textproduct: NWS Phoenix

UPDATE...Updated 12z Aviation Discussion

KEY MESSAGES

- Above normal temperatures with moderate HeatRisk will prevail through the remainder of the week before retreating closer to normal by the end of the weekend.

- Dry conditions under mostly sunny skies will prevail through at least the middle part of next week.

- Breezy conditions will develop for the end of the week and into the weekend, particularly across the lower Colorado River Valley and higher terrain communities of Arizona.

SHORT TERM /Today through Sunday/

The upper-level pattern has come slightly more organized over the past 24 hours, but still appears quite complex thanks to a plethora of weather regimes over and around the CONUS. The Desert Southwest is under a microcosm of this greater pattern, as multiple areas of low pressure flank the region to the north and south, while flat ridging encompasses the eastern Pacific. The interplay between these features will result in a tightening of the regional pressure gradient over the next few days, resulting in increasing wind gusts through the front half of the weekend. Gusts this afternoon will reach upwards of 20-30 mph with the higher end of that range focused over the higher terrain areas of south-central Arizona and the Lower Colorado River Valley. An approaching disturbance, currently positioned in the Gulf of Alaska, will further squeeze the gradient for Saturday, allowing for stronger gusts closer to 30-35 mph, mainly for parts of SW AZ and SE CA, though elsewhere across the region can still expected gusts around 20-30 mph. These stronger gusts, combined with regional RH values hovering close to 10% and very dry fuels, will result in widespread elevated, to locally critical, fire weather conditions. In turn, A Fire Weather Watch has been posted for Saturday over the areas mentioned above that will observe the strongest gusts. Once the previously-mentioned low swings through the Great Basin Sunday, winds should relax slightly, but breezy conditions are likely to continue to most of our forecast area.

The regional height field is still leaning above normal for the front part of June, which has resulted in near to above normal temperatures to start the month, but nothing completely abnormal. Even with two areas of low pressure in relative proximity, a few locations almost reached the 110F mark for the first time, owing to the longer daylight hours and strong/direct insolation. Thankfully, it looks as if we will keep the 110s at bay for at least a little while longer as troughing encompasses the the region in the short term. However, triple digits will be common for the lower desert with this afternoon likely being the hottest of the next several days as highs range between 103-109F. Heights aloft closer to normal will help "cool" weekend temperatures a bit, but values between 100- 107 will be common.

LONG TERM /Monday through Thursday/

It appears that ensembles have come into further agreement regarding the pattern evolution for next week. Signs point towards a secondary shortwave diving into the Pacific Northwest and northern Rockies, reinforcing troughing across most of the western CONUS. While conditions are expected to remain dry as this follow-on system will not provide any moisture flux to the region, but what we can expect is a continuation of breezy conditions across the region. Some subtle model discrepancy remains, mainly about strength and position of the disturbance, so wind forecasts are subject to change, but it is not out of the realm of possibility that gusts daily afternoon gusts of 20-30 mph stretch into Wednesday, which would also create a prolonged period of elevated fire weather conditions. The cyclonic pattern will not do much to budge temperatures during this timeframe, as current NBM forecasts have steady readings between 98-105 for the lower deserts. However, much like the wind forecast, more noticeable changes, either up or down, may come to fruition depending on model trends over the next few days.

AVIATION

Updated at 1100Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: Elevated wind gusts later this afternoon/evening will be the main aviation weather issue throughout the TAF period. The overall wind pattern will follow the typical diurnal tendencies with easterly winds this morning shifting out of the west by late morning. Speeds this morning will remain below 10 kts before increasing to 10-15 kts with afternoon/evening gusts peaking at 20-25 kts. Other than some high-based CU expected across the mountains east of Phoenix this afternoon, generally clear skies will prevail.

Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation weather concerns under mostly clear skies can be expected throughout the TAF period. At KIPL, winds will generally be out of the southeast throughout most of the period, with the exception of a possible westerly shift for a few hours this evening. At KBLH, winds will generally be out of the south to south-southwest. Overall wind speeds will fluctuate between 8-15 kts with occasional afternoon gusts upwards of 20-25 kts at KBLH.

FIRE WEATHER

A Fire Weather Watch has been posted for portions of SW Arizona and areas around the Lower Colorado River Valley for Saturday afternoon and evening. Dry fuels, RHs around 10%, and gusts upwards of 35 mph will result in critical fire weather conditions for these areas. Elsewhere, gusts 20-30 mph will be common, resulting in elevated fire weather conditions. Outside of Saturday, daily breezy conditions can be expected from today through at least the front half of next week, resulting in a prolonged period of elevated fire weather conditions for most of the region. MinRHs will hold steady close to 10% across the region, while overnight recoveries only offer poor to modest recovery, with MaxRHs near 15-45%.

PSR WATCHES/WARNINGS/ADVISORIES

AZ...Fire Weather Watch from Saturday morning through Saturday evening for AZZ131-132.

CA...Fire Weather Watch from Saturday morning through Saturday evening for CAZ231.