textproduct: NWS Flagstaff

SYNOPSIS

Drier and slightly breezy conditions through Thursday, with only isolated-scattered showers and thunderstorms each afternoon and evening. Precipitation chances increase again beginning Friday and into the weekend.

DISCUSSION

A large trough is visible in mid-level WV satellite imagery, with its axis currently extending across northern California. In general this is introducing drier mid-level air through southwesterly flow across northern AZ, and will act to subdue thunderstorm activity over the next few days. However current mesoanalysis reveals that a plume of higher low-level moisture is being wrapped into the flow and spreading northward. A few isolated storms began to fire as of 1 AM MST as this air reached Yavapai and Coconino county. These storms will likely remain very isolated and continue to propagate northeastward through the early morning.

Into the daytime today, activity will likely remain similar to yesterday. PW is forecast to stay the same or fall slightly from yesterday with the continued entrainment of drier air aloft. However with plenty of lingering surface moisture (dewpoints in the 50s) and likely cloud-free morning skies, modest instability will build and allow for isolated thunderstorms. A few stronger thunderstorms will be possible especially towards far northern AZ. Storm motion will be fast, which should help to reduce flash flood risk unless storms train. The west coast troughing will also act to bring breezy southwest winds with gusts up to 30 mph as well as daytime temperatures a few degrees below normal for early September.

By Thursday, the ridge to our east begins to nudge towards us enough to steer moisture into far eastern AZ. Higher coverage of thunderstorms are possible across the White Mountains on Thursday afternoon as a result. Outside of this area, most of northern AZ will remain drier with isolated storms during the day on Thursday. Into Thursday evening, a continued surge of moisture is expected into eastern and central AZ. We may see thunderstorm activity well into Thursday night/Friday morning for these regions, and the current forecast maintains a 30-50% chance of precipitation. By Friday and into the weekend, the surge of moisture is forecast to spread westward. These moisture increases will in part be due to influences from Tropical Storm Marie. Unfortunately, there is uncertainty in the exact track of the tropical system and thus in where the deepest moisture will land. Regardless, an increase in moisture with widespread 30-60% precipitation changes remains in the forecast each day Saturday through Tuesday. The current outlook calls for a stormy holiday weekend, but stay tuned to future forecasts for any updates.

AVIATION...Wednesday 02/12Z through Thursday 03/12Z

Mainly VFR conditions expected. Isolated -SHRA along/west of a KPGA-KFLG line through 15Z, with some clearing after. SHRA/TSRA redevelop along higher terrain again from 18Z-02Z. Gusty/erratic winds possible near storms. Winds are SW 10-20 kts gusting 25-30 kts from 17-03Z, light and VRB or terrain driven otherwise.

OUTLOOK...Thursday 03/12Z through Saturday 05/12Z...VFR conditions expected, with brief MVFR conditions near SHRA/TSRA. Winds are SW 10-20 kts gusting 25-30 kts each afternoon, and light and VRB or terrain driven each night. ISO-SCT SHRA/TSRA each day, with the highest chances along the White Mountains. Storms may continue Thursday evening into Friday morning over the Eastern Mogollon Rim and the White Mountains.

FIRE WEATHER...Wednesday and Thursday

Drier and breezy conditions continue, with mostly isolated shower and thunderstorm chances each the afternoon/evening. Higher coverage of storms are possible over the White Mountains on Thursday afternoon. Winds are southwest 10-20 mph with gusts up to 25-30 mph, strongest in northwest AZ. Daytime highs slightly below normal. Minimum RH is 30-50% each day.

Friday through Sunday...Increasing moisture will cause shower and thunderstorm coverage to increase Friday through Sunday. Best chances will be seen near the White Mountains each day, with elevated potentials along other areas of higher terrain. Winds during the day will be southwest 10-20 mph with gusts to 30 mph on Friday, then south through southwest 5-15 mph Saturday and Sunday. Light and variable or terrain driven winds overnight.

FGZ WATCHES/WARNINGS/ADVISORIES

None.