Under The Scope
Frozen Jambalaya
What do portions of the Houston metro area, Galveston, Beaumont, Lafayette, Baton Rouge and New Orleans all have that a certain city in Montana doesn't have so far this season? More snowfall. Yep, all of those cities have more snow this season than has been recorded in Missoula, Montana where they've only seen 0.6 inch. Six tenths of an inch that's it? Come on, you're late to the party what with the snow bound Houston metropolitan area seeing up to 5 inches of snow, Galveston with an inch, Beaumont with 2.5 inches, Lafayette with an inch, Baton Rouge with 3 inches and New Orleans with 1 inch, you'd think a town in the northern Rockies in Montana would have tons more. Nope not this year. This is one of the earliest snows on record for portions of the west central Gulf Coast. And one of the heaviest for December. I don't think you believe me, well check out this radar capture 
...this from 9am this morning eastern, 8am central time and that blue on the radar in Louisiana, that's snow. Associated with an upper level area of low pressure which contained cold enough air above the surface to allow for this to happen. Last night that was over into southeastern Texas but it migrated northeast overnight and through the day today. Hey its cold enough for the snow just look at the 850 temperatures in the colors and the 1000-500 mb thickness with the lines here 
. That was from this morning and sub freezing temperatures where you want them to be at 5,000 feet over eastern Texas into western Louisiana but that was migrating east. Interesting that the thicknesses were not very low, usually you'd look for 5400m but you see the 5460m line going through LA/TX with lower thicknesses, that 540 line if you will off the coast. And especially if you're talking snow in this area you'd need it below 5400m due to the elevation which in many levels is below sea level and due to the maritime climate. But this was a very dynamic system, even brought thunder snow to Baton Rouge and brought an eighth of a mile snow to New Orleans for a time at mid morning. With this not being a very cold system, temperatures were marginal at the surface hovering at or above freezing through much of the event. So despite its ferocity, it didn't accumulate as much as it could have if there was a better supply of cold air at the surface and aloft. It could have been a lot more. Typically a 1-3 hour period of snow. Here's the tail of the tape...as much as 8 inches fell in Amite, LA where 30% of Tangiphoa Parish without power. The weight of the snow collapsed 2 roofs over businesses and numerous tree limbs were down. That was common with the wet snow for trees and power lines to be down across southeastern Louisiana and into southern Mississippi. Most of this collected on the grass but there were icy roads and some areas changed over to freezing rain and sleet briefly but widespread major problems seem to be avoided because temperatures were mostly above freezing. After school activities were canceled and some let out early.
Scoping It's Perspective
This was the first snow in New Orleans since Christmas of 2004. That's when a half inch to an inch of snow fell on the city. Here was the weather pattern that day 
...and much like this event, temperatures were marginal or even milder. The 850 mb 0 degree line was to the north of Lake Pontchartrain, the upper level low was south of Texas, this had to have occurred from overrunning which is evident with the upper level flow and if you look to the north on the surface a 1027 mb high from Texas to the Ohio Valley. That had to have seeped in cold enough air at the surface to allow for this to happen. This is a different kind of set up to what occurred today as today's instance was not overrunning it was with a cold core low on top of them. The cold air wasn't on top of them on Christmas 2004 and they were on the northern extent of the precipitation shield. In fact the snow was a little bit more robust to the south of New Orleans as well. It was an efficient storm and the snow then lasted a little bit longer, about 4 hours with some sleet mixed in and that occurred in the afternoon hours. Snow was not as heavy as it was in today's instance, visibilities only went down to a mile. And temperatures were at 33 that was the lowest it went. It's a rare event, since 1850 there have only been 17 instances of more than a trace of snow in New Orleans. Today's snow was the earliest recorded in city history.
Elsewhere putting it in perspective over the remainder of southern Louisiana, in Lafayette today was an all time record snow for the month of December with 1 inch. In fact there has never been recorded measurable snow in the month of December in city history. HOWEVER this is not the earliest snow for them, the earliest snow occurred on November 30, 1936 when 1.1 inches fell. Meanwhile in Lake Charles, 0.4 inch of snow fell, earliest snow in the city ever, most snow ever in the month of December and the last time it snowed in December was on the 22nd in 1989 which was the only other time that it ever snowed in this month there. In that instance it was bitterly cold with temperatures at 17 degrees when the snow fell for 2 hours. And this wasn't in the middle of the night, we're talking 9:30-11:30 in the morning! Before that they had freezing rain and it was in the upper teens and low 20s. Geez think it was a dry snow then as opposed to the wet snow today with temperatures of 33 degrees when it fell for 3 hours early this morning? Yeah I think so too.
Scoping The Numbers
8 inches of snow, that was in Bogue Chitto, Mississippi today. It's part of a snowy calendar year there in southern Mississippi, this area north of McComb. Back on January 19th of this year up to 5 inches of snow fell causing some trees and limbs to fall in power lines in the region. That occurred during the morning and also in nearby McComb, temperatures never got below 33 degrees and snow dropped visibilities down to a half mile. So was it like today's system? No, there was no cut off upper low but in fact it was a marginal situation, 850 temperatures did not go below 0 degrees C but the weight of the low level cold air was just enough to allow this to happen. Had a 1040 mb high over Colorado shunting very cold low level air southward, meanwhile there was a low pressure system south of Louisiana and a broad area of moisture to the north of there across the Deep South just below a very strongly positively tilted upper trough.
