re: Winter thread: 3.5" officially in BR on the 8th day of meteorological winter!!

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Has the snow made the northern turn yet?

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COME TO CENLA!!!!!!!!!!!!!!!!!!!!!

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modeling hurricanes is infinitely easier than accurately predicting wintery precipitation in the south.

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tGOAT radar makes an appearance again for the anticipated snow

LINK

Going by this I will get better than a inch and half of snow. What are the odds that this actually happens?

Area Forecast Discussion
National Weather Service New Orleans LA
403 AM CST Wed Dec 6 2017

.SHORT TERM...
Radar mosaic showing a steady stream of rain associated with the
post frontal moist southwest to west flow aloft. The upper low
that brought us the 30 to 40 degree temperature drop from
yesterday is now over the southern tip of Hudson Bay. Very cold
rain today for nearly the whole forecast area today with highs
in the 40s and 50s. Fairly similar similar today and tomorrow
with cold temperatures both days yet a lower chance for rain
on Thursday.

.LONG TERM...
Spend most of the midnight shift looking at the forecast for
Thursday night into Friday. The upper level pattern shows another
trof digging off the Canadian low pressure system. The trof
digs in earnest overnight Thursday bringing another push of very
cold winter temperatures. This will be the system that eventually
clears us out Friday night for the weekend bringing sunny but
very cold winter days. The big forecast challenge is the chance
for snow Thursday night into Friday northern areas of the forecast
area. Very subtle strength and timing issues are keeping the
models not in agreement with the NAM quite aggressive, the GFS
least aggressive, and the Euro in between. NAM tabular MOS
guidance changes over to snow north of Lake Pontchartrain, but not
until 18Z Friday.

So, here is a brief breakdown of the situation. There are some
indications of some snow flurries on the very back edge of the
exiting precipitation as the cold air pushes south Thursday
overnight and Friday morning. Again, this is areas in the northern
potion of our forecast area. All about the timing here as how much
moisture will there be when the colder temperature push arrives.
Forecast sounding thermal profiles support all snow and not a mix
bag, yet vary on the amount of moisture. Climatological snow
events here are usually associated with a Gulf of Mexico low
pressure system or a very slanted advance of cold air and
overrunning precipitation. This situation will bring a more
upright tilt to the advancing cold, although not totally vertical.
Confidence is low at this point until we can sample the next
upper level jet that still needs to move up and over the west
conus ridge and the subtropical jet coming off the Pacific Ocean
into the desert southwest. A jet analysis shows the situation
Friday morning as the area being in the right rear quadrant of an
exiting jet moving to the northeast US. A digging jet dives south
over the midwest as the subtropical jet moves across Texas. Any
kink in the subtropical jet as it intersects with the digging jet
would increase omega values enough to enhance precipitation
chances. We will get a much better handle on the strength of these
jets as they reach the shore and get sampled with the upper air
balloon data. A stronger system would sweep out the moisture
before the cold air while a weaker system could keep the moisture
around with the cold air. And there lies the differences in the
models and the forecast challenge at the moment. Looked at some
winter weather parameters in the model data including the SFC
thickness snow likely data. The rain snow line for the NAM is
further south than the GFS ensembles and the ECMWF. Early in the
shift the line for 12Z Friday was from Gonzales to Slidell to
Poplarville yet retreated about 20 miles north in the latest run
based on SFC data. Looked at decreasing 1000mb to 700mb thickness
values for each model run as the cold air advances. Old rule of
thumb from the 1960s was 2840m was a good separator for a rain
snow line. NAM has the the line from Gonzales through St Tammany
Parish to just south of Poplarville. The ECMWF has the line from
Clinton to McComb. The GFS has the line from Bayou Sorrel to Bush
to Wiggins, MS. Subtle but important differences as the cold air
interacts with the remaining moisture.

With uncertainty comes meteorological pontification as this AFD
has become. The takeaway is confidence will grow over the next few
days. There is a chance of snow flurries on the back edge of
exiting moisture with advancing cold air associated with another
push of very cold air Thursday night into Friday. Clear skies
return for the weekend, but winter has a grip with lows in the
upper 20s inland and low to mid 30s coastal. Warmer temperatures
are expected next week.

Channel 9 Weather on morning news just said there a possibility for wintry mix snow on Friday morning/ending by lunchtime. Meteorologist said the atmosphere will be cold enough, but models are split 50/50 as to whether the moisture will still be around.

Here's my "I'll believe it when I see it" story.

I had to drive to Illinois early this year to bring my mom's car to her post- Great Flood of 2016 (she moved after).

Of course, I had to go in mid-January. All I heard the entirety of the week before I left was MAJOR WINTER WEATHER ICE STORM THE WHOLE WAY DANGER.

I picked out a couple of routes in case that became true, followed local NWS on Twitter and took off. I took my usual route (I-55, I-57). Now, the weather was shitty almost the whole way - it was rainy and cold. But the freezing line stayed about 5-10 miles west of I-57 and the whole drive was just fine and there was no ice and no snow.

Cliff's Notes:

Good luck trying to predict the freezing line/precipitation line.

Get out of here with your nonsense

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Going by this I will get better than a inch and half of snow. What are the odds that this actually happens?

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Seems like it will have a difficult time accumulating since the ground temps will still be well above freezing, but snow flurries are a decent possibility.