SW Louisiana Forecast Discussion...The weather has been quite nice, a little cold, but overall nice since our latest snow disappointment Tuesday night. This will be changing in a big way to close out the last work week in February. Today started out on the cold side with a cold dome of high pressure in place. This resulted in an area wide freeze to start the day with temperatures in the mid 20s to lower 30s. It was a terrific Thursday with mostly sunny skies and pleasantly cool temperatures for afternoon highs in the mid 50s. A southerly flow commenced across the area as the large controlling high shifted Eastward during the day. Low level moisture is slowly increasing tonight, and the cloud cover isn't far behind now as our next unwelcome visitor hangs in the balance. The lower levels will continue to moisten up tonight and the clouds will increase from W to E overnight. It will be a good 10-15 degrees warmer across the forecast area overnight with mid 30s to lower 40s expected.
The last Friday of February will be one of the wettest days of the month. The strong El Nino system is visible on satellite imagery tonight. It is cutting through NW Texas in the vicinity of Amarillo. It is in the form of a potent short wave (disturbance) that is coming out of the Rockies. The active Subtropical Jet Stream will come into play as well, and as this energy dives SE towards the forecast area Friday, it will help to engender a surface low over the NW Gulf of Mexico. Warm air will surge up and over the cool air at the surface (overrunning), and as this isentropic ascent increases Friday morning, areas of light rain will break out across the forecast area. This should occur in the mid-late morning hours. The best chances for rain will come during the afternoon hours Friday as the low forms off the coast of SE Texas, and traverses the Northern Gulf waters through the afternoon. This will send additional surges of moisture Northward across the forecast area, and rainfall will increase in areal coverage and intensity. Rain could be heavy at times Friday afternoon. Greater instability and Jet energy will move in at this time as well. There will be plenty of cold air aloft generated by the upper level low, and this is what leads to the instability in the atmosphere. The increased amounts of instability could lead to a few thunderstorms during the afternoon or evening Friday. The track of the surface low will preclude any severe weather across the area, however, there will likely be some elevated convection due to the instability values in place. Thus, the possibility of some thunder during the afternoon. With plenty of cold air aloft I wouldn't rule out the possibility of some small hail or what is known as graupel. Graupel is basically a supercooled water droplet. It often takes on the appearance of a small hail stone or a snow grain, but it is more in the ice family. Temperatures will remain on the cool side with highs struggling to reach 50 with the rain. No frozen precipitation is expected. Rain will be in the likely category, nearly maxing out. Rainfall totals will likely be on the average of 1" or so, but some areas especially those closer to the coast could stand to see 2". The QPF chart displaying expected rainfall follows. The surface low will not only help bring rain to the area, but it will also help to stiffen the pressure gradient across the realm of the forecast area. Thus, some gusty winds are expected up to 20 mph at times. The low will slowly move Eastward in tandem with the departing ULL Friday night, and some colder air will filter into the region on its backside. Rainfall will gradually end from west to east, as a cold front is pulled through the area behind the surface low. Some moisture could linger keeping a chance for some showers in the forecast through early Saturday. No frozen precipitation is expected at this time, but models do insist that temperatures aloft will be cold enough for sleet/snow by Friday night, however, surface temperatures will be too warm to support any frozen precipitation. I will keep an eye on the model trends, but for now all precip should remain liquid in this forecast area. The Northern half of the state could see a changeover to snow late Friday through early Saturday, but even this is a marginal prospect right now. Temperatures will cool into the mid to upper 30s by Saturday morning. Conditions will drastically improve just in time for the weekend, and the majority of the weekend is shaping up nicely.
Clouds hang around for a short time Saturday morning with wrap-around moisture in place and a temperatures inversion from 925-850 mb., however, this will quickly change as the drier air lagging behind in the boundary layer finally catches up, skies will clear and become sunny by noon Saturday as a renewed area of high pressure in the wake of the Gulf low builds down into the region from the NW. It will remain on the cool side with a high only reaching the lower 50s. Sunny skies are expected for Saturday afternoon with benign weather in place with no rain expected through Sunday. Chilly weather is in store for Saturday night with high pressure right overhead. The clear skies and calm winds will provide for maximum radiational cooling, and while temperatures will be below normal, they should remain above freezing with readings in the mid 30s on average. The coldest locations of the forecast area will likely see a light freeze heading into Sunday morning. Sunday looks to be a great day to close out the month of February. There will be lots of sunshine, and it should be pleasantly mild with a high around 60. The controlling high in place for the weekend will slide Eastward into Dixie Sunday afternoon, thus establishing a return flow ahead of an even strong Pacific storm system. The weekend is going to be a sandwich....so I hope you're hungry!!! Eat up the pretty weather!
The specifics of this next event will come over the weekend, as we put the Friday system behind us. However, it is certain that we'll be facing another El Nino system and wet weather maker on Monday. The saying "March comes in like a lion" will come to fruition in 2010. The persistent Pacific parade of storms will simply just not give up its fight. A largely amplified trough digging through the Rockies will help to carve out another short wave. This wave will move into range Monday, and the active Subtropical Jet Stream will lead to Gulf cyclogenesis one more time. Rain will overspread the area once again as overrunning conditions intensify. Rain could be heavy at times once again, and I wouldn't rule out some thunder as well with plenty of instability in place. The surface low should once again remain offshore, keeping the forecast area in the cool sector. The surface low will move East, and be deepening (strengthening) at the same time, and this will in turn increase the pressure gradient over the area once again. Winds will be a factor as well. There will once again be lots of cold air present aloft, and models once again insist that there will be a changeover to frozen precip on the backside of the system. However, surface temperatures once again look to be too warm to support this idea, so this is once again left absent from the forecast at this time. Once again, this is something that I will closely be monitoring trends for. It is a tough task when forecasting winter weather, as you found out earlier this week. It certainly does look like Monday will be a day with falling temperatures. Temperatures could very well be confused for the Sunday night/Monday period as it is possible temperatures will rise overnight Sunday with the developing low and associated weak WAA, and then as the low goes by and CAA is established once again Monday afternoon temperatures will fall. This is reflected in the forecast at this time. Best guess is that temperatures will be near 50 in the morning, and fall to near 40 by evening. Rain chances will once again be very close to maxing out if not totally. It could rain all day on Monday as there will be overrunning rains ahead of the low, and wrap around rains behind it. The rain chances will begin as early as late Sunday night with the onset of the overrunning, and continue into Monday night as the post-low moisture hangs around with the colder Canadian filtering in. Look for blog entries over the weekend on this second system. The 5 day total rainfall accumulation map is included below.As of right now 1-2" of rainfall looks likely for Monday.
