Friday 8:15 a.m.
Temperatures will stay in the 60s and 70s across New Jersey and Pennsylvania today, the coolest day so far this summer. Many areas from Chicago to New York City have had significant rain. Does this mean the over dry spell is over? Does this mean the heat has had it? No. Looking at the GFS ensemble forecast for the next 16 days in Philadelphia, today and tomorrow are the coolest days between now and Aug. 4. However, last night's run did not show temperatures returning to this week's extreme.
In terms of the drought vis a vis (as that really a term?) recent rain in parts of the drought-stricken area, I have these thoughts. 1. Where places got more than about a half inch of rain it was helpful for the short term for grasses and flower beds. Where rain was much heavier, a good part may have run off, but in the short term was helpful. 2. The key now is whether the rain is a one and one thing or the start of some new pattern that will cause more frequent rainfall in the future. If that turns out to be the case, the recent rain will be seen as the turning point. If new rain fails to materialize, then those areas will revert back to the same conditions that have worsened all summer.
This video looks at the weekend and early next week.
This pressure analysis shows the boundary between hot air to the south and cooler air to the north. You can see a few low pressure areas along the front, each increasing the rainfall as it approaches, then introducing some drying upon departure.
So, I hereby pronounce that in the Great Lakes and Northeast March came in like a penguin and goes out like a chameleon. In contrast, by tradition, March comes in a like a lion (roaring cold winds) and goes out like a (gentle) lamb.
Winds aloft are coming from Canada, but later (as shown on the map) this week will come from the Southwest states. That should promote a major, though temporary, warmup in the Middle and North Atlantic states.
Lake-effect snow hit Chicago this morning. This happens when cold winds at low cloud height are from the northeast. When the flow is from the west or northwest, the Michigan and/or Indiana snow belts come alive. These maps show the setup from this morning.
This map shows a low pressure center along a cold front that will cross the Eastern states today. From southern Pennsylvania southward, a few thunderstorms can develop this afternoon and evening, but everyone in the Middle and North Atlantic state should get some rain.
One way of displaying a forecast is by using a meteogram. Items like temperature, wind and precipitation are distributed across a chart so you can see what is supposed to happen and when. This cart is a meteogram for New York City. Three details are highlighted.
Thunderstorms broke out last night ahead of the warm front that will bring milder air to the Northeast on Thursday. Hundreds of lightning strokes occurred from Nebraska and Missouri into western Illinois. This picture shows a shaft of lightning about a mile from my home a couple of years ago.