SW Louisiana Forecast Discussion...It was a splendid Sunday across the area, and a wonderful weekend for the most part after some early clouds Saturday. This came in the wake of our last wet weather maker on Friday. It will seem like a bad case of deja vu, perhaps worse on Monday. Temperatures on this Sunday afternoon reached the mid 60s...just about normal for the end of February. It was a cold start across the entire realm of the forecast area this morning with minimums in the 30s. Some locations saw a light freeze. There was also some areas of fog this morning with the residual lingering effects from Friday's rain and a night of maximum condensation with clear skies and calm winds. The fog quickly scoured out after sunrise, and skies were cloud-free from that point on. The controlling high pressure from the weekend is heading East down I-10 tonight, and on its heels is our next in the never-ending Pacific parade of storms. This is what will be making its presence felt across the forecast area on Monday as we start March and meteorological Spring.
This highly progressive pattern will result in a quick turnaround with rain chances back in the forecast overnight. Do you remember the scenario that played out Friday? This scenario will be repeated Monday, albeit a bit stronger this time around. The current dry air mass will quickly be displaced overnight as clouds return this evening, and as the strong upper level impulse approaches from the West rain will develop overnight as a term I've discussed a nauseum this winter season comes into play once again, overrunning (isentropic lift). The strong upper level impulse will interact with the ever-present Subtropical Jet Stream to add energy to the mix. This will engender cyclogenesis in the Western Gulf again, and that will result in widespread rain across the area Monday. The low will likely form off the coast of South Texas late tonight into Monday morning, and then trek NE through the coastal waters. The trajectory of the low should keep the forecast area in the cool sector, but the eventual track will be very close to the coast, thus heavier rain is expected during the day Monday. Clouds increase this evening, and then rain should begin to spread into the forecast area after midnight. Rain chances will be in the likely category once rain begins overnight, and be maxed out on Monday.Temperatures will be on the cool side, but will be several degrees warmer than last night. Expect temperatures to range from around 40 well inland to near 50 at the coast.
The upper level low is currently situated near ELP (El Paso, TX). It will quickly slide Eastward through Texas tonight, and be on our doorstep Monday. The ULL and surface low will produce this widespread rainfall event across the area, but they will also generate lift and an unstable air mass over the area. What this means is the potential for some thunderstorms throughout the day on Monday, most likely from around 10a.m. to 4p.m. at which times the instability will be at its greatest. The air at the surface will be cool and stable, but the ULL will produce very cold air aloft (instability). Thus, the threat for elevated thunderstorms exists. Some of the storms could be strong enough to produce small hail or graupel. See the previous post, to learn what grapuel is. All severe weather should remain in the coastal waters in the vicinity of the surface low. The threat for a thunderstorm will be less the further inland you go, but it could certainly happen at any particular location across the area. The heavy rain threat will exist for the entire forecast area as well, but the highest rainfall amounts will be closest to the coast. Average rainfall amounts (QPF) should be 1-2" with isolated amounts near the coast up to 3". A flood watch is not anticipated, though there could be some localized flooding where the heaviest rains occur especially since grounds are still saturated across the area. The atmospheric sounding shows the cool layer of air at the surface, then a layer of warm air generated by the Gulf low exists from about 2,000 to 5,000 feet up, then the extremely cold air exists up above that. This is a classic overrunning situation, but since you have to have the presence of cold air aloft to generate thunderstorms, this is added to the equation this time around. There was a bit of thunder and lightning with the preceding system on Friday, and I believe that'll be the case on Monday as well. Thankfully, the low will track through the Gulf, so there will not be a severe weather threat. Rain will encompass the entire forecast area for the duration of Monday into Monday night as the system slows down a bit because of Gulf cyclogenesis. The Gulf low will only slowly lift NE and be near the Mouth of the Mississippi River Monday night. As I've mentioned the forecast area will remain in the cool sector of this complex storm, and this will add insult to injury temperaturewise. March will still off with below normal temperatures. After morning lows in the 40s, only a modest warm up of 3-5 degrees is expected. Temperatures along the I-10 corridor will likely not get much above 50, and many locations will remain in the 40s. Along the coast, a bit more of a warm up is expected due to their closer proximity of the surface low. Coastal locations could reach close to 60, but this is still on the cool side. The pressure gradient will tighten as well with the surface high to our East and the developing and strengthening surface low in our backyard. Expect NE over 20 mph at times, and this will also add a bite to the chill. This is the same song and dance we've experienced all winter, and the first day of meteorological spring will be a raw, winter day indeed. The old bit of weather folklore..."March Comes in Like a Lion" will come to fruition.
