textproduct: NWS Flagstaff

SYNOPSIS

Deep monsoonal moisture will remain over the area through at least mid week, with a slight decrease later in the week. With this moisture comes the daily threat of thunderstorms, along with the risk for locally heavy rainfall and flooding. Daytime temperatures will remain at or below normal much of the week, with hotter temperatures toward the weekend.

DISCUSSION

An upper level disturbance is moving northwest into east central Arizona now and then into north central Arizona tonight. While there was a slower start to convection over much of our area today, the deep moisture and instability in place is allowing numerous storms to develop. The greatest coverage is over eastern Arizona, spreading westward and impact the rest of northern Arizona later in the afternoon and evening. The primary threat continues to be heavy rainfall and flash flooding, especially considering the wet ground conditions and many streams/rivers are already flowing and elevated. For this reason, there is a Flash Flood Watch in effect through late this evening for all of our forecast area excluding the far northeast corner. There continues to be a localized strong wind/hail threat today, especially over northeast Arizona through the early evening. As the disturbance moves northward Wednesday, scattered thunderstorms are expected in the afternoon, especially over the higher terrain with a somewhat lower threat of heavy rainfall. From Thursday into the weekend, the center of high pressure to our east is forecast to shift toward Arizona. While moisture levels will drop, there will still be enough for daily scattered storms over the higher terrain, but more isolated for the valleys. Temperatures will also begin to heat up to above normal levels. Temperatures by the weekend may approach warning levels for the lowest elevations of the Grand Canyon so we'll keep an eye on that.

AVIATION...Wednesday 22/06Z through Thursday 23/06Z

Look for mainly isolated -SHRA/-TSRA through 18Z. After 18Z, Another round of SHRA/TSRA developing. Stronger storms will be capable of producing hail, wind gusts to 45 kts and brief MVFR and IFR conditions. Outside of storms, winds light and variable. Activity diminishing to isolated after 02Z.

OUTLOOK...Thursday 23/06Z through Saturday 25/06Z...Expect SHRA/TSRA activity through the period, most numerous during the afternoon/evening hours. Coverage of SHRA/TSRA decreasing a bit each day and mainly focused over higher terrain. Stronger storms will produce brief MVFR and IFR conditions, gusty winds to 40 kts and hail. Outside of storms, surface winds light and variable.

FIRE WEATHER...Today through Thursday

A medium to high grade monsoon environment continues today. Most storms will produce wetting rain and any stronger storms may produce flash flooding, hail, and wind gusts to 50 mph through this evening. Activity slightly declines in coverage/intensity on Wednesday, then more so on Thursday. Scattered thunderstorms are still expected each afternoon/evening, with continued threat of localized flash flooding. Winds are generally light through the period outside of outflow and thunderstorm activity.

Friday through Sunday...Chances for showers and thunderstorms continue, though coverage will be more isolated to scattered. Generally light winds outside of outflow and thunderstorm activity. Most storms will produce wetting rain and any stronger storms could produce localized flash flooding. Expect a warming trend and minimum RH down to 20% for the lowest elevations.

FGZ WATCHES/WARNINGS/ADVISORIES

None.