CAPE

Latest AFD from Mount Holly- Signals in the upper level pattern by late week and the weekend becomes quite active between the northern and southern stream jets. The key elements embedded in these features are currently located over the Arctic and the Pacific Ocean, so it`ll likely take at least a couple more days for guidance to have a good handle on this system. However, almost all available guidance depicts an area of low pressure developing near Texas Friday before tracking eastward along the Gulf coast into Saturday. Beyond Saturday there still remains forecast uncertainty regarding the details of how this system will play out for the east coast. However, at this time most forecast guidance tracks the low north and east towards the North Carolina coast and then off to the north and east from here by the Sunday into Monday time frame. This track puts the mid Atlantic region on the northern side of the system with the main question then becoming just how close to us does the low track. There will be a very strong and broad arctic high to our north and some of our prior guidance had suggested this may be strong enough to suppress the system just south of the area. But over the past 12 to 24 hours there`s been a general trend northward in guidance suggesting the precipitation shield will make it into our area. In fact, snow probabilities of the NBM now show a 60-70% chance of 2+ inches of snow and a 40-60% chance of 6+ inches of snow for areas roughly along and south of the I-95 corridor with decreasing probabilities farther north. These probabilities are higher than with the prior forecast cycle. So while this system still is about 5 days out, the signal for a winter storm to impact at least parts of the area is higher than usual. The timing of this would be as early as very late day Saturday continuing through Sunday and potentially even lingering into Monday depending on the system`s speed.

At first glance I read that as " Big Stout" lol. Which reminds me I need to get some before the weekend. OK back on topic!

Google AI- Key Methods for Determining Snow Ratios in NBM: Temperature-Based Algorithms: The SLR is highly dependent on boundary layer and low-level temperatures (surface to 850 mb). Generally, colder air results in higher ratios (fluffy, dry snow), while temperatures near freezing produce lower ratios (wet, dense snow). Melting Rates for Marginal Temperatures: For temperatures at or above 32°F, the NBM v4.2 incorporates idealized melting rates. The total SLR is reduced based on the ratio of melting to accumulating snow, effectively lowering the ratio if the snow melts as it falls. Dynamic/Algorithm-Based Ratios: Instead of a default 10:1, the NBM uses algorithms that consider factors such as: Wind Speed: Higher wind speeds can lead to lower ratios due to snowflake fracturing. Cloud Structure: The presence of supercooled water droplets (higher riming) vs. depositional growth influences the ratio. Ensemble Member Blending: The NBM uses output from several models (HRRR, GFS, ECMWF) to calculate a probabilistic snowfall, utilizing the best-performing models to determine the most likely ratio for a given area. Elevation Adjustments: Ratios are adjusted upward at higher elevations to account for colder, drier conditions in mountainous terrain.

That's what we are talking about lol. Already posted.

Yeah looks like it factors in multiple variables for SLR.

I would assume so.

Latest blend. I think we got us a solid signal across guidance for a major winter storm lol

2 ft in southern VA including the Northern neck lol

It is 'funny' how Josh Allen mistakes are downplayed while Lamar's are magnified. Imagine if Lamar turned the ball over 4 times in a playoff game then cried afterward. The hate would be off the charts. Good player, but the Josh Allen love by the media is nauseating.

I just want a long duration snow event with temps in the mid teens. Strong lift through the DGZ with 15:1 or better ratios. Is that too much to ask? Been awhile.

Yeah this wont be the final answer. Hopefully better.

Latest blend. NWS relies pretty heavily on this product at range when there is still some disparity among guidance. Don't see this often 5 days out.

Yeah its not done-

I agree(you saw my post a couple pages back). 12z does actually eject significant energy from the SW, via a partial phase with the energy dropping south from the Pac NW. 18z doesnt, its flatter, but is slightly better with the silly snow maps. Ofc that's only part of the story- the timing/depth of NS energy associated with the TPV is another component.

On the GFS its mostly how much interaction/phasing occurs out west- more on the 12z while 18z pretty much misses, so ends up flatter/souther downstream with the precip. (see my post a page back) The 18z GEFS is closer to 12z wrt that interaction, but a tad later.

Subtle differences in the interaction between the pieces of h5 vorticity make a pretty significant difference at the surface downsteam- one such difference occurs here with a lack of phasing between the NW energy dropping southward and the Baja vortex. Compare to 12z- some phasing occurs and vorticity from the SW energy ejects eastward contributing to more amplification and sooner.

This should be a separate thread lol. J/k. Nice job.

12Km NAM posts should be hidden in a serious storm threat thread at this range, or any range come to think of it. It is about to be retired, and should already be. The Panasonic(which doesnt really exist) is better.

Maybe, but there was a big jump in snowfall from 12z to 15z run, and 18z looks exactly the same.

Latest Natty blend- I think it has ingested the 12z model runs..

LOL just realized there is an actual thread for this threat. Kind of early but the signal is strong.

We we are close enough for snowfall maps to be useful given the strong signal for a storm across guidance.

Latest AFD from Mount Holly on the upcoming potential event- KEY MESSAGE 3...There is signal for an impactful winter storm to impact portions of the area this weekend, however quite a bit of uncertainty remains. Signals of the upper level pattern by late week and the weekend becomes quite active between the northern and southern stream jets. The key elements embedded in these features are currently located over the Arctic and the Pacific Ocean, so it`ll likely take a few more days for guidance to become better aligned. In the meantime, almost all available guidance depicts an area of low pressure developing over the Southern Plains on Friday before tracking eastward into the Deep South on Saturday. Beyond Saturday, its uncertain where the track of the low may go. The main player here is the Arctic high to the north and how strong the high becomes. Some guidance depicts a very strong high near 1044mb, which results in a suppressed storm track keeping any significant precipitation to the south. Whereas, a weaker high would result in a more northerly storm track and potentially bringing significant accumulation to the area. Considering that the system is 5-6 days out, the signal for a winter storm to impact at least portions of the area do appear to be stronger than usual. In fact, snow probabilities of the NBM show a 40-60% chance of 2+ inches of snow and a 20-40% chance of 6+ inches of snow for areas south of Philadelphia. Probabilities do lessen further north. Even the Probabilistic Winter Storm Severity Index (WSSI-P), depicts a 40- 60% chance of moderate level winter storm impacts to the south of Philadelphia. Obviously a lot can change between now and the weekend, but users should keep a close eye on the forecast over the coming days.

Ok just looked at the GEFS and EURO AI Ens runs. They look supportive of the GEFS and EPS respectively, but more juiced up.