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November 2016

Weekly Rainfall Review

Posted: November 14th, 2016

Winds at about 20,000 feet, smashing into the Cascades, as the front passed late Sunday.


Last Monday’s forecast summary:

• Light rain ending this morning.
• Near-record high temps are expected to peak in the mid-60s tomorrow.
• Steady rain is likely again on Friday.
• Extended forecasts have 4-5 systems, none appearing strong, arriving over the next 2 weeks.


The 7-day precipitation forecast called for 1- to 2-inches across the Tolt and Cedar watersheds, with a little uncertainty and possibility of higher amounts toward days 6 and 7. National Weather Service maximum forecast intensities, or “bulls-eyes,” were for 0.23 inches during the 12-hour period ending at 10am on Wednesday, and 0.52 inches during the 24-hour period ending at 4am Saturday—nothing concerning.


Freezing levels were expected to remain relatively high, but extended forecasts (North American Ensemble Forecast System) hinted at cold, snow-producing conditions beyond day 7.


In the City, the 7-day forecast had 0.5- to 1.0-inches, with “bulls-eyes” of 0.18 inches during the 12-hour period ending at 4am on Wednesday, and 0.41 inches during the 24-hour period ending at 10pm Friday. High-intensity, short-duration events were not expected during the period.


7-day Precipitation Observations:

Watersheds: 0.8- to 1.9-inches.
City: 0.35- to 0.75-inches.


Rainfall was lighter than expected, especially on Friday. The bulk of the rainfall totals came at the very end of the week, which had been a possibility, and really hit on the following Monday. That the previous week was light made late Sunday’s rainfall more tolerable, though it still made for a busier start to the next week for watershed managers. In the City, only 2 combined sewer overflows occurred all week, both on Wednesday when a few thousand gallons spilled into our waterways.