Winter Storm on the Way...

Sunday, January 9, 2011

This is a special blog entry to update you on what will unfold across the area later today. There is no video blog, and this is not a regular formatted text block either. This will only include a forecast discussion The blog will return to regular format on Monday. I will have additional blog posts later today.


*Major Storm to Impact the Region Sunday.*

SW Louisiana Forecast Discussion...Wow! what a pretty day it was on Saturday. You would hardly even know that the weather is in the process of taking a big turn for the worse. The much advertised winter storm that we've discussed au nauseum this week is bearing down on the state. This will come after near perfect weather on Saturday with sunny skies and highs into the lower 60s for most. Temperatures are only slowly falling tonight as cloud cover overspreads the area. Temperatures are currently running in the mid 40s, not overly cold. You look at that and you might think how can we be talking about frozen precipitation if temperatures are this warm? There is a lot to discuss, and explicit details follow as to what we can expect later today into Monday as the vigorous storm moves across the state.

Scattered areas of light rain have begun to form across SW Louisiana as convergence and forcing increase. The potent upper level low is coming out of the Desert SW tonight, and a surface low pressure has formed along the weak cold front that moved through early Saturday. The surface low is in the Rio Grande Valley, and will gradually eject NE through the day, intensifying all the while. As all of this moves ENE rain will continue to form, and increase in coverage and intensity as we head towards daybreak. There is still some dry air in place in the boundary layer, and some evaporative cooling will take place at the onset of the rainfall. Dew points are generally running in the low to mid 30s across the area. Temperatures will fall off more rapidly once the precipitation begins as it helps drive colder air aloft towards the surface. Rain will be widespread, and will impact the entire forecast area throughout the day. The rain will not be the only issue. Strong winds and some coastal flooding will exist across the area. The offshore waters will be a mess as well. Rain will be heavy at times as convergence reaches a maximum, and we max out in forcing as well. A copious amount of Pacific and Gulf of Mexico moisture will be in place thanks to the synoptic features. The surface low will help enhance moisture, producing periods of heavy rain. Isolated thunderstorms can't be ruled out as well given the large amount of instability in the upper levels. Thank goodness, this low is tracking through the coastal waters, or we would deal with a very serious tornado threat on Sunday. Severe weather may occur over the coastal waters.

Over land, rain will be present throughout the day and will be heavy at times. Expect 1-2" of rain on average with higher amounts in excess of 3" possible. Temperatures will be on the cold side as the orientation and track of the surface low lead to increased CAA. It will be cold and raw with temperatures starting out generally in the mid 30s to lower 40s after evaporative cooling processes take shape. These temperatures won't change all that much Sunday, and in fact, it may actually drop a few degrees during the day as the low enhances CAA. There in lies the other issue with this major storm. Certainly, a good portion of the Northern half of the state will deal with significant amounts of snow, sleet, and freezing rain. I would expect many locations up that way to be shut down with travel being near impossible by Sunday afternoon and extending into Monday. A crippling ice storm is likely for some folks North of this forecast area, and snow will likely fall on top of that. Places such as Shreveport, Ruston, Monroe, Tallulah, and Natchitoches will experience major problems from this winter storm. We will have our own problems down here as well given the heavy rain threat and the strong, gusty winds. We could winds in excess of 50 mph at times, this is into tropical storm force, just to put things into perspective.

The strong winds and the trajectory of the surface low will cause water to pile up along the coast, thus inducing the coastal flooding situation and causing tidal back up. Water levels will rise with the strong winds and lowering pressures, with some minor flooding extending up the rivers and bayous at least to the I-10 corridor. Gale Warnings are in effect for the coastal waters, and a Coastal Flood Advisory is in effect for the coastal counties and parishes. The National Weather Service has also issued a Wind Advisory for all counties and parishes along and South of I-10 for Sunday. These will be the main issues in this forecast area, but as the day wears on the chances increase slightly for some frozen precipitation to occur across this area, at least for along and North of I-10. Temperatures will slowly fall, and the atmospheric profile suggests that the cold air in place at the surface will nose upward as the low pushes further East. That means that as rain continues to fall, the possibility of some sleet, snow, or freezing rain may mix in with the rain. The threat for heavy precipitation will also exist, but the heaviest precipitation will come in the form of rain, and that should be from around sunrise to early afternoon. Lighter precipitation is expected for the mid-late afternoon hours into Sunday night.

