textproduct: NWS Phoenix

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/

Mid level WV imagery and RAP40 500mb analysis show the cut off low to continuing to progress northeastwards into southwestern Texas and is expected to eject into the Plains by Sunday morning. Meanwhile, another disturbance, currently in the Gulf of Alaska, is expected to descend down into the NW pacific by early Saturday, and then continue further inland to encompass the northwestern states with a positively tilted axis through California/Nevada by Saturday night/Sunday morning. As this next system approaches, tightening in the pressure gradient will lead to breezy to windy conditions, especially along the Colorado River Valley, over the weekend. Gusts will be strongest Saturday afternoon/evening where speeds will be around 30-35 mph for parts of SW AZ and SE CA, while elsewhere across the region expected gusts around 20-30 mph are expected. In addition to gusty conditions, minimum RH values are hovering near to slightly below 10% leading to elevated to locally critical fire weather conditions. Due to this the previous Fire Weather Watch has now been upgraded to a Red Flag Warning starting Saturday 9 AM MST through 11 PM MST for Yuma and La Paz Counties to includes the Colorado River Valley.

Today and Saturday will remain several degrees above normal with afternoon highs in the mid to upper 100s across the lower deserts. Widespread Moderate HeatRisk will persist through Saturday with these temperatures, and will downgrade to Minor HeatRisk starting Sunday as the afomentioned trough in the Pacific NW will begin to lower heights over the Desert SW. However, even with this next system approaching it is not expected to dive south enough to bring significant cooling the the region, with H5 heights lowering from 585-588 dam on Saturday to 582-585 dam on Sunday, resulting in temperatures only cooling into the low to mid 100s, which will remain near to 2F-3F degrees above normal for this time of year.

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 1825Z.

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 westerly winds this afternoon shifting out of the east during the overnight hours and then back westerly early tomorrow afternoon. Wind gusts this afternoon/evening will peak at 20-25 kts. Otherwise wind speeds will be aob 10 kt. Other than some high- based CU expected across the mountains east of Phoenix this afternoon, generally clear skies will prevail through most of the TAF period. FEW high clouds will start to move in from the west by late tomorrow afternoon.

Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation weather concerns are 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 5-15 kts with occasional afternoon gusts upwards of 20-25 kts at KBLH. Skies will remain mostly clear through the overnight period with increasing high clouds beginning around sunrise tomorrow morning.

FIRE WEATHER

The previous Fire Weather Watch has now been upgraded to a Red Flag Warning 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...Red Flag Warning from 9 AM to 11 PM MST Saturday for AZZ131-132.

CA...Red Flag Warning from 9 AM to 11 PM PDT Saturday for CAZ231.