textproduct: NWS Flagstaff

SYNOPSIS

Widespread showers, along with increased thunderstorm activity, is expected today, continuing the heightened risk of flooding. A Flood Watch remains in effect for northern Arizona through this evening. Chances for showers and thunderstorms continue across eastern Arizona on Wednesday, before warmer and drier weather returns Thursday and into the weekend.

DISCUSSION

The mid/upper-level trough with a closed low at its base is starting to push into Arizona as tropical moisture continues to sit across northern Arizona. Meanwhile, Hurricane Polo moving across Baja California. Radar shows heavier showers and thunderstorms are developing across eastern AZ, and this will be pushing W to NW across the State today as the trough and close low move eastward today. This will support impactful weather across northern AZ today, with a greater focus over eastern AZ this evening and Wednesday.

From this morning through Wednesday morning, the low is forecast to move across northern Arizona. As it does so, additional atmospheric moisture from Hurricane Polo will be entrained into the low. With increased synoptic-scale forcing associated with the passing low, greater storm activity and higher rainfall rates are forecast. High-resolution model guidance continue to highlight the eastern Mogollon Rim and White Mountains as the area with the highest flood risk with 24 hour rainfall totals up to 3 inches. An another signature of an inch or greater is starting to appear in the 3-hr QPF HREF guidance near the UT and AZ border, near Lake Powell, this afternoon and early evening hours so this will be a trend to watch. We will also see higher 0-6km Bulk Wind Shear, with values ranging from 40-60 kts. Despite the strong shear, forecast CAPE values at or below 600 J/kg may limit the overall severe thunderstorm threat, though isolated severe storms cannot be ruled out given the benefit of forcing from the low. So, all things considered, we are looking at a moderate/high risk of flooding/flash flooding, with a lower risk of strong storms producing large hail and severe wind gusts. A Flood Watch remains in effect for northern Arizona through Tuesday evening.

On Wednesday, the low center moves into New Mexico, with chances for showers and storms primarily remaining across eastern Arizona. High pressure is forecast to bring a return of dry weather, with daytime temperatures warming to near average on Thursday and into the weekend.

AVIATION...Tuesday 29/06Z through Wednesday 30/06Z

Look for isolated TSRA and scattered to numerous SHRA through the period. Brief IFR conditions in heavier showers and thunderstorms, or patchy fog. Showers and storms most active along and south of a KGCN-KFLG-KSOW line through 00z. After 00Z, the most active area shifts to the north of the above line. Winds south 5-15 kts daytime, light and variable overnight. Gusty and erratic winds near storms.

OUTLOOK...Wednesday 30/06Z through Friday 02/06Z...Expect scattered to numerous showers and thunderstorms area wide through Tuesday night with the focus of precipitation then shifting towards eastern Arizona on Wednesday. Look for areas of MVFR conditions with brief IFR conditions in heavier showers and thunderstorms. On thursday, VFR conditions and fair weather arrives. Daytime winds, west to northwest at 5-15 kts Wednesday, turning variable on Thursday. Winds light and variable at night.

FIRE WEATHER...Today through Wednesday

Precipitation chances will remain high today with widespread wetting rain and isolated embedded thunderstorms across the region, becoming more focused over eastern Arizona this evening into Wednesday. This will present a moderate flood and burn scar flash flood risk. Western Arizona will start drying out Wednesday. Winds N-NE 10-20 mph today, NW-N 5-15 mph on Wednesday.

Thursday through Saturday...Dry with no precipitation across the state, minimum RH drops to the 20s and 30s percent by Saturday. Daytime high temps will also become near to slightly above normal across western AZ and near to just below normal for eastern AZ. Winds light and variable 5-10 mph Thursday, light and variable most areas Friday/Saturday with the exception of some winds E 5-15 mph along the Rim.

FGZ WATCHES/WARNINGS/ADVISORIES

Flood Watch through this evening for AZZ004>018-037>040.