textproduct: NWS Phoenix

KEY MESSAGES

- Scattered showers and isolated weak thunderstorms will remain in the forecast across the Arizona high terrain through the afternoon.

- Near normal temperatures early this week will cool by midweek with highs in the mid to upper eighties across the western deserts to the lower nineties in the Phoenix area. - Breezy to locally windy conditions will develop on Tuesday across southeast California and then areawide on Wednesday.

SHORT TERM /TODAY THROUGH WEDNESDAY/

A weak but still fairly pronounced shortwave trough is currently tracking east northeastward through the Desert Southwest. The strongest forcing will be situated across the northeastern 2/3rds of Arizona through sunrise with scattered showers and a few isolated thunderstorms affecting portions of south-central Arizona before lifting northward by mid morning. As the center of the disturbance tracks into central Arizona late morning into the afternoon, the bulk of the forcing will shift into northern and far eastern Arizona. Drier air will also surge northward into southern Arizona by this afternoon leaving sunny skies. Rain chances this afternoon will be confined to the Arizona high country, but chances will be gradually lowering as the system continues to lift to the northeast.

By tonight into Tuesday, an unseasonably strong Pacific low will move through the Pacific Northwest reaching northern/central California and western Nevada by Wednesday morning. Increasing negative height anomalies and a tightening gradient will lead to breezy to windy conditions developing across southeast California on Tuesday with Advisory level winds likely for western portions of Imperial County by Tuesday evening. Model agreement is excellent showing the center of the Pacific low moving farther southward toward southern California later on Wednesday.

The main forecast concern for our region with this next weather system will be the increase in winds bringing elevated fire weather conditions. Wednesday is forecast to bring more widespread stronger winds with the majority of the area having wind gusts of 20-30 mph during the afternoon and evening. Advisory level winds will also again be possible across the western half of Imperial County on Wednesday. Temperatures will also cool off significantly across the western deserts starting Wednesday with highs only in the mid to upper 80s, or around 10 degrees below normal. For Phoenix, highs Wednesday are still expected to easily top 90 degrees with readings closer to 95 degrees.

LONG TERM /THURSDAY THROUGH SUNDAY/

Model guidance continues to trend toward a slower progression of the Pacific low later this week with the low gradually filling beginning Thursday before finally lifting northeastward through the Great Basin on Friday. The close proximity of low on Thursday and probably even Friday will continue to keep temperatures below normal across our area with highs at most in the lower 90s either day. Thursday is expected to be another breezy day across south- central and eastern Arizona, but gusts should mostly stay below 25 mph.

The weather pattern going into next weekend is likely to result in an upper level ridge building across at least eastern portions of the Southwestern U.S. leading to warming conditions. Models favor another Pacific low, but staying mostly off the Pacific Northwest coast allowing ridging to build over the Central U.S. and likely extending into our region. NBM forecast temperatures reflect this building ridge by calling for highs back into the normal range for the coming weekend and potentially even above normal with the start of June.

AVIATION

Updated at 0900Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: Winds will be the main forecast challenge though Tuesday morning with SCT-BKN midlevel decks this morning clearing by this evening. Some form of an easterly component should prevail through the morning, though a slight chance (10%) of a shower across the airspace could create some variability. Otherwise, a brief period of light southerly cross runway winds are likely late morning/early afternoon before completing the switch to SW by mid afternoon. Scattered SHRA/TSRA will develop over the mountains well north and east of the terminals, but could send a NE outflow into parts of the Phoenix area this evening. Confidence is low regarding far into the metro any outflow could progress and whether gusts would survive, but would be most likely to impact KSDL and KDVT.

Southeast California/Southwest Arizona including KIPL and KBLH: No major weather issues will exist through Tuesday morning under clear skies. Confidence is very good that wind directions at KIPL will oscillate between a daytime SE direction and evening/overnight westerly directions with enhanced gustiness upwards of 30kt this evening. KBLH will generally maintain a southerly component, though may have periods of light and variable winds.

FIRE WEATHER

A mostly dry weather system will exit the region later today, but it will allow for continued chances for showers and isolated thunderstorms over the Arizona high terrain through this afternoon. There is a 20% thunderstorm threat across Gila County and far northeastern Maricopa County, but with limited rainfall potential the threat for new wildfire starts due to lightning strikes will be heightened. MinRHs will mostly stay between 10-15% across the lower deserts to 15-20% over higher terrain areas. A second much larger weather system will then dive southward into the Southwestern U.S. by mid week creating breezy to locally windy conditions. Elevated fire weather conditions will become a concern starting Tuesday as winds pick up, but a dip in temperatures and a slight increase in RHs will somewhat help to curtail the threat. The gusty winds will be the most pronounced on Tuesday and Wednesday for the western districts and Wednesday and potentially Thursday for the eastern districts. As winds die down late week and through the weekend, temperatures are forecast to rise to above normal while afternoon RHs fall to around or even below 10%.

PSR WATCHES/WARNINGS/ADVISORIES

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