SW Louisiana Forecast Discussion...Rain moved out of the early in the early morning hours the latest Gulf system accelerated and plagued the SE U.S. today with flooding rains and severe weather. Low clouds hung tough throughout the day, keeping the cold and damp conditions in place. Temperatures hovered around 50 all day, but it felt much cooler than that with the wind and occasional drizzle. Clouds continue to blanket much of the region, though some clearing has occurred around Beaumont and Lake Charles. The low clouds will slowly erode overnight as drier air temporarily moves in, and erodes a low-level temperature inversion. Many areas will remain cloudy through the overnight hours, but conditions will be dry with no chance of rain expected. CAA continues tonight as another cold front has moved through behind the departing low. This will make for a very chilly night with lows down into the mid to upper 30s for most areas. Acadiana will likely stay in the low 40s with the low clouds hanging in a bit longer. Frost should not really be a concern with the wet ground, and cloud cover in most areas. A very active pattern will continue, and before we can even blink the clouds will be returning. The signs of the next system will already be moving in later tonight with an advanced guard of high clouds streaming in from the SW via the Subtropical Jet, but for the most part clear skies are expected once the low clouds vacate your area. The departing system from this morning will turn up the Atlantic Seaboard and tap into energy from the Gulf Stream and be a big weather story for the next couple of days.
Thursday is shaping up to be fairly and offers a brief reprieve from the clouds and rain. However, I dropped a hint in the previous paragraph about the next system coming down the pipe. The high clouds will continue to across throughout the day, filtering the sunshine at times. More clouds will roll in during the afternoon, and a return to Mostly Cloudy conditions is possible, but either way Thursday will be dry. Cold air will remain in place as well, and there will continue to be a definitive chill in the air with highs reaching the low to mid 50s. At this same time, the next storm system will be coming together downstream. A strong disturbance (short wave) currently over Montana coming out of the Canada will be diving quickly to the SE along the Jet Stream, the driving force of all weather. Clouds will continue to increase as the mid and upper levels moisten up ahead of this feature. Thursday night will continue a dry period, and also cold with temperatures similar to tonight in the mid to upper 30s. It is on Friday when the excitement ensues.
Speaking of Friday, here we go...The advertised short wave will be diving into Texas Friday morning, and at the same time energy embedded in the Subtropical Jet will help to aid in Gulf cyclogenesis once again. This will cause precipitation to break out across Texas underneath the surging Arctic air. The stage could be set for the earliest winter weather event on record in SW Louisiana, surpassing the record set last year on December 11. There is still so much that has to come together to make this happen, but there is very good agreement among the model suite for a snow event across the majority of the forecast area Friday and Friday night. I note my disclaimer from last night once again...Forecasting snow in SW Louisiana, or anywhere for that matter, is by far the most difficult feat in meteorology. Anyway, not getting too side-tracked here...A very complex situation develops Friday as the embedded short wave and Gulf low work in tandem to sling moisture across the area. At the same time, colder air from the Arctic will be sweeping into the forecast area. All sounding data and model output continues to suggest snow as the only form of frozen precipitation. Snow will develop across Central Texas early Friday, and move Eastward during the day, and as the Jet Stream energy taps into Gulf moisture, additional precipitation will develop over our area by noon Friday. It will likely start as light rain for at least the Southern half of the forecast area. Northern sections of the forecast area may be cold enough to see all precipitation fall as snow. It is a wait and see game with this entire event. Often times the best rule of thumb for forecasting snow in South Louisiana, is to wait and see what's happening downstream to have an idea of what will happen here. The predicted amounts of snow from the forecast models vary to some degree on each run, but the consensus is there for some sort of snow on Friday. Here is my take on the situation based on what I have analyzed from the models...The precipitation will likely begin as a cold rain Friday morning with temperatures around 40 or so, but it should be snowing downstream at that time perhaps approaching Houston by this time. Rain should begin to mix with snow around noon for the Northern half of the forecast area, and by mid-afternoon for Lake Charles to Lafayette, a little sooner for Beaumont. This rain/snow mix will transition to all snow across the Northern half of the area by mid-afternoon, and by 6p.m. for Lake Charles & Vicinity, and a bit later for Acadiana. Snow should occur even down to the coast, but it may stay more of mix for almost the entire event. As the system winds down, the conversion to all snow could occur even at the coast. With the forecast confidence increasing for this unprecedented snow event, it is time to start discussing the possibility of accumulations. I don't want to get very specific right now on this possibility, due to the reasons cited earlier. However, some significant accumulations could occur across a good chunk of the forecast area. That being said, for now, I will forecast up to an inch along the I-10 corridor, and up to 2" for the Northern half of the forecast area. This will certainly be revised as we get closer to the event, and more model guidance comes in. I will have some graphics in a moment that show the precipitation underneath the cold air. As for temperatures, Friday it's going to be very cold snow or not!!! I don't expect very much warming at all. Morning temperatures should be in the mid to upper 30s across the area, but highs should only reach near 40 along I-10, and stay in the 30s North. Temperatures will fall beginning around noon as the precip begins to fall. Northern portions of the forecast area should reach temperatures near freezing during the afternoon, while temperatures around Lake Charles should drop back into the mid 30s. Even with readings in the mid 30s, snow can fall in this situation since the air column will be cold all the way up. The deep moisture will be place, and the cold air will be in place, so precip is certain, but will the column of air be cold enough all the way through to support snow? Time will tell. I want to illustrate exactly the time frame we're looking at here, so you might better understand.
