textproduct: NWS Phoenix

UPDATE

18Z Aviation Discussion.

KEY MESSAGES

- Temperatures will gradually warm through the rest of the work week and the weekend, with afternoon highs topping out around 110 degrees across the lower deserts during the weekend.

- Breezy conditions will linger today, particularly across the Arizona higher terrain areas, maintaining an elevated fire danger threat.

- An increase in moisture by the end of the week and weekend will lead to isolated thunderstorm activity across the Arizona higher terrain areas.

SHORT TERM /Today through Thursday/

Current objective analysis reveals continued broad troughing over the most of the western CONUS while sub-tropical ridging encompasses the southeastern tied of the country. The Desert Southwest finds itself under the confluence of these two weather regimes, helping to induce relatively enhanced flow aloft. This somewhat tight pressure will help to keep breezy conditions in place, this time focused over high terrain areas of south-central Arizona. Peak gusts should hover close to 25 mph, but some localized higher readings cannot be completely ruled out. With atmospheric heights on the rise, signaling the presence of a warmer atmospheric profile compared to days prior, we can expect surface temperatures to be a tick or two hotter this afternoon with readings ranging generally between 100- 106 degrees across the lower deserts. The gradual uptrend in heights will continue through the next 24-36 hours before leveling out through the back half of the week. In turn, day-to-day temperatures will follow a similar trend, reaching upwards of 102-108 degrees Wednesday, with similar observations expected for Thursday.

LONG TERM /Friday through Monday/

Temperatures are forecast to increase even further heading into the upcoming weekend as the subtropical ridge, forecast to be centered near the Gulf Coast region, expands westward. With 500 mb heights forecast to increase to around 590dm, the latest NBM is depicting temperatures breaching the 110 degree mark for both Saturday and Sunday across the majority of the lower desert communities. Temperatures of these magnitudes will be enough to result in a high-end Moderate to localized Major HeatRisk across the region.

Model guidance continues to be consistent in showing moisture increasing across the region starting Friday and persisting throughout the weekend as the combination of the subtropical high located to the east and a weak upper-level low riding northward off the Baja Peninsula will induce a southerly flow. The latest EPS and GEFS mean show PWATs peaking at 1.1-1.4" across much of southern AZ and 0.7-1.0" across the higher terrain areas. Thus, enough moisture will be present to result in the development of higher terrain, and maybe some lower desert, shower and thunderstorm activity each day starting as early as Friday and continuing through the weekend. Moisture looks to decrease by early next week as westerly flow settles over the region.

AVIATION

Updated at 1735Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No aviation weather concerns will exist through the TAF period under clear skies. Winds will shift out of the west by late morning, with occasional gusts reaching into the middle to upper teens by mid afternoon and persisting into the early evening. The typical easterly diurnal shift should occur between 07Z-10Z overnight with speeds remaining aob 8 kts.

Southeast California/Southwest Arizona including KIPL and KBLH: No aviation weather concerns are expected through the forecast period under clear skies. At KIPL, expected SE winds to continue through this afternoon and then switch out of the SW/W this evening. Occasional westerly gusts to around 20 kts will be possible at KIPL around sunset. Winds will favor S to SW at KBLH with high confidence in afternoon gusts peaking around 20 kts for a few hours. Outside those periods with gusts, wind speeds will generally remain light, AOB 10 kts.

FIRE WEATHER

Elevated fire weather conditions will continue today as elevated breeziness combine with very low RH values of near 10%. Afternoon breeziness will peak at 20-25 mph, particularly across the AZ higher terrain areas. Even though lighter winds are expected Wednesday, with MinRHs bottoming out in the single digits, even some marginal breeziness can create locally elevated fire weather conditions. MinRHs will increase closer to 15% towards the latter half of the week and upcoming weekend as moisture increases.

PSR WATCHES/WARNINGS/ADVISORIES

AZ...None. CA...None.