Date & Time: 07/23/2021 10:00 AM MST
Forecaster: Henz, D.
We’ve got lots to talk about as we’re still in the early stages of a high impact Monsoon setup that will continue to play out into this weekend. Widespread t-storms brought heavy rain and localized flooding to the eastern half of County overnight and activity is still ongoing this morning. A remnant wave can be seen spinning across the region and will continue to funnel storms south into central and eastern zones the remainder of the morning. The big picture remains intact with high pressure near the Four Corners and large inverted trough slow moving west through NM. This disturbance will continue to be a strong catalyst for additional waves of organized storms capable of heavy rainfall the remainder of today and into the weekend. Flash/urban flooding will be our main concern from now at least into Saturday, especially across higher terrain watersheds and burn scars north and east of the Phoenix Valley. A Flash Flood Watch will remain in effect through Sunday morning.
For the rest of the morning plan on showers/t-storms moving south mainly across the eastern half of the County. Afternoon temperatures will likely remain limited to the 80s due to cloud cover and variable winds will hover in the 5-10mph range with gustier conditions near storms. We expect current storm activity to wane into the early afternoon providing a brief lull period. Guidance continues to struggle with timing but current thinking suggests our next wave of organized storms will arrive tonight/overnight into Sat AM. As we’ve seen, storms are efficient rainmakers capable of producing 1.00”-2.00”/hour. Most watersheds around the County are now saturated and will be highly susceptible to runoff in area washes/streams. Furthermore, urban flooding will continue to be a problem on area roadways, channels, low lying areas with additional rainfall. Conditions will continue to be monitored closely and additional updates/details, especially in regards to flooding concerns, will be issued in statements as needed.
For tomorrow plan on another wet/cloudy start with lingering storms possible across most of the region. Even if we end up a little less active overnight, daytime temperatures are still expected to remain limited to the 80s to low 90s around the Valley. In regards to storm potential, we’ll see how tonight evolves, but we fully expect a third wave of organized storms to pinwheel through the County tomorrow bringing additional heavy rain and exacerbate flooding issues, especially across our higher terrain watersheds/and recent burn scars to the north and east of the Valley. We may also start to see longer duration flows in the bigger area streams (Centennial, Hassayampa, Cave Creek, New River, Agua Fria, etc). Finer details as to timing and spatial coverage of impacts will evolve over the coming day or two and new details will be included in subsequent Outlooks.