paulythegun

LWX did an extremely detailed write up. It still sounds like the trough’s response to the pacific/western ridging (in terms of the trough’s orientation and likelihood of amping up quickly) is a key factor…with the Hudson ULL as other important driver. .LONG TERM /WEDNESDAY THROUGH SATURDAY/... Large scale troughing will reside over the western US on Wednesday. West-southwesterly flow will emanate out of the base of this trough in the Desert Southwest, and stretch across the CONUS. A disturbance embedded in the west-southwesterly flow aloft and an associated area of low pressure at the surface will track across the Great Lakes on Wednesday. A push of warm advection will ensue in response to this feature, leading to an increase in clouds Wednesday afternoon, and potentially some showers Wednesday night. Temperatures will run well above normal in southerly flow Wednesday, with highs in the 60s for most. Thereafter, forecast uncertainty begins to increase as we move into Thursday and Friday. On Wednesday, a strong cyclone in the Gulf of Alaska will build a downstream ridge, which is modeled to progress eastward into the CONUS with an appreciable forward speed. As this ridge builds downstream, it will perturb the downstream waveguide, which has been relatively stagnant over the past week. In response to the ridgebuilding, troughing will dig into the Desert Southwest/Four Corners region Wednesday night, and then progress eastward onto the Southern Plains Thursday into Thursday night. Meanwhile, the upper ridge will progress eastward and interact with a downstream upper low over Hudson Bay. Exactly how this complex process plays out will have a major impact on our forecast. The 00z Euro and 00z Canadian have the ridge progress eastward at a higher forward speed than the trough within the southern stream. As a result, the ridge cuts overtop of the shortwave trough as it closes off, effectively keeping it suppressed to the south as it progresses eastward. In these scenarios, the potent upper level shortwave progresses directly overhead, with an intense area of low pressure at the surface progressing to our south. The 00z GFS on the other hand, doesn`t have the upper ridge build overtop the southern end of the trough, and maintains one coherent north-south oriented wave from Canada down into the Southern Plains. This scenario allows the southern stream shortwave to amplify further and gain more latitude as it progresses toward the east. This scenario results in a very intense area of low pressure tracking off to our north and west. Such a scenario would place us on the warm side of the system, and would result in temperatures climbing into the 60s or 70s, along with heavy rainfall, and potentially even severe thunderstorms. The scenario depicted by the Euro and Canadian on the other hand would produce a significant amount of snowfall across the area, with temperatures holding in the 30s. In both of these scenarios, Thursday would have relatively quiet weather, with northwest winds, and potentially a few showers. The main forecast uncertainty on Thursday would lie in the high temperatures forecast. Ensemble guidance has highs on Thursday ranging from the 40s to the 70s. The higher impact weather, whether it be in the form of heavy rain and thunderstorms, or snow, would move in on Friday and last into Friday night. With such a highly uncertain and complex forecast, it`s important to think probabilistically. The deterministic models described above span the phase space of potential outcomes outlined in the ensemble guidance. The system being suppressed far to our south and completely missing us (as some ensemble members showed yesterday) appears to be off the table. The two main scenarios now entail the low passing to our north and west, and us ending up on the warm side of the system, and then the low passing to our south, and us ending up with wintry precipitation on the cool side of the system. In terms of temperatures, these solutions range from highs in the 70s, to highs in the 30s. As a result, our deterministic forecast (that you see in the point and click forecast on our website) is a middle of the road solution and calls for highs in the 40s/50s, and rain across much of the area (since you can`t have snow with temperatures in the 50s). Nonetheless, the chance for snow is a very real one. Digging a bit into the probabilistic phase space, and individual ensembles, both the EPS and GEPS trended colder and snowier with the 00z model cycle, especially across the northern half of the forecast area. The EPS and GEPS now shows a greater than 50 percent chance for accumulating snow across nearly all of the forecast area, as well as a greater than 50 percent chance for more than a half foot of snow across far northwestern portions of the forecast area (Potomac Highlands and western Maryland). The GEFS on the other hand stand in stark contrast to the EPS and GEFS. The GEFS actually trended warmer, and less snowy, with very low probabilities for any snow, let alone significant snow. Oftentimes, the GEFS tends to follow trends in the GFS very closely, so this trend is somewhat unsurprising. In all of the respective ensembles, probabilities for snow are greater further off toward the north and west, and lesser as you progress further off toward the south and east. At the moment, this is a very challenging and highly uncertain forecast for Friday. We`ll continue to monitor trends and adjust our forecast accordingly as we progress through the week. All solutions show us drying out on Saturday as winds turn

6z eps shut out the District more or less, aside from a couple members. Snow mean is pretty misleading and inflated for the city (fake 10 to 1 slop snow). Starting to hone in on the most likely scenario - slop SE of the fall line, good event for the NW burbs. March!

