Detailed Forecast

6AM Tuesday- NowCasting Storm Update 4

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NowCasting Storm Update #4-

Radar will fill back in this morning as Nor Easter deepens, some dry slotting is occurring this morning, this was expected and forecasted.

Snowfall lingers through 9PM, heaviest and most persistent across NE parts of the region and east of the river.

Data continues to support our change to lower amounts across SW parts of the region where back edge a lower snowfall rates will impede accumulations. This potential was mentioned as early as Sunday evening.

Localized area of down-sloping highlighted 24 hours ago remains an issue for parts of Ulster and points SW.

Additional accumulations between 6am- 9pm, in areas not impacted by down-slope noted below, and back edge of precipitation. 6”-15”. Additional accumulations where precipitation ends prematurely on SW edge, or where downslope persists throughout the day may be as little as 1”-6”

Final snow-map remains in place with down slope concern area highlighted within a red circle.

A wild morning across the region, with all of the complexity we imagined coming to fruition. Incredible observations coming in with wildly varying snowfall totals over short distances. A localized downslope across Ulster into parts of Orange forecasted in our yesterday morning update, has been observed and continues to be present in data.

Snowfall rates of 1-3 inch per hour have occurred in portions of the region. Power outages where snow has fallen the heaviest are ongoing.

Data continues to project that the radar will once again fill in this morning with heavier bands of 1-2”+ per hour snowfall returning to the region as our Nor Easter continues to deepen to our east and is pulled west to a near stall by the energy phasing into it. The latest HRRR showing what the radar will look like at 5PM. Heavy snow region wide with the exception of a localized area of down-sloping, as NE winds sink off the Catskills to the north. Notice the sliver of rain surround by snow? Just how localized is the downslope? We have a township that has nothing but rain on its west end, and 2-4” on its eastern end.

Through 9PM a band is still sitting over the Hudson Valley. The next two images are the NAM and HRRR projected snowfall, you can see two features, the back edge we mentioned as a concern yesterday morning and the localized downslope impacts.

Monday 8PM NowCasting Update 3

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NOWCAST UPDATE #3: Mon-Wed Nor’Easter
CHANGES TO SOME DETAILS

Summary:

Timing:
Rain Changes to Snow: 10pm to 2am Tuesday
Stop : 4pm Tuesday to 12am Wednesday

Consistency- temps near freezing = heavy, wet snow
Wind gusts 25mph to 40mph Tuesday PM

Heavy Snow rates, 1 to 2” per hour in some areas
DRASTIC changes in snow accumulation over short distances
Downsloping event likely for parts of the region (Central Ulster)

Accumulation
– Eastern Catskills: 20 to 30 inches +
– Catskills & Upper Hudson Valley: 8 to 16 inches +
– Mid & Lower Hudson Valley: 6 to 12 inches
Central/Lower Ulster County: 2 to 7 inches
– Extreme Lower Hudson Valley: 2 to 7 inches

DISCUSSION
We waited until the last second to issue this adjusted snowfall map. The reason being that the data with this storm continues to change, even at this moment. We like to issue a snow map, and only change it when necessary. The last thing we want to do is change a snowfall forecast, and then have to back track.

WHAT CHANGED??
The low pressure system is now very likely to take a track MUCH further east. This will have several effects on what we see in the Hudson Valley.

1. The eastern track is all but surely going to pull the heaviest snow that we highlighted on Sunday… east of where we expected. Instead of the Catskills and western Hudson Valley getting the heaviest snow, it now appears that the eastern Hudson Valley, as well as Connecticut and Massachusetts will see the heaviest snow overnight tonight into Tuesday morning. East of the Hudson River, snowfall rates 1 to 2 inches per hour are possible.

2. The Low pressure is expected to loop into Massachusetts from the Atlantic Ocean. This could have severe impacts on snowfall for the Mid Hudson Valley, especially parts of Ulster County. The winds would shift out of the NNE, and this would result in significant downsloping from the Kingston area, down toward New Paltz & Wallkill (the exception being the Shawangunk Mountains). If this setup unfolds, those areas may mix with rain on and off through the storm. And snowfall accumulations could struggle to reach 6 inches there.

