textproduct: NWS Flagstaff

SYNOPSIS

A quiet day is expected Saturday with dry weather and seasonal temperatures. Starting Sunday afternoon an incoming trough from the West Coast will interact with tropical moisture potentially bring heavy rain, strong thunderstorms and possible flash flooding. Widespread precipitation chances continue through Tuesday before declining by midweek.

DISCUSSION...Today

Following the passage of a weak upper-level trough yesterday, brief ridging with much drier air has taken hold today. Precipitation chances drop to zero across all of northern Arizona as a result. Expect a pleasant day with south to southwest afternoon breezes and near normal daytime temperatures.

Sunday through Tuesday...We are setting up to have an active stretch of weather to begin the week. A pair of tropical systems in the Pacific (Hurricane Polo and Hurricane Odalys) are forecast to drift north through the period. Meanwhile, a deep west coast trough is forecast to dive southeastward along the California coast on Sunday- Monday, then eventually cross directly over Arizona. While the remnant tropical circulations will not directly impact northern Arizona, the trough will interact with the enhanced field of moisture around the systems and we will see a deep surge of moisture into the region.

Upper-level moisture looks to arrive as early as Sunday morning as a subtle shortwave ripples ahead of the deeper west coast low. We may begin the day with some high-based activity, but will quickly moisten up in the lower levels by Sunday evening. Precipitation chances ramp up Sunday night, becoming widespread by Monday as moisture continues to stream in ahead of the approaching trough. Given the setup, there is risk of heavy rainfall and flash flooding through the period. The latest WPC ERO puts all of northern Arizona in the Slight risk category on Monday. Also, enhanced shear from the trough could allow for better storm organization and some threat of severe storms. There still remains a degree of uncertainty among ensemble guidance on how progressive the trough will be, however confidence is increasing towards a slower set up that will bring another active day on Tuesday with more flooding threats and severe threats. Besides precipitation, expect breezy south-southwest winds on Sunday and Monday and cool daytime temperatures to start the week.

Wednesday through Friday...By Wednesday, the trough axis will be pushing out of our area. Precipitation chances will decline from west to east as much drier air and subsidence follows in its wake. Expect dry conditions with warming daytime temperatures to end the week.

AVIATION...Saturday 26/06Z through Sunday 27/06Z

VFR conditions, with VRB winds 5-10 kts, becoming S/SE after 18Z.

OUTLOOK...Sunday 27/06Z through Tuesday 29/06Z...VFR conditions through 21Z Sunday-03Z Monday, with periods of MVFR expected in SCT- NMRS SHRA/TSRA thereafter. Daytime winds S/SW 5-15 kts on Sunday, becoming S on Monday. Overnight winds light and variable.

FIRE WEATHER...Today through Sunday

Dry conditions are expected today, then slight chances for showers and thunderstorms return by late Sunday afternoon. Precipitation chances continue to ramp up overnight Sunday. Winds are S-SW 5-15 mph on Saturday, then 10-20 mph gusting to 30 mph on Sunday.

Monday through Wednesday...Prolonged widespread precipitation chances Monday through Tuesday as an approaching weather system combines with tropical moisture. Precipitation chances decline from west to east overnight Tuesday into Wednesday morning. There is a threat of heavy rainfall and flash flooding on Monday-Tuesday for all of northern AZ. Winds S-SW 10-20 mph on Monday, shifting N-NE 10- 20 mph on Tuesday, then NW-N 5-15 mph on Wednesday.

FGZ WATCHES/WARNINGS/ADVISORIES

None.