Area Forecast Discussion
Issued by NWS Flagstaff, AZ
Issued by NWS Flagstaff, AZ
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724 FXUS65 KFGZ 112334 AFDFGZ Area Forecast Discussion National Weather Service Flagstaff AZ 434 PM MST Thu Jul 11 2024 .SYNOPSIS...Hot temperatures will continue through Friday, with a slight cooling trend for the weekend. Moisture will slowly return to the region, with chances for afternoon showers and thunderstorms increasing each day, becoming widespread by the weekend and into early next week. && .DISCUSSION...Anomalously strong high pressure remains positioned over southern NV/UT and northwestern AZ today. This continues to drive our hot summer weather pattern, while keeping monsoon activity limited to the Mogollon Rim and southward so far. Steering flow today is again from the north which will keep the focus of afternoon/evening thunderstorms south of the Rim in Yavapai/Gila counties, where the best moisture and instability reside (on the order of 500-1000 J/kg of CAPE). Some vertical wind shear (20-30 kts) is present across central AZ today and will help lead to a few severe and/or prolonged storms capable of hail, damaging wind and brief heavy rain. Storms will dissipate later this evening and overnight with the loss of daytime heating. The high pressure center begins to slowly drift eastward tonight and Friday, centering closer to the four corners for the upcoming weekend. This will open the door to increasing moisture and thunderstorm chances during this period. The moisture still looks relatively high-based on Friday with the low levels beginning to moisten up and more widespread activity expected for Saturday through Monday. Strong wind gusts will remain a high concern through Friday, transitioning to more of a heavy rain threat over the weekend. In terms of heat, the Excessive Heat Warnings remain in effect for the lower valleys of Yavapai county through tonight and Grand/Glen Canyons through Friday. The additional storm coverage and cloud cover on Friday is expected to limit the heat threat in Yavapai county Friday, but less cloud cover and closer proximity to the high pressure center will keep the heat warnings going for Grand Canyon. There is potential for the Grand Canyon heat warnings to be extended, but confidence is not high enough with the increasing moisture to extend just yet. The moderate monsoon pattern will continue through early next week as the high pressure center makes little movement. However, confidence in the moisture sticking around begins to decrease late next week. Models are suggesting another amplification of the western U.S. ridge parking itself over Nevada, which is a nearly identical pattern to what we`re seeing right now. Under this pattern, it`s likely far northern AZ will see drying with areas south of the Rim continuing to see thunderstorm chances. Hot temperatures are likely to develop again, and we`ll have to watch for additional heat impacts. && .AVIATION...Friday 12/00Z through Saturday 13/00Z...Scattered showers and thunderstorms across Yavapai County will continue to move southwest and weaken, with little to no storm activity across northern Arizona after 02Z. Quiet conditions overnight. Another round of scattered thunderstorms will form after 19Z Friday, with the greatest activity along and southwest of a KSOW- KFLG-KGCN line. Strong wind gusts 40-50 kts, hail, and brief heavy rain possible with stronger storms. Outside of storms, look for winds 5-15 kts varying in direction. OUTLOOK...Saturday 13/00Z through Monday 15/00Z...Shower and thunderstorm activity is forecast to increase in coverage and spread across all of northern AZ on Saturday and Sunday. Brief MVFR conditions possible under stronger storms, otherwise VFR conditions. Outside of thunderstorms, expect prevailing winds generally 10 kts or less. && .FIRE WEATHER...Today through Saturday...Hot temperatures continue through Friday with scattered thunderstorms focused along and south of the Mogollon Rim. Strong outflow winds, hail and brief heavy rain possible in the strong storms. Expect increasing moisture, lower temperatures, and more widespread thunderstorm activity beginning Saturday. Sunday through Tuesday...Seasonable temperatures return along with scattered to widespread showers/thunderstorms. A mixture of wetting rains, hail, and gusty winds are possible. Outside of storm driven winds, expect generally west through southwest winds 5-15 mph. && .FGZ WATCHES/WARNINGS/ADVISORIES... Excessive Heat Warning until 8 PM MST /9 PM MDT/ Friday for AZZ005-006. Excessive Heat Warning until 8 PM MST this evening for AZZ037. && $$ PUBLIC...MCT AVIATION...RR FIRE WEATHER...MCT For Northern Arizona weather information visit weather.gov/flagstaff