textproduct: NWS Phoenix

UPDATE

Updated 06Z Aviation Discussion.

KEY MESSAGES

- Breezy to locally windy conditions return over the weekend with the strongest gusts across Southeast California and the Arizona high terrain.

- Elevated to critical fire weather conditions this weekend, particularly on Sunday for the Eastern Arizona higher terrain, where a Red Flag Warning will be in effect.

- Afternoon high temperatures 4 to 6 degrees above normal through Saturday will drop into a near normal range Sunday and below normal Monday, followed by a warming trend through the rest of next week.

SHORT TERM /TODAY THROUGH MONDAY/

Broad troughing has now encompassed much of the western CONUS, with the axis currently extending through western Nevada and down into southern California. This troughing feature will continue diving down the into the Desert SW with the core expected to clip northern Arizona by Sunday night into early Monday morning before ejecting into the Plains early next week. Over this weekend, as this trough strengthens, ensembles are pointing towards another shortwave impacting the region Sunday night into early Monday morning. This second shortwave will have a stronger core of vorticity and negative midlevel height anomalies than the short wave that swept through the region this morning. Temperatures across the region today will be almost identical to yesterday's, in the upper 90s. However, by Sunday temperatures will begin to be influenced by the approaching trough and negative height anomalies as the afternoon highs will dip into the lower 90s and into the upper 80s Monday, 5-7 degrees below normal and will be the coolest day this week.

Pressure gradient are beginning to tighten as the trough dives southwards resulting in breezy to locally windy conditions across the region, particularly in the western desert today. Due to this a Wind Advisory is in effect for the SW portion of Imperial County as wind gusts have already peaked to 53 mph in the Mountain Springs area this afternoon. The wind advisory will expand further east into the Imperial Valley later this afternoon as winds continue to increase to between 20 to 30 mph and gusts upwards of 40 mph. Winds will increase further starting Sunday afternoon, peaking late Sunday night/early Monday morning as the core of the system passes just north of the region and the aforementioned shortwaves swing through. This will result in gusts between 20-30 mph in the Arizona lower deserts, 30-40 mph in the eastern higher terrain, and 45-55 mph in SW Imperial County.

There will be a window where relative humidities drop below 15% as wind gusts increase through Sunday afternoon into the evening, this has lead the elevated fire weather to become critical fire weather primarily over the Eastern AZ high terrain. As a result a Red Flag Warning has been issued for the eastern higher terrain areas, to include southern Gila County and Tonto National Forest.

LONG TERM /TUESDAY THROUGH FRIDAY/

As the core of the weekend system departs northeastward, some measure of broad cyclonic flow over the Western US will remain and likely evolve into quasi-zonal flow through the middle of the upcoming work week. Heights aloft will rebound closer to seasonal averages and so temperatures are expected to warm through the middle of the week, with dry conditions continuing. Meanwhile, a strong midlevel ridge will remain nearly stationary off the Pacific Northwest Coast through much of next week, with most global guidance showing a subtropical jet forming under the ridge and developing a few weak disturbances, a few of which may be sent downstream and near/over the Southwest US. Regardless of the details and how weak troughing over the West-Central CONUS eventually resolves, essentially all solutions currently show the region remaining completely dry, with periods of mid-high level clouds and gradually warming temperatures through the work week.

AVIATION

Updated at 0535Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: The main aviation concerns will continue to be a period of elevated cross-runway winds at KPHX late tomorrow morning along with gusty W-SW winds tomorrow afternoon. W-SW winds will remain elevated (8-13kt) into the overnight hours before going back E-SE around 08-10Z and decrease to below 10 kt. A period of southerly crosswinds expected again during the late morning hours with wind speeds increasing to 10-15kt. Winds will then go W-SW during the afternoon with gusts up around 20kt. Winds will then increase to around 25kt around 01-02Z and continue through 06Z. Confidence is low that winds will go E-SE tomorrow night at KPHX and may just stay S-SW, so VRB has been entered in the TAF for now. Skies will remain mostly clear through tomorrow morning with FEW high clouds moving in tomorrow afternoon and evening.

Southeast California/Southwest Arizona including KIPL and KBLH: Periods of gusty winds will be the main aviation weather issue throughout the TAF period. At KIPL, winds will maintain a westerly component while at KBLH winds will fluctuate from the south to southwest. At KIPL, wind gusts reaching 25-30 kts at times will continue into the overnight hours. Winds will then decrease to around 10 kt early tomorrow morning and continue into the afternoon. Wind speeds will pick up again early tomorrow afternoon with gusts of 20-25kt expected. A period of stronger winds (30-35kt) is again possible tomorrow evening (01-05Z). At KBLH, winds will remain elevated (10-15kt) over the next couple hours before decreasing to around 5 kt for the overnight and morning hours. Wind speeds will then pick up with gusts around 20 kt beginning during the afternoon hours, a period of higher wind gusts (around 25kt) is possible during the evening hours (01-05Z). Skies will remain mostly clear through tomorrow morning with FEW high clouds moving in tomorrow afternoon and evening.

FIRE WEATHER

A weather system has moved inland, approaching The Great Basin area resulting in increased winds and elevated to locally critical fire weather conditions across the area this weekend. Afternoon/early evening wind gusts will commonly peak between 20-35 mph today, with locally stronger gusts in Southeast CA. The strongest gusts by Sunday will likely be confined to Eastern AZ higher terrain, where gusts between 30-40 mph will be common. A Red Flag Warning will be in effect starting Sunday 11 AM MST for Southern Gila County and Tonto NF foothills. Afternoon minRHs mostly between 8-15% today will increase to 10-20% areawide Sunday. Overnight recoveries between 30-50% tonight will improve primarily for the eastern districts Sunday night to around 40-60%.

PSR WATCHES/WARNINGS/ADVISORIES

AZ...Red Flag Warning from 11 AM to 11 PM MST Sunday for AZZ133.

CA...Wind Advisory until 11 PM PDT Sunday for CAZ562.

Wind Advisory until 11 PM PDT this evening for CAZ563-566-567.