A Wind-Driven Soaker Tonight!

PROVIDENCE, R.I. (WLNE) — Ready the rain gear for moderate to heavy rain with a gusty wind developing after this evening’s commute.  Temperatures rise overnight with a strong southerly wind gusting 30 to 40 mph in the pre-dawn hours of Friday.  No surge of arctic air expected in the next 7 to 10 days, however, a colder pattern with the chance for snow may be in the offing for the last full week of January.

Highest wind speeds will occur between midnight and 8 am.

Here is the area of low pressure that is tracking through New York state tonight and into the Quebec Province of Canada Friday. We’ll stay on the mild and wet side, although northern New England will receive 2 to 6 inches of snow before mixing and changing to rain there. Good news for skiers and snowboarders with some fresh snow for the weekend!

Rain will end by mid-morning Friday.

It’s a soaker! We’ll accumulate near an inch for much of southern New England overnight Thursday.

 

This Afternoon: Damp with scattered light rain showers or drizzle.  High near 44. Becoming breezy by evening. SE wind increasing to  10-15 mph.

Tonight: Steady rain, moderate to heavy at times. Windy. SE gusts 20 to 35 mph. Nearly an inch of rain expected overnight.

Friday: Morning Rain ending after 9 am.  Near 54 early. Dropping temperatures into the 40s during the afternoon. Windy. S shifting to WSW 15-25 mph.

Saturday:  Sun and clouds.  Lows near 30,  Highs upper 30s. NW wind 10-15 mph. Feels like upper 20s.

Sunday: Sunny with a lighter wind. High near 38.

Martin Luther King Jr. Day: Sunshine, 42.

 

Hydro what? Meteorologists study hydrometeors, hence, where the name comes from. Hydrometeor (a water meteor) is just a scientific way of saying precipitation. Most precipitation begins as snow/ice crystals in clouds. As this snow falls, it encounters a variety of temperatures. It can fall through a warm layer, then cold, then warm again and vice-versa. Meteorologists look at the three-dimensional atmosphere using data from weather balloons and computer models that use physics to create a future result, or a forecast. It’s ultimately up to the scientist to determine what will happen. Will it rain? Will snow survive the fall from the cloud? Will the snowflakes melt, then refreeze? If it refreezes in the air before reaching the ground sleet pellets are created and if it rains and surfaces are very cold, below 32 degrees, that rain can freeze on contact and that’s the most dangerous condition; freezing rain. Icing is extremely dangerous and can accumulate on trees and power lines creating power outages. There is a chance for this type of precipitation today and especially tonight in Worcester county.

The forecaster needs to determine what type of precipitation will fall. With the information age, there is a multitude of data sets, computer generated forecasts, and weather data analysis at our fingertips. Looking for the temperatures at several layers of the atmosphere, and something we call ‘thickness’ of the air helps us determine if snow will fall. One key temperature is the 0 C temp at 850 millibars which is around 3000 ft above the ground. Generally a snowflake can survive a drop of 2000 ft into air above 32 F. How much snow will actually be measured? There’s a lot that is considered. Ground/soil temperatures, amount of insolation (sunlight) prior to a snow event, solar angle at the time of the snow, pre-existing snowcover, dry air intrusions in a storm, warm layers above that may change the snow from fluffy to sticky and of course how much actual precipitation will fall from the cloud.

Typically, a 1 to 10 ratio of liquid (rain) to snow is average, but the ‘fluff factor’ can create a 1 to 30 or even 40 ratio. This happens in the arctic where the air is very cold. The snow crystals (dendrites) that form stand on end with each other and there is a lot of air in between them when they land.

For more on snow science, visit this National Weather Service page!

https://www.weather.gov/apx/snowflakescience

So, an inch of liquid could give you 3 feet of snow! This isn’t typical, however. Generally an inch will yield about a foot of snow. In spring and fall, mild layers of air or mild air near the ground can give you as little as 5 inches of snow per 1 inch of liquid. This is also not typical. Another factor is whether the snow will melt as it hits the ground and for how long during the storm. When will it ‘stick’? That’s when it begins to accumulate. Ground temperatures are very important in determining this.

Bottom line, there are a lot of factors to determining what type of hydrometeor will fall and then how much of it will accumulate and it’s NOT easy!

Categories: National and World News