It’s beginning to look a lot like fall in terms of the weather pattern. A strong upper level disturbance is digging south into the northern Plains states and ahead of it seasonably strong low pressure will develop driving a fairly strong cold front into the area Sunday night into Monday morning. During this time, showers and a few storms are likely to drop some beneficial rains. Cool, dry, awesomely comfortable air will settle in as strong high pressure builds overhead for Tuesday through Thursday. After Thursday, the high moves offshore and an approaching front will bring more warm air into the region before more showers and storms at some point next weekend.
Today’s forecast worked out well with dry conditions, sunny skies, and light NW breezes. A sea breeze has developed along the coast bringing slightly cooler temps there. Temps are currently ranging from the mid 70’s north to the mid/upper 80’s south which is right in line with the forecast. This is one of those straightforward days where not a whole lot can/did go wrong in terms of the forecast. Days like this are a rarity in Maine!
The upper air setup looks a lot like fall with a deep trough beginning to evolve to our west. This trough will continue to strengthen and begin to tilt negatively as it moves east. Ahead of the trough, a ridge will build, slowing the eastern progress of the trough. This ridge does not look as strong as once modeled and thus the front is likely to keep moving a little faster than it looked a couple of days ago. Regardless of speed, a line of tropical downpours is likely ahead of the front. The heaviest rain will be over northern areas where better upper level dynamics are likely.
The weather for the next several days can be seen in this map of moisture from the GFS. Increasing clouds and moisture ahead of the front tomorrow and to a larger degree Sunday will result in lower temps but dew points will be on the rise leading to more humidity. That humidity will fuel tropical downpours along the front before dry Canadian air sweeps south bringing comfortable humidity back. How do dew points in the 40’s sound? Yeah, that’s happening Tuesday and Wednesday.
The significant heat relief will be short lived as SW breezes bring warmer and more humid conditions into the region late next week. A frontal boundary will sag south during this time crossing the area at some point this weekend with more showers and storms possible. The timing of this remains uncertain. While temps and dew points will be higher than Tuesday and Wednesday, they still don’t look oppressive. The true dog days of summer may be numbered.
I want to end with a quick note on the tropics. There is a cluster of thunderstorms over the open ocean roughly half way between the Caribbean and Africa. Some computer model guidance has indicated that this cluster will evolve into a tropical storm that could threaten the US. It is important to note that this tropical storm that some models predict hasn’t formed yet. This means that the models are having a hard time figuring out what it is right now (models don’t often “see” thunderstorms as they actually are because thunderstorms are almost always too small for the model’s grid points). The pattern is favorable for this cluster of storms to develop gradually and the NHC has given it a 50% chance to develop in the next 5 days.
This does not mean that the computer model maps showing a large hurricane over *insert US city here* have any merit. If you are taking a vacation to Puerto Rico, Barbados, or any of the other eastern Caribbean islands in the next week, keep an eye on this system. Otherwise, this is not something to worry about. Should that change as the system moves west, I’ll be sure to let you know. Please don’t fall for model hype that can be found on social media. As always, continue to keep tabs on the forecast through the official NWS channels such as the National Hurricane Center and the local NWS office in Gray.
More info tomorrow.