textproduct: NWS Flagstaff

SYNOPSIS

Increasing moisture will bring scattered showers and thunderstorms through Thursday, mainly during the afternoon and evening. Drier conditions are expected Friday and Saturday, with rain chances increasing again early next week.

DISCUSSION

The upper low that brought windy conditions to our area on Tuesday continues to lift into the northern Rockies. A significant plume of deep monsoon moisture continues to flow northward into New Mexico, with widespread rain and thunderstorms. Over northern Arizona, drier air remains for much of Coconino/Yavapai counties early this morning, with dewpoints in the 30s/40s. Farther east, dewpoints have risen into the 50s. The air mass is forecast to moisten from east to west through the day, with scattered thunderstorms forecast to develop along the higher terrain of the Mogollon Rim, White Mtns, and Yavapai County by early afternoon. Isolated showers and thunderstorms will be possible elsewhere. Storms are forecast to drift south through the lower elevations of Yavapai/Gila counties into the late afternoon/early evening hours. Some localized heavy rainfall/flash flooding will be possible, though storm intensity may not be too extreme as CAPE values are generally forecast to remain <1000 J/kg per the latest HREF. On Thursday, elevated precipitable water values remain over the area, along with a disturbance moving in from the south providing lift. Another round of scattered showers and thunderstorms is expected during the afternoon and evening. Again, the primary threat with these will be locally heavy rainfall and flash flooding. By Friday, the upper level disturbances will be east of our area, with some drying from west to east. There is still a slight chance of some afternoon storms, mainly near the AZ/NM state line with a 10% chance as far west as Flagstaff.

Majority of the guidance indicates drier conditions Saturday and most of Sunday. By later Sunday into Monday, we'll need to monitor the possibility of deeper moisture getting pulled northward into a developing west coast trough, originating from a couple of tropical systems off the Baja coast. For now, PoP values move back upward to 20-30% late Sunday and 30-60% for Monday. There is still quite a bit of uncertainty in the details of the interaction between the trough and the tropical moisture during this period, with a few of the ensemble solutions showing a threat of heavy rainfall. This will be something to monitor over the next few days.

AVIATION...Wednesday 23/18Z through Thursday 24/18Z

Mainly VFR. ISOLD-SCT SHRA/TSRA 19Z to 03Z over the higher terrain, most numerous S/W of a KGCN-KFLG-KSOW line. There is a slight chance for -SHRA/-TSRA continuing overnight. Brief MVFR conditions and gusty erratic winds expected near TS. Winds NE-SE 5-10 kts.

OUTLOOK...Thursday 24/18Z through Saturday 26/18Z...Mainly VFR. SCT SHRA/TSRA on Thursday, becoming ISOLD on Friday. Brief MVFR conditions and gusty erratic winds expected near TS. Winds VRB 5-10 kts on Thursday, becoming S-W on Friday.

FIRE WEATHER...Today through Thursday

Shower and thunderstorm activity will increase today, with the highest coverage along and south of the Mogollon Rim and White Mountains, and near the New Mexico line. Scattered storms are expected over all of northern and central Arizona Thursday. Stronger storms will bring heavy rainfall and gusty/erratic winds. Outside of storms, winds will be variable at 5-15 mph.

Friday through Sunday...Slight chances for showers and thunderstorms continue Friday, then mostly dry conditions are likely Saturday. Rainfall chances may begin to increase early next week, however there is considerable uncertainty at this time. Winds will be southwest 5-15 mph on Friday and Saturday increasing to 10-20 mph on Sunday.

FGZ WATCHES/WARNINGS/ADVISORIES

None.