Another active week of weather is in store for the United States, as multiple weather systems move through while fall-like temperatures intrude parts of the western and central US.
This is your 5 Things to Watch This Week.
Rosa to Bring Heavy Rain to Southwest:
Rosa, now a tropical storm, will make landfall on the northern Baja California Peninsula Monday night, eventually tracking into the Four Corners states midweek. Given the fact that this is a tropical cyclone, there will be copious amounts of moisture associated with the system.
Heavy rain and flash flooding will be the main risk from Rosa in the Southwest. According to Head Meteorologist Joshua Feldman, “Initially, the heaviest rain will be focused in the vicinity of the low over the south-central Sonoran desert east of Yuma. The left exit region of the remnant wave’s impressive low-mid level jet will drop the heaviest and most widespread downpours directly across the center of the state. Phoenix, Scottsdale, and Prescott will all be in the path of these concentrated downpours. Up to 4″ of rain will fall in these cities, which could be enough to grind life to a halt. The rocky desert has very poor drainage, so water will quickly pool and gush down slopes that face the Sonoran basin.”
Read more in the Sunday Storm here.
A round of severe weather will be possible later this Monday across parts of the Midwest, specifically from eastern Iowa through the Chicago area. A cluster of intense thunderstorms is expected to develop along a warm front this afternoon, posing all sorts of hazards. That includes damaging winds, large hail, and even a couple tornadoes.
As the same disturbance tracks east, there will then be the risk for severe weather in parts of the Northeast, although this risk will be less substantial than this Monday’s in the Midwest thanks to cloud cover and a weak cold front. This threat on Tuesday will span from Lake Erie through the central Hudson River Valley in New York. Damaging winds and small hail will be the main hazards these storms may deliver.
Cool West, Warm East:
Fall has arrived in the West while warmer weather streams back into the East, making for a sort of delayed start to fall. Persistent troughing over the western US will trigger numerous ridges of high pressure over the eastern half of the country through at least mid-October. High temperatures will generally be 5-15 degrees above average from the Midwest through the southern Plains and all locations east of there, while to the west highs will be the exact opposite.
The most significant of the warmth looks to take place around this coming weekend and into early-next week as heights within the ridge of high pressure approach or possibly even reach record levels, indicating how highly anomalous this warmup will be.
There’s still two months left of hurricane season in the Atlantic basin, but the ocean is showing some signs of a quieter environment. There is currently only one active tropical cyclone in the basin at this time, which is Tropical Storm Leslie. Otherwise, no new tropical cyclones are forecast to form next week. Since we are moving away from the peak of the season’s typical activity, our area of focus through the end of the season will return closer to home. In fact, some of the model guidance is suggesting we’ll have to watch the western Caribbean Sea and the southwestern Atlantic Ocean for potential development next week. We’ll keep you updated, but there is no imminent or substantial threat at this time.
Growing Snow Chances:
The risk for snow continues to grow across the western US, especially in the Northwest and northern Plains. As the storm track becomes more active across these regions while cooler air becomes dominant, this may make conditions conducive for snow instead of rain. In fact, the average first snow takes place in October across many of these areas that may witness their first snowfall of the season. As of now, the best risk for snow will be in the northern Rocky Mountains next week, but the model guidance is suggesting that a strong low pressure forms over the Plains, which may bring snow to the northwestern side of the storm and to parts of the northern Plains as well as the leeward side of the central Rocky Mountains.