The departure of the low will be a slow process, and there will certainly be wraparound moisture. The ULL will likely pass overhead overnight, and there could very well be a break in the rain as the low pulls to our East. As the ULL moves into and through our vicinity, the leftover moisture will get wrung out, as the pocket of cold air creates the dynamics to cause the additional rainfall. Temperatures will remain on the chilly side, likely falling a few degrees on the backside of the low as weak CAA takes over. There is some cold air bottled up to our North, and some of this will be pulled Southward into the area as the low departs. Rain should continue most of the night Monday, but conditions will begin to improve after midnight. The colder air filtering in would suggest the possibility of a changeover to frozen precipitation overnight into early Tuesday, however, the temperature profile isn't favorable for such an occurrence anywhere in the forecast area. Colder air will be filtering in at the low-levels, but we have to look at the temperature all the way up through the atmosphere. This is the problem. The air will simply be too warm in the lowest levels of the atmosphere from the surface to about 2,000 feet. This is too much of a warm pool of air to support anything frozen. All models indicate that the 0 C line at 850 mb. (a good measure of determining where the rain/snow line will be) will be in the Northern Gulf of Mexico, but at the same time the models clearly show the deep layer of above freezing air. So, no frozen precip is a no-go this time. This could certainly change, but it doesn't appear likely. For that matter, no frozen precip should occur anywhere in the state. Temperatures for Monday night into Tuesday should be on the cold side, and certainly unseasonable for early March. Expect readings to be fairly uniform with mid to upper 30s across the area. Some light rain and/or drizzle may carry over into the early daylight hours of Tuesday, but for the most part the rain should be over with before daybreak. Clouds will linger for a time longer.
A pattern shift follows the departing low. Much better weather will be in store for the rest of the week. It will be more representative of early March, although it will be on the cold side for a few days as CAA continues behind this low. Clouds will clear out Tuesday as drier air filters in at all levels of the atmosphere. It will be cold with highs struggling to reach 50. A tight pressure gradient on the backside of the low will keep it rather breezy across the area as well. Morning wind chills will be in the 20s. Clear skies and lighter winds in place Tuesday night will set the stage for a late season light freeze. Temperatures should range from the upper 20s to near freezing. The immediate coast should avoid a freeze, though certainly the mid 30s seems feasible with the drier and colder air mass in place. High pressure will be in control for the Wednesday through Friday period. A slow moderation is expected in regards to temperatures. Mornings will be cold through Friday with lows in the low to mid 30s on Wednesday night/Thursday morning and mid to upper 30s on Thursday night/Friday morning. Highs for the same time will rebound to the mid to upper 50s on Wednesday, upper 50s to mid 60s Thursday, and mid to upper 60s on Friday. It will be very pleasant each day with limited surface moisture in place resulting in low humidity values. Though temperatures will be moderating for this period, this is still below normal. Finally, for the weekend the moderation will continue. Saturday looks great at this time with temperatures approaching normal. Morning lows should be in the 40s while afternoon highs approach 70 topping out somewhere in the upper 60s. The controlling high should slowly shift Eastward as we get into the weekend, and a return flow will likely commence either late Friday or early Saturday. There is still some uncertainty involving the next weather maker. Timing issues arise. The consistency is there that another system will be on the horizon towards the end of the forecast period. The uncertainties are with the timing and strength of this system. For now, a chance of rain is reflected on Sunday. It is too early to decipher if we'll have any thunderstorms or a severe weather threat, but it certainly looks much warmer next time around. Temperatures could eclipse the 70 degree threshold for highs on Sunday, after a mild morning with a low above 50. This is seasonal for early March. Further fine tuning is expected as we go through this first week of March. The bottom line is that the pattern is shifting, even if it is perhaps only temporary. The El Nino will still be present through the month of March, so I would expect more topsy-turvy weather. A likely transition into severe weather season is expected as well with the active El Nino and an active Southern storm track. March can be a month of great variability as we see the evidence of the changing seasons. March is often one of the driest months of the year across our part of the world, but who knows if it will be in 2010 with the present El Nino.
Preliminary Numbers & Zone Forecast:
LCH 45/51 37/48 31/54 60 100 60 0 0 0
LFT 44/53 37/47 30/54 40 100 70 0 0 0
BPT 47/52 38/49 32/54 60 100 40 0 0 0
AEX 40/45 35/45 28/51 30 100 60 0 0 0
POE 40/45 35/45 28/51 40 100 50 0 0 0
ARA 44/55 37/47 31/54 40 100 70 0 0 0
Tonight...Mostly Cloudy and Not as Cold with rain developing towards morning. Low 45. East wind around 10 mph. Chance of rain 60% after midnight.
