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Pittsburgh Weather: Early Morning Fog Gives Way To Possible Afternoon Rain

PITTSBURGH (KDKA) - Good morning, expect patchy morning fog today with a couple of spotty showers and maybe even a weak thunderstorm to be around this afternoon.

Even with the active weather day expected today, it's actually tomorrow morning's weather that I think is the most interesting.

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That's when we have the possibility of seeing lake effect rain showers coming in off of Lake Erie.

So cool!

Before we chat a bit about the lake effect rain/snow, let's talk about today's weather.

Morning temperatures will be in the mid to upper 50s for most with highs in the low 70s. There will be a persistent northwest wind this afternoon of around 10mph. Wind speeds could pass 15mph at times.

High Temperatures
Photo Credit: KDKA Weather Center

As a trough of colder and drier air drops down from the north late this morning into the afternoon expect to see some light rain and maybe even a weak storm developing. Rain chances will be the highest today from 11:00 a.m. to 5:00 p.m.

I have today's rain chance at 40 percent coverage.

Tomorrow I drop our rain coverage to just 20 percent with light drizzle being possible for the morning. While the chance for rain is lower, I find that the set-up for tomorrow is a lot more interesting.

That's because any precipitation we receive tomorrow will be from lake effect rain showers developing. Lake effect rain or snow needs a couple of things to occur in order to happen.

The first thing is cold temperatures around a thousand feet above the lake. In fact, the temperatures around this thousand-foot mark need to be around 18° celsius colder than lake water according to my college professor.

Lake effect precipitation can occur at temperature differences as little as 15°C though officially. I am seeing lake water temperatures coming in at 74°F. That is 23.3°C. I have 850 temperatures (generally just above 1000ft) coming in at 6.7°C in Erie. Temperatures are colder on the north side of the lake. The difference in water temperature and air about 1000ft up is going to be around 17°C on Friday morning.

The other main thing you need to see lake effect precipitation is a long enough fetch. Fetch is defined as the distance over water that air travels. You put all this together and there should be sufficient cooling occurring tomorrow to get precipitation squeezed out of the air as the warmer moisture-rich lake air quickly cools as it is forced south and up.

I probably get way too excited about lake effect moisture early in the season, but hopefully, you can admit that it is pretty cool.

7 Day Forecast
Photo Credit: KDKA Weather Center

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