textproduct: NWS Flagstaff

SYNOPSIS

Expect very active Monsoon conditions for the rest of this week, but especially for Wednesday and Thursday. A downturn in Monsoon activity is possible by the weekend, as drier air moves into the region. Temperatures will move lower, even below normal in some spots, as cloud cover and precipitation persist.

DISCUSSION

High pressure will slowly and grudgingly retreat eastward over the next several days, as a long-wave trough forms over the eastern Pacific. In fact, much of the next 10 days looks like an ongoing battle between the high pressure to our east and the troughing to our northwest.

What does this do? Well, in the short term, it allows capping to weaken and southerly flow to increase across the region. As long as the moisture remains in place, this is a very good recipe for active weather. Today looks like the most active day, with slight downturns and a eastward shift in activity afterwards. We expect moderate to high grade Monsoon conditions today as a result and a Flash Flood Watch has been issued.

Why has a Flash Flood Watch been issued? Many locations are quite saturated at this point and when combined with increased instability values, shear and PW values over the 90th percentile, the chances for flooding are greatly increased.

By the end of the week and into next weekend, there is potential for some drying, as the west coast trough attempts to move inland. This could bring drier, mid-level air and effectively reduce convection over our state. However, if the trough does not move inland as much or if it ejects farther north, it may just keep our active weather going. For now, we have tapered off PoPs a little bit, but we will need to watch this pattern closely, as any change on the trough position could make a big difference.

Temperatures will continue to trend down with the cloud cover and precipitation, heat related headlines will not be needed.

AVIATION...Wednesday 12/12Z through Thursday 13/12Z

Mainly VFR conditions away from thunderstorms. SCT-NMRS SHRA/TSRA and ISOLD +TSRA through the period, but especially in the afternoon/evening hours. Stronger storms may produce brief MVFR/IFR and wind gusts as high as 45kts. Sfc winds are not anticipated to affect flight operations, but will trend W-SW10-15kts Wednesday afternoon.

OUTLOOK...Thursday 13/12Z through Saturday 15/12Z...Mainly VFR conditions away from thunderstorms. SCT SHRA/TSRA and ISOLD +TSRA through the period, but especially in the afternoon hours. Storm trends shift eastward by Friday. Stronger storms may produce brief MVFR/IFR and wind gusts as high as 45kts. Expect daytime sfc winds W-SW10-15kts.

FIRE WEATHER...Wednesday and Thursday

Expect active Monsoon conditions for each day, with numerous showers and thunderstorms. Outside of thunderstorms, expect southwest winds from 10 to 15 mph. Daytime temperatures will keep decreasing as cloud cover and rainfall increase.

Friday through Sunday...Some drying develops during this forecast period, with the emphasis for activity shifting eastward. Daytime temperatures will continue to trend downward. Expect southwesterly winds at 10 to 15 mph each afternoon.

FGZ WATCHES/WARNINGS/ADVISORIES

Flood Watch from Noon MST Wednesday through Midnight MST Wednesday evening for AZZ004>018-037>040.