3. The bulk of the precipitation is further east than projected on Sunday. This means much less precipitation (snow) for the SW viewing area. Some guidance pulls the back edge of the snow into the mid Hudson Valley by morning on Tuesday. Eventually the snow band pivots over the Hudson Valley, but the question is how much snow is left over Orange and Sullivan counties when that happens. In the worst case scenario, locations closest to the NY/PA and NY/NJ borders could taper off completely for a time early on Tuesday.

This storm continues to throw surprises our way, and is very likely to have more “booms” and “busts” heading our way. Stay safe, as more updates are coming through the night and day on Tuesday.

-Bill

Nowcasting Storm Update 2

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11AM NowCasting Storm Update #2
Trends Towards Forecast- Poor ( See below areas of concern)
**Few things to discuss with the morning data that we feel is throwing some red flags
 

*** Concerns ***

Latest NAM/HRRR Models
 
1- Red Circle-
Images:  NAM and HRRR models:
Have had a concern since last night on the proximity of the back edge of the precipitation lingering so close to the region. You can see both models imageskeep this edge close, although the HRRR provides more of a buffer. This is concerning because it leave no room for error in terms of the final track of the storm. Further NE and this back edge is into the region.
 
2-Yellow Circle and Arrow
Images Yellow Arrow from images above, results in snow maps shown below:
As the models trend the storm a bit further NE it is also shifting the best atmospheric lift to the NE. This is a critical component of the forecast as the lift is needed to produce higher snowfall rates and in return cool the lower levels of the atmosphere. By tomorrow the Nor Easter will be taking control of our weather, NE winds will increase around that area of low pressure as noted by the curved arrows.
Directly to our NE is the higher elevations of the Berkshires, looking back at recent history, this is a bad combination for snow production. A few years back a storm was forecasted to impact the entire region, while surrounding areas were impacted heavily, parts of Orange and Ulster were never quite able to switch over to snow. The reason for this was a combination of storm NE winds, and mild surface temps. This combination caused a downslope off the Berkshires to translate SW into these counties.
Part of being a forecaster is learning form those burns and getting ahead of them in the future when the data begins to throw small flags. Notice the decreased snowfall amounts within the zones we described? Notice the simulated radar from both models indicating a small SW to NE sector of rain instead of snow?
 
With that said, we pride ourselves on accuracy and in forecasting this goes two ways, first to be right but also first to call out concerns with the forecast, not only our but many forecasts in place for the region. We have concerns with the circled area failing to achieve forecasted amounts, we will monitor afternoon data and update this afternoon. The models can flip back and forth from run to run, but this very well not be a blip, but instead a trend. There’s a lot of volatility with the evolution of this storm, this tends to cause an equal amount of havoc in the data.
Last and final image is to communicate that if you live along that red line, the snow will flip back and forth between rain and snow as cold air battles daytime heating and warmth surging north. The previous post times the expected collapse of the rain/snow line throughout the day into the overnight and tomorrow AM.

NowCasting Storm Update 1

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NowCasting Storm Update #1

Remember this storm is a marathon not a sprint, the evolution of this storm will be of a long duration, scattered precipitation as early as 5am and precipitation not ending until 9pm tomorrow.

Let’s talk timing the change over, this is an important thing to monitor throughout the day as a pulse check on the health of the current forecast. If the changeover to snow is faster, more snow. If the change over is slower, less snow.

So what do the models think?

NAM- Higher terrain west of river start and remain snow for the duration. For lower elevations, everyone north of 84 will be snow by 10pm tonight, with the line slowly collapsing south with Rockland and Westchester remaining rain until 6-7AM from North to South. All areas remain snow through 9PM tomorow.

HRRR- Higer terrain west of the river start and remain snow for the durations. For lower elevations, everyone north of i84 remains rain till 4AM with the areas closest to river being the last to transition to wet snow.
The snow line then slowly fights its way south the Westchester and Rockland transitioning by 6-7AM from north to South. All areas snow through 9pm tomorrow.

So what do our two best pieces of guidance agree on?

