Archival of Blogger and Move To Substack

Hello everyone, I'm making this post as a formal gesture that I have fully moved to Substack and will not be using this website anymore. It will still be up for archival purposes and for reference, but it will no longer be updated. The reason for this move is that I found it much easier to work with Substack in terms of the text editor, but mainly with formatting images. Posting images on Blogger is usually of much lower quality due to overcompression, and it can sometimes be a pain to adjust everything. I don't have to deal with that on Substack, and it generally looks nicer and is easier to use. That being said, I might update my snowfall tracker with data from 2023-2025 if I have some spare time. Most of my work will be through the avenues of my personal substack and MoCoClosures, an organization dedicated to predicting weather impact on school operations, but we do more than that. I will be posting my work on a seasonal forecast (along with a few other forecasters) through MoCoClosures. Thank you for reading my posts over these several years, and I hope to see you over on MoCoClosures and my personal substack. 

My Substack: https://darkshark.substack.com/

My Twitter: https://twitter.com/shark_wx

MoCoClosures Substack: https://mococlosures.substack.com/

MoCoClosures Instagram: https://www.instagram.com/mococlosures/

Pattern Change for Northern Hemisphere Early-Mid December

There is high confidence in a significant pattern change happening for North America, bringing a much colder airmass to the central and eastern US. In this thread, I will explain the specifics of why.

Firstly, the storm on the 28th will bring in the Arctic airmass after it moves out, which will be coming from Siberia due to the -WPO/-EPO. This is accompanied by ridging in western NA building due to an equatorial jet extension.

Next, let's focus more on Asia. An +EAMT event is predicted, which indicates a jet extension, and we can see this from the AAM spiking. This jet will also be more equatorial rather than poleward, so as a result of this, the jet will speed up into the north-central Pacific, with lower heights expected downstream from Japan to north of HI. 

Due to the equatorial shift -> extension, not only is downstream ridging built over western North America, but blocking is set up north of the jet across the far north NPAC, forcing strong blocking over the high latitudes; Siberia/Asia to Alaska/N America(-WPO/-EPO), which forces an arctic airmass into the mid-latitudes of North America. Furthermore, because of the western ridge, it specifically goes into the central-eastern US.

Looking at the MJO, the MJO is very weak and slow-moving over the MC, showing that teleconnections are overriding the MJO. The jet is in the right place; with the +AAM being strong enough to extend the jet to a favorable position but not strong enough to overextend the jet. This, along with the slow-moving and weak MJO is good for maintaining this pattern in general, though I'd expect a small reset at some point as we reload again(mid December?).

This pattern is also going to cool the warm pool off of Japan and warm the GOA and West Coast, so we should expect to see the PDO rise. It will not flip this winter but we should see some significant rises given how sustained this pattern looks to be.

As for the NATL, although we have an -NAO, I don't expect anything sustained in response to the wave reflection in the NPAC(-EPO); it will probably be replaced by a Hudson Bay vortex. In my opinion, while we probably will have -NAO at times in this pattern, it will be happening because of wavebreaking/intensifying 50/50 lows - so more shortlived. Generally, I'd favor a neutral NAO for the upcoming time period, but I'd assume after the next reload that we start seeing more HB vortex. 

After the Arctic airmass moves in, the eastern US will have significantly well below normal temperatures. A tall western ridge will create split flow, with the NS going through the northern portion of the ridge and the southern stream undercutting the ridge. However, the first part the pattern will be cold and dry as the baroclinic zone gets suppressed well to the south and there isn't any room for NS waves to amplify or southern stream disturbances to bring moisture up. This holds from the very start to ~Dec 5-7, but this will set a very favorable and cold antecedent airmass in place for when the trough lets up a bit and there's more legroom for waves to properly amplify, with a taller/stronger +PNA that looks to connect more with the WPO/EPO ridge, providing a more amped pattern. I'd say Dec 5 to the start of mid-Dec is the most viable time period for snow in the mid-Atlantic/Northeast.

