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Area Forecast Discussion
Issued by NWS Flagstaff, AZ
Issued by NWS Flagstaff, AZ
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122 FXUS65 KFGZ 111116 AFDFGZ Area Forecast Discussion National Weather Service Flagstaff AZ 416 AM 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...Tranquil weather conditions are taking place across northern Arizona early this morning with little to no wind and near average temperatures. High pressure remains in place over the Great Basin and much of the Southwest for today as it continues to migrate slowly towards the east. Hot temperatures will persist to end the work week, 5-10 degrees above average. Excessive Heat Warnings remain in effect for lower valley/canyon locations below 4000 feet through this evening, however, the end is in sight. As the high pressure system gradually shifts eastward, southerly flow returns allowing an increase in monsoonal moisture advection from the south. Surface to mid-level moisture will continue to increase slowly as a result with good agreement in ensemble guidance suggesting a return to normal PWAT values for this time of year (0.7-1.0") by this weekend. As for this afternoon, both the HREF and HRRR guidances have isolated shower and thunderstorm coverage developing after 1200 MST, continuing through this evening. Much of this afternoon`s development will be confined to locations south of the Mogollon Rim, with greatest chances (25-55%) near Prescott, Payson, and the White Mountains region. Surface moisture should still be lacking this afternoon with widespread minimum humidity of 5-15%. Multiple model soundings from across northern Arizona all show the "inverted-V" signature from the surface up to 400-500 mb, suggesting that any thunderstorms that do form should be high- based. This means that the main threats from storms this afternoon will likely be the potential for dry lightning, gusty outflow winds, and hail. Given that surface winds are forecast to be primarily from the north today, showers and storms should move southward, 10-20 mph. POPs and thunderstorm coverage increases on Friday, becoming widespread for Saturday and Sunday. Activity will likely follow the diurnal pattern each day, with storms developing in the early afternoon over the high terrain, then spreading across northern Arizona through the afternoon and into the evening. Temperatures on Friday are forecast to remain above average, with an Excessive Heat Warning continuing for the Grand Canyon and up to Page, cooling and returning to normal for this weekend across the region. With monsoonal moisture likely to become abundant for this weekend as dewpoints rise to the 50s-60s range, any storms should produce a sufficient amount of rainfall (>0.10"), reducing the threat of dry lightning and new fire starts. With good model agreement in regards to the high pressure system centered over the Four Corners region for Sunday into Monday, another widespread activity day is forecast for Monday afternoon. As we head into the middle of next week, long range models suggest a shift in storm coverage towards the east with greater chances favoring locations along and east of the Mogollon Rim. Since confidence is on the lower side at this time, POPs and QPF have been reduced for much of next week after Monday as the current NBM guidance is a bit high and not quite in line with the GEFS and EPS. However, a persistent drying out and warming period, like the one we have been experiencing this last week, does not look likely for next week at this time. && .AVIATION...Thursday 11/12Z through Friday 12/12Z...Mainly VFR conditions will persist through the TAF period, minus brief periods of MVFR conditions in heavier SHRA/TSRA. Expect greatest potential for showers/thunderstorms along and south of a KP23-KFLG-KRQE line. Outside of gusty/erratic storm driven winds, look for winds 5-15 kts varying in direction. OUTLOOK...Friday 12/12Z through Sunday 14/12Z...VFR conditions will prevail outside of periods of MVFR conditions from SHRA/TSRA. Chances for showers/thunderstorms will increase each afternoon. Outside of gusty/erratic storm driven winds, look for winds 10-20 kts varying in direction. && .FIRE WEATHER...Today and Friday...Hot temperatures continue today, with slightly cooler temperatures on Friday. 15-30% chance of showers/thunderstorms across Yavapai County today, and 30-60% chance across the Rim and White Mountains. Look for increasing coverage for showers/storms on Friday. Expect winds 15 mph or less and varying in direction both afternoons outside of gusty/erratic outflow winds. Saturday through Monday...Seasonable temperatures return along with scattered to widespread showers/thunderstorms. A mixture of wetting rains, small hail, gusty winds, and lightning will be possible each afternoon/evening. 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...LaGuardia AVIATION...Konieczny FIRE WEATHER...Konieczny For Northern Arizona weather information visit weather.gov/flagstaff