Rain changes to steady snow by daybreak Tuesday

Heavy snowfall makes for potentially hazardous morning commute…

TONIGHT: Rain Develops. Rain Changes to Snow near 4am.

TUESDAY MORNING: Transitioning to Snow after 4 AM, Heavy at Times, Accumulating between 5 AM and 8 AM. Snow Tapers by 10 AM.

TUESDAY AFTERNOON: Clearing, Cold. Hi 43.

There’s a lot to unpack with this upcoming snow event Tuesday morning, which will be the focus of this article. The models have shifted over the course of the past 24 hours so that at present, the bulk of snow accumulation will now occur over much of central and eastern PA. What that means is that things get just a little snowier for the Midstate, although the question of “how much will stick?” is still in play. Let’s break it down.

We kick off after sunset Monday night, with the arrival of rain showers, transitioning to steady rain by 11pm. Expect rainfall to continue through midnight. Between 2-4am is around the time when the very northern tier of our viewing area will start to see the changeover from rain to snow. This transition will occur from north to south and will continue until 5am, when the majority of southern central PA will be seeing snowfall at that point. Heaviest snowfall rates will occur between 5am and 8am so the morning commute will likely prove hazardous, with reduced visibility. Snowfall should come to an end by 10am.

The primary issue we will be running into when it comes to accumulation is air temperature. Most of the developing snow will fall at temperatures just below or at the freezing point, while much of the air close to the surface will be at or just above that freezing mark. The relative warmness of this air means that snow-to-liquid ratios (SNL) will be about 6:1, meaning big, wet, fluffy flakes. A lot of this snow at least initially will melt upon reaching the surface, hindered by the mild, rain-moistened surface. It will be during the time of heaviest snow fall, that 5am to 8am time frame, that we see sticking occur as the flakes reaching the ground do not have enough time to melt. This problem extends across the Midstate, barring some locations in the mountains, which are likely to see higher totals.

With all that said, the expectation is for between 1 and 4 inches of snow accumulating across the Midstate, with locally higher amounts in the mountains. Temperatures warming into the low 40s Tuesday afternoon will begin to melt much of what gets accumulated that same morning. Lows at or near freezing will help retain what snow is left.

The next chance for rain and snow showers will not be as substantial as tonights. We do expect a mix of rain and snow showers late Thursday into early Friday morning from a clipper system. Then the guidance keeps things mainly quiet through next weekend with temperatures in the mid-40s.

-Meteorologist Eric Finkenbinder & Jackson Chastain