textproduct: NWS Flagstaff

SYNOPSIS

Active monsoon weather continue through late tonight, with drier conditions returning for the middle of the week. Additional showers/thunderstorms likely Friday through the weekend.

DISCUSSION

Most activity on-going at the moment is across northern Apache County and areas south of I-40. The complex of showers and storms is from a MCS that formed across central Arizona earlier this evening. We anticipate these showers/storms to continue to push northward toward the Flagstaff area overnight, so you may hear a few rumbles of thunder and wake up to the smell of rain. If the recent run of the U of A WRF model is accurate, there will be showers/thunderstorms across much of central/northern AZ through the next 24 hours. Hence, the Flash Flood Watch continue for our entire CWA through Monday night at midnight. Although flash flooding is a primary concern, especially for recent burn scar locations, storms will also be capable of producing hail, frequent lightning, and gusty/erratic winds. Be sure to have a way to receive warnings if you're out and about.

Despite hi-res guidance being fairly persistent with activity for later this afternoon/evening, a lot may also depend on how worked over everything is after tonight. It could simply delay the start for showers/thunderstorms this afternoon, but it could also keep things fairly tame. A shortwave looks to clip the northwestern corner of the state today, so this will also help with keeping moisture funneling into our CWA and ensuring the proper dynamics are in place for continuous convection. In short, the ingredients are there for an active day, but patterns like this can be tricky when we are dealing with overnight convection.

Tuesday through Thursday...A large trough over the Pacific Northwest with an embedded shortwave across the Great Basin region will suppress monsoonal moisture through the middle of the week. We aren't expecting to completely dry out, but showers/storms will become very limited over the higher terrain each afternoon.

This short break from active weather doesn't look to be long- lived, as more chances for showers/thunderstorms look to return Friday through the weekend. This return of active weather will be from high pressure strengthening across the central US and also a tropical disturbance forecast to move northward along the California Baja coast. There is still some uncertainty with the exact trajectory of this tropical system, but even without that additional moisture, the ridge should end up in a more favorable monsoon pattern.

AVIATION...Monday 31/12Z through Tuesday 01/12Z

VFR conditions expected outside of areas of MVFR/IFR from stronger SHRA/TSRA. Greatest coverage for showers/storms will be between 18Z-03Z. Gusty/erratic winds possible near storms, with W-SW winds 10-20 kts otherwise. Light and variable winds look to return after 06Z.

OUTLOOK...Tuesday 01/12Z through Thursday 03/12Z...VFR conditions expected. Look for SW winds 10-20 kts each afternoon, becoming light and variable overnight. Slight chances for -SHRA/-TSRA across higher terrain each afternoon, with main impacts being gusty/erratic winds.

FIRE WEATHER...Monday and Tuesday

Widespread showers and thunderstorms forecast to continue throughout Monday, becoming more isolated over the higher terrain on Tuesday. Heavy rain leading to flash flooding, especially over recent burn scars, will continue to be a main concern. Storms will also be capable of producing hail, gusty/erratic winds, and frequent lightning. Outside of storm driven winds, look for SE through SW winds 5-10 mph Monday and SW winds 5- 15 mph Tuesday. Expect daytime highs 5-15 degrees below normal.

Wednesday through Friday...A brief drying trend is expected Wednesday and Thursday, although an isolated hi-based shower is not out of the question. Friday appears to be more active across central/northern Arizona in terms of showers/storms. Temperatures look to slowly warm through the period, becoming closer to seasonal norms. Expect southwest winds 10-20 mph each afternoon, becoming light and variable overnight.

FGZ WATCHES/WARNINGS/ADVISORIES

Flood Watch through this evening for AZZ004>018-037>040.