That the region sees precipitation through 9pm tomorrow.
That Westchester and Rockland will be last to change to snow.
The both produce similar snowfall maps

That our current forecast is sound

The higher terrain west of the river may see amounts reaching 30”

What do they disagree on?

The timing of the change over in the lower elevations north of i84 this evening.

The Images- For the sake of remaining grounded and leaning into the trends this winter, we have attached the HRRR timeline of events. These frames are as follows, 8PM,10PM,12AM,2AM,4AM and 6AM, these projected radar images give the timing of the warmer HRRR change over to snow.

Thoughts- Our forecast remains unchanged and has been barely changed since the issuance of our first map almost 48 hours ago. The GFS and Euro have been inching this storm impact NE over the last several runs. The back edge of the storm will be always flirting with the SW parts of our region, if that’s accurate it would degrade the forecast, we will be watching.

 

 

Storm Update #2: Monday – Wednesday Nor’easter

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Summary:

Timing:
– Light snow (mixed with rain) 6am to 6pm Monday
– Snow Intensifies : 6pm to 10pm Monday
– Stop : 6pm Tuesday to 6am Wednesday
Hazards:
… temps near freezing = heavy, wet snow
… Wind gusts 25mph to 40mph
** Low Confidence on Details due to storm track
** Heavy Snow rates, over 2” per hour
** Blowing & drifting snow = low visibilities
** Long duration event 36+ hours
Accumulation (subject to additional changes)
– Eastern Catskills: 20 to 27 inches +
– Catskills & West of Hudson River: 8 to 16 inches +
– East of Hudson River: 6 to 12 inches
– Extreme Lower Hudson Valley: 2 to 7 inches
…Synopsis…
An area of low pressure will emerge off the NC coast tomorrow AM and progress Northeastward. As the storm tracks NE an Upper Level Low (ULL) will be tracking in from the west, these two pieces will phase off the coast and undergo a rapid deepening or bombogenesis off the coast of New England dropping from 1003MB down into the 970’s by Tuesday. This storm will have copious amounts of moisture associated with it, and thanks to the capture of the energy by the ULL it will be slow to depart and may even loop off the coast of Cape Cod. The combination of Atlantic moisture, gusty winds, and it’s slow departure, will be the recipe for a long duration event with potentially severe impacts on parts of the region.
Light snow and rain showers are expected to develop during the day on Monday as early as daybreak. Due to the airmass being marginal, and this being a mid March storm, valley temperatures may be in the mid to upper 30s Monday, causing the storm to begin as rain. The exception will be for locations west of the river and at higher elevations where precipitation may fall as snow throughout the day Monday. Accumulations of 1-3” are possible in these locations by sundown.
As the coastal storm begins to deepen and phase with the ULL, surface temperatures will fall into the low 30s, and any rain will transition to snow after dark on Monday. Snow/rain line will slowly collapse southward through the valley, with the southern most parts of our region holding onto rain the longest. This holding power of this warmth is a key element to the forecast, with some data suggestion rain continues till daybreak Tuesday in the southern most valley locations.
Snow will intensify overnight with snowfall rates of 1-3” per hour by daybreak, this will overcome any surface temp issues with snow rapidly accumulating on all surfaces. Localized banding will develop, while its exact location cannot be predetermined, where these bands do occur amounts will exceed upper ends of forecasted amounts. The behavior of these bands are a second major component to the forecast. Banding will move into the region and eventually it’s northward progress will halt, and it will stall and begin to pivot. Locations beneath these stalled/pivoting mesoscale bands will experience intense snowfall rates. Snowfall rates of up to 3” per hour with embedded thunder are possible. Where these bands occur they will bust the upper end of the forecasted totals for that area. Since their position is impossible to forecast, we can only include this in our discussion and not reflected in the snow map.
