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

Strong high pressure centered near El Paso will persist through Thursday, bringing above normal temperatures that should peak today before dropping slightly Wed/Thu due to some moisture moving in. This moisture is moving up from the south and has already started to enter our region this afternoon, with some isolated high-based convection developing into this evening, primarily along and north of the Mogollon Rim. This activity should only produce spotty light rain amounts, but gusty winds are likely with any showers or storms. Very hot temperatures continue this afternoon at the lower elevations of the Grand Canyon where an Extreme Heat Warning continues through 7 PM MST. Temperatures at the bottom of the canyon will reach near 112F, hiking at the lower parts of the canyon is dangerous and discouraged in this heat. By Wednesday and Thursday, moisture values increase a bit more, with mean precipitable water values reaching 0.80" to 1.00" area wide which is well above normal for this time of year. Isolated to scattered showers and thunderstorms are forecast each afternoon and evening, with PoPs up to 30-50% mostly along/north of the Mogollon Rim. Gusty winds and a few lightning fire starts will be the main threats with storms Wed/Thu, with mostly light rainfall amounts. Any heavier downpours will be very spotty as the activity will be moving quickly toward the northeast.

Friday through Sunday - strong low pressure for this time of year is forecast to drop down into the northwest United States. This is likely to bring windy conditions along with a drying trend, leading to a high chance of critical fire weather conditions over nearly all of northern Arizona. Combined with a potential for some new lightning-caused fire starts the preceding few days, this fire weather pattern is concerning. In our latest forecasts, southwest wind gusts of 30-40 mph are expected Friday afternoon, increasing to 40-55 mph Saturday and then 35-45 mph Sunday. A Fire Weather Watch has been issued for all of northern Arizona from Friday through Sunday. Daytime temperatures will be decreasing as this trough moves into the western US and pushes the ridge well to the south. Highs over the weekend should drop to near or even a bit below normal. The main trough is forecast to shift eastward by Monday, with a bit lower wind speeds. Near-critical fire weather may persist into Monday.

AVIATION...Wednesday 24/06Z through Thursday 25/06Z

Mainly VFR conditions. ISO SHRA through 15Z, mainly along and north of a KGCN-KRQE line through 14Z. SCT SHRA/TSRA return after 18Z-20Z. Light and variable winds overnight, increasing to SW-W 10-15 kts gusting 25-30 kts after 18Z. Gusty, erratic outflow winds possible in and around TS.

OUTLOOK...Thursday 25/06Z through Saturday 27/06Z...Mainly VFR conditions. SCT SHRA/TSRA Thursday afternoon and evening, mainly along and north of a KPRC-KJTC line, becoming ISO SHRA/TSRA on Friday, mainly along and east of a 0V7-KJTC line. Daytime winds SW 10-20 kts with gusts to 30 kts on Thursday, increasing to 15-25 kts with gusts to 35 kts on Friday. Expect light and variable winds 5-10 kts overnight. Gusty, erratic outflow winds possible in and around TS.

FIRE WEATHER...Wednesday and Thursday

A chance for afternoon thunderstorms are expected each day, primarily along and north of the Mogollon Rim. Winds SW 10-20 mph each day. Minimum afternoon RH values 15-25% each afternoon.

Friday through Sunday...A Fire Weather Watch has been issued from Friday AM to Sunday PM for all northern Arizona fire zones. Critical fire weather conditions are expected all weekend as drier and breezier conditions set in. Winds SW 20-25 mph, gusts 35-40 mph on Friday, SW 20-30 mph, gusts 45-50 mph on Saturday, SW 15-30 mph, gusts to 40 mph on Sunday. Minimum afternoon RH each day ranges from 5% in the high deserts of northeastern Arizona to near 20% in areas along the Mogollon Rim and White Mountains.

FGZ WATCHES/WARNINGS/ADVISORIES

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