918 FXUS65 KFGZ 071612 AFDFGZ Area Forecast Discussion National Weather Service Flagstaff AZ 912 AM MST Mon Sep 7 2020 .SYNOPSIS...Dangerous conditions due to heat exposure are likely in the lower elevations today with an Excessive Heat Warning remaining in effect. Starting Tuesday, an unseasonably strong weather system will deliver windy, cooler and unsettled weather to northern Arizona, lasting through at least Thursday. Possible warming again by the coming weekend. && .DISCUSSION...We will endure one more day of hot weather before a strong cold front brings much cooler weather to the area. The Excessive Heat Warning for our lower elevations remains in effect through early this evening and no changes are needed to that product. Visible satellite this morning shows a deck of altocumulus clouds over north-central Arizona along with a large area of lofted smoke across California, Nevada, Utah, and Colorado. This smoke will continue to drift toward the southeast today with hazy skies likely across much of northern Arizona. Based on the latest hi-res guidance, an isolated high-based shower cannot be ruled out along the Mogollon Rim southeast of Flagstaff this afternoon. A strong trough and associated cold front are still on track to impact the region Tuesday-Thursday. Latest model guidance remains in line with the previous forecast of much cooler temperatures and chances for thunderstorms from Flagstaff eastward on Tuesday. High pressure looks to return over the upcoming weekend with warming temperatures. However, this high will not be nearly as strong as we have seen over the past several days. Only minor changes were made to the short-term forecast this morning. && .PREV DISCUSSION /332 AM MST/...High pressure was in the process of shifting to the northwest in response to a trough diving out of Canada. Just one more day of blazing heat under the influence high pressure with daytime temperatures ranging from 10 to 20 degrees above normal. A few record high temperatures are likely again this afternoon. For elevations below 4000 feet within the Grand Canyon and the desert areas of central Arizona, temperatures will range from 105 to 113 degrees thus an Excessive Heat Warning remains in effect. Take extra precautions and avoid outdoor activities and recreation during the hottest part of the day. Locations throughout Navajo Nation are expected to have lofted smoke today which will create a hazy skyline, especially in locations which are north of Interstate 40 and east of US Highway 89. The smoke will primarily be from California and Colorado wildfires that is being transported around the high pressure. For Tuesday through Thursday...An unseasonably strong trough and associated cold front will dive southward across the Rocky Mountains on Tuesday. The result will be much cooler temperatures and gusty winds across northern Arizona starting Tuesday, lasting through at least Thursday. Daytime high temperatures will drop by 15 to 25 degrees on Tuesday and Wednesday, warming a bit by Thursday. Considering the recent hot and dry conditions the gusty winds on Tuesday will raise some fire weather concerns but probably not to the level of a Red Flag Warning. Later on Tuesday as the cold front plows into richer moisture located across east- central Arizona there will be a good chance of showers and thunderstorms. The extent of the precipitation band will be from about Flagstaff eastward with the heaviest showers along and southeast of a line extending from the Four Corners to Payson. There will be enough instability and vertical wind shear for a few severe thunderstorms. We will know better on Tuesday the extent of this threat. In addition, cold morning lows are on the way, likely below freezing, at many locations at elevations above 6500 feet. Currently the focus for any freezing temperatures looks to be Wednesday and Thursday mornings. Snow showers over the highest mountain peaks will be possible along and behind the cold front. From Friday onward...High pressure (nothing like what we just experienced) makes it's return with a warming trend through the coming weekend. There will be enough moisture for a slight chance of showers and thunderstorms over the White Mountains region. && .AVIATION...For the 18Z package...VFR conditions are expected through the TAF period, though a 5-15% chance of showers may develop along the higher terrain between KFLG and KSOW today. Winds will increase into Tuesday morning, especially along and north of the high terrain in favored downslope areas. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Hot and dry weather will continue today. A strong cold front will bring cooler temperatures and gusty winds Tuesday with near critical fire weather conditions for northern and western zones. A slight chance of showers and thunderstorm is possible east of Flagstaff. Wednesday through Friday...Cool and dry conditions are expected Wednesday and Thursday. Friday begins a warming trend as another high pressure system builds in over the region. && .FGZ WATCHES/WARNINGS/ADVISORIES...Excessive Heat Warning until 8 PM MST this evening FOR AZZ006- 018-037. && $$ PUBLIC...TPS/McCollum AVIATION...KD FIRE WEATHER...KD For Northern Arizona weather information visit weather.gov/flagstaff