31 degrees this morning for a low temperature in Harlingen, Texas. That's the coldest temperature there since February 12, 2006. A 1034 mb high was over areas to the west of the Rio Grande River at the time with a broad positive tilt upper trough over the eastern portion of the country and 850 temperatures taking a dive and cold down to the south. Today there was a 1032 mb high over northern Mexico and an upper level trough is pretty well positive but its not digging as far south as the one over 2 years ago did because of the upper level low in the western Gulf. So if that low wasn't there, temperatures could have been colder this morning, that upper is just blocking the real cold surge from plunging south.
Region Scope
Northeast: A tenth to as much as 0.35" of ice has fallen from the Mid Hudson Valley of New York into western Massachusstts today. 0.21" of ice in Goshen, New York helped to contribute to an 11 vehicle accident this morning on the Newburgh-Beacon Bridge which injured 8 people. This is the first time since at least 1993 that there has been injuries due to ice in Orange County, New York where this accident took place today. The last time ice collected to a great degree was on February 13 of this year where up to a half an inch occurred. That was a more classic icing set up than today because then there was a 1030 mb high over southern Canada blowing down very cold air at the surface and there were a couple of surface lows moving up the western slopes of the Appalachians so that cold air was hard to dislodge especially at the surface. Today's high pressure area is more transient and not as strong so thus far not seeing the ice accumulations that was seen 10 months ago.
Tennessee Valley: They're calling it a gravity wave that blew through northern Alabama mid morning today which knocked down trees in the Florence and Muscle Shoals areas. It was raining at the time and heavily with gusts around the time of impact from 10:01-10:53am at KMSL gusting as high as 46 mph. That wasn't a continuous gust but they were frequently over 23 mph in that time frame. The last documented gravity wave wind damage event was on December 12-13, 2002 in that area. Then the synoptic situation was one with a surface low pressure area south of the southwestern Louisiana coast with an upper level trough over the central Plains with a negative to neutral tilt east of there, a good southwesterly winds over northern Alabama and the bulk of the moisture well to the south. Winds only gusted as high as 30 mph at KMSL just after midnight on the 13th but a few trees and power poles were blown down, a carport was blown over in Marion County. Wind gusts were estimated at 35-45 mph. By the way 2 inches of snow fell in Marion County today in Hackleburg behind the weather system that moved through.
City Scope
Dallas-Fort Worth, TX
So each edition we'll go down each market from biggest to smallest and give a little insight on what they have to offer weather wise and otherwise.
Evan Andrews KDFW Dan Henry KDFW David Finfrock KXAS Jennifer Lopez KXAS Steve MacLaughlin KXAS James Aydelott KXAS Greg Fields WFAA Steve McCauley WFAA Jeff Jamison KTVT Kristine Kahanek KTVT Larry Mowry KTVT
By the way in the last city scope for Philadelphia, the high was 45 degrees. The GFS Lamp scores another one, it was closest with a 46. Meanwhile the NGM and GFS were at 47 and the NAM went 48. Not bad, not bad models. Skies were partly sunny through the day as well. *applause*
Broadening The Scope
Alright on the last update, the 12z European hinted at an arctic plunge for December 6-7 through the Great Lakes, northern Plains and Upper Midwest and it was ascertained that Minneapolis could have gone below freezing during this outbreak, notably on December 7th. Unfortunately that didn't happen. The model showed a 1030 millibar high on the North Dakota/Minnesota/Canada border and in fact there was a 1030 mb high but a little further to the south. The model showed 850 mb temperatures at -16 degrees C and that did verify. So for the most part the pattern verified, its just the temperatures did not get as cold as I thought. It was 3 degrees for a low on the 7th. But that wasn't the coldest temperature of the month, it reached 2 degrees on the 10th. Just did not get cold enough to go sub zero despite the fact that the model basically verified, good for the European. Any other surprises? What is to come, we take a look at the wild and crazy model solutions in this section. This is the 18z GFS and its showing a dive in thicknesses through California, could this be snow into the hills of San Francisco and even down to the valley floor in Sacramento on Monday morning December 15 
...I mean if you look at the extracted info for KSAC on the GFS from the 12z run it is going snow and even thundersnow in a continuous period from 18z on the 13th through the 19th. At this time it was showing 850 mb temperatures of -3.2 to -3.9 as the lowest with 1000-500 mb thicknesses down to 5260 m. It's a little bit higher on this map at just over 5280 m. The most snow in the city of Sacramento occurred in January of 1888 when 3.5 inches occurred. 1.69" of qpf projected from the 12z GFS during the period of snow that I mentioned, a simple 10:1 ratio would equate that to 16.9 inches of snow. Uhhh yeah well I mean its on there, maybe it would happen. Or could this not happen at all....
Scoping The Weather Tracks
With the snow there in the bayou, what better song to have and what better artist than to have something that reminds you of the season and fits the overall weather mood in Louisiana today than from a native. A New Orleans native where they got an inch of snow today. If he was still alive, he'd be playing it loud and proud. It's the great Louis Armstrong with Winter Wonderland taking us home tonight! Till later!
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