The Alaskan ridge will retrograde westward into Siberia eventually, which will retract the jet(reload), but with the continuing +AAM, I doubt we switch to a canonical Nina pattern rather than just a small reset. Thus, the Aleutian trough will back away eventually as it loses momentum from this week's +EAMT/jet extension, but I'd assume we get the AK ridge to move poleward again with another small jet extension that brings cold air eastward again. MJO will enter WPAC which will regenerate westerly momentum again.

Overall, a cold pattern will take place for the central-eastern US, and will have legs for most of December due to the favorable atmospheric conditions in place.

2/17 Overnight Moderate Event for DC/Balt Metros

A low-pressure system tracking in southern VA will bring our region snow again. It will move out fast, but will bring good dynamics with it, and intensify as it slides across, bringing heavy rates. Winter storm warnings are up for those in the I81 corridor and N of I66 for 4-6" of snow, with more in the mountains.

A strong 170-200kt UL jet will lead to divergence(therefore, rising air) on the left exit of the jet(over us). This, along with strong frontogenesis/WAA will support lift, which looks to stretch throughout the DGZ, leading to optimal snow growth and support for heavy banding. The intensifying low pressure will also deepen the lift in the DGZ even more, strongly supporting the idea of 1-3"/hr rates and higher accumulations; despite short duration. 

A sounding in N MoCo indicates a favorable environment for snow growth barring the above-freezing surface temps. N of 66 and NW of 95 temps should be 30-32 during the peak precip, and we should dynamically cool to around 32 when the precip sets in.

Additionally, the 850 MB low(image 2) is in a favorable position for those just north of its track, and the SLP is in an ideal location. We will see strong WAA(image 1) and healthy PVA(image 3). Large dynamic cooling is expected given the rates of the precip and the profile being dry enough right now(image 4). 

Thus, 1-3"/hr rates are expected with this system. The duration will be around 3-6 hours, but the impressive dynamics and rates will make up for the short period of time, in my opinion. The overall setup is just supportive of heavy snowfall rates, and ratios aren't horrible either(should be around 10:1, slightly higher in peak banding). Overnight timing also really helps here with any melting/sun angle concerns, so long as we are around or below freezing it will have no problem sticking.

Thus, this is why I went aggressive with my snowfall and forecasted widespread 4-6" N of 66, with mountains getting 6-8" because of orographic lift leading to heavier rates in banding(as well as being colder). Thundersnow is possible too due to the strong forcing and instability in the column. Heavy snow is almost a lock, but this event will almost fully wrap up by 7-8 am. Although the warm is ground initially, initial precip should help saturate the column and enforce dynamic cooling for the heavier rates. It will stick to roads due to the overnight timing and rates. Precip type should generally be all snow N of 66(maybe you might see a bit of rain mix in at the start but should transition quickly), S of there you should start as rain first but transition to snow. Overall, a solid snowstorm is upcoming for N and W of DC! 

2/13 Rain to Snow Event for Morning Commute

This will be a quicker post since I only have a little time today. But we went from a generally all-rain storm to potentially quick heavy snow in less than 24 hours. The South trends on modeling with this short of a lead time are quite remarkable, and I'm not sure if I've seen anything like this, at least recently.

 A dynamic system will be approaching from the TN valley, bringing precipitation to the mid-Atlantic and Northeast, a lot of which will be snow. Winter weather advisories are up for those NW of 95 and N of I66. 

We will start as rain, but likely switch over to snow and see accumulations in these areas. For us, we get cold enough to snow from dynamic cooling; this system will be very dynamic. It depends on rates, and the boom/bust scenarios are equally likely. The bust scenario would be that we do not get heavy rates and little to no accumulation; the boom is that we get heavy rates for a few hours. Despite marginal temps(33-34), heavy snow rates will accumulate, even on sidewalks/roads if heavy enough. This storm will be more of a latitude and elevation-based storm rather than longitude. That's why central/northern MD is more favored in this setup. Even with heavy rates, your ratios will be low and it will be a wet snow.

Precip will likely onset between 5-8 AM, with central MD expected to be all snow by 7-8 AM. Guidance is indicating heavy precip rates, which timed with the morning commute will make it hazardous. It's not more so about the actual amounts, but the heavy rates expected and the timing are perfect to impact the commute. This storm has trended so far south that Maryland gets in on the main snow shield; and not just the backend. Our storm's preformance will depend on these rates. 

