textproduct: NWS Flagstaff

SYNOPSIS

Gradually warming temperatures and dry conditions are in store through the weekend, along with typical afternoon breezes. On Memorial Day, a passing low will bring chances for high-based showers and thunderstorms to the higher terrain. Windier and cooler conditions look to return by the middle of next week.

DISCUSSION

Tranquil weather conditions are taking place across northern Arizona this afternoon with clear skies and near average temperatures. Humidity remains low, below 15% for most locations, with west-southwest winds at 10 to 25 mph. Typical spring day across the region.

A gradual warming trend continues Friday and Saturday as heights increase and a shortwave ridge tries to develop over the Southwest. By Sunday, temperatures become roughly 5 degrees above average with a slight increase in humidity. Conditions become a bit more unstable as well on Sunday in response to an upper-level low pressure system developing off the California coast. Afternoon southwest winds, 10-20 mph, remain in place through the weekend with slight chances for high-based thunderstorms and/or virga showers to develop over the White Mountains on Sunday.

A bit more weather action is forecast for Memorial Day with increasing cloud cover and scattered showers and hybrid thunderstorms thanks to a passing low pressure trough from the west. Atmospheric conditions cool above resulting in instability, coupled with increasing moisture. Precipitation chances are greatest (30-60%) along the high terrain across northern Arizona for Monday afternoon with the biggest threat of dry lightning and gusty/erratic outflow winds. This could potentially result in new fire starts in regional forests. Even with the increased moisture, model guidance at this time indicates it will not be enough to produce greater coverage of wetting rains (>0.10") as the boundary layer should remain on the drier side.

As we head into Tuesday, temperatures return to near average with drier conditions in place. With the low exiting towards the east and another larger/deeper trough develops over the Intermountain West, southwest winds are forecast to become stronger with widespread gusts of 20-30 mph. With these winds and the potential for dry lightning on Monday, the spreading of any new fire starts is possible. Something to keep in mind as we enter into peak wildfire season for our region.

AVIATION...Friday 22/00Z through Saturday 23/00Z

Expect VFR conditions. Daytime sfc winds SW-W5-15g20-25kts in the afternoon hours, otherwise light.

OUTLOOK...Saturday 23/00Z through Monday 25/00Z...Expect VFR conditions. ISOLD VIRGA showers possible Sunday. Daytime sfc winds SW-W5-15g20-25kts in the afternoon hours, otherwise light.

FIRE WEATHER...Friday and Saturday

Dry conditions along with a gradual warming trend continues. Humidity will also gradually increase each afternoon, however, will remain below 15%. Plan on west-southwest winds, 10 to 20 mph, each day.

Sunday through Tuesday....The warmer and wetter trend persists for Sunday and Monday with chances of precipitation. Anticipate high- based thunderstorms and/or virga showers over the White Mountains on Sunday, with coverage extending across much of the high terrain of northern Arizona on Monday. Look for dry lightning and erratic outflow gusts from any storms each day. Drier conditions return on Tuesday with average temperatures. Outside of any gusty outflow winds from storms, plan on southwest winds, 15 to 20 mph, on Sunday and Monday followed by stronger southwest winds, 20 to 30 mph, on Tuesday.

FGZ WATCHES/WARNINGS/ADVISORIES

None.