Area Forecast Discussion

KEY MESSAGES

- Dry, tranquil weather conditions with near to slightly above normal temperatures will continue through the first half of next week.

- A low pressure system with returning moisture will yield renewed rainfall chances to at least the high terrain of northern and eastern Arizona during the latter half of next week.

SHORT TERM /Today through Monday/

Early afternoon WV imagery depicts a seasonally deep midlevel cyclone over the Great Basin with a southerly extended trough axis sweeping into eastern Arizona. With the central negative height anomaly filling and weakening, little in the way of height falls or cooling will affect the SW Conus, however the resultant flow pattern will become increasingly westerly as the region preeminently transitions out of monsoon. Lingering shallow moisture in the form of 8-10 g/kg mixing ratios and total column PWATs near 0.75" over the eastern half of the CWA will be further scoured away with vertical mechanical mixing in the dry westerly flow this afternoon reaching levels of 5 g/kg and 0.50" respectively. While shallow, low level moisture will occasionally slosh back into parts of the CWA over the next 48 hours, the overarching drying environment will preclude deep convection and rainfall chances into the middle of next week. Otherwise, H5 heights will remain fairly steady around 588dm with only modest height falls entering the region Monday. As a result, forecast confidence is excellent that temperatures will hover within a few degrees of the seasonal normal yielding only minor HeatRisk.

LONG TERM /Tuesday through Friday/

On Tuesday, an upper low will slowly weaken as it moves northeast into NV/UT before getting swept up into the large scale flow on Wednesday moving into the northern Plains. At the same time, a weak ridge over TX and will start to strengthen on resulting in southwesterly flow over our area. With moisture return and some upper level forcing from the aforementioned low, rain chances will return to the higher terrain areas in northern and eastern Arizona. Weak large scale troughing will remain across the eastern Pacific/West Coast through the end of next week, battling the ridge of high pressure over TX. By the end of the week, the ridge will try to retrograde into NM/AZ. Additionally, ensemble members bring a surge of moisture into our area from the SE, pushing PWATs back into a 1.0-1.3" range. As a result, NBM/WPC PoPs for the end of next week reflect a 30-50% chance of showers and storms across the higher terrain in southern Gila County, and around 10-20% across the lower deserts of south-central Arizona.

Temperatures next week will remain largely unchanged in the upper 90s to low 100s across the lower deserts, and in the upper 80s to mid 90s across the higher terrain. Morning lows will generally be in the 70s to to low 80s across the lower deserts, and in the 60s across the higher terrain areas. Morning lows should start to creep up by the end of next week (more morning lows in the low 80s across the lower deserts). As a result, widespread minor HeatRisk will continue through the beginning of next week with moderate HeatRisk returning to the lower deserts for the latter half of next week as the morning lows creep up and daily normals decrease.

AVIATION

Updated at 1710Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No aviation weather concerns will exist through the TAF period under clear skies today, followed by increasing high clouds Sunday. Winds will follow a near persistence forecast from the past 24 hours, with fairly typical diurnal trends. A period of southerly cross-runway winds at KPHX or VRB winds is likely ahead of the typical SW/W shift, which is expected by mid-late afternoon. Speeds will remain light, AOB 10 kts.

Southeast California/Southwest Arizona including KIPL and KBLH: No aviation weather concerns will exist through Sunday morning. Clear skies will prevail today, followed by increasing high clouds tonight into Sunday. Winds will remain light, generally below 10 kts at both terminals. However, a period with some westerly gusts into the mid teens will be possible at KIPL this evening. Anticipate winds to favor directions between SE and W with extended periods of variability to nearly calm conditions.

FIRE WEATHER

Overall there are no fire weather concerns through the next week. Conditions will continue to dry out today with no chances for rain continuing through Monday. Slight chances for showers and storms return to the higher terrain areas of southern Gila County beginning on Tuesday. MinRHs will be around 10-25% today and tomorrow before increasing to around 15-30% for the first half of next week. Overnight recoveries will range from fair to good across the region through the middle of next week. Besides a potential increase in breeziness early next week with a weather system, winds will mostly follow typical diurnal patterns with modest afternoon upslope/upvalley gustiness (15-25 mph).

PSR WATCHES / WARNINGS / ADVISORIES

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