There is the potential for 1-3 hours of 1-2"+ rates during the morning commute. With these rates, it will accumulate, even on side roads and paved surfaces. Heavy rates always beat marginal temperatures or any other factor. The previous rain will also make pretreatment impossible. The heaviest rates will likely be just after the switchover(when dynamics are the most favorable), with thundersnow possibilities being hinted by guidance. We won't know what this storm will do until we get there; it is fully dependent on the level and location of banding.

Snow Map + School Predictions:

HREF forecast for the next 24 hours; 2-4" NW of 95 and N of 66 with 4-6" for 70 and north

This is my snow forecast for the event; I think there should generally be at least a solid inch for N of 66; further south should stay under an inch. 3-6" for elevated areas near the MD line and of course, the mountains look like a good call. especially with the recent trends. I would not be surprised at all of the warnings were issued last minute for those regions. The plus in the 1-3 zone is mainly for higher elevated areas. This is a very difficult forecast, with an equal chance for a boom and bust. 1-3" is just in the middle zone and I feel like it will either be a bust/boom. Either way, the morning commute is looking awful, and there will be impacts. As for school impacts...

Prediction: 3 Snowflakes
I'd expect many school impacts, with widespread delays and even closures, especially for counties in the 3-6" zone. The timing of this is perfect to at the very least delay. There is also a 50/50 chance for a closure depending on how long the rates last, and how intense they get. If the rates last for long enough, schools will be forced to close, and there will be enough accumulation on the roads. With the current forecast in place. and the rates guidance is showing,  there is really no way schools can open on time tomorrow.

Overall, a nice sneaky event. I think this is going to surprise a lot of people; enjoy the snow!

1/19 Light-Moderate Snow Event

Synoptic Setup 

A vigorous shortwave/trough will move through the area around tomorrow at midday, providing strong lift to generate snow and sufficient dynamics from the strong upper jet, in addition to PVA and modest WAA. These dynamics will allow heavy precip to be brought about just ahead of the shortwave and a more expansive precip shield, which guidance has been trending to. Guidance, in addition to the more expansive precip shield, has brought the vort-max further south, allowing for higher amounts of QPF. The heaviest snow/concentration of precip will just be north of the vort-max; putting us in a more favorable position. 

This is ahead of a great antecedent airmass, with already existing snow cover contributing to it even more. However, the absence of deep moisture, and generally low precip amounts, as well as the general storm being too progressive will inhibit this from becoming a major storm - despite the favorable H500 pattern. Nonetheless - a moderate storm for the area is looking likely, with ample cold. Ratios will be high due to a cold, saturated profile in the DGZ and the rest of the column, leading to modest dendrite growth. Surface temps will also be in the upper 20s and lower 30s the entire event; below freezing the entire time. 

We should see a good thump of snow not too far from onset; making morning commute extremely hazardous. Shortwave forcing by that time is very good and would support locally heavy rates; despite low lift in the DGZ. This will likely be another high-ratio, generally low-rates event. Roads will become slick and snow-covered extremely quickly, with lingering snow expected to last through the evening rush hour. Thus, most schools/offices have closed in person. Snow will continue throughout the rest of the day, but will become lighter after the morning thump. 

Snow Map

This is my forecast:

I went extremely bullish due to the uptrends today and the overall setup. The most snow will be N of I70 in NE MD due to great dynamics and precip from the IVT(which won't have that much of an impact closer to DC). N of I-66 should generally see 2-4"+ (why I brought my 3-5"+ zone further south), with the south of it generally seeing 1-3". Although this is bullish -  please keep in mind that just cause a specific area is in the 3-5"+ zone doesn't mean they will be seeing the higher amounts of the range. Most areas S of 70 in that zone will likely stay under 5". The further north and east you are, the better for this setup(outside of the mountains). The exact location of the bands and the heaviest QPF/snow are uncertain, thus why I added the plus for any isolated spots above the range. The general consensus should be another nice high-ratio, low-rate snow event - on top of already existing snow, something that is quite rare in the mid-Atlantic. This storm will have a large impact on the morning commute and bring about hazardous travel.

