Cold. High 47. North wind 5-10 mph.
Wednesday Night...Cloudy and Cold with a 30% chance of light rain and sleet after midnight. No sleet accumulation. Low 32. NE wind 10 mph. Wind chills in the 20s.
Thursday...Cloudy, Cold, & Windy with Rain likely. Sleet possible in the morning. No sleet accumulation. Rain heavy at times. 1-2" of rainfall expected. High 38. NE wind 15-20 mph and gusty. Chance of precipitation 100%. Wind chills in the 20s.
Thursday Night...Cloudy, Cold, & Windy with Rain likely before midnight. Rain and Snow mix after midnight. Possibly all snow around sunrise. Little or no snow accumulation. Precipitation heavy at times. Low 33. NE wind 15-20 mph and gusty. Chance of precipitation 100%. Wind chills in the 20s.
Friday...Cloudy, Cold, & Windy with rain and snow mix likely in the morning. All snow possible from around sunrise til mid-morning. Precipitation ending in the afternoon. Little or no snow accumulation. High 39. North wind 15-20 mph and gusty. Wind chills in the 20s. Chance of precipitation 80%.
Wednesday 2/10/10 Daily Planner
7a.m.
Sky: Sunny, Cold
Temp: 28
Precip: 0%
Wind: N 8
Noon
Sky: Partly Cloudy, Cold
Temp: 42
Precip: 0%
Wind: NE 11
5p.m.
Sky: Mostly Cloudy, Cold
Temp: 45
Precip: 0%
Wind: NE 9
Drew's 7 Day Outlook
Wednesday
2-10-10
Low: 28
High: 47
Precip: 0%
Wind: N 5-10
W.C.: 20-30
Thursday
2-11-10
Rain/Sleet...No Accumulations
Low: 32
High: 38
Precip: 100%
Wind: NE 15-20
W.C.: 20-25
Friday
2-12-10
Rain/Snow...No Accumulations
Low: 33
High: 39
Precip: 80%
Wind: N 15-20
W.C.: 20-25
Saturday
2-13-10
Low: 30
High: 45
Precip: 0%
Wind: N 5-10
W.C.: 20-30
Sunday
2-14-10
Valentine's Day
Low: 33
High: 51
Precip: 0%
Wind: NE 10
W.C.: 25-40
Monday
2-15-10
President's Day
Lundi Gras
Low: 36
High: 46
Precip: 30% AM
Wind: NNW 10-15
W.C.: 20-30
Tuesday
2-16-10
Mardi Gras
Low: 28
High: 46
Precip: 0%
Wind: N 10
W.C.: 20-35
...Marine Forecast...
Tonight...North winds 15 to 20 knots. Seas 2 to 4 feet.
Wednesday...Northeast winds 10 to 15 knots. Seas subsiding to 2 feet.
Wednesday Night...Northeast winds 5 to 10 knots increasing to 10 to 15 knots after midnight. Seas 2 to 3 feet. A chance of rain after midnight.
Thursday...Northeast winds 10 to 15 knots becoming east 15 to 20 knots in the afternoon. Seas 2 to 4 feet. A chance of rain in the morning...then rain in the afternoon.
Thursday Night...Northeast winds 15 to 20 knots. Seas 3 to 5 feet. Rain.
Friday...Northeast winds 15 to 20 knots. Seas 2 to 4 feet. A chance of rain.
Good night and God bless!
-DM-
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