Here's a look at 2 of the most reliable forecast models I use when forecasting: the NAM and the GFS. First, the NAM at 48, 54, and 60 hrs. This is Friday Afternoon through Saturday Morning.
You can see the moisture indicated by the green and blue over Texas and much of the Gulf Coast. The red and blue lines indicate temperature at the 850 mb. (5,000 ft.) level. This is a very good indicator to determine whether or not snow will fall. The magic line to look at is the 540 line (the first blue line). This is the 0 degree C line (all model data gives temperatures in C as opposed to F.) You can a good deal of snow shown across Texas into Louisiana. This is 6p.m. Friday on the NAM model. This run delays the timing until a bit later in the day, but I am mainly showing this to you to illustrate the possibility. Timing will be pinned down as we get closer to the event.
Fast forward 6 hrs. now to 6Z Saturday (Midnight CST)
The heaviest precip at this time looks to be over Louisiana with a surface low off the coast of SE Louisiana. The snow will be tapering off across SE Texas at this time.
6 more hours out---6 AM CST Saturday:
The snow should be coming to an end around sunrise Saturday across much of the forecast area, with a little lingering light snow or snow flurries shown at this time. The more significant snow at this time should be into Central Mississippi down towards the Northshore of Lake Pontchartrain.
Switching models now, here's the GFS for the same time frame...48, 54, and 60 hrs. out. I should note here before I forget that this is the 0Z 3 December run of these models. The models run 4 times a day at 0, 6, 12, and 18Z. Z is 6 hrs. ahead of CST. So, this is the 6p.m. Wednesday run of the forecast models. The model data runs at the aforementioned time, but is not displayed publicly until about 3 hrs. later. The 0Z run becomes available around 9:30p.m. CST.
The GFS at 6p.m. Friday:
The look of the GFS is very similar to the NAM. The Gulf low shows up nicely off our Coast while the S/WV energy is back over Central Texas with snow starting to spread into SW Louisiana as the colder Arctic air builds in noted by the large high pressure near El Paso and another one over Colorado.
GFS---Midnight Saturday:
The low is in a bit different placement on the GFS at this time, but still shows significant snows across Louisiana with heavier amounts from Central Louisiana to the Coast. Overall, the model is very close to the output shown by its NAM counterpart.
GFS 6a.m. Saturday:
The GFS and NAM are in very good agreement on the timing of the snow. Everything should be tapering off by early Saturday morning with just lingering light snow or flurries at this time. Heavier snow is shown across SE Louisiana including New Orleans and up towards Jackson, MS.
I hope that helps illustrate the situation. We'll divulge into more details of this snow potential on Thursday. My best guess for the end of this event based on forecast data should be early Saturday morning. I believe it may end a bit faster than what is shown by the forecast models above due to the extremely fast Jet Stream over the area. These NW flow systems typically move very fast. So, I will end precip by sunrise Saturday. Friday night will not only bring snow, but also be the coldest temperatures so far this season with a freeze expected area wide with the possible exception of the immediate coast. Morning lows should range from the mid 20s for Alexandria to near 30 for Lake Charles to around 33 or 34 at the coast. Areas that reach freezing will obviously have the best chance to see any snow accumulation, and a remote possibility of whatever falls and sticks to still be on the ground as the sun comes up Saturday. If the snow does occur, it would be historic in more ways than one. As I stated earlier, it would eclipse the snow event from last December 11 to go down in history as the earliest snowfall of record across SW Louisiana, and it would also be the first time in recorded history that it snowed in consecutive Decembers. It has snowed in back to back years before, but never in December. In history, there has only been 16 measurable snowfalls in Lake Charles since records have been kept dating back to 1895. This is about an average of once every 7.5 years or so. Interesting to say the least. Stay tuned for further revisions tomorrow!
For the weekend, the snow is gone Saturday, and skies will quickly clear out as Arctic high pressure moves in behind the snow. It will be sunny for a good part of the day Saturday, but it will remain cold. Model guidance suggests lower 50s Saturday, but with the Arctic air in place, 40s seem more logical, especially if there is snow on the ground. I will forecast mid 40s at the this point, as the cold December sun will try to warm us up. Clear and cold weather is in store for the Saturday night//Sunday period with another light freeze possible Sunday morning as high pressure slowly slides Eastward. Clouds return on Sunday as the largely progressive pattern continues. The Subtropical Jet will remain active, and another trough will be digging. Gulf cyclogenesis could occur yet again, and bring forth another chance of rain by Sunday night. Sunday should be dry for the daylight hours, and a modest warming trend sets up. Highs should be in the low to mid 50s. Again, I am undercutting guidance as it will try to erode the cold air too quickly. Bottom line...the first weekend of December will be cold!