Additionally, radar looks good right now, with virga saturating the column currently, as well as a decent precip shield in the OH Valley/Midwest. MPING reports confirm this is all reaching the ground over there. Earlier today, HRRR underdid the moisture in IA and didn't see the snow shield reaching Cincinnati (all related to our storm system). Current observations look good so far and aren't indicative of any major concerns.

Overall, the last-minute uptrend on the vort-max being further south and a more expansive, robust precip shield have led to totals becoming higher in the DMV.

Here are the current NWS warnings/advisories map, and precip onset:

1/6/2024 Small Wintry Mix Event

We have a small wintry mix event for NW of 95 that will result in some minor impacts, with impacts increasing the further north and west you go. A low pressure system will track northeastward off the gulf coast and into the Delmarva as it intensifies over SE VA. Precip will overspread the DMV in the morning, starting out as wintry precip for most. Areas along and E of 95 are expected to see very minimal accumulations and a quick transition to a cold rain. 

As the event progresses, strong WAA will warm the 850 mb temps to above freezing as a warm nose is pushed northwestward, while cold air is still at the surface. Unlike a few days ago, this opens the potential to overall wintry precip rather than just snow to rain. These 850mb temps will vary, with the coldest temps being in the mountains and W of the Blue Ridge. Here, the primary ptype will likely be snow. It is very likely that everyone E of the BR will warm enough to see a wintry mix of sleet, freezing rain, and rain(more wintry precip the more NW you go).

The confidence of this storm is generally very low even this close to the event, due to the extremely tight gradient setting up near the RS line; this is going to be a nowcast event. A 1-3 degree difference will make or break this setup. Due to the preceding temps and low wetbulb temps, wintry precip(where it does happen) should stick pretty easily. The best confidence for significant snow is W of I81, the Catoctins and westward, into the mountain counties. Although it seems surface temps were colder than modeled, the 850 mb temps according to IAD sounding look just as modeled, this doesn't really mean anything yet. Nonetheless, most of the region will see some wintry precip, with accumulations starting as soon as you head N and W from the cities.

Making a snow map for this event was difficult, but here are my general thoughts as of now:

Everyone E of 95 sees all rain, this is medium-high confidence. At the very most a couple of flakes may mix in at the border parts, but very little to no wintry precip is expected here. 95 and just NW is looking to see a T-1"(trace does not mean measurable snow). I think everyone here sees at least wintry precip falling, even with a quick transition to rain. This area also has low confidence, and will setup the start of the very large gradient. The more snow accumulation the more NW you go. Immediately NW of DC/Balt(outside the cities), there is some chance for some very minor ice/snow accumulation. This will be washed away quite quickly however.

The light blue zone(for areas closer to DC) I think will see enough snow/sleet to accumulate, as well as some ice accumulation. This area is extremely uncertain though, with the lowest confidence. The dark blue zone is the same idea as the light blue, but more snow/sleet and more ZR. Again, extremely low confidence in these areas; small temp differences can make or break this.

However, the light blue area near I81 is likely going to see large ice accumulations(potential of 0.1-0.25"+ here). This area is W enough to have enough cold air at the surface but WAA will quickly turn most precip here into freezing rain. The predominant ptype here looks like freezing rain, but some sleet/snow will likely fall.

The purple area is much more confident as this area likely stays snow long enough to see moderate accumulations(3-5"). Even here, there is a slight concern that mixing will cut down a bit, but any mixing shouldn't be too long. The predominant precipitation type here is snow. The red area is the bullseye and the mountainous areas. These areas have higher confidence.

Here are the current onset and warning maps, WSWs are up for just E of I81 and westward, as well as Frederick/Carroll Counties. WWAs are all the way down to the metros, primarily due to ice concerns. Generally, if you can avoid travel near I70/I81, do so, but closer to DC, travel shouldn't be too bad. We see an areawide E of I81 transition to mix and then rain by 10AM to 2 PM.