textproduct: NWS Phoenix

KEY MESSAGES

- Breezy conditions will linger this morning in Southeastern CA.

- The weather system will then pass just south of the area early next week, increasing chances for showers and potentially some thunderstorms.

- High pressure returns midweek, allowing temperatures to warm back up into a well above normal category, with lower desert highs likely reaching the nineties by Thursday.

SHORT TERM /TODAY THROUGH TUESDAY/

Midlevel water vapor imagery and 500 mb RAP analysis show the core of the cut-off low, that fully developed yesterday, now positioned off the Western coast of Northern Baja. Ensembles remain in good agreement that the upper low will stay far enough to the southwest today so that positive midlevel height anomalies will fill back in over the region. In response, afternoon highs today will ramp up into the mid to upper 80s across the lower deserts and even into the mid to upper 70s in the higher terrains. Temperatures in this range will be generally 10-13 degrees above normal in South-Central AZ and 6-10F above normal across the western deserts. Temperatures will cool by Monday and Tuesday as the low progresses and is expected to bring some isolated to scattered showers. Monday and Tuesday's high temperature across the lower deserts will be in the mid to upper 70s with localized areas in the low 80s.

The low will begin slowing moving eastwards starting Monday afternoon across Northern Mexico/Southern Arizona and is expected to be to the region's east by Tuesday afternoon. This will lead to moisture advection into the region with PWAT anomalies reaching 180-220% of normal during this time. Over the past few model runs both PoPs and QPF totals continue to trend upwards, with the precipitation chances (30-45%) starting Monday morning in SE CA/SW AZ. However the best time and areas for precipitation will be Monday evening over South- Central AZ (50-65%), and Eastern AZ into the higher terrain areas (70-80%). In conjunction to PoPs, as the low progresses the threat of thunderstorms will be possible Monday evening into the early Tuesday morning as MUCAPE ensemble means are between 200-500 J/kg. With these thunderstorms, small hail will possible, with 500 mb temperatures in a -20C to -25C range and decent instability in the hail growth zone. While, confidence in PoPs have grown, uncertainty remains in the exact locations of the activity, as showers are expected to be isolated to scattered. Even though some areas may not receive any rainfall, the average QPFs totals across South-Central AZ are between 0.10-0.25" and Eastern AZ/higher terrain between 0.25-0.40".

LONG TERM /WEDNESDAY THROUGH SATURDAY/

By Wednesday the cut-off low will be well into Western Texas, allowing upper level ridging to develop over the Desert SW. Mid to late week temperatures will return to well above normal resulting in area wide Minor HeatRisk. During this time H5 heights are expected to be above the 90th percentile of climatological normal. The lower deserts on Wednesday will climb back into the low to mid 80s. The remainder of the week will continue to warm into the low to mid 90s. This will result in multiple days with the potential for new record highs in Phoenix, with Friday having a 95% chance of surpassing the previous record high of 92 degrees set in 2017.

AVIATION

Updated at 0530Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: A brief period of gusty E-NE winds Sunday morning will be the primary aviation weather concern throughout the period. W-NW flow has been observed across the metro terminals and will remain for the next couple hours. Winds will then revert back out of the east late tonight with speeds generally aob 10 kts, although KSDL may see periodic gusts near 20 kts through the overnight hours. All terminals will likely see elevated easterly flow with gusts into the teens by Sunday morning until the sfc gradient subsides and winds relax by the early afternoon. Skies should remain mostly clear through the first half of Sunday before SCT mid-high lvl clouds arrive Sunday evening.

Southeast California/Southwest Arizona including KIPL and KBLH: Aviation weather concerns will remain minimal through the forecast period. Winds at KIPL will shift out of west during the overnight hours and return to the E-SE by tomorrow afternoon. Winds should remain N-NE at KBLH through the entire period. Speeds at both terminals will remain generally aob 11 kts. Skies should remain generally clear through the first half of Sunday before high clouds begin to arrive Sunday evening.

FIRE WEATHER

Dry conditions will persist today across the region with minimum relative humidity values staying entrenched between 10-15%. Lingering breezy conditions across southeast California and over higher elevations will continue through this morning, leading to locally elevated fire weather concerns before slight increase in moisture arrives Monday. Monday's weather system will help increase MinRHs to between 30-40% with good overnight recoveries before returning to drier conditions by the middle of the week.

PSR WATCHES/WARNINGS/ADVISORIES

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