textproduct: NWS Flagstaff

SYNOPSIS

Increasing moisture will bring scattered showers and thunderstorms today with more isolated coverage on Friday. Dry weather is expected Saturday and much of Sunday before rain chances may increase again early next week.

DISCUSSION

At 230 AM, there are a few showers and thunderstorms over central Yavapai County from around Prescott to Crown King, otherwise dry conditions are being observed. There is a distinct area of low pressure over northern Mexico this morning, and this feature will drift northward into southern Arizona through the day. With well above average moisture remaining over our area, we expect another round of scattered showers and thunderstorms this afternoon and early evening, with the highest coverage (30-50%) along and south of the Mogollon Rim/White Mtns and 10-30% to the north. With the upper level feature approaching, there is a chance that storm activity continues later into the night especially along/east of the low. This is generally east of the I-17/US89 corridor. With slow storm motion and plenty of available moisture, the main threat with today's activity will be locally heavy rainfall and flash flooding. By Friday, the upper low moves northeast of our area with a drier westerly flow behind it. This will bring a decrease in storm activity, with isolated to scattered showers/storms over the eastern half of the state. Saturday is looking storm free at this time as even drier air moves in from the west.

Sunday through Monday - a trough developing along the west coast is forecast to move eastward across our region. Moisture associated with two tropical cyclones (Hurricane Polo forecast to be off the southern Baja at this time and TS Odalys much farther west) will be pulled northeastward into the southwest United States in advance of this trough. There is still plenty of model spread regarding the depth/speed of the developing trough as well as the location of the deepest moisture plume from the south. Although shower and thunderstorm chances will increase quickly by late Sunday through Monday, it's still too early to tell how heavy the rainfall might be and where the heaviest rain will be placed. The timing of the trough combining with the moisture would need to line up just right for this to happen, but it's not out of the question. Around 10-20% of the ensembles from the latest 00Z runs show a heavy rain signal (1-2"+) for our area, though a large majority show at least some rainfall. We'll need to wait a couple more days to get a better handle on this so stay tuned. Rain chances could linger into Tuesday depending on the timing of the trough, then dry weather looks to return by mid week.

AVIATION...Thursday 24/18Z through Friday 25/18Z

Mainly VFR conditions, brief MVFR near heavier thunderstorms. Scattered to numerous showers and thunderstorms develop between 18-21Z and last through 03Z-05Z. Another wave of showers and thunderstorms may move in overnight after 06Z across the area mainly south of Interstate 40. Winds NE-SE 5-10 kts daytime, light and variable or terrain driven overnight. Gusty and erratic winds possible in the vicinity of thunderstorms.

OUTLOOK...Friday 25/18Z through Sunday 27/18Z...Mainly VFR conditions, brief MVFR near heavier thunderstorms. Isolated to scattered showers and thunderstorms develop between 18Z Friday to 03Z Saturday. After 03Z Saturday things dry out. Winds S-W 5-15kts daytime each day, light and variable or terrain driven overnight.

FIRE WEATHER...Today through Friday

Scattered showers and thunderstorms are expected across northern and central Arizona today. Stronger storms will bring heavy rainfall and gusty/erratic winds. Drier air moves in on Friday for only a slight chance of showers and storms for most of the area. The best chances on Friday will be confined to the mountains of far eastern Arizona. Outside of storms, winds will be variable at 5-15 mph.

Saturday through Monday...Expect fair and dry weather on Saturday. Shower and thunderstorm chances look to increase on Sunday and Monday but considerable uncertainty remains in this portion of the forecast. Winds will be southwest 5-15 mph on Saturday increasing to 10-20 mph on Sunday and Monday.

FGZ WATCHES/WARNINGS/ADVISORIES

None.