12-hour Forecast valid 00 UTC Day 3 (Hour 48)

Hypothetical skewt plot of a sounding for precipitation type forecasting

The model forecast sounding for 00 UTC on Day 3 shows further erosion of the cold air near the surface, as winds veer to SE at low levels.

Task 4: Analyze this model forecast sounding to forecast what type of precipitation will be occurring 12 hours later (00 UTC on Day 3). (To assist with this question and others that follow, you can open the interactive skew-T with this sounding).

Which of the following factors will be important in forecasting the type of precipitation for 12 UTC on Day 2?
(Choose all that apply, then click Done.)
a) Depth of cold air (T<0°C) near the surface
b) Wet-bulb zero level
c) Freezing level

The correct answers are all of the above. The existence and depth of cold (T<0°C) air near the surface can be a significant determinant of precipitation type. The wet-bulb zero level and freezing level can be important in determining whether snowflakes will fall through a sufficient depth to melt should the surface temperatures be above freezing.

Given this forecast sounding, what type of precipitation do you expect to be observed at the surface at 00 UTC on Day 3?
(Choose the best answer, then click Done.)
a) Rain
b) Snow
c) Ice pellets (sleet)
d) Freezing rain
e) Hail
The correct answer is a) Rain. The surface temperature is predicted to warm to +2°C, and the freezing and wet-bulb zero levels are 733 and 734 hPa, respectively, so the snowflakes will fall through an above freezing layer over 250 hPa (8000 feet) deep, which is sufficient to melt the snowflakes before they reach the surface.
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