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

Arizona remains under a very dynamic weather pattern today with upper level low pressure centered over western Arizona and moisture from Hurricane Polo streaming northward. Continued shower/thunderstorm development is expected through tonight and into early Wednesday morning before coming to an end. A Flood Watch remains in effect for all of northern Arizona through this evening, and has been extended slightly across northeastern Arizona until early Wednesday morning.

Thus far, widespread rainfall has been observed across northern Arizona with the heaviest amounts favoring areas along and south of the Mogollon Rim and White Mountains. Many of these locations have seen amounts of 1.00 - 2.50 inches. Further north, rainfall amounts have been in the 0.50 - 1.00 inch range. All of this antecedent rainfall is saturating the ground across northern Arizona and will lead to a faster flood response with additional rain through the rest of today and tonight. The most widespread rain today has been across eastern Arizona, and this area will continue to be favored with potentially an additional 1-2 inches of rain. Further west, enough clearing in the dry slot of the low has allowed scattered convection to develop. The enhanced moisture will interact with limited instability to support this development through this evening. Though heavy rainfall and flash flooding are the primary threats, strong 0-6km wind shear of 40-60+ kts will result in a secondary threat for isolated severe storms (large hail and damaging wind).

Later tonight as the upper level low progresses across northern Arizona, moisture wrapping around the northern periphery will bring another round of rain with a few embedded thunderstorms. The latest hi-res model guidance favors this activity to remain primarily along and north of the Mogollon Rim and this is why the Flood Watch was extended there overnight.

Showers will continue across eastern portions of the state on Wednesday as the low moves into New Mexico. The rest of the area will see improving conditions through the day. Temperatures will remain quite cool through Wednesday given the rainfall and trough passage. Thursday morning will be quite cool in the wake of the trough with clearing skies and some high elevations cold spots may drop close to freezing.

The remainder of the week features high pressure building across the southwest, resulting in a drier period with near average temperatures. The dry weather looks to persist into next week.

AVIATION...Tuesday 29/18Z through Wednesday 30/18Z

The most widespread SHRA/TSRA will favor areas north/east of a KGCN-KFLG- KPAN line this afternoon where MVFR and local IFR conditions can be expected. Further west, coverage will be more scattered, but another round of TSRA is expected to develop during the afternoon/early evening hours bringing periodic MVFR/IFR conditions. Moisture wrapping around the low pressure system tonight will bring another round of SHRA with some embedded -TSRA aft 06Z persisting into Wednesday morning. Expect areas of MVFR/IFR overnight with some local LIFR possible in areas of fog. Winds today will be easterly at 5-15 kts, becoming light and variable overnight.

OUTLOOK...Wednesday 30/18Z through Friday 02/18Z...SHRA/TSRA will continue on Wednesday afternoon primarily along and east of a K0V7-KKINW line where MVFR to IFR conditions are possible. A few showers lingering over the White Mountains Wednesday evening with showers ending Wednesday night. Elsewhere should see improving conditions through the afternoon Wednesday. Winds Wednesday becoming W/NW around 5-15 kts, decreasing after sunset.

FIRE WEATHER...Wednesday and Thursday

Scattered to numerous showers with embedded thunderstorms will continue today and tonight. There will be an elevated threat for flooding with a few severe storms also possible through tonight. Showers will shift to eastern Arizona by Wednesday afternoon with drier weather returning Thursday. Winds will be northwest on Wednesday around 10-20 mph, becoming north/northeast around 5-10 mph Thursday.

Friday through Sunday...Expect a dry weather pattern through the weekend with near average temperatures and decreasing humidity. Expect daytime winds to be east/northeast around 5-15 mph, lighter overnight.

FGZ WATCHES/WARNINGS/ADVISORIES

Flood Watch through late tonight for AZZ004>007-009>015-039-040.

Flood Watch until 11 PM MST this evening for AZZ008-016>018-037- 038.