textproduct: NWS Flagstaff

SYNOPSIS

The eastern half of the state will see a good chance for showers and thunderstorms on Saturday with the western half remaining dry. On Sunday the northwestern part of the state becomes the focus for shower and thunderstorm activity while with the exception of the White Mountains most of the eastern part of the state dries out. Thunderstorm activity will concentrate on the eastern half of the state Monday and Tuesday while the western half remains dry.

DISCUSSION

Main player in the weather over this weekend will be the early season trough parked over the West Coast. It's brought some mid and upper level drying which as shown on the 18Z sounding puts a pretty strong cap over the western half of the state. Despite having some good low level moisture today which has produced some low elevation cumulus fields, thunderstorms will be hard to come by west of I-17 and US-89 for the rest of the afternoon. The eastern mountains like the Whites, Chuskas and East Rim don't have as much capping so some scattered showers and thunderstorms will be possible there this afternoon. A similar scenario is expected for tomorrow as capping keeps the western half of the state dry, with more moisture and less capping over the eastern part of the state allowing some showers/storms during the afternoon.

Now for Sunday, how things play out depend on how much moisture the West Coast trough can tap from Hurricane Marie. Right now a moisture plume will extend across southern California into Nevada with the eastern edge moving over the northwestern quarter Arizona, including the Grand Canyon region. This combined with a shortwave wrapping around that trough could bring some heavy rain to this area. WPC does have this area in a slight risk for excessive rainfall so will have to keep an eye on things to see how much of a flash flooding threat will materialize. The rest of the state is expected to remain relatively dry as it'll be east of the band of moisture. Some monsoon moisture may remain in far eastern Arizona, enough for shower/storm chances over the White Mountains.

By Monday this moisture plume will push out of the area and the ridge of high pressure over the southeastern US will start flexing back westward towards us again. This will draw in monsoon moisture for the eastern third of the state bringing that region some shower and thunderstorm chances. By Wednesday onward it flexes west enough to bring shower and thunderstorm chances back to most of the state.

AVIATION...Saturday 05/00Z through Sunday 06/00Z

Expect mainly VFR conditions. ISOLD -SHRA/-TSRA over Apache County through 02Z. ISOLD -SHRA/-TSRA AFT 18Z-20Z Saturday. Sfc winds decreasing after sunset tonight, then S-SW10-20kts AFT 18Z Saturday.

OUTLOOK...Sunday 06/00Z through Tuesday 08/00Z...Expect mainly VFR conditions. Isolated to scattered -SHRA/-TSRA each day. Activity is most likely over southern Apache County both days, as well as mainly west of a KCMR-KPGA line on Sunday. Daytime sfc winds are not anticipated to affect flight operations.

FIRE WEATHER...Saturday and Sunday

Increasing moisture will result in expanding shower and thunderstorm coverage across northern Arizona. On Saturday, mainly isolated activity spreads area wide. better chances arrive on Sunday, especially across northwest Arizona. Winds south to southwest 5-15 mph with gusts to 25 mph each afternoon. Little change in temperatures.

Monday through Wednesday...A bit drier air will push across northern Arizona on Monday with showers and thunderstorms mainly confined to the White Mountains area. On Tuesday and Wednesday high pressure builds in from the east with increasing moisture and monsoon activity across northern Arizona. Winds south through southwest 5-15 mph each day, then generally light and variable overnight. Little change in temperatures.

FGZ WATCHES/WARNINGS/ADVISORIES

None.