The combination of winds gusting 20-40 MPH with extremely high snowfall rates will lead to treacherous to impossible travel in the hardest impacted parts of the region. The combination of this being a long duration event with snow possibly not tapering off until early Wednesday, and this being a heavy wet snowfall, combined with gusty winds, will lead to significant to severe impacts to travel a commerce
…Boom or Bust…
A key component to the evolution of this storm system and the verification of this forecast is tied to the phasing of the energies. The timing of this phase is critical. Data today has flirted with allowing the surface low to escape fairly far NE before capturing it and pulling it NW. the problem with a late phase is we do not get the upper level dynamics associated with the deepening low pressure. It’s these dynamics that help cool down the atmosphere with its Cold Air Conveyor Belt, this gets our valley locations colder faster and abates the northward progress of a warm nose of air up the valley. In addition this lift and upper air dynamics increases precipitation rates faster and assists in the expediting the dynamic cooling process. A late capture means areas east of the river may be longer delayed in their transition to snow, therefore proving limitations to achieving the upper end of the forecasted amounts. This coupled with the ever present downslope effect from strong easterly winds off the Taconic and Berkshires is a recipe for underachieving forecasts and underproducing snowfall.
If the capture is swift, and the atmospheric ballet is flawlessly executed, in its timing, a surface low will develop closer to the coast, and rapidly deepen. While slowing to a near stall near Cape Cod and potential make a full loop before becoming occluded and meandering its way NW, having exhausted its fuel and rich Atlantic fueling moisture payload. This would result in a widespread heavier snowfall, and would be how areas east of the river and south can break past its current forecasted amounts.
These factors, combined with the impossible to pinpoint location of banding, will result in widely varying snow totals. Within each zone your final totals will depends on these factors, and your geographic and topographic position within your forecasted areas. For lower elevations, southern zones, and areas close to the river valley floor, and east of the river. Assume the lower end of these ranges, unless the scenarios described above come to fruition. If you are west of the river, your elevations will matter, as will what side of the local topography you live on. If you are on the leeward side of an eastern or southern facing slope you may see a bit less. If your are on the upslope side of an eastern or southern facing slope this will be an impressive snow event. Areas of the eastern Catskills Escarpment above 1500’ will see the lions share of high end snowfall from this system. Some of the highest peaks and summits may exceed 30” of snowfall.
We will have a lot of Nowcasting to do with this system, and there is a lot of things that can go wrong, as you certainly saw from the data we shared earlier, it’s a complicated science. We have data showing 24” while having other data showing 1” for the same locations. These are our tools, this what makes this a fascinating science and storms like this can turn kids into adults who start weather Facebook pages. So while we obsess over being right or close to it, sometimes you have to sit back and just take in the incredibly unpredictable force of nature.
-Alex

