Rain and Ice Thursday into Friday AM, here’s what’s to expect.
When Spring and Winter begin their sibling rivalry, your can always bet on icing.. 
Once again we are monitoring the potential for icing across parts of the region, and as it always goes with these set up’s- +/- a degree or two, or in this case also a few hundred feet of elevation gain can drastically change the outcome.
Precipitation arrives tomorrow around 6AM, (don’t worry parents) it arrives in the form of rain, spreading SW to NW between 6-10AM. It remains rain through the afternoon, the only exception may be across some of the highest peaks and ridges of the Catskills (above 2700’) where hikers may find freezing rain from the onset and through the duration of the event.
As the afternoon progress into the evening, colder air at the mid levels will begin to cool from colder air damming in from the north. As this layer of cold air in the mid to low levels begins to deepen, the freezing line will begin to slowly decrease in elevation. This will begin to be realized after 6pm, as the freezing rain and sleet line begins to drop into the lower elevations and hillier terrain east and west of the river valley.
Futurecast 6pm Thursday
Futurecast 11pm Thursday
Above are the NAM precip type at 6pm and again at 11pm, you can see how the area of freezing rain (pink), really expands in coverage. You will also noticed that the lowest elevations of the Hudson river valley remain rain, as warmer air isn’t as easily evicted from these locations. For areas away from the river floor, such as the Catskills, Hudson Highlands, and higher terrain of eastern Dutchess and Columbia Counties- icing remains possible beyond 7pm.
The HRRR model is less impressed with this event and has a much warmer outcome, with that said we have seen multiple setups this year that have been over modeled on warmth. So we will lean into the colder solution once again. For now the NWS has split the data and placed WWA’s for only the higher terrain of western Greene and Ulster, which is fair at this point, but the chance for icing exists beyond these locations overnight tomorrow.
Total Rainfall Projected
Another point worth mentioning is that it will rain and a pretty decent amount- arguably one of our heavier rainfalls in months. Anywhere from .50”-.80” of rain will fall before 7pm with total rainfall nearing 1-1.5” in spot. Thursday night rainfall may be heavy at times especially south of I84 between 11pm and 3am. With lots of areas still dealing with snow cover, large snow piles and banks, blocked storm drains and potholes the size of Vespa’s- be prepared for ponding in roadways and localized street flooding, also realize that those may be small craters posing as normal puddles on Friday morning.
We will monitor the overnight data and early morning data for colder trends, and update as needed, but this should cover the higher end potential should the storm land on the colder end. If warmth wins- this is more of a widespread rain event. It should also be noted that freezing rain accretion maps shouldn’t be taken verbatim with this type of set up. Warm temps today, mild temps overnight, followed by hours of plain rain isn’t the best environment for ice accretion at onset. Freezing rain that does fall will struggle to ice up initially, bridges, overpasses and elevated surfaces would be first and may take 1-3 hours, so there’s a lot to factor.
We will have more- but that’s about as nerdy as we can get at the moment. Be prepared from 7pm to 8am Thur/Fri for icing potential, especially east and west of the valley floor. Keep a close eye on the morning and afternoon updates on how this are trending. Have a nice night!
-Alex