textproduct: NWS Flagstaff

SYNOPSIS

Cooler temperatures are expected again today, along with scattered to numerous showers and thunderstorms. Flash flooding will be possible this afternoon across portions of northwestern Arizona. Gradually warmer temperatures and more isolated coverage of storms is expected through the weekend into next week.

DISCUSSION...Today

Ahead of an approaching trough, deep monsoonal moisture will be advected northward along the Colorado River Valley. 06Z RAP guidance forecasts around 1.00-1.20 inches of PWAT across much of western Arizona, with around 0.80-1.00 inches elsewhere. While 15-25 kt storm motions may limit the overall residency time of a single storm, the potential for training storms will largely negate this. Therefore, flash flooding will be the primary threat today. The greatest risk looks to be largely across northwest Arizona, where coverage of storms (and potential for training) will be the greatest. HREF PMM for >1" of rain in 3 hours largely pin point this area as well. A Flash Flood Watch is in effect for portions of northwestern Arizona through this evening for this threat.

In addition to the flash flood threat, a few strong to severe storms can not be totally given 0-6 km shear of around 25-35 kts per the 06Z RAP. Instability may be limited by cloud coverage this morning, however any areas that remain fairly clear through the morning and early afternoon will be at the greatest risk for stronger storms. Gusty outflow winds and large hail will be the main hazards from any severe storms.

Otherwise, much cooler temperatures are forecast today given the increase in cloud cover. Afternoon highs look to be around 5-10F below normal for this time of year.

Saturday and Sunday...The aforementioned trough lingers across the west on Saturday, before lifting by Sunday. The center of the high pressure remains pushed to the east, over the Ark-La-Tex region.

Coverage of showers and thunderstorms begins to tick downwards through the weekend. For Saturday, the isolated to scattered storms look possible from the Mogollon Rim and northward. By Sunday, the focus looks to shift further east, with the best chances across the higher terrain of eastern Arizona. Flash flooding will remain the main concern through the weekend, but a couple stronger storms will be possible given the influence of the trough still. Outside of storms, slightly warmer, but still cool temperatures remain over northern Arizona with less and less cloud cover expected each day. Monday through Thursday...High pressure slowly begins to retrograde and strengthen over the southwest through the coming week. Warming temperatures ensue across northern Arizona as a result, with afternoon highs returning to near-normal to slightly (~5F) above normal.

With monsoonal moisture still in place, precipitation chances look to still continue into the coming week. However, as the ridge strengthens, afternoon convection will become suppressed. Therefore, much of the activity looks to be isolated in nature, and largely focused on the higher terrain.

AVIATION...Friday 14/12Z through Saturday 15/12Z

ISOLD SHRA/TSRA from east of KCMR to KGCN through 16Z. SCT-NMRS SHRA/TSRA expected 19Z to 03Z, with the greatest coverage INVOF a KGCN-KPGA line. SHRA may linger through 07Z/08Z INVOF KGCN/KPGA. Periods of IFR/MVFR possible within +TS. Otherwise, VFR conditions with W/SW winds 5-10 kts, becoming light and VRB after 03Z.

OUTLOOK...Saturday 15/12Z through Monday 17/12Z...ISOLD SHRA/TSRA each day from 19Z to 03Z, mainly over the higher terrain. Periods of IFR and gusty outflow winds possible in and around TS. Otherwise, VFR conditions with daytime winds W/SW winds 5-10 kts, becoming light and VRB overnight.

FIRE WEATHER...Today and Saturday

Cooler. Numerous showers and thunderstorms across northwest Arizona, generally scattered for the remainder of the area. Coverage on Saturday becoming isolated to scattered from the Mogollon Rim and northward. Outside of storms, winds generally southwest/west 5-10 mph.

Sunday through Tuesday...Gradually turning warmer. Isolated showers and thunderstorms each day, especially over the higher terrain and across eastern Arizona. Winds light and variable on Sunday, becoming south through west 5-10 mph on Monday and Tuesday.

FGZ WATCHES/WARNINGS/ADVISORIES

Flood Watch from 11 AM MST /noon MDT/ this morning through this evening for AZZ004>006.