Area Forecast Discussion
Issued by NWS Flagstaff, AZ
Issued by NWS Flagstaff, AZ
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778 FXUS65 KFGZ 201128 AFDFGZ Area Forecast Discussion National Weather Service Flagstaff AZ 428 AM MST Thu Jun 20 2024 .SYNOPSIS...Daily chances for showers and thunderstorms are forecast through the weekend and into early next week, along with warming temperatures. && .DISCUSSION...Today...A large area of high pressure sits over the eastern-half of the United States, with a trough situated over much of the west. Meanwhile, Tropical Storm Alberto is approaching the eastern coast of Texas and Mexico. As Alberto moves across Mexico, the trough over the west begins to lift northward and the ridge begins to retrograde. As a a result, a surge of sub-tropical moisture is initiated into Arizona. Surface dewpoints have already begun to rise into the 50s F and 60s F across much of New Mexico and into far eastern Arizona, as the moisture begins to inch closer to Arizona. PWATs look to rise to around 0.75-1.00 inches over Arizona by this afternoon, well above the 90th percentile for this point in the year. 00Z HREF guidances shows strong support for destabilization later this afternoon, with 700-1200 J/Kg of surface-based CAPE. 0-6km shear is a bit on the lower-end but with the influence of the trough, areas across northern Arizona could potentially see a few stronger thunderstorms with 25-35 kts of shear. Latest CAM guidance has the bulk of the activity this afternoon north of a Grand Canyon to St. Johns line, with lesser coverage along the Mogollon Rim as well. The greatest threat from this storms will be gusty outflow winds, brief heavy downpours, and small hail. However, a couple strong to severe thunderstorms can not be ruled out. Friday...The greatest moisture looks to move in on Friday, with PWAT values of around an inch for much of northern Arizona to upwards of 1.2 inches in the Lower Deserts. Even with the increased moisture, coverage still looks best over northern and eastern Arizona during the afternoon on Friday, and to a lesser extent over central Arizona. HREF and CAM guidance does show an increase in 0-6 km shear as the trough lifts northward. Thus, the threat for a couple of stronger thunderstorms remains. Localized flash flooding will also remain a possibility through the Four Corners region given the amount of moisture available, however storm motions of 20-25 kts may limit the residency time of any one storm. Saturday into Next Week...By the weekend the ridge has shifted full into New Mexico, moisture remains in place, keeping daily chances for showers and thunderstorms in the forecast. However, as the heights continue to rise with the ridge building into the Southwest, temperatures begin to warm once again for the start of next week. Coverage and intensity of showers and thunderstorms may begin to wain into next week as subsidence increases aloft. && .AVIATION...Thursday 20/12Z through Friday 21/12Z...Mainly VFR with periods of MVFR after 18Z due to SHRA/TSRA. Greatest chances for showers/thunderstorms will be along and east of a KPGA-KPAN line. S-SW winds 15-25 kts with gusts 30-40 kts. Gusty and erratic winds in the vicinity of thunderstorms. OUTLOOK...Friday 21/12Z through Sunday 23/12Z...Mainly VFR with periods of MVFR in SHRA/TSRA. S-SW winds 10-20 kts on Friday, becoming lighter on Saturday. Gusty and erratic winds in the vicinity of thunderstorms. && .FIRE WEATHER...Today and Friday...Increasing chances for showers/thunderstorms from east to west today and Friday. South to southwest winds 15-25 mph, with gusty and erratic winds in the vicinity of storms. Increasing RH values from 15-30% today to 30-50% on Friday. Saturday through Monday...Chances for showers and thunderstorms each day. South to southwest winds around 5 to 10 mph Saturday and Sunday becoming more westerly at 5 to 15 mph Monday. Gusty and erratic winds possible in the vicinity of storms. Decreasing moisture will result in lower RH values, generally between 20-30%. && .FGZ WATCHES/WARNINGS/ADVISORIES...None. && $$ PUBLIC...Humphreys AVIATION...Meola FIRE WEATHER...Meola For Northern Arizona weather information visit weather.gov/flagstaff