FXUS65 KFGZ 191048 AFDFGZ Area Forecast Discussion National Weather Service Flagstaff AZ 348 AM MST Tue Aug 19 2025 .SYNOPSIS...Isolated showers and thunderstorms will be possible this afternoon over eastern Arizona, with hot and dry conditions expected elsewhere. Monsoonal moisture looks to increase over the coming days, with scattered to widespread storms developing by weeks end. Otherwise, hot temperatures and light winds look to prevail. && .DISCUSSION...Today...Hot and mainly dry conditions and expected today across northern Arizona as a strong area of high pressure begins to build into the Four Corners region. Given the more favorable position of the high, moisture does look to gradually increase starting today. However, much of the activity will looks to be limited to the eastern portions of Arizona and potentially extended up the Mogollon Rim. Even so, given the 596-598 dam ridge, strong subsidence aloft will act to suppress any storms that do develop, thus mainly isolated activity is expected at best. Wednesday and Thursday...Heights continue to rise as the ridge continues to strengthen over Four Corners. As a result, high temperatures look to remain hot for most of the area, with highs around 5-10F above normal for this time of year. An Extreme Heat Warning remain through Wednesday for the lower elevations of the Grand Canyon, with a watch then following. Additional headlines may be need for some of the lower elevations of Yavapai for Thursday, but to what extent increased moisture (and thus increased cloud cover) may affect the temperatures is still not certain. While monsoonal moisture does look to continue to increase, the strength of the high looks to continue to be the limiting factor. Model soundings do some to indicate a slightly weaker cap by Thursday as the ridge starts to weaken and begin to retrograde. However, some uncertainty still remains here. Additionally, decaying storms over northern Mexico may become a favor in leading to increased storm chances. As of now, coverage looks to be mainly focused over the higher terrain with some isolated storms potentially moving into the lower elevations in the late afternoon and evening hours. Friday through Monday...As heights begin to fall with the weakening ridge, the odds for showers and thunderstorms look to increase by the end of the week and into next week. Ensemble guidance from the EPS, GEFS, and CMCE all continue to signal a notable increase in PWATs through the weekend. Thus, a period of active monsoonal activity, with a threat for flash flooding, looks probable. && .AVIATION...Tuesday 19/12Z through Wednesday 20/12Z...VFR conditions with VRB winds 5-10 kts. ISO -SHRA/-TSRA possible east of a KPAN-KINW-KRQE line from 02Z to 07Z. Gusty outflow winds possible in and around TS. OUTLOOK...Wednesday 20/12Z through Friday 22/12Z...Mainly VFR conditions with VRB winds 5-10 kts each day. ISO-SCT SHRA/TSRA possible each afternoon/evening, mainly over the higher terrain. Brief MVFR conditions and gusty outflow winds possible in and around TS. && .FIRE WEATHER...Today and Wednesday...Hot and mainly dry conditions continue. Isolated showers and thunderstorms today, mainly across eastern Arizona then spreading further westward on Wednesday. Winds generally variable 5-10 mph. Gusty and erratic winds possible in and around thunderstorms. Minimum afternoon RH values 10-30%, highest across the White Mountains. Thursday through Saturday...Chances for showers and thunderstorms increase each day, with wetting rain possible by the weekend. Winds will primarily be variable 5-10 mph. Gusty and erratic winds possible in and around thunderstorms. Minimum afternoon RH values 10- 30%, highest values across the White Mountains and Mogollon Rim. && .FGZWATCHES/WARNINGS/ADVISORIES... Extreme Heat Warning from 10 AM this morning to 8 PM MST Wednesday for AZZ006. Extreme Heat Watch from Wednesday evening through Friday evening for AZZ006. && $$ PUBLIC...Humphreys AVIATION...Humphreys FIRE WEATHER...Humphreys For Northern Arizona weather information visit weather.gov/flagstaff