Area Forecast Discussion
Issued by NWS Flagstaff, AZ
Issued by NWS Flagstaff, AZ
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115 FXUS65 KFGZ 170850 AFDFGZ Area Forecast Discussion National Weather Service Flagstaff AZ 150 AM MST Tue Sep 17 2024 .SYNOPSIS...Showers and thunderstorms will continue over eastern Arizona through the early afternoon. Below normal temperatures and breezy conditions continue through the rest of the week. Mostly dry conditions are also expected, with only a slight chance of showers late Thursday and Friday over far northern Arizona. && .DISCUSSION...this morning...Current meso analysis early this morning shows a pocket of instability over Apache and Navajo counties this morning, with around 500-1000 J/Kg of MUCAPE. A sharp moisture gradient is also in place across central Arizona, with dewpoints in the upper 20s F to mid 30s F near and west of the I-17/US-89 corridor and upper 40s F to mid 50s F to the east. Given this, the precipitation chances for the overnight and into the morning hours will largely be limited to Apache and Navajo counties. As the trough axis approaches, upward motion will increase over the area which should lead to storms developing over eastern Arizona this morning. While much of this activity should be minimal, the added upper-level dynamics could lead to a few stronger (and potentially severe) storms around day break, however widespread severe weather is not expected. This afternoon through Wednesday...Mainly dry, cool, and breezy conditions are expected today as the trough axis sweeps through Arizona and departs to the east. A couple of isolated showers can not be entirely ruled over the Chuska and White Mountains this afternoon, but the vast majority of the area will remain dry. Afternoon highs today are expected to be around 8 to 14 degrees F below normal for this time of year. Overnight lows will similarly be below normal, with near-freezing to event some sub-freezing temperatures expected across the High Country. Thursday and Friday...A second trough drops southward on Thursday, and ejects off the Pacific into southern California. While the system will move into Arizona with favorable dynamics and flow, the system overall looks to be moisture starved. There is some uncertainty into exactly how much moisture can be advected northward as the trough moves through, and this will play a critical role in determining the impacts from this system. A drier, solution will result in another mainly wind event. If sufficient moisture can be advected northward, there will be the possibility for showers and thunderstorms to develop over Arizona, along with a non-zero chance for a few strong to severe thunderstorms. Current ensemble guidance favors the drier solution, but time will tell as model solutions evolve. Regardless of the moisture, below normal and breezy conditions will continue through Friday. Saturday through Monday...Heights rise behind the trough as an upper- level ridge builds over the southwest. Dry conditions, lighter winds, and more seasonable temperatures look to return for the weekend and start of next week as a result. && .AVIATION...Tuesday 17/06Z through Wednesday 18/06Z...Isolated to scattered SHRA/TSRA are forecast to persist across portions of Navajo and Apache counties through around 15Z. MVFR conditions and hail are possible with any stronger storms that develop. In addition, there is a 30%-50% chance that some localized MVFR cigs will develop over high terrain areas including KGCN/KFLG between 06Z and 15Z. Breezy overnight winds will increase in speed after 15Z, becoming southwest 15-25 kts gusting 25-35 kts through 02Z Wednesday. OUTLOOK...Wednesday 18/06Z through Friday 20/06Z...VFR conditions expected. On Wednesday and Thursday, southwest winds at 10-20 kts gusting 20-30 kts. A few showers are possible in northwest Arizona late Thursday. && .FIRE WEATHER...Today through Wednesday...Scattered showers and thunderstorms are expected through this morning, mainly east of a Payson to Four Corners line. Dry weather will arrive by this afternoon. Today look for south to southwest winds at 10 to 25 mph with gusts of 25 to 35 mph. Wednesday will see afternoon southwest winds at 10 to 15 mph with gusts to 25 mph. Thursday through Saturday...Remaining cool, breezy and mostly dry. Another low pressure system could bring a few showers to northwest Arizona late Thursday into Friday. Look for southwest winds at 10 to 20 mph gusting to 30 mph Thursday and Friday, becoming light northerly by Saturday for most areas. && .FGZ WATCHES/WARNINGS/ADVISORIES...None. && $$ PUBLIC...Humphreys AVIATION...RR FIRE WEATHER...McCollum For Northern Arizona weather information visit weather.gov/flagstaff