textproduct: NWS Flagstaff

SYNOPSIS

High pressure will continue to dominate the Southwest through the forecast period. This pattern will allow for above normal temperatures and daily chances for showers/storms. Greatest coverage will be across the higher terrain each afternoon/evening.

DISCUSSION

Isolated showers and thunderstorms have fired up across portions of the High Country this afternoon. Storm motion is relatively slow, so this will increase the potential for flash flooding, especially for storms that continue to back build. There's decent instability across our CWA this afternoon, but with little to no shear, we aren't anticipating many, if any, severe thunderstorms.

As for the synoptic pattern...A strong ridge will continue to build across the Four Corners through the next couple of days before the high slightly wobbles eastward. Even with a slight shift in the general placement of this pressure system, above normal afternoon high temperatures and daily thunderstorm chances will remain through the entire forecast period. We are also expecting an influx of additional moisture from the southeast starting tomorrow and lasting through the first half of next week at least. Then we could see a slight downward trend in daily precipitation chances, although we aren't expecting to "dry out". An Extreme Heat Warning remains in effect for elevations below 4000' at the Grand Canyon and for Marble and Glen Canyon through Sunday evening. Although these are the only areas where we have a heat product in effect, all lower elevation locations will be experiencing hot daytime highs through the next several days, so avoid strenuous activity during the middle of the afternoon and stay hydrated! As for precipitation, greatest chances will be across the higher terrain each afternoon/early evening. Flash flooding will likely be the main concern with all the recent rainfall across our CWA.

AVIATION...Friday 24/18Z through Saturday 25/18Z

Expect mainly VFR conditions. ISO-SCT SHRA/TSRA between 18Z-03Z and mostly over or near higher terrain features. Brief MVFR/IFR conditions in stronger storms. Outside of any thunderstorms, expect light and variable or terrain driven winds.

OUTLOOK...Saturday 25/18Z through Monday 27/18Z...Expect mainly VFR conditions. SCT-NMRS SHRA/TSRA between 18Z-03Z each day. Brief MVFR or IFR conditions in stronger storms. Outside of any thunderstorms, expect light and variable or terrain driven winds.

FIRE WEATHER...Saturday and Sunday

Very hot at lower elevations that do not receive rain or outflow boundaries. Otherwise, expect scattered showers and thunderstorms each day. Storms will be most common over the higher terrain, due to weak steering flow. Moisture values remain high, so any storms that do develop are capable of producing localized flooding. Outside of storm activity, expect generally light winds.

Monday through Wednesday...Expect active Monsoon conditions, but still hot at lower elevations that do not receive rain or outflow boundaries. Steering flow does improve during this period, from the south, so expect greater coverage as storms move off of terrain each afternoon and evening. Outside of thunderstorm activity, expect generally light winds.

FGZ WATCHES/WARNINGS/ADVISORIES

Extreme Heat Warning until 8 PM MST /9 PM MDT/ Sunday for AZZ005- 006.