The threat for the aforementioned frozen precipitation seems to be increasing for the East Texas Lakes Region into Central Louisiana. The threat for any mixed precipitation is lessor towards I-10, but this is still possible. I would expect that the main p-type other than rain across this area will be sleet. I would also surmise that some accumulation of sleet is possible for the Northern portion of the forecast area including such locales as Alexandria, Pineville, Fort Polk, Leesville, DeRidder, Oakdale, Opelousas, Bunkie, and Marksville. Whether or not accumulation occurs in this area is a borderline situation, and is not currently reflected in any forecast. The mention of some mixed precipitation itself will be in the official forecast even for the Lake Area, but certainly there is almost no chance that any sleet that would fall here would accumulate. Things can change, and I advise you to stay tuned. Whether or not any frozen precipitation occurs along I-10 at all is an even more borderline situation, but given the colder solution depicted by model runs tonight I have enough confidence to insert it into the forecast. Understand, that the frozen precipitation will be much more of a problem from Central Louisiana Northward, and the heavy rain and wind will be the issue here locally. The window of opportunity for anything frozen around these parts will come from about 4p.m. Sunday afternoon through around sunrise Monday.

I would expect rain to be falling by sunrise over the entire area, and winds will gradually increase in response to falling pressure overnight. The weather will get worse after daylight Sunday when the heavy rain threat begins. It will be a wet, windy, and cold venture out to church, and I would suggest letting that be the only place you have to go on Sunday. If you have travel plans into North Louisiana, it it strongly advisable to change them. Road conditions up there will be poor. Remember, in Louisiana, we don't have snow plows or salt trucks like they have up North. The stiff NE wind will create wind chills in the 20s and 30s all day, and I expect the high temperature for the day to be reached between midnight and sunrise. Temperatures will likely start out around 40 here in the Lake Area with middle 30s up towards Alexandria. By the afternoon, temperatures will likely be at or below freezing across the Northern portion of the forecast area, and in the mid to upper 30s for Lake Charles. Rain will begin to taper off after sunset, but there will be plenty of residual moisture hanging around until the low moves further away. Rain chances will be tempered downward overnight after being maxed out during the day Sunday. Temperatures will continue to slowly fall overnight Sunday as the Arctic air continues to filter in. The main shield of precip exits stage right as the low pulls away, but we will remain Cloudy. The boundary layer will remain nearly saturated, and this atmospheric set up will favor scattered pockets of light rain or drizzle on the backside of the departing low. Herein, lies another problem heading into Monday morning.

These pockets of light rain or drizzle will be falling into the cold air at the surface, and temperatures are expected to bottom out in the mid 20s north to just above freezing at the coast for Monday morning. I expect a low right around 30 here at LCH for Monday morning. This raises the red flag and my concern for the possibility of scattered light freezing rain and/or freezing drizzle in the overnight hours through Monday morning. This, once again, is a small possibility, but can't be ignored especially since models are trending colder and a bit slower on the departure of the precipitation. I will not get to adamant about this yet, and since this is a very fine line here and a precarious situation I will defer being more specific about this until Sunday afternoon after perusing more model data. If this were to occur, then we would likely deal with some minor icing issues for Monday morning. All it takes is a little bit of ice to create major headaches for a morning commute, so once again I am monitoring this very closely, and urge you to check back for later updates. This next 24-36 hours isn't going to be very much fun to be in, but it makes for a lot of fun in the weather department, as well as a lot of headaches. Ice or not on Monday morning, it will be very cold with temperatures running in the upper 20s to lower 30s, and continued gusty North winds wind chills will likely be in the 15-25 degree range.

Clouds will hang tough through much of the day Monday, but after the patchy morning light precip it should generally be dry. It will remained cold for Monday and for much of this week with Arctic air in place. Highs will struggle to make it 45 or so. Morning freezes are expected through Friday morning with a potential for hard freeze conditions on Wednesday and Thursday. An additional shot of colder air will arrive Tuesday evening into Wednesday morning. Moisture will be limited, so no chance of rain or other precipitation is highlighted. Clouds will be in and out for much of the week, but we will see some sunshine as well by Tuesday. The cloud cover and continued Northerly winds will save us from a severe freeze this go around, but it will still be plenty cold. Highs each day through Thursday will not make it to 50 degrees, and will struggle to even reach 40 on Tuesday and Wednesday. Temperatures could be a few degrees colder than forecast depending on how much snow falls to our North. Models don't take snowpack into consideration. If there is a solid snowpack across North Louisiana, then the air will not modify at all as it moves our way since the winds will be coming straight off of said snowpack. This is to be considered for future forecasts. Moderation should begin on Friday as we see a return of Southerly winds ahead of another cold front that should arrive at the end of this forecast period on Saturday. That one could bring in another dose of Arctic air behind it for the remainder of the Martin Luther King, Jr. Holiday weekend. It remains to be seen, but the overall pattern favors more cold weather through the middle of the month.


Stay tuned for more updates later today!


Good night and God bless!
-DM-