textproduct: NWS Flagstaff

SYNOPSIS

Windy and cooler conditions today with an upper- level low approaching from the west. Critical fire weather conditions will continue over portions of northeastern Arizona. Thunderstorm chances continue in northern Coconino County through the early evening. Warmer conditions and lighter winds return over the weekend.

DISCUSSION

A low pressure system currently centered over southern Nevada is visible on mid-level WV satellite imagery. The low is forecast to follow a northeast trajectory and clip northwest Arizona today. The majority of our CWA will stay dry under this regime, however modest instability and dynamics will lead to showers and thunderstorms in northwest Coconino County. Showers and thunderstorms have already begun to fire as of noon MST, and activity will continue through the day before quickly diminishing around 4-6 PM. Gusty outflow winds and lightning look to be the main threats from any stronger storms that develop this afternoon. Anyone planning recreation on Lake Powell this afternoon should pay particular attention, with erratic gusts to 40-50 mph possible near storms.

Away from storms, windy conditions with elevated fire weather concerns are expected today. A Wind Advisory is in effect today for areas along and north/east of the Mogollon Rim, where more widespread SW gusts of 40-50 mph are forecast. Although winds will be strong along the Rim, humidity will remain high enough to limit fire weather concerns. East of the Rim, critical fire weather conditions are still expected to develop. Because of this, a Red Flag Warning will be in effect for the Little Colorado River Valley and Navajo Nation.

The trough departs tomorrow and heights aloft begin to build. Expect several days of lighter winds, mostly clear skies, and warming temperatures through the beginning of next week. Long term ensemble guidance hints that shower and thunderstorm chances will return by the middle of next week as higher PW surges into the area. At this time, showers chances are confined to far eastern AZ beginning Tuesday.

AVIATION...Friday 29/18Z through Saturday 30/18Z

VFR conditions. SHRA/TSRA possible through 01Z along and west of a KGCN-KPGA line, gusty erratic winds possible in and around TS. Winds S/SW 15-25 kts with gusts 30-40 kts through 02Z-03Z, then subsiding to 5-10 kts. Daytime winds Saturday W/SW 5-15 kts.

OUTLOOK...Saturday 30/18Z through Monday 01/18Z...VFR conditions. Daytime winds W/SW 5-15 kts each day, becoming light and VRB for the overnight hours.

FIRE WEATHER...This afternoon through Sunday

Near-critical to critical fire weather through early this evening with a Red Flag Warning for most of northeastern Arizona until 8 PM MST/ 9 PM MDT. Winds south/southwest 15-25 mph with gusts 35-45 mph through early evening, highest gusts across eastern Arizona. Isolated thunderstorms in northern Coconino County through sunset. Dry over the weekend with winds west/southwest 5-15 mph. Minimum afternoon RH 10-20% Saturday, 5-15% Sunday.

Monday through Wednesday...Warmer. Chance of showers and thunderstorms near the White Mountains Tuesday, spreading to the eastern Mogollon Rim by Wednesday, mainly dry elsewhere. Winds west/southwest 5-15 mph. Minimum afternoon RH 5-15% through Tuesday, increasing slightly Wednesday.

FGZ WATCHES/WARNINGS/ADVISORIES

Red Flag Warning until 8 PM MST /9 PM MDT/ this evening for AZZ109>114-139-140.

Wind Advisory until 8 PM MST /9 PM MDT/ this evening for AZZ009>017-039-040.