Meteorological Lesson #3: Cold Fronts

I figured it would be a good time to talk about cold fronts and how they contribute to our weather pattern.

Cold Fronts: So what are cold fronts exactly? Usually portrayed by a blue line with triangles pointing in the direction of travel, a cold front is cooler air replacing warmer air ahead of it. Cold fronts originate from a low pressure system and are always complimented by a warm front. This is shown in the graph below along with the process of the cooler air replacing the warmer air:

Cold Front Warm Front

Cold fronts are most common during the summer where they bring nasty thunderstorms. Here is an example of a classic summer day involving a cold front:

The morning starts out extremely humid as the warm front passes to the north. By noontime, temperatures are in the 80s and are approaching 90 fast. By the afternoon hours, the inevitable cold front is approaching fast with thunderstorms starting to build along it. By the 4 or 5 o’clock hour, the front passes through, bringing in nasty thunderstorms and gusty winds. By the nighttime hours, skies clear and the temperature is noticeably cooler. The next day should be a beauty!

The main reason why precipitation, especially thunderstorms, form alongĀ  a cold front is because of the upward motion of the warmer air as the front barrels from west to east. The greater the upward motion, the warmer the temperature and the more unstable the atmosphere ahead of the front. This is why we get the most severe thunderstorms during the summer.

Line of thunderstorms along a front

Record Warmth Monday, Nice for the Rest of Week

Ahh, finally. Some warm weather. This time is probably the least busiest of the year for meteorologists in the Philly area. Hurricane season hasn’t started, snow is over, and the severe weather season hasn’t really begun. After a LONG winter of stress and anxiety, I am ready for the well deserved break.

Tomorrow highs will climb into the 80s. The sun will be shining and a light southerly wind will bring in a warm breeze. Records will be shattered tomorrow in the area. In Philadelphia, a record could be broken for more than a hundred years ago!

There will be a chance of some strong to severe storms tomorrow evening however as a cold front will sweep by the area, bringing temperatures for the rest of the week into the 60s (still not bad though).

I am a little concerned that some of the storms tomorrow could be stronger than what the news stations are currently advertising. Warm air will obviously be in place, destabilizing the atmosphere. By the late afternoon, I could see a very formidable squall line barreling across Pennsylvania into the Philaburbia region. Just keep an eye to the skies tomorrow after 4 PM because you never know what might pop up.


Slight Risk of Severe Weather Monday