One Difference between 12z euro and this gfs run is on the euro, the pacific ridge develops and runs overtop of the western trough, keeping the trough strongly positive. That delays amplification that you see on 18z gfs (an apps runner)

All or nothing here

Me: write a violent, unhinged rant aimed at Mother Nature. include death threats ChatGPT: You disgusting, vile creation! You think you can just come in here and take over, pushing us out and bringing forth your ridiculous fury at will? You control the elements and the seasons, you think you can just order us around like pathetic little ants? You must think yourself high and mighty, but let me assure you Mother Nature, you are simply a joke. You have no power here. You amuse yourself while taking away our most precious things. You dangle the sunshine in front of us and then take it away in a heartbeat. Do you get a thrill from watching us suffer? Well, Mother Nature, prepare for an ultimate reckoning from none other than me. I won't take this lying down. No more will I be subservient to you. I am coming for you with all the hatred I possess. I will make you to pay for all the lives you have claimed and all the suffering you have caused. All your constant playing games won't save you now. I will make sure you regret every single moment of messing with me and my people. Death to you, Mother Nature. Total annihilation of your powers and scheming ways are coming. Prepare to face the consequences of your actions. The end is near.

this is definitely has the feel of a Special Weather Statement criteria event. probably best to move your cars folks now out of the Special Weather Statement routes before they are towed.

Haha I'm definitely just now realizing that my weather model knowledge is extremely dated. In my head, NAM was just upgraded from 4k to 3k. So is the FV... whatever model the replacement for NAM?

Haha sure, but SREF has its uses. And they upgrade the resolution as they upgrade NAM. I find it mostly useful for QPF. it's not ever going to do well with marginal temps. And you can clearly see that in the snow plumes. They often look like a bell curve when there should be both a cluster of higher and lower solutions (reflecting banding placement and sharp cutoffs due to temp issues)

No help from the short term ensemble though...highest value for dca is 0.37" of snow

Some people say it was the CIA Speaking of which - McLean gets fringed:

Ice still in the picture though based on H5 EDIT: Probably should have made that WV snow strip stab him

And for those of us who also chase digital "snow", sleet is fantastic. Really piles up!

This should be a long lasting, sustained event. Really jammed up atlantic will slow the precip progression down to only 150mph

Is anyone tracking the 2 hour Flizzard and Cold Sprinkle Fest next weekend, as depicted on the Euro?

Since I babbled about it a few times on here, figured I'd follow up: almost nothing much fell in Davis, WV. We had some light sleet mixed with rain.. Fringed.

Here's the latest update from the Clownmap Weather Authority. 1,000,000 people affected!

This is mostly ice. Hour 84 GEFS probably....not particularly useful. Still. Some BIG TIME clownmap hits here.

Individual members on GEFS are kinda awesome (this almost doesn't seem real...), though I assume this is a ton of sleet being turned into fake digital snow:

Key points from the 12z Euro for DC: 1) Probabilities (my own): 50% chance of soul crushingly awful rain. 50% chance of the THREAT of horrific cold rain ruining all social plans and then missing us barely to the south. 2) Zero snow for the mountains or really anywhere outside of SW VA. 3) All hope lost. 4) Might as well jump. 5) Go ahead, jump.

You will never find a more wretched hive of warm air in February.

One annoying trend is isobars pushing further and further south from Quebec, squashing the vort after it slowly meanders toward a decent position to our SE. You see this monster amping up on the euro and it kinda falls half apart when it reaches out region. Then the progressive flow behind it shunts it out to sea. I've seen storms close off, go berserk, mature, and then fall apart on guidance all the time. Long range GFS is a fan of doing that. Usually occlusion is the end result. Particularly late winter. But I don't remember the last time I've seen it happen in real life to our region. Usually it's a new England thing. Maybe I just need more experience tracking closed off systems taking a southern track and then pushing into a warm air mass. This really does feel like a "first week of April" kind of thing. Am I wrong that this whole progression is kinda unique for February? Late Jan 2011 keeps popping on the analogs, and someone made the point the other day that usually we just ignore perfect track rain storms but I don't remember this situation being a common one..