textproduct: NWS Flagstaff

SYNOPSIS

We remain in an active pattern through the week. Isolated to scattered showers and thunderstorms are expected Monday and Tuesday afternoon/evening. High chances for showers and thunderstorms beginning Wednesday morning and continuing through Thursday as a strong weather system approaches. There will be risk of Flooding and Flash Flooding, especially across eastern Arizona. Also expect increasing winds and below normal temperatures through the week.

DISCUSSION...Today

A low pressure system currently located over western Arizona continues to drift northeastward while weakening. Enhanced moisture and large-scale lift still accompany this system, and weak showers continue to fire through the early morning as a result. Some patchy fog has also been observed as mid-upper level clouds begin to clear, and areas of fog will be possible through the remainder of the morning. Low level moisture lingers into the daytime today, and partly clearing skies will allow for modest destabilization and diurnal scattered shower and thunderstorm activity. A few stronger thunderstorms may be possible especially towards eastern Arizona where higher shear will be found. Besides the potential for storms, expect steady winds with slightly below normal temperatures.

Tuesday...Another low pressure system is visible in mid-level water vapor satellite imagery, currently located off the the coast of the Northwest CONUS. This system is forecast to rapidly dive southward along the west coast on Tuesday. This will assist in lifting the lingering disturbance northeastward out of Arizona, and will phase with a strengthening ridge over the central CONUS to reinforce a pressure gradient bringing south-southwesterly flow to our region. There will be continued diurnal shower activity, though a slight downtick is anticpated from Monday due to the departure of the weak disturbance. Also expect breezier south- southwest winds and near-normal temperatures, likely the warmest of the week.

Wednesday and Thursday...The strong low pressure system will begin to push inland and carry a deeper surge of moisture. PWAT values (a measure of atmospheric moisture) are forecast to range from 0.7-1.0 inches on Wednesday. This is very anomolous for this time of year. High chances for showers and thunderstorms are expected as a result, beginning Wednesday morning and continuing through Thursday. Most areas are forecast to recieve at least 0.5 inches of rain, but local regions across eastern AZ may see 1-3 inches or locally higher, including the Eastern Mogollon Rim, White Mountains, and the Navajo Nation. Ensemble guidance still does have some spread in the trajectory and how progressive the trough will be, so there is room for change in total accumulations. WPC has introduced a Slight Risk of excessive rainfall for all of Northern and Central Arizona on Wednesday and Thursday. A risk of both Flooding and Flash Flooding will be in play through the period. Also of note is a potential developing severe threat. SPC has introduced a Marginal (category 1 out of 5) risk of severe weather on Wednesday. High shear is likely as a strong 500mb jet streak moves overhead, but there is considerable uncertainty in available instability. For now there is at least a mentionable threat of severe weather through the period. Besides the rain and thunderstorm threats, expect gusty daytime winds up to 30-40 mph each day.

Friday and onward...Activity is expected to trend downward by Friday into the weekend after the main trough axis pushes past Northern AZ. Some slight chances for showers may linger depending on a potential remnant cut-off low, but there is considerable uncertainty. Expect lighter winds and temperatures remaining below normal otherwise.

AVIATION...Monday 19/06Z through Tuesday 20/06Z

Mainly VFR with localized MVFR possible in heavier showers. Showers and thunderstorms redevelop, mainly over the higher terrain between 18-21Z Monday and dissipate between 00Z-03Z Tuesday. Winds light and variable or terrain driven overnight, S-SW 5-10kts Monday afternoon.

OUTLOOK...Tuesday 20/06Z through Thursday 22/06Z...Mainly VFR with brief MVFR in heavier showers. Isolated showers or thunderstorms along the higher terrain on Tuesday afternoon, becoming more numerous Tuesday night into Wednesday. Daytime winds S 10-20kts with gusts to 30kts on Tuesday and Wednesday. Expect light and variable winds during the overnight period.

FIRE WEATHER...Today through Tuesday

Cool conditions expected to continue through the period. South winds 5-15 mph on Monday, increasing to 10-20 mph on Tuesday. Scattered showers and thunderstorms again on Monday, with a slight chance of showers and thunderstorms on Tuesday.

Wednesday through Friday...Cool temperatures continue. Showers and thunderstorms likely on Wednesday and Thursday with most areas seeing wetting rains, then scattered activity expected on Friday. South winds 15-25 mph with gusts 30-40 mph on Wednesday and Thursday, becoming south through southwest 10-20 mph with gusts 25- 30 mph on Friday.

FGZ WATCHES/WARNINGS/ADVISORIES

None.