textproduct: NWS Flagstaff

SYNOPSIS

Hot temperatures continue through much of the week, along with increasing chances for showers and thunderstorms over the higher terrain through Thursday. Drier and much windier conditions return by Friday and the weekend, with critical fire weather conditions expected.

DISCUSSION...Today and Thursday

A ridge of high pressure over southern New Mexico continues to pump sub-tropical moisture northward into Arizona today. As a result, scattered showers and thunderstorms are expected to develop across portions of northern Arizona today and on Thursday.

An outflow boundary moving out of the Lower Deserts on the initial push of moisture has resulted in mid-level cloud cover and a few showers this morning. Much of this activity is expected to be minimal, and mainly concentrated across western Arizona. These showers will gradually diminish through the morning as they move northward with the surge of moisture. Storms look to then redevelop later this afternoon along the Mogollon Rim, exactly where will depend upon where the boundary sets up between areas that do destabilize this morning and those that are still under debris clouds. As the morning cloud cover moves northward through the early afternoon, coverage of storms will also spread as surface heating increases.

While much of the storm activity looks to diminish with the loss of daytime heating, a few isolated showers and thunderstorms look to remain into the late evening and overnight. Latest UofA WRF runs support this, with the greatest chances mainly from Flagstaff, north and east. Another round of storms looks to then develop on Thursday afternoon, again primarily along and north of the Mogollon Rim. However, morning debris clouds could potentially limit the overall coverage.

While mid-level moisture has increased, a still very dry surface layer will limit the overall rainfall amounts of any one storm. However, any more persistent storm may saturation the sub-cloud layer enough for some brief heavy downpours but not enough for an elevated flash flood risk. Regardless, the main threats with these storms will primarily be gusty outflow winds and dry lightning.

Friday through Tuesday...A strong trough looks to approach Arizona by the weekend. Slighty cooler, but winder conditions look to ensue over much of the region as a result. Moisture is quickly suppressed back to the south as soon as Friday, with only a few isolated storms possible near the White Mountains on Friday before turning dry through the weekend.

Gusty winds look to set in by Friday and continue through the weekend. As of now Saturday looks to be the windiest day, with gusts upwards of 40 to 50 mph possible. Given that afternoon relative humidity for much of the region is expected to be in the 10-15% range, critical fire weather conditions look to return. Combined with the potential for a few new lightning-caused fire starts from the preceding few days, this fire weather pattern is concerning. For this reason, a Fire Weather Watch remains for Friday into the weekend.

As the trough begins to lift early next week, lighter but still breezy winds look to set in. Temperatures also look to begin to climb once again.

AVIATION...Wednesday 24/12Z through Thursday 25/12Z

Mainly VFR. SCT -SHRA/TSRA expected 19Z to 03Z, mainly north of a KPRC-KPAN- KJTC line. Additional ISO -SHRA possible thereafter. Gusty outflow winds possible in and around TS. Winds VRB 5-10 kts, becoming W/SW 10-20 kts 18Z to 03Z.

OUTLOOK...Thursday 25/12Z through Saturday 27/12Z...Mainly VFR. SCT -SHRA/TSRA expected 19Z Thu to 03Z Fri over the higher terrain. Gusty outflow winds possible in and around TS. Winds SW 10-20 kts with gusts 25-30 kts on Thursday, increasing to 15-25 kts with gusts 30-40 kts on Friday.

FIRE WEATHER...Today and Thursday

Chance for high-based showers and thunderstorms each day, mainly from the Mogollon Rim and north. Winds southwest 10-20 mph, gusting 25-30 mph, and minimum afternoon RH 15-25% each day.

Friday through Sunday...Critical fire weather conditions expected across all of northern Arizona with drier and windier conditions. Winds southwest 15-25 mph with gusts 30-40 mph on Friday, increasing to 20-30 mph with gusts 40-50 mph on Saturday, subsiding slightly on Sunday to 15-25 mph with gusts 30-40 mph. Minimum afternoon RH 8-16% each day.

FGZ WATCHES/WARNINGS/ADVISORIES

Fire Weather Watch from Friday morning through Sunday evening for AZZ104>118-137>140.