textproduct: NWS Flagstaff

SYNOPSIS

Increasing moisture will bring chances for showers and thunderstorms in eastern Arizona today. Precipitation becomes more widespread Wednesday and Thursday as deeper moisture and a low pressure system impact the area. Drier conditions are possible by Friday and the weekend with only slight chances for rain.

DISCUSSION...Today

An upper low is currently centered over eastern NV and moving to the northeast. This feature brought a minor surge in moisture and instability this morning, with weak isolated showers and thunderstorms across NW AZ. Showers in this region have ended as the trough lifts northeastward, and a weak cut-off low will be left behind off the coast of Baja California. Meanwhile, a shortwave currently located over Mexico will be slowly drifting northward over the next few days, following a trajectory into NM and eastern AZ. A much larger surge of moisture will accompany this feature. PW values this afternoon will reach above the 95th percentile for this time of year across eastern AZ. Scattered showers and thunderstorms are firing mainly near the AZ-NM border as of 1200 MST. This activity is forecast to increase in coverage and continue through the afternoon and overnight. A few instances of flash flooding will be possible across Navajo and Apache counties today.

Wednesday and Thursday...By tomorrow, the main axis of the wave ripples through our area. Moisture will spread further west, and shower/thunderstorm chances will extend to Coconino and Yavapai counties. Further east, rainfall may transition into more of a stratiform type, however heavy accumulations are still possible. The WPC excessive rainfall outlook puts most of northern AZ in a marginal risk for flash flooding tomorrow. On Thursday, the aforementioned low off the coast of Baja California makes a push inland. The result will be continued showers and thunderstorms across much of northern AZ.

Friday and onward...Ensemble guidance tends to bring a downturn in activity on Friday then more so on Saturday after the wave departs and brief ridging with drier air remain dominant. By early next week there is considerable uncertainty hinging on a pair of tropical systems and a Pacific trough that may form. The current forecast calls for a widespread area of 30-60% PoPs across northern AZ on Monday, however there is a lot of room for this to change.

AVIATION...Tuesday 22/18Z through Wednesday 23/18Z

Primarily VFR conditions are expected through the forecast period. Scattered SHRA/TSRA developing mostly east of a K0V7 (Kayenta) to KINW (Winslow) line after 18Z and persisting through the nighttime hours into Wednesday morning. Isolated pockets of MVFR/IFR possible in +RA. Expect erratic wind gusts up to 30-40 kts possible in/near storms. Outside of storm activity, expect S winds 10-15 kts gusting up to 25 kts through about 02Z before becoming lighter overnight.

OUTLOOK...Wednesday 23/18Z through Friday 25/18Z...Mainly VFR conditions. SCT SHRA/TSRA Wednesday afternoon through Thursday across much of northern and central AZ. Areas of MVFR over higher elevations east of 0V7-KINW-KPAN through Thursday. Localized/brief MVFR and gusty winds possible in/near TS. Daytime winds E/SE 4-8 kts, becoming light and variable overnight.

FIRE WEATHER...This afternoon through Thursday

Scattered shower and thunderstorms will continue mainly across Navajo and Apache counties today. Activity will spread west to include much of northern AZ on Wednesday and Thursday. Stronger storms will bring heavy rainfall and gusty/erratic winds. Outside of storms, winds are south through southwest 10-20 mph gusting to 25 mph today, then variable at 5-15 mph on Wednesday and Thursday.

Friday through Sunday...Slight chances for showers and thunderstorms continues Friday, then mostly dry conditions are possible by Saturday. Rainfall chances may begin to increase early next week, however there is considerable uncertainty at this time. Winds will be southwest 5-15 mph on Friday and Saturday increasing to 10-20 mph on Sunday.

FGZ WATCHES/WARNINGS/ADVISORIES

None.