textproduct: NWS Flagstaff

SYNOPSIS

Dry conditions and lighter east winds are expected through this afternoon, then a weather system brings chances for showers and thunderstorms this evening through Sunday. This active pattern continues through most of next week with continued daily shower chances, occasional gusty winds, and below normal daytime temperatures. The highest chance of rain next week is on Wednesday and Thursday.

DISCUSSION...For today and Sunday

a low pressure system was seen spinning just off the Baja California coast Saturday morning. Over the next 24- to 36-hours the low center will track toward then across Arizona, weakening and filling as it goes. The low will bring with it upward motion and increasing moisture. By Saturday night scattered showers and isolated thunderstorms will develop from south to north across Arizona starting, then last through Sunday. A few limiting factors with this low. First, the air mass across Arizona is very dry and it will take a bit for the depth of the atmosphere to moisten. In addition, the flow associated with this low is weak so very little if any orographic lift. Another factor, it will remain mostly cloudy as the low moves across the area with little impact due to daytime heating. As a result, looking at generally light precipitation totals of 0.10 inches or less through early Monday (higher amounts over the highest mountain peaks perhaps as much as 0.50 inches). In any case, this is a warm system so snow levels are expected to remain primarily above 11,000 feet but can't rule out snow levels briefly dipping a bit lower at the onset of precipitation due to evaporational cooling. Easterly winds Saturday afternoon will become light and variable on Sunday as pressure gradients become indeterminate. There will be a cooling influence from the light precipitation and clouds with high temperatures dropping by around 5 degrees on Sunday compared to Saturday.

For Monday and Tuesday...A strong low pressure system dropping southward from the Gulf of Alaska will begin to approach Arizona. Moisture will continue to linger in advance of this low with chances for showers or a stray thunderstorm continuing mostly in the afternoon due to daytime heating. Winds will turn more southerly at 5-15 mph on Monday in response to the approaching then strengthen some on Tuesday as the low draws closer to Arizona. High temperatures will warm a bit as southerly flow pushes a mild air mass across Arizona.

From Wednesday onward...Models remain consistent on pushing the Pacific low across Arizona tapping into moisture of subtropical origins. The result, widespread showers and likely a few thunderstorms, especially on Wednesday and Thursday. The most substantial moisture, with origins from over the Gulf of California and northwest Mexico, will likely move across Arizona from about Flagstaff eastward where local rainfall totals of 1 to 2 inches will be possible. The area of the highest rainfall totals includes the White Mountains, eastern Mogollon Rim and Navajo Nation. Further west looking at amounts of 0.25-0.75 inches. Once again the snow level will remain elevated for much of the storm due to the subtropical nature of the moisture, perhaps dropping as low as 8500 feet as the low is exiting Arizona next Saturday. Pressure gradients will strengthen with breezy south to southwest winds developing. High temperatures will be on the decrease under the influence of perception, clouds and cooler air associated with the low.

AVIATION...Sunday 18/00Z through Monday 19/00Z

Mainly VFR but MVFR may be possible at higher elevations after 18Z due to lower ceilings. Expected scattered showers throughout the area throughout the TAF period, best chances for showers along higher elevations. Winds variable 5-10kts.

OUTLOOK...Monday 19/00Z through Wednesday 21/00Z...Mainly VFR, but brief MVFR possible near heavier showers. Isolated to scattered showers and possibly thunderstorms expected throughout the TAF period, mainly along the higher terrain. Winds S-SW 5-15kts Monday and Tuesday.

FIRE WEATHER...Sunday through Monday

Cool temperatures with light and variable winds on Sunday, becoming south 5-15 mph on Monday. Scattered showers with isolated thunderstorms through Sunday afternoon, then isolated to scattered showers are expected on Monday. Minimum RH between 40-70% both days.

Tuesday through Thursday...Cool temperatures continue through the week. Slight chance of showers and thunderstorms on Tuesday, becoming likely showers and thunderstorms on Wednesday and Thursday. South winds 10-20 mph with gusts to 30 mph on Tuesday, increasing to 15-25 mph with gusts 30-40 mph on Wednesday and Thursday.

FGZ WATCHES/WARNINGS/ADVISORIES

None.