Stormy Sunday update

Update #585d

Hello again, I’m back with an update on the Sunday situation. Be aware and tread carefully: it could go boom, it could go bust!

It’s a storm whose impact will be highly variable across the region, with the worst weather largely tied to elevation. For much of the region, especially near and north of I-84, accumulating wet and heavy snow is possible for a time from Sunday morning until the early afternoon. Key word: possible.

Because of the complexities of this storm, it’s challenging to convey the impact in a concise manner.

I’ll try to simply things using an analogy: much like the moon, this storm will have phases.

Phase 1 — the beginning (new moon 🌑)

• Precipitation will begin between 3:00 - 6:00 am Sunday in the form of rain for most of the region

• The rain will ‘dynamically cool’ the atmosphere, seeing temperatures become cold enough for snow around about 6:00 am on Sunday

• A process called frontogenesis, which will cause heavier precipitation rates, may cause heavy, wet snow from Sunday morning until the early afternoon

• A wet, pasty 1-3 inches may occur across the Hudson Valley during this time with higher amounts for the Catskills — road conditions could go downhill on Sunday morning, particularly in hilly, elevated parts

• The whole thing is on an absolute knife edge: for much of the Hudson Valley, about a single degree will be the difference between rain and snow, which is well within a margin of error

• In a boom scenario, 3-6 inches could conceivably fall in parts of the valley, with a bust scenario only producing up to an inch

Phase 2 — the middle (crescent 🌙)

• By Sunday afternoon, precipitation rates will begin to ease as the frontogenesis pushes to the north

• This will likely see snow mix with or change to rain and sleet for much of the region outside of the Catskills

• During this phase, it’s possible that sporadic bursts of heavier precipitation cause rain and/or sleet to change back to snow

• Road conditions should gradually improve, but caution is still advised

Phase 3 — the end (full moon 🌝)

• Late Sunday afternoon and evening, the air about a mile above the ground will gradually becoming cold enough to support snow

• The rain/sleet/snow mix will probably flip back to all snow, again favoring areas near and north of I-84

• However, by this point, the storm will be pulling away, with precipitation rates gradually waning through the evening

• The storm’s broad precipitation shield will likely result in light, largely non-accumulating wet snow and flurries up until Monday morning

• With temperatures generally remaining above freezing in valley locations on Sunday night, the impact of this phase looks minimal, but the same can’t be said for elevated parts of Sullivan, Ulster, and Dutchess County

• At this time, the aforementioned counties would have the highest delay chances on Monday

At the end of the day, the region should be wary of a storm whose impact will not be uniform in time nor space across the region, with accumulating wet and possibly heavy snow for a time from Sunday morning into the early afternoon, lasting longest in the Catskills. The difference between rain and snow is indescribably small and I’m grateful that this one is not happening on a school day!

The map below shows a rough estimation of storm total snowfall, noting again how elevated areas are favored to receive the most.

In the broadest of senses, 1-3 inches of wet, pasty snow may fall in the Hudson Valley with 3-6+ inches in the Catskills. However, a boom scenario could produce 3-6 inches in parts of the valley, with a bust resulting in an inch or less.

Get ready for Mother Nature’s grab bag! 🎁

Next update: Sunday morning.