For the Monday-Wednesday period rain chances are retained for each day with an overall cool and wet pattern in place. Subtropical Jet Stream energy will continue streaming over the area bringing periodic perturbations (disturbances) each day to aid in the development of rain across the area. Another Gulf low is possible towards the end of the forecast period on Wednesday as another sharp trough digs into the Great Plains out of the Arctic. This will likely increase rain chances back into the likely category for Wednesday. Temperatures will generally remain below normal to near normal with lows in the 40s and highs in the 60s. The overall pattern favors a big time invasion of Arctic air into the contiguous 48 states towards the middle part of next week. The jury is out as to how far South this air will get, but it could reach the Gulf Coast in the latter half of next week.
This Date in History...December 2: Severe weather can certainly occur in December. Here is a good illustration of that. December 2, 1950...A late season tornado killed four persons in Madison County and Bond
County, east of St Louis MO. Three tornadoes touched down in Illinois
that afternoon, compared to just half a dozen tornadoes in the month of
December in 115 years of records up until that time. Thunderstorms also
produced hail which caused more than four million dollars damage in the
St Louis area, it was the most damaging hailstorm of record for Missouri.
Preliminary Numbers & Zone Forecast:
LCH 38/54 38/41 29/45 0 0 0 60 70 20
LFT 39/55 38/42 30/44 0 0 0 50 70 30
BPT 37/55 38/40 28/46 0 0 0 60 70 20
AEX 35/52 35/38 26/40 0 0 0 60 70 30
POE 36/53 35/37 27/41 0 0 0 60 70 20
ARA 41/56 40/44 31/45 0 0 0 50 70 30
Tonight...Partly Cloudy becoming Mostly Clear. Cold. Low 38. NNW wind 10 mph.
Thursday...Mostly Sunny becoming Partly Cloudy. Continued Cool. High 54. North wind 5-10 mph.
Thursday Night...Mostly Cloudy. Cold. Low 38. NE wind 10 mph.
Friday...Cloudy, Cold, and Windy with rain developing and becoming likely by noon. Rain mixing with snow in the afternoon, before changing to all snow during the evening. Little or snow accumulation. High 41. Temperatures falling into the mid 30s in the afternoon. NE wind 15-20 mph and gusty. Wind chill readings 25-30. Chance of precipitation 60%.
Friday Night...Cloudy and Cold with Snow likely. Snow accumulations up to 1" possible mainly on grassy and elevated surfaces. Low 29. North wind 15-20 mph and gusty. Wind chill readings 15-25.
Saturday...Lingering Snow Flurries Early otherwise Becoming Sunny and Continued Cold. High 45. North wind 10-15 mph. Wind chill readings 15-30.
Drew's 7 Day Outlook for Lake Charles & Vicinity
Thursday
12-3-09
Low: 38
High: 54
Precip: 0%
Wind: N 5-10
Friday
12-4-09
Low: 38
High: 41
Falling to 35 in the afternoon...Rain Mixed w/ Snow...Changing to Snow Late
Precip: 60%....70% Overnight
Wind: NNE 15-20
W.C.: 25-30
Saturday
12-5-09
Low: 29
High: 45
Precip: 0%
Wind: N 10-15
W.C.: 15-30
Sunday
12-6-09
Low: 32
High: 53
Rain: 0%
Wind: NE/E 10-15
W.C.: 25-40
Monday
12-7-09
Low: 48
High: 59
Precip: 40%
Wind: E 10-15
Tuesday
12-8-09
Low: 55
High: 65
Precip: 60%
Wind: SE 10-15
Wednesday
12-9-09
Low: 56
High: 62
Precip: 40%
Wind: E/NNW 15-20
...Marine...
Thursday...North winds 10 to 15 knots. Seas 2 to 3 feet.
Thursday Night...Northeast winds 15 to 20 knots. Seas 2 to 3 feet building to 2 to 4 feet after midnight.
Friday...Northeast winds 15 to 25 knots becoming 20 to 25 knots in the afternoon. Seas 3 to 5 feet building to 4 to 6 feet in the afternoon. A chance of rain.
Friday Night...North winds 20 to 25 knots. Seas 4 to 6 feet. A chance of rain.
Saturday...Northeast winds 15 to 20 knots. Seas 3 to 5 feet.
...Tide Data...
Thursday Tides @ Calcasieu Pass
Low: 8:49a.m. 9:11p.m.
High: 4:48p.m. 11:34p.m.
...Toledo Bend Pool Level...
171.31'
...Lake Charles Climate Summary...
Wednesday, December 2, 2009
Low: 44
Normal Low: 46
Record Low: 23-1896
High: 54
Normal High: 66
Record High: 86-1912
Precipitation
Today: 0.11"
Month to Date: 1.35"
Normal Month to Date: 0.30"
Year to Date: 65.89"
Normal Year to Date: 52.89"
Record: 3.00"-1897
Sunrise Thursday: 6:53a.m.
Sunset Thursday: 5:12p.m.
Thursday Hunting Times: 6:23a.m.-5:42p.m.
Good night and God bless!
-DM-
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