textproduct: NWS Phoenix

UPDATE...Updated Aviation Discussion

KEY MESSAGES

- Temperatures into early next week will fluctuate up and down with readings cooling into the 70s by Friday, warming back up over the weekend before cooling briefly again early next week. - A dry weather system will bring widespread breezy to windy conditions today and lingering into Saturday across the western deserts.

- A stronger and slower moving weather system may bring some chances for rain showers Sunday into Monday.

SHORT TERM /TODAY THROUGH FRIDAY/

A troughing feature can be seen on satellite imagery currently extending through northern Nevada. Today's afternoon highs across the lower deserts will be in the upper 70s with localized areas reaching 80 degrees. The trough is expected to continue digging down the Desert SW today and into Friday which will cool temperatures down further for tomorrow. In turn, Friday's high temperatures will be in the low to mid 70s in the lower deserts.

Other than cooling temperatures this incoming system will bring an increase to wind speeds, especially across southeastern California, where a Wind Advisory has been issued for Eastern Riverside County through parts of Northern Imperial County. While this advisory is in effect wind gusts between 35-45 mph can be expected. Areas outside of the advisory may also see gusts between 25-35 mph during the afternoon hours today.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Models continue to show good agreement in the incoming troughing feature developing into a cut off low starting Saturday. The core of this developing cut- off low will likely set up just off the coast of Northern Baja Peninsula as early as Saturday afternoon, and looks to remain fairly stationary over the weekend. This system is not expected to bring any notable moisture into the region until Sunday afternoon but some uncertainty still remains with the extent of moisture increase and location. However, even with this uncertainty models are still suggesting PWATs increasing to anywhere between 150-180% of normal by Sunday night. This has led to models projecting the best chances for precipitation Sunday night into Monday afternoon. Eastern Arizona in the higher terrain areas have the best PoP chances, near 40-50% with QPF values most likely no more than 0.25". Outside of the higher terrain, QPF totals are expected to be mostly between 0.05-0.10", while many areas may not see any precipitation at all as the activity will be very light and scattered across the lower deserts.

Afternoon high temperatures will continue to fluctuate through early next week then steadily climb starting Tuesday through the rest of the week. As the cut-off low begins to set up over Baja on Saturday, the region will be under the influence of lingering negative height anomalies, keeping high temperatures in the mid to upper 70s. As the cut-off low tightens over the NW Baja coast, the region will begin to warm as the lower heights will be too far to the region's SW. This will lead to afternoon highs Sunday warming back into the low to mid 80s. These temperatures will lead to the lower desert areas being under Minor HeatRisk throughout the weekend. As the core of the cut-off low progresses eastwards over Northern Mexico starting Monday, temperatures yet again will cool slightly in response. High temperatures Monday are expected to be in the mid to high 70s. By Tuesday the cut-off low will be to the region's east, ejecting into Western Texas and into the Plains. Over the Desert SW H5 heights will then be able to steadily climb, leading to a steady increase in temperatures with highs back in the mid to high 80s by around Wednesday.

AVIATION

Updated at 1140Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: East winds will persist into late morning before quickly shifting out of the west around 18Z and become gusty by the afternoon across the terminals. Gusts around 25 kts are expected this afternoon, likely peaking late afternoon. High clouds early this morning will push to the east leaving clear skies for the rest of the period. Some slantwise visibility impacts from lofted dust cannot be ruled out in the mid-afternoon through sunset today.

Southeast California/Southwest Arizona including KIPL and KBLH: The primary aviation weather concerns during the period will be the potential for brief LLWS conditions at KBLH early this morning followed by gusty northerly winds beginning mid morning at both terminals. Confidence is low that LLWS criteria will be met at KBLH, but the best timing for LLWS conditions will 12-15Z. Winds will remain light (under 10 kts) and generally contain a westerly component until mid morning, with periods of variability possible. Afternoon wind gusts of 25-35 kts are expected at KBLH, which may also bring with it some blowing dust and brief reductions in surface visibility. Afternoon gusts will not be as strong at KIPL, mostly around 20-25 kts. Anticipate mostly clear skies through the period.

FIRE WEATHER

The weather pattern will become increasingly active through the rest of the week as a series of dry disturbances cross the Southwest. The current passing system continues to bring light diurnal winds which will begin to strengthen bringing breezy to windy conditions today. Dry conditions will persist across the region with minimum relative humidity values staying entrenched between 10-15% through Saturday, while overnight recoveries will only reach the 30-50% range. Winds are expected to strengthen significantly after sunrise Thursday, with west gusts of 25-35 mph in the Phoenix area and peak WNW gusts of 30-45 mph across southeast California, leading to elevated fire weather concerns before a potential slight increase in moisture arrives Sunday into Monday.

PSR WATCHES/WARNINGS/ADVISORIES

AZ...None. CA...Wind Advisory from 7 AM this morning to 6 PM PST this evening for CAZ560-561-564-568>570.