textproduct: NWS Phoenix

KEY MESSAGES

- Temperatures will begin a cooling trend reaching below normal levels over the weekend.

- Unusually strong winds will impact the region starting this evening through Sunday resulting in areas of blowing dust and critical fire weather conditions.

- More tranquil weather conditions and a slow warming trend will arrive during the middle of next week.

SHORT TERM /Today through Sunday/

GOES mid-level WV imagery and RAP-40 500mb analysis show the subtropical high positioned over Northern Mexico as broad troughing over the western coast continues to suppress the subtropical high to the region's south. This troughing feature along the west coast will progress further westwards over the weekend leading to extreme negative height anomalies, especially over the Great Basin region, where anomalies will be near 4 normalized standard deviations below normal. Above to near normal temperatures are expected across the lower deserts with highs between 104F-110F today, cooling 3F-4F degrees by Saturday. As the aforementioned trough approaches from the west temperatures will begin to be influenced by the negative heights, this will cause afternoon highs to trend below normal by Sunday with temperatures between 95F-103F, or roughly 5F-7F degrees below normal for late June.

This pattern set up will allow the pressure gradient to tighten leading to increased W/SW winds starting Friday evening. Winds in the SW corner of Imperial County will pick up starting this evening with speeds between 25-35 mph and gusts up to 55 mph. By Saturday evening elevated winds will expand include the Lower Colorado River Valley with 20-30 mph winds and gusts up to 45 mph. Due to these speeds wind advisories have been issued for these locations. This can also lead to difficulties traveling in high profile vehicle, and localized dense blowing dust may be common. In addition, Red Flag Warnings continue through the lower Colorado River valley and eastern parts of the CWA where combined wind gusts, low humidity levels, and very dry fuels receptive to fire could result in extreme fire behavior and uncontrolled wildfire growth. Even in areas not covered by the warning, an elevated fire danger will exist due to minimum RH values hovering in the 5-15% range throughout the weekend.

LONG TERM /Monday through Friday/

The large pacific trough that will begin to push inland over the weekend will remain over the Western CONUS through much of next week. With negative height anomalies remaining in place temperatures will remain a few degrees below normal through mid next week, with highs in the upper 90s to lower 100s. NBM guidance shows very little spread between the 25th and 75th percentile for high temperatures through mid-week before ensembles shows the troughing feature beginning to be displace by the subtropical high trying again to build over the Desert SW. As the high begins to build back over the region temperatures will begin to warm back towards normal, or in the mid to upper 100s. Otherwise, while the wind advisories will expire by the end of the weekend, breezy conditions are likely to persist into early next week.

AVIATION

Updated at 0520Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: The main aviation concerns will be breezy conditions during the afternoon hours Friday, with gusts around 20-25 kt. Familiar directional patterns can be expected, with winds likely taking a little longer than usual to fully turn out of the W/SW, creating a few hours window of S'rly cross winds at KPHX and KDVT. SCT mid- level clouds will stick around through the morning hours before skies become mostly clear later in the forecast window.

Southeast California/Southwest Arizona including KIPL and KBLH: Breezy to windy conditions Friday afternoon and evening will be the main aviation concern. Gusts out of the W and SSW/SW at KIPL and KBLH respectively will reach upwards of 25-30 kt, with KIPL likely seeing a window during the evening hours when readings could reach upwards of 35 kt at times. Although not included in the TAF at this time due to low confidence, it is not out of the question that these enhanced winds may result in reduced VIS due to BLDU. Guidance does hint at some virga and light shower activity Friday morning around KBLH, but any radar echoes that are observed are not expected to result in any operational impacts. Mid-level clouds tonight will give way to mostly clear skies during the back half of the forecast.

FIRE WEATHER

Elevated to critical fire danger will continue today due to low humidity, very warm temperatures, and afternoon upslope/upvalley breezy conditions. Red Flag Warnings have been issued starting today through Sunday for much of the area. Expect MinRHs today into the single digits across the western districts, but closer to 20% in the east. These values will fall closer to 5-15% starting today and stay in this range for several days. Winds will increase this evening with gusts into a 20-35 mph range and locally higher over higher terrain areas. Winds are likely to peak on Saturday with gusts commonly reaching 25-40 mph. These windy and dry conditions will combine with the very dry fuels to create a risk of extreme fire behavior. Temperatures will cool off this weekend reaching to slightly below normal starting Sunday. Winds are expected to gradually diminish next Monday into Tuesday.

PSR WATCHES/WARNINGS/ADVISORIES

AZ...Red Flag Warning from 11 AM this morning to 8 PM MST Saturday for AZZ131.

Wind Advisory from 11 AM to 11 PM MST Saturday for AZZ530-533.

Red Flag Warning from 11 AM this morning to 8 PM MST Sunday for AZZ133.

CA...Red Flag Warning from 11 AM this morning to 8 PM PDT Saturday for CAZ231.

Wind Advisory from 11 AM to 11 PM PDT Saturday for CAZ564>567- 569-570.

Wind Advisory from 5 PM this afternoon to 11 AM PDT Sunday for CAZ562.