Anybody in the mood for more snow? A noon-time cold front passage quickly followed by a shortwave disturbance above it will kick off some sort of precipitation this afternoon. Whether that precipitation falls as snow or rain makes for a little meteorological puzzle.
Most precipitation, even in the warm parts of the year, begins as ice crystals in clouds agglomerate and start falling. If the air beneath the cloud is sufficiently warm, the falling snow melts and we get rain. The challenge to today's forecast is whether or not the air below the cloud is warm enough to melt the snow.
This morning's weather balloon launch shows that the lowest half-mile or so of the atmosphere is above freezing and we'll have a high in the upper 30s this afternoon. The Weather Channel thinks that is sufficiently warm that any precipitation will fall as rain. However, the snow is starting from a very cold place—the temperature drops to well below freezing just above the warm lower layer of the atmosphere.
The National Weather Service and AccuWeather are counting on the initial fall of those very cold snowflakes to melt and evaporate before they hit the ground. Doing so will quickly lower the temperature of the lower atmosphere, allowing the subsequent snowflakes to survive their downward journey. If they are right we'll see between a half-inch to an inch of new snow this afternoon.
Seasonable weather will stick around tomorrow when we will again see a high in the upper 30s. Westerly winds, and plenty of clouds, will make it feel somewhat cooler than that, especially in the morning. The wind will start coming out of the south later in the day on Saturday, and that's our first signal of high pressure pushing offshore and bringing warmer weather.
Sunday is going to be mild, with some sun and a high in the mid 40s. The high could hit 50 degrees on Monday with a slight chance of showers in the afternoon. Tuesday won't be quite as warm, with the high sticking to the upper 40s. Wednesday is looking warm and wet, as in upper 50s for a high and a chance of thunderstorms in the afternoon. A cold front and a trough of low pressure will return the temperatures closer to average by next Thursday.
