Snow Done, cold and Sea Smoke defined

Good morning Augusta.

This morning it is overcast with a chance of snow, then partly cloudy. High of 27F with a windchill as low as -2F. Breezy. Winds from the NNW at 10 to 20 mph. Chance of snow 20%.

Tonight it will be clear , then partly cloudy. Low of 12F. Winds less than 5 mph.

The readings from my own instruments are:

The humidity is 83% with a Dew Point of 10ºF and a wind chill of 11.2ºF.

The temperature Is 18.7ºF.

We have West Southwest winds between 5.8 MPH and 10.0 MPH.

Our Barometric pressure is 30.22 HPA 1013 and falling with a weather graphic indicating snow.   

We have a UV rating of 0 out of 16, sunset will be at 4:01 PM with Moon Rise at 5:33 p.m. EST and the moon phase is a Full Moon.

For the pilots out there, Raw Metar readings are:

SPECI KAUG 181302Z AUTO 35013KT 9SM BKN014 OVC029 M09/M11 A2991 RMK AO2 T10891111

Visibility is 9.0 miles/14.5 Kilometers with mostly cloudy conditions to 1,400 ft / 426 m.,  and overcast to 2,900 ft / 883 m.

We have had 1.5 inches of snow here in the past 24 hours.

What causes "Sea Smoke"?

Recall that recent spate of bitter cold we had a few days ago, and if you live near the Atlantic, you may have seen "Sea Smoke"

Sea smoke, or arctic steam fog, is a cloud over the sea, which could otherwise be called fog, and is usually formed when very cold air moves over warmer water. The physics are in principle similar to lake-effect snow.

Evaporation from exposed water surface depends upon its vapor pressure. If the water temperature is greater than that of the nearby air, the evaporation continues faster than the air can absorb the water vapor, even though the cool air's relative humidity is 100%. This further evaporates immediately and re-condenses as visible fog, which rises up in convective currents. If the wind blows across cold icy areas like the Arctic, the breaks in the ice sheets where clear water is exposed, the water surface steams up into the air, producing fog.

The conditions required for such fog formation include not only low surface temperature but also a preexisting surface inversion of temperature to inhibit the rapid development of instability.