Right now just liquid in the forecast for me in Thibodaux Tuesday night. But with temps rapidly dropping below freezing, I think that anything that falls will be snow. Most of the forecasts are still showing 50%
From this afternoon's New Orleans discussion. No kidding about the large font though. I cannot believe they're actually talking about it this early:
.LONG TERM... The base of the upper trough currently in place over the southeast conus will lift slightly on Monday. This will allow for local air mass modification and moderate temperatures a bit. Highs will rise back into the 50s, but only for a day and not to return until the end of this week. This is because yet another polar trough will come barreling south across the mid section of the country Tuesday into Wednesday, bringing with it very cold air and the chance for frozen precip.
The forecast period from about 18Z Tuesday to 12Z Wednesday will be the most challenging of the next 7 days. As with most wintry potential events in this part of the country, timing will be everything. Will cold air deep enough in the column move into the area while precipitation is still falling? Model soundings began to indicate that possibility last night and even moreso today as they show precip slower to come in and cold air faster to come in. Southwest Mississippi zones stand the best chance to see any snow or sleet mix as the cold air looks to get there quicker. It could begin as early as early afternoon and carry on into the evening hours. Further south, along the I-12 corridor, a mixture may begin in the late afternoon to early evening hours before cutting off by midnight. Lastly will be the Mississippi Gulf coast. The GPT sounding is supportive of a mixture as well but for possibly just a few hours. It should be noted that even the MSY sounding showed a little sleet mixed in but confidence was too low to include it in the forecast there.
Wintry forecasts are typically low confidence and this one is no different, especially considering we're talking about 4 days out. Don't be surprised to see changes in timing, duration, location and possibly completely removing it all together from the forecast by the time Tu/We rolls around.
Freezing Days for Winter 21/22: TBD Freezing Days for Winter 20/21: 24 Wunderground ID: KLAPONCH50 - Downtown Ponchatoula NWS COOP ID: 16-7425-08 CoCoRaHs ID: LA-TG-22
Post by mobileweatherwatcher on Jan 12, 2018 18:08:35 GMT -6
From the late afternoon discussion from the NWS Mobile:
LONG TERM /Tuesday Through Friday/...The broad upper longwave trough east of the Rockies over Canada, the U.S. and northern Mexico will be reinforced and dig a little further southward through Tuesday night as strong upper level impulses embedded in the trough from the Great Lakes to the southern plains move eastward. A 100 to 130 knot jet stream along the periphery of the trough will move southeast, with the strongest upper level winds occurring over the eastern conus Tuesday and Tuesday night, putting our area in the right entrance region of the upper jet. This will enhance lift across the area and could promote periods of rain or a mix of rain and snow Tuesday afternoon.
A strong surface cold front will continue moving south across the Gulf of Mexico, allowing very cold temperatures to advect into the forecast area from the north through Tuesday night. Sub-freezing temperatures are expected to push all the way to the gulf coast by late Tuesday night, allowing the light rain to change over to all snow as far south as the northern gulf.
Snow accumulations will be determined at a late time, but a blend of the GFS and ECMWF currently have up to one inch snow north of I-10. Snow accumulations may end up being even higher as the thermal profiles may still be a bit a underdone. Dynamic cooling in the lower levels due to evaporative cooling and the "dragging" of cold air aloft closer to surface is sometimes not accounted for in the models, and additional moisture may be drawn in ahead of the system. This system is pushing through rather fast, so the entire event will be less then 24 hours. Dry conditions will follow Wednesday and Thursday behind the cold front. Much below normal temperatures will persist through the long term. /22
Can’t ever recall MOB talking about a potential winter event days in advance
Post by Zack Fradella on Jan 12, 2018 18:43:05 GMT -6
Before we go any further, please don't live and die by the snow total maps with every run. Like Mobile NWS mentions, the models will probably not account for the amount of moisture in the end and usually the cold air moves in faster than models think.
The December snow had most locations staying between 1-2" when multiple locations came in 3-5". I'm not saying we are going for a repeat but just don't complain with every snow plot.
We are still in the EARLY stages, we need to make sure the upper environment will play out like the models are seeing it now before we start talking totals.
Post by cajunsneauxmaker on Jan 12, 2018 19:12:13 GMT -6
TWC Moved the totals up from less than an inch to 1-3 inches 40 miles north of me in Alexandria, but left me at less than an inch. But as Zack says, I'm not buying into either of those forecasted totals, 40 miles is not very far, but I guess the difference could possibly be how long before the transition happens. I'll wait and see, and to be honest, I'd be happy with a couple of inches, as my wife is
Looking at the GFS sounding forecast and Euro's columns' temp forecast while the precip moves over SE LA I only see a mostly sleet event for the south shore before precip ends with a warm nose near h85 slow to cool down, unless the cold air moves in faster at h85 than the precip. You have to wait for the NAM to get within range, it nailed the last two snow events across the deep south, except that it exaggerated the snow totals across SE GA but it was the only one that nailed it when the GFS, CMC and Euro were initially not showing the snow in SE GA.
If we get the wintry weather next week, what the timeframe? During the day or night?
For Tuesday, north LA during the late morning-early afternoon, SW LA during the early afternoon into the early evening, SE LA from late afternoon into the evening, closer to midnight to be over on the north shore, a little past midnight to be over on the south shore, by looking at the latest GFS sounding forecast & Euro.
Edit: actually the 12z Euro is a little faster than the GFS, it has the precip moving in and moving out a good 3-4 hours faster than the GFS.