textproduct: NWS Flagstaff

SYNOPSIS

A pleasant day on Sunday before a low pressure system brings in some scattered showers and thunderstorms across the higher terrain on Monday. Continued troughing for the rest of the week will keep things on the cool and breezy side.

DISCUSSION

A weak area of high pressure will begin pushing off to the east starting tomorrow as a trough makes its way in off the west coast. This trough will bring in a little more moisture than previously thought with POPs and QPF amounts rising with the latest model runs. This event won't be completely driven by surface heating as some showers could enter the southeastern and eastern part of the state as soon as early Monday morning. However surface heating will play more of a part for the rest of the area as CAPE values approach 400-500 J/kg by midday Monday and that will likely generate the showers/thunderstorms along the Mogollon Rim and Kaibab Plateaus with some isolated higher based showers and storms possible over the northern high deserts later in the afternoon. Rainfall amounts will be anywhere from a trace over the high deserts, around a tenth of an inch over the Rim, and a tenth to a quarter inch in the White Mountains. Gusty winds and cloud to ground lightning could be some hazards possible around these showers/storms.

The moisture will move out of the area by Tuesday but troughing remains over the area for the rest of the week as a strong and unseasonably cold upper level Low parks over western Nevada. This keeps our temperatures about 5-10 degrees cooler than average for most of the week. Wednesday and Thursday look to be relatively breezy days with southwesterly winds approaching 20 mph, gusting to 30 mph. Any breezy day this time of year raises some fire weather concerns, but it looks like minimum RH values stay in the 10-20% range, likely aided by our cooler than average temperatures so that could be the saving grace. Nevertheless will be watching midweek to see if things change and fire weather is a concern.

AVIATION...Saturday 23/18Z through Sunday 24/18Z

VFR conditions. Expect SW to W winds at 5-15 kts gusting to 20-25 kts through 03Z, then turning light and variable.

OUTLOOK...Sunday 24/18Z through Tuesday 26/18Z...Mainly VFR conditions. Increasing moisture will result in isolated virga showers and local gusty/erratic winds on Sunday. Moisture will increase further on Monday and interact with a passing weather system to produce scattered -SHRA/-TSRA. Gusty and erratic winds and brief MVFR conditions in the vicinity of storms. Otherwise, look for SW to W winds at 5-15 kts gusting to 20-25 kts each day.

FIRE WEATHER...Sunday and Monday

Dry and warm weather will continue on Sunday. Look for west to southwest winds at 10-20 mph with minimum afternoon RH between 10-20%. On Monday, moisture will be on the increase. As a result, expect isolated to scattered showers and thunderstorms across much of northern Arizona. Dry lightning and erratic outflow gusts will be possible. Outside of storms, southwest winds at 10-20 mph on Monday.

Tuesday through Thursday....Mainly dry, seasonably cool and breezy to windy weather developing. A slight chance of showers and thunderstorms lingering into Tuesday toward the Four Corners and along the Arizona/New Mexico border. Otherwise, expect southwest winds at 10-20 mph with gusts to 30 mph on Tuesday, increasing to 15- 25 mph with gusts to 35 mph Wednesday and Thursday. Afternoon minimum RH 10-20% each day.

FGZ WATCHES/WARNINGS/ADVISORIES

None.