textproduct: NWS Flagstaff

SYNOPSIS

High pressure will deliver warmer temperatures, breezy afternoon winds and mainly dry conditions through Thursday. Enough moisture will linger for a stray shower or thunderstorm each afternoon. On Friday and over the weekend, drier air will move in from the west putting an end to any thunderstorm chances. Otherwise, look for breezy afternoon winds and slightly cooler temperatures.

DISCUSSION

High pressure aloft will linger over Arizona into Thursday before a dry trough moves across the southwest United State from Friday into early next week.

This afternoon through Thursday...Anticyclonic flow, as can be seen on visible satellite imagery Tuesday afternoon, is indicative of the high pressure system that is stationed over northern Arizona. This general pattern is expected to remain in place. Due to the flow around the high, moisture will continue to linger from the Mogollon Rim southward. The result will be the continuation of some instability due to daytime heating with isolated showers and thunderstorms possible each day. Further north, the flow around the high will continue to drag in drier air from over the Great Basin resulting in near zero chances for any showers or storms north of the Mogollon Rim. Winds will be surprisingly gusty from the west to southwest each afternoon. This is partly in response to large-scale mountain/valley flow that develops with daytime heating (surface winds tend to strengthen and flow from the lower desert to the Great Basin/Intermountain West with daytime heating during late spring and summer heating). Winds will generally moderate overnight where weak inversions set in. However, downwind of terrain features, where to flow is disrupted, inversions likely will not develop with locally gusty winds persisting much of the night. It will get warmer under high pressure, with high temperatures climbing to above average. In association, we are looking at highs around 110 degrees at Phantom Ranch with an Extreme Heat Warning below 4000 feet through at least Wednesday.

From Friday into early next week...A weak trough moves over the southwest United states from the west. Such systems normally deliver drier air this time of year and the weekend trough will be no exception. The trough will bring with it a bit cooler temperatures but nothing too dramatic. Pressure gradients associated with the trough will support afternoon breezes of 10-20 mph each day, enhanced by the diurnal mountain/valley heating mentioned above.

AVIATION...Wednesday 17/00Z through Thursday 18/00Z

Mainly VFR conditions. ISO -SHRA/-TSRA continues south of a KGCN-KFLG-KSJN line through 03Z. ISO-SCT SHRA/TSRA returns south of a KFLG-KINW- KSJN line after 18Z. Brief MVFR conditions and erratic gusts 30-40 kts in and near storms. Outside of storms, winds are W 10-20 kts remaining elevated downwind of the terrain overnight. Winds become W-SW 15-20 kts with gusts 25-35 kts after 18Z.

OUTLOOK...Thursday 18/00Z through Saturday 20/00Z...Mainly VFR conditions. ISO-SCT -SHRA/-TSRA on Thursday afternoon south of a KFLG-KSJN line, then mostly dry on Friday. Winds SW to W 10-20 kts with gusts 25-30 kts each day. Overnight winds remain elevated downwind of the terrain features.

FIRE WEATHER...Wednesday and Thursday

Continued warm temperatures and mostly dry conditions. Isolated showers and thunderstorms in the afternoons, mainly over the White Mountains. Localized downpours and wind gusts to 40 mph possible with any thunderstorms. Outside of storms, expect west to northwest winds at 15-25 mph with gusts to 25-35 mph on Wednesday. Winds on Thursday become west to southwest at 10-20 mph with gusts 20-30 mph. Winds remain elevated each night downwind of terrain features. Minimum RH around 10-20% each day. Near-critical fire weather conditions across far northern and eastern Arizona each day.

Friday through Sunday...Dry, breezy, and slightly cooler weather expected. Expect southwesterly winds at 10-20 mph with gusts of 25-30 mph Friday and Saturday. Winds decrease slightly on Sunday to the 10-15 mph range. Minimum RH drops to 5-15% each afternoon. Enhanced fire weather conditions across northeast Arizona each day.

FGZ WATCHES/WARNINGS/ADVISORIES

Extreme Heat Warning until 8 PM MST Wednesday for AZZ006.