Area Forecast Discussion
Issued by NWS Flagstaff, AZ
Issued by NWS Flagstaff, AZ
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810 FXUS65 KFGZ 161642 AFDFGZ Area Forecast Discussion National Weather Service Flagstaff AZ 942 AM MST Mon Sep 16 2024 .SYNOPSIS...Gusty winds area wide, and chances for showers and thunderstorms across the eastern half of the state will continue through tonight. Mostly dry, cool, and breezy weather then returns on Tuesday through much of the week. && .UPDATE...A sharp dividing line between a very dry air mass and deeper moisture lies near the I-17/US89 corridor at 8 AM. Surface dewpoints to the east of this line are in the 50s and low 60s, while west of the line readings in the 20s and 30s are common. Showers and a few thunderstorms continued overnight southeast of a Payson to Window Rock line, with some moderate rainfall amounts measured in the White Mtns region (just over 0.50" in Pinetop- Lakeside to nearly an inch on the southern slopes of the mountains). We`re in a lull of activity currently, but with the approach of the upper low and some meager daytime heating we expect some additional shower and thunderstorm development east of the I-17/US89 corridor later this morning through early evening, then confined mainly east of Payson-Window Rock overnight through around sunrise Tuesday. The other story today in the gusty southwest winds, expected to gust 40-50 mph for much of northern Arizona. A Wind Advisory goes into effect at 10 AM MST and continues through 7 PM. && .PREV DISCUSSION /450 AM MST/...Today...A trough sits over northern California and will gradually rotate it`s way through the Great Basin today. While upper-level dynamics will increase with the trough, the anticipated moisture surge has been fairly underwhelming, with moisture largely limited to the eastern portions of the state. For most everywhere else, the main impacts from this system will be gusty southwest winds this afternoon. Gusty winds of 35-45 kts look likely across much of the higher terrain, especially where deeper mixing occurs. Areas downwind of the Mogollon Rim into the Little Colorado River Valley could see strong gusts upwards of 45-50 kts. Guidance does suggest that winds could remain somewhat elevated overnight, especially downwind of the terrain, however to what extent remains uncertain as soundings suggest that most locations should decouple overnight. Currently, storms have fired over southeastern Arizona, and should continue to move northeastward and increase in coverage. Latest hi- res guidance continues to keep most of the activity over Navajo and Apache counties, with some isolated activity potentially making it as far west as the I-17/US-89 corridor. A couple of strong to maybe severe storms can`t be fully ruled out, but widespread severe weather is not anticipated. Additionally, given storm motions of around 30-40 kts and PWATs of 0.80-1.00 inches, widespread flash flooding is not anticipated. The only exception would be areas of training storms or any very flood sensitive areas Tuesday and Wednesday...Drier, and colder air sets in for Tuesday with afternoon high temperatures nearly 10 degrees below normal for this time of year. The coldest temperatures look to occur overnight Tuesday into Wednesday morning, with some much of the High Country dipping into the 30s F and even into the upper 20s F in the typically colder locations. A couple of isolated showers can`t be fully ruled out early in the day as the last of the moisture and upward motion moves out of Arizona. Otherwise, the vast majority of the area will remain dry and breezy through Wednesday. Thursday through Sunday...Unsettled weather continues into the end of the week as another trough digs southward along the California Coast on Thursday. As the trough ejects off the Pacific, it moves across the lower Great Basin, keeping the system fairly moisture starved. As a result, mainly isolated coverage of showers are expected. However, there is a slight signal towards an attempt to advect some moisture northward from the Gulf, but this looks limited. Dry conditions look to return for the weekend as the trough moves into eastward. Temperatures will continue to be cool through much of the period with the influence of the trough, along with breezy winds. After the trough, temperatures look to try to rebound with near-normal afternoon highs by the afternoon. && .AVIATION...Monday 16/18Z through Tuesday 17/18Z...Isolated to scattered SHRA/TSRA are forecast to persist east of a KPAN-KFLG- KOV7 line through around 02Z, then confined east of a KPAN-KRQE line through around 15Z Tuesday morning. MVFR conditions and hail are possible with any stronger storms that develop. Outside of storms, expect southwest increasing to 15-25 kts with gusts 30-40 kts. Wind speeds decreasing after 02Z but remaining elevated at 10-20 kts overnight. There is a chance that some localized MVFR cigs will develop over high terrain areas including KGCN/KFLG between 06Z and 15Z Tuesday. OUTLOOK...Tuesday 17/18Z through Thursday 19/18Z...VFR conditions with dry weather expected area-wide. Southwest winds 15-25 kts gusting 25-35 kts Tuesday, decreasing to southwest at 10-20 kts gusting 20-30 kts on Wednesday. && .FIRE WEATHER...Today through Tuesday...Scattered showers and thunderstorms are in the forecast through Tuesday morning, mainly east of a Payson to Page line. Drier weather will arrive later on Tuesday. South to southwest winds at 15 to 25 mph with gusts of 30 to 45 mph will develop by this afternoon, decreasing to 10 to 20 mph with gusts of 25 to 35 mph on Tuesday. Daytime temperatures cooling by 5 to 10 degrees compared to the weekend. Wednesday through Friday...Remaining cool, breezy and mostly dry. Another low pressure system could bring a few showers to northwest Arizona on Thursday. Look for southwest winds at 10 to 20 mph gusting 30 mph on Wednesday and Thursday, then becoming west to northwest at 10 to 20 mph for Friday. && .FGZ WATCHES/WARNINGS/ADVISORIES... Wind Advisory until 7 PM MST /8 PM MDT/ this evening for AZZ004>009-012-013-015-016-038>040. && $$ PUBLIC...JJ/Humphreys AVIATION...JJ FIRE WEATHER...McCollum For Northern Arizona weather information visit weather.gov/flagstaff