Timing uncertainties exist with the Monday system. Moisture could hover into early Tuesday, but this is not currently reflected. Either way, conditions improve greatly for Tuesday. High pressure builds in and takes control of the weather in the wake of the Monday storm. I should note that both the Friday and Monday storm will take the corner and go on to be big snowstorms for the East coast after they affect our region. The system that affected us this past Tuesday is dumping on them tonight. The stretch of below normal weather will continue for Tuesday as the colder Canadian resides over the area. Skies should be clear, and there will be plenty of sunshine with conditions on the cool side. Highs should reach the low to mid 50s. The remainder of the forecast period looks quiet with the high pressure continuing to dominate. A late season freeze could make a visit to the area on Wednesday with the core of the high over the area. Winter just doesn't want to loosen its grip. Light winds and sunny skies will result in a fast warm up Wednesday. This will also be a return flow off the Gulf as the high slides Eastward late in the day. The atmosphere will very remain dry at this time, so it is likely that it won't be a noticeable moisture at first. Highs will be closer to 60. Thursday remains dry, but low-level moisture increases. Temperature modification continues in earnest as well. Some clouds will dot the landscape Thursday, but after morning lows near 40, highs should be well up into the 60s. Could it actually transition to Spring that fast? While the temperatures will begin to reflect the changing of the seasons, and that yes, we are heading to spring, the active El Nino pattern will not fade away just yet. Another El Nino type system looms just beyond the forecast period. Temperatures approach 70 around this time, but this could also set the stage for some big storms in the day 8-9 time frame. It is also possible that we will transition right into severe weather threats from the frozen precip threats that we've had of late. Stay tuned as there are no dull moments in the world of weather anytime soon..
Preliminary Numbers & Zone Forecast:
LCH 40/53 38/52 35/58 20 90 30 0 0 0
LFT 41/53 38/51 36/59 10 90 30 0 0 0
BPT 43/54 39/53 37/60 30 90 30 0 0 0
AEX 36/48 35/50 31/55 20 80 30 0 0 0
POE 36/48 35/50 32/56 20 70 30 0 0 0
ARA 42/55 40/53 36/58 20 90 40 0 0 0
Tonight...Becoming Cloudy and Not as Cold with a 20% chance of showers towards morning. Low 40. SE wind 5-10 mph.
Friday...Cloudy with rain likely by afternoon. Rain could be heavy at times with embedded thunderstorms in the afternoon. Rain could contain small hail or graupel in the afternoon. High 51. NE 10-20 mph. Chance of rain 90%.
Friday Night...Cloudy with a 30% chance of rain. Ending late. Low 38. NNW wind 10-15 mph.
Saturday...Becoming Mostly Sunny and Cool. High 52. North wind 10-15 mph.
Saturday Night...Clear and Cold. Low 35. Light North wind.
Sunday...Sunny. High 58. NE wind becoming SE 5-10 mph.
Friday 2/26/10 Daily Planner
7a.m.
Weather: Cloudy
Temp: 40
Precip: 20%
Wind: NE 12
Noon
Weather: Rain
Temp: 48
Precip: 60%
Wind: NE 17
5p.m.
Weather: Rain
Temp: 51
Precip: 90%
Wind: NE 14
Drew's 7 Day Outlook
Friday
2-26-10
Low: 40
High: 53
Precip: 90%
Wind: NE 10-20
Saturday
Low: 38
High: 52
Precip: 0%
Wind: N 10-15
Sunday
2-28-10
Low: 35
High: 58
Precip: 0%
Wind: NE/SE 5-10
Monday
3-1-10
Low: 52
High: 41
Precip: 70%
Wind: NNE/NNW 20-25
W.C.: 30s PM
Tuesday
3-2-10
Low: 36
High: 53
Precip: 0%
Wind: N 10-15
W.C.: 25-35
Wednesday
3-3-10
Low: 32
High: 58
Precip: 0%
Wind: NE/SE 10
W.C.: 25-40
Thursday
3-4-10
Low: 39
High: 63
Precip: 0%
Wind: SSE 10-15
...Marine Forecast...
Friday...Southeast winds 10 to 15 knots becoming southwest 15 to 20 knots in the afternoon. Seas 3 to 4 feet. Rain likely.
Friday Night...Northwest winds 15 to 25 knots becoming north 20 to 25 knots after midnight. Seas 3 to 4 feet building to 3 to 5 feet after midnight. A chance of rain.
Saturday...North winds 15 to 25 knots decreasing to 10 to 15 knots in the afternoon. Seas 3 to 5 feet subsiding to 2 to 3 feet in the afternoon.
Saturday Night...Northwest winds around 10 knots becoming north after midnight. Seas 2 feet.
Sunday...East winds 10 to 15 knots. Seas 3 to 5 feet. A chance of rain.
Good night and God bless!
-DM-
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