textproduct: NWS Flagstaff

SYNOPSIS

Showers and thunderstorms will gradually diminish across eastern AZ this morning, then isolated activity will return on Friday afternoon. Dry weather is expected Saturday before rain chances trend upward early next week.

DISCUSSION

A trough is currently centered over AZ visible in mid-level water vapor satellite imagery. Large scale lift associated with this feature is bringing areas of showers and thunderstorms this morning, primarily across northern Gila and southern Navajo/Apache counties. A few stronger thunderstorms bringing small hail and heavy rainfall have been observed and will remain a possibility over the next few hours. Showers are forecast to continue through the rest of the morning while gradually diminishing and drifting eastward. The trough axis looks to move past AZ by this afternoon. Subsidence and a drier westerly flow will follow in its wake, but enough moisture will remain for lingering isolated showers and thunderstorms during the daytime today. By Saturday, a much drier and capped airmass will drop precipitation chances to near zero.

We may see an active stretch of weather to begin next week. A deep Pacific trough is forecast to dive southeastward along the coast of CA on Sunday-Monday, then move across our region on Tuesday. A pair of tropical systems (Hurricane Polo and Tropical Storm Odalys) will likely enhance any moisture surge associated with the trough. There is potential for impactful rainfall, and the current Excessive Rainfall Outlook from WPC puts all of Northern AZ in the Slight risk category by Monday. However plenty of uncertainty still remains among ensemble guidance, and will hinge on the exact timing and trajectory of the features. For example, LREF clusters highlight a lower end precipitation scenario where the trough follows a more progressive and northern trajectory, and a higher end scenario where the trough is deeper and slowly moves across northern AZ. Nevertheless, virtually all guidance has somme precipitation returning through the period. The current forecast has slight chances for shower and thunderstorm activity as early as Sunday as a weaker shortwave propagates ahead of the deep trough, then widespread precipitation chances by Monday-Tuesday. There is room for the details to change, so we encourage you to check back in future forecast periods!

Besides precipitation, expect breezy south-southwest winds and cooler temperatures early next week. Much drier conditions, warming temperatures, and lighter winds are forecast to return by midweek into the weekend.

AVIATION...Friday 25/12Z through Saturday 26/12Z

Mainly VFR. Areas of SHRA/TSRA continue this morning, mainly south of a KINW- KRQE line. ISOLD activity over the higher terrain possible again from 19Z-02Z. Brief MVFR conditions and gusty winds possible in and around TS. Winds VRB 5-10 kts, becoming S-W after 18Z.

OUTLOOK...Saturday 26/12Z through Monday 28/12Z...VFR conditions through 18Z Sunday, with MVFR possible in SCT-NMRS SHRA/TSRA thereafter. Daytime winds S 5-15 kts on Saturday, then S-SW 10-20 kts on Sunday.

FIRE WEATHER...Today through Saturday

Isolated showers and thunderstorms are expected today, mostly along the higher terrain. Things will dry out for Saturday with no precipitation expected. Outside of storms, winds will be SW 5-10 mph on Friday, S-SW 5-15 mph on Saturday.

Sunday through Tuesday...Slight chances for showers and thunderstorms on Sunday, becoming widespread by Monday afternoon. Precipitation chances beginning to decline from west to east by Tuesday afternoon. There is considerable uncertainty in this portion of the forecast, but there is some potential for heavy rainfall with flash flooding on Monday-Tuesday. Besides rain, expect cooler temperatures with breezy winds. Winds S-SW 10-20 mph on Sunday and Monday, shifting NW-N 10-20 mph on Tuesday.

FGZ WATCHES/WARNINGS/ADVISORIES

None.