Sunday Morning

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Happy Sunday!

The clock in my car is finally right again!

A beautiful start across the region this morning with wall to wall blue skies. Highs today should respond nicely with temps bouncing into the low to mid 40’s for most. Enjoy that sunshine while you can, clouds begin to increase by this afternoon as we begin to see the first signals of our impending weather.

We have no changes to our forecast posted last night. We will likely spend the day pouring over the new data as it becomes available. With an issuance of a final snow map later this afternoon/evening.
Things yet to be resolved, how far north the warm air aloft will reach, exact track of the LP and where banding of heavy snow will set up and eventually pivot over the region. Good day to wrap up any storm preparations you may need to make.

-Alex

Storm Update #1 : Monday – Wednesday Nor’easter

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Summary:
– Timing
… Light snow (mixed with rain) 6am to 6pm Monday
… Snow Intensifies : 6pm to 10pm Monday
… Stop : 6pm Tuesday to 6am Wednesday
– Wind gusts 25mph to 40mph
– Low Confidence on Details due to storm track
– Heavy Snow rates, over 1″ per hour
– Blowing & drifting snow = low visibilities
– Heavy wet snow expected, temps 29° to 34°
– Long duration event
— Accumulation (subject to change):
– Eastern Catskills: 12 to 24 inches
– Upper & Mid Hudson Valley: 8 to 16 inches
– Western Catskills & Lower HV: 6 to 12 inches
– Extreme Lower Hudson Valley: 2 to 6 inches
STORM SYNOPSIS: An area of low pressure will emerge off the NC coast on Monday AM and progress Northeastward. As the storm tracks NE an Upper Level Low (ULL) will be tracking in from the west, these two pieces will phase off the coast and undergo a rapid deepening or bombogenesis off the coast of New England dropping from 1003MB down into the 970’s by Tuesday. This storm will have copious amounts of moisture associated with it, and thanks to the capture of the energy by the ULL it will be slow to depart and may even loop off Cape Cod. The combination of Atlantic moisture, gusty winds, and it’s slow departure, will be the recipe for a long duration event with potentially severe impacts on parts of the region.
Light snow and rain showers are expected to develop during the day on Monday. Due to the airmass being marginal, and this being a mid March storm, valley temperatures may be in the mid to upper 30s Monday, causing the storm to begin as rain. As the coastal storm begins to deepen and phase with the ULL, surface temperatures will fall into the low 30s, and any rain will transition to snow after dark on Monday. Snow will intensify overnight with snowfall rates of 1-3” per hour, this will overcome any surface temp issues with snow rapidly accumulating on all surfaces. Localized banding will develop, while its exact location cannot be predetermined, where these bands do occur amounts will exceed upper ends of forecasted amounts.
The combination of winds gusting 20-40 MPH with extremely high snowfall rates will lead to treacherous to impossible travel in the hardest impacted parts of the region. The combination of this being a long duration event with snow possibly not tapering off until early Wednesday, and this being a heavy wet snowfall, combined with gusty winds, will lead to significant to severe impacts to travel a commerce.
—- Wildcards —-
One of the key components to this storms evolution is the phasing of the two pieces of energy, the GFS model is a bit later on the phase. This results in the low pressure being captured later and deepening further east. By the time the system retrogrades back to the west it is beginning to occluded and it’s western precipitation is collapsing east. This results is heavier snowfall focused slightly NW with lesser impacts west and south. This could very well be a part of the SE bias of the GFS Model. The European model continues to project all of the components of a blockbuster HECS “Historic East Coast Storm”. The storm is captured, it makes a full loop over the cape and slowly departs NW, if the Euro model proves correct in its handling of the players on the field, then our prelim snow-map would be underdone, region wide.
Our current snow-map is reserved and blended with multiple model data and ensemble data, it is strong enough to highlight the need for preparation, but cautious with the knowledge that there are some things can alter the outcome of this storm. We will have very heavy coverage on this storm over the next few days, we will issue additional snow-maps as confidence continues to increase. As of now, north of i84 and away from the valley floor west of the river on the eastern facing slopes of the higher terrain, confidence is highest for 18”+. As stated above, if the dynamics all align, parts of the Catskills may exceed 24” of snowfall.
This is going to be a very complex situation as it develops, expect regular updates over the next 48 hours as we continue to hone in on what may be instore for the Hudson Valley Monday through Wednesday.
-Alex, Todd & Bill-

