textproduct: NWS Flagstaff

SYNOPSIS

Overall dry, breezy, and hot conditions are forecast through Tuesday. Chances for showers and thunderstorms returns by the middle of the week.

DISCUSSION

We remain enveloped in a very dry airmass following the passage of a shortwave trough. The dry conditions will lead to efficient radiational cooling and chilly temperatures along the high terrain this morning. Localized wind protected areas at high elevation will dip into the 30s and possibly briefly touch freezing. Things will warm quickly once the sun rises, with near- normal June daytime temperatures expected today. Winds will be less breezy than yesterday as the gradient aloft relaxes and flow turns more zonal. Forecasted relative humidity this afternoon remains very dry in the 4-8% range, however the magnitude of the winds comes down enough to keep us below Critical fire weather thresholds. Nevertheless, expect Elevated to Near-Critical fire weather conditions across northern AZ.

Starting tomorrow, heights begin to increase aloft as high pressure builds to our southeast. A gradual warming trend will bring daytime temperatures 5-10 degrees above normal by Tuesday. An Extreme Heat Warning has been issued for the lower elevations of the Grand Canyon on Monday and Tuesday where afternoon temperatures will reach 102-112F. Heights aloft remain above normal into Wednesday, however an expected increase in clouds and precipitation chances is a complicating factor in extending the warning any longer.

The placement of the high centered to our southeast will allow for the return of subtropical moisture into the region. Moisture begins streaming into the region by the middle of the week, and the ensemble mean PW peaks at 0.70"-0.90" on Wednesday-Thursday. The current forecast calls for a 10% chance of showers and thunderstorms along the higher terrain on Tuesday, increasing to 20-40% on Wednesday, peaking at 25-50% across most of northern AZ on Thursday. By the end of the week, there is a signal that another Pacific trough will brush by and sweep out the moisture once again. This could bring another period of strong winds and low humidity into the weekend.

AVIATION...Sunday 21/12Z through Monday 22/12Z

VFR conditions expected. Period of light morning HZ/FU possible near KSEZ due to a local wildfire. Additional HZ/FU impacts possible near KFLG after 18Z. W-SW winds 5-15 kts after 18Z, becoming light and variable overnight.

OUTLOOK...Monday 22/12Z through Wednesday 24/12Z...Mainly VFR conditions expected. Periods of HZ/FU possible near KFLG during the afternoon, becoming focused over KSEZ overnight due to a local wildfire. S-W winds 10-20 kts forecast each afternoon, becoming light and variable overnight.

FIRE WEATHER...Today and Monday

Very dry and breezy conditions will bring areas of elevated fire weather. Winds will generally be southwest to west 10-15 mph with gusts to 25 mph. Warm conditions persist with minimum RH 4-10%.

Tuesday through Thursday...Breezy with gradually increasing moisture and continued above normal temperatures. Slight chance (10%) of thunderstorms along the Mogollon Rim and White Mountains Tuesday afternoon. Thunderstorm chances increase to 20-40% over all of northern Arizona for Wednesday and Thursday. Southwest to west winds 10-20 mph with gusts around 25 mph each day. Minimum RH 10-15% on Tuesday, then 15-20% Wednesday and Thursday.

FGZ WATCHES/WARNINGS/ADVISORIES

Extreme Heat Warning from 10 AM Monday to 7 PM MST Tuesday for AZZ006.