textproduct: NWS Flagstaff

SYNOPSIS

High pressure will influence our weather through the next week. A slight decrease in moisture will bring isolated chances for showers and thunderstorms, mainly across the higher terrain over the weekend and into next week. Hot daytime temperatures are expected, with a slight cooling towards the middle of the week with a gradual increase in moisture returning.

DISCUSSION

Very strong high pressure remains settled across Arizona today, with little movement expected over the next couple of days. This will allow for a slight drying trend, though moisture doesn't look to fully abate across the region. Showers and thunderstorms will remain isolated each day, remaining focused across the higher terrain and mainly towards the White Mountains each day. Storm activity will remain diurnally driven with showers and storms dwindling in coverage as we head into the evening each day.

With the downturn in storm activity, we will see increasing heat build across the region. Expect hot daytime temperatures to continue, likely the hottest of the season so far. Extreme Heat Warnings and Heat Advisories remain in place through early next week. Lower elevations of the Grand Canyon may see the heat continue into Wednesday but with some uncertainty as to the placement of the high, we have held off on any additional extensions.

The high starts to elongate on Sunday and is strong enough to suppress any approaching troughs through the week. Moisture looks to increase across the region for the first half of the week, with chances for scattered showers and storms each day, especially across the higher terrain. As we head towards the latter half of next week, the high will start to shift. Models are split on whether the shift will be to the north or the west and each will have different impacts for the region. A more westerly shift would mean drier and hotter conditions, while a northerly shift would signal increasing moisture, cooler temperatures, and potential for thunderstorms each day. The uncertainty with the timing and placement of the high means there is less confidence in the forecast, especially for Thursday onward. However, the ensemble guidance has been trending towards more active monsoon as we move through the week. Stay tuned!

AVIATION...Saturday 01/18Z through Sunday 02/18Z

VFR conditions expected. Isolated showers/storms possible along the Mogollon Rim and White Mountains between 19Z to 03Z. Winds light and variable at 5-15kts day and night time. Gusty and erratic winds possible near showers/storms.

OUTLOOK...Sunday 02/18Z through Tuesday 04/18Z...VFR conditions, isolated showers/storms 18Z to 03Z each day near the White Mountains, dry elsewhere. Winds light and variable 5-15kts. Gusty and erratic winds possible near showers/storms.

FIRE WEATHER...Sunday and Monday

Hot with temperatures 10-15 degrees above average. Isolated showers and thunderstorms each afternoon/evening over the higher terrain of eastern Arizona. Winds light and variable 5-15 mph. Minimum RH values 5-15% deserts, 15-25% mountains.

Tuesday through Thursday...Cooling down but still 5-10 degrees above average. Monsoon coverage increases and expands westward along the high terrain as the week progresses. Daytime winds generally SW-W at 5-15 mph each day. Minimum RH values increase as the week progresses, 7-25% Tuesday, 10-35% Wednesday and Thursday.

FGZ WATCHES/WARNINGS/ADVISORIES

Extreme Heat Warning until 8 PM MST /9 PM MDT/ Monday for AZZ005- 018-037-038.

Extreme Heat Warning until 8 PM MST Tuesday for AZZ006.

Heat Advisory until 8 PM MST /9 PM MDT/ Monday for AZZ009-010- 012>014-040.