Saturday Morning Thoughts on Nor’easter Potential

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A snowy and slushy morning across the Hudson Valley, and we’ll have some analysis on the exiting storm this afternoon. But let’s talk about the Monday/Tuesday storm potential. These maps all showcase surface pressure forecast with this system. These images are generally all showing Tuesday around mid day.
The first two images are the “ensemble mean” position for the storm. An ensemble runs the scenario with minor variations, multiple times… (30 different times on the GFS, and 50 times on the European). The images shown represent the blend of all those scenarios. They’re useful because in a setup like this one, we’re seeing the operational runs of the models shift east and west every few hours. The ensembles give us a better idea of the average, which is helpful in picking up any trends in the overall data. It’s also helpful for seeing if the various ensemble scenarios are similar with each other, or if they’re spread far apart. In this time frame, with this type of system, the ensembles are an excellent tool for projecting where this storm will track. You can see the European ensemble mean (average) is a bit further east than the GFS. That’s largely because the European has a few outlier solutions that are well east of the mean.
The 3rd and 4th images are the “deterministic” or “operational” runs of the European and GFS models. These are the solutions from the individual run of the model. Notice the pressure is lower than the mean, that’s because the individual solution shows only 1 scenario of the storm, while the ensemble mean blends the pressures of the various solutions together. The deterministic runs are also further inland than the ensemble mean, an indicator that the well out to sea solutions are unlikely.
The last image shows the spread of the ensemble low pressures on the European (50 different low positions). You can see how wide the distribution is. This represents that there is still considerable uncertainty with how this storm will track. This gives us low confidence on the exact impact here in the Hudson Valley, because depending on the track of the Low, the resulting impact in the Hudson Valley changes dramatically….
– Yellow Circle: If the low tracks in the Yellow circle, the heavy snow and wind would be east of the Hudson Valley. A strong nor’easter would batter the New England coast, with 12″+ likely from Maine to Rhode Island. The Hudson Valley would see a couple of inches of snow, possibly 6″ closer to the NY/CT border.
– Blue Circle: Hudson Valley would be in the battle zone. Worst conditions would be east of the Hudson River, where 12″ or more could fall. West of the Hudson would still see a formidable storm, with 6 to 12 inches possible. But the worst impacts likely would be just east of the NY/CT and NY/MA border.
– Red Circle: A Major Nor’easter for the Hudson Valley. Snow rates over 2″ per hour at times, blowing and drifting snow, extremely hazardous travel. Snow accumulation region wide could exceed 1 foot, with some areas possibly approaching 2 feet of snow.
Right now, the ensembles are on the edge of the Blue and Red circles. The deterministic runs of the GFS and European are both in the Red circle. So we are certainly tracking what could be a major nor’easter for the Hudson Valley. We’ll monitor the trends, and keep you updated on what becomes more likely. Buckle up for a wild ride over the next few days!
-Bill

Widely Varying Conditions This Morning

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This is why we put a boom or bust section in the forecast! There has been a bit of both with this storm, and the bust’s have occurred where we expected in our final forecast. Sorry for those hoping for snow in the bust zones, and your welcome for those who didn’t want it in the first place. We added back in the pictures, the parts of the final forecast mentioning this possibility in case you missed it.

Areas of rain/snow linger through about 9AM, especially south, models indicate some additional accumulations of up to an inch, but the models have struggled to realize the surface warmth, so we take this with a grain of salt.

Our concern for warmer air and lower snowfall amounts across the valley locations and Westchester and Rockland counties has in fact occurred (mentioned in final forecast). In some cases even warmer than we were worried about, with some of these locations never switching over to snow. Based on current observations anywhere from 0-7” of snow has fallen, in some cases that range exists within a few miles.

Snowfall amounts west of the river were heavier as we expected, and elevation has played a large role in who saw what. We have locations reporting six inches and right down the road and inch or two. Where snow as fallen it is extremely moisture laden, measuring will be tough, as  warm ground has continued to actively melt snowfall, in addition the heavy wet nature of the snow continues to compact it down. Its consistency has caused it to stick to almost every surface and made for a photogenic mornings in the snowier locations.

For those of you that have to shovel, be careful with the weight, take your time!

-Alex

Storm Watch : Potential Strong Nor’easter Mon 3/13 – Tue 3/14

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We are hours away from what should be a 3 to 6 inch snow for many of us… but our eyes are already looking beyond this storm, and closely monitoring the potential for a stronger snowstorm early next week.
A deep trough digs into the northeast on Monday, and a low pressure will rapidly intensify off shore. Thanks to strong blocking east of Canada, the storm will be a slow moving system. That will allow a rapidly intensifying nor’easter to impact parts of the Northeast for over 24 hours. Some of the impacts could include:
– Periods of heavy snow, at rates over 1″ per hour
– Gusty winds with blowing snow & low visibilities
– Very hazardous travel conditions Monday night & Tuesday
– Snow accumulations 6 to 12 inches or more
If you’ve been an HVW viewer for any period of time, you know we would not make this post without good cause. We are a little over 3 days away from this storm system, and have strong agreement with computer model data on a nor’easter Monday into Tuesday. There are differences in the details, but that is to be expected at this point. We have above average confidence that a nor’easter will develop, the key to determining the impact in our area, will be the exact track of the low pressure. If this storm shifts a bit further east, it could pull the area of heaviest snow to our east. But as of this discussion, the Hudson Valley appears likely to see significant impact from this storm system.
 
We will be tracking this very closely, and providing updates regularly going forward. But first… let’s get through THIS snow event.
-Bill