Monday...Cloudy, Cold, & Windy with widespread rain and a few thunderstorms likely.Some small hail possible. Rain heavy at times. 1-2" of rainfall expected. High 51. Temperatures falling in the afternoon. NE wind 15-25 mph and gusty. Chance of rain 100%. Wind chill readings 35-45.
Monday Night...Cloudy and Windy with rain likely before midnight. Rain tapering off after midnight. Colder. Low 37. NNW wind 15-25 mph and gusty. Chance of rain 60%. Wind chill 25-30.
Tuesday...Cloudy early. Decreasing Cloudiness through the day. Becoming Sunny in the afternoon. Cold. High 48. Continued windy with NNW winds 15-20 mph and gusty. Wind chill 25-40.
Tuesday Night...Clear and Cold. Low 31. NW wind 10-15 mph. Wind chill 25-30.
Wednesday...Sunny and Warmer. High 54. North wind 10 mph.
Drew's 7 Day Outlook
Monday
3-1-10
Low: 45
High: 51
Precip: 100%
Wind: NE 15-25
W.C.: 35-45
Tuesday
3-2-10
Low: 37
High: 48
Precip: 0%
Wind: NNW 15-20
W.C.: 25-40
Wednesday
3-3-10
Low: 31
High: 54
Wind: N 10
Precip: 0%
W.C.: 25-30
Thursday
3-4-10
Low: 36
High: 62
Precip: 0%
Wind: N 5-10
Friday
3-5-10
Low: 39
High: 65
Precip: 0%
Wind: NE 5-10
Saturday
3-6-10
Low: 45
High: 68
Precip: 0%
Wind: SE 5-10
Sunday
3-7-10
Low: 50
High: 72
Precip: 20%
Wind: SSE 10-15
...Marine Forecast...
* Small Craft Advisory in effect through Tuesday afternoon. *
Tonight...Southeast winds 15 to 20 knots in the evening increasing to around 20 knots after midnight. Seas 1 to 3 feet. Rain likely after midnight.
Monday...Southeast winds around 20 knots becoming east 20 to 25 knots in the afternoon. Seas 3 to 5 feet. Rain and scattered thunderstorms.
Monday Night...North winds 20 to 30 knots. Seas 3 to 4 feet. A chance of rain.
Tuesday...North winds 15 to 25 knots becoming 15 to 20 knots in the afternoon. Seas 2 to 4 feet subsiding to 1 to 3 feet in the afternoon.
Tuesday Night...North winds 15 to 20 knots decreasing to 5 to 10 knots after midnight. Seas 1 to 3 feet subsiding to 1 foot after midnight.
Wednesday...Southeast winds 5 to 10 knots. Seas 2 feet or less.
...Tide Data...
Monday Tides @ Calcasieu Pass
Low: 9:20a.m. 9:17p.m.
High: 1:53a.m. 2:40p.m.
...Toledo Bend Pool Level...
171.66'
...Lake Charles Climate Summary...
Sunday, February 28, 2010
Low: 37
Normal Low: 47
Record Low: 26-1913
High: 65
Normal High: 68
Record High: 85-1932
Precipitation
Today: 0.00"
Month to Date: 4.33"
Normal Month to Date: 3.28"
Year to Date: 7.68"
Normal Year to Date: 8.80"
Record: 1.44"-1995
Sunrise Monday: 6:39a.m.
Sunset Monday: 6:12p.m.
...Lunar Table...
Full Moon- Tonight February 28
Last Quarter- Sunday March 7
New Moon- Monday March 15
First Quarter- Tuesday March 23
This Date in Weather History...February 28, 1987: March often comes in like a lion, but in 1987 February rolled out with a fury! Severe thunderstorms occurred across the Gulf Coast in response to a strong Pacific storm. At mid-morning on this Saturday a violent tornado touched down near Moselle, MS. It would grow to a width of two miles as it passed very near Laurel, MS. This long-track F4 tornado traveled a distance of 40 miles, killed 6 people, injured 330 others, and inflicting $28.5 million in damage. An elementary school was nearly completely destroyed, but thankfully it was a Saturday, so no one was there. The tornado swept homes right off their foundations, & tossed 18-wheelers around like play toys. Strong straight line winds over 70 mph caused damage at Jonesboro, AR and Carbondale, IL.
Good night and God bless!
-DM-
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