textproduct: NWS Phoenix

KEY MESSAGES

- Near normal temperatures through mid week will turn hotter going into the weekend with lower desert highs into the nineties as early as Friday.

- A weather system for Thursday will bring an increase in rain chances with the best area of focus across southeast Arizona.

SHORT TERM /TODAY THROUGH WEDNESDAY/

Quiet weather continues today as dry quasi-zonal flow persists over the region. Meanwhile, a weak shortwave is noted over central California, while downstream height rises are occurring over the Southwest. Given this, temperatures will rise through tomorrow with daytime highs Wednesday forecast to top out in the upper 80s to around 90 degrees across the lower deserts. In addition to the aforementioned weak shortwave, a Pacific closed low is seen spinning roughly 800 miles off the southern California coast. Ahead of the low, the subtropical jet will help to advect upper level moisture and cloud cover tonight into Wednesday. Despite the increase in cloud cover, temperatures should still manage to warm near to slightly above normal tomorrow.

LONG TERM /THURSDAY THROUGH MONDAY/

The uncertainty with the Pacific weather system is still an issue, but model trends over the past 24 hours have pulled the track more to the south across northern Mexico. If these trends hold true, the system should bring less impacts to our area than previously thought. The latest NBM PoPs reflect the more expected southern track with PoPs decreasing by an average of 10-15% from the forecast package 24 hours ago. PoPs now show 10-25% across the south-central Arizona lower deserts to at most 30-40% over the eastern Arizona higher terrain. The more southern track would lead to less moisture and instability, so the chance for any isolated thunderstorms has also gone down to more of a 5-10% chance on Thursday. In addition to the lower rain chances, forecast temperatures have also gone back up for Thursday with readings now back into the upper 80s in the Phoenix area to the lower 90s across southeast California.

Starting Friday, we may start to have some influence from a ridge building in from the west. Temperatures may also respond to this incoming ridge with highs rising into the mid 90s across the western lower deserts to the lower 90s in the Phoenix area. Another developing Pacific low off the coast of California over the coming weekend may cause the ridge to amplify even more across our region potentially pushing daytime highs into the upper 90s by Sunday. Eventually, this large Pacific low is favored to inch into our region early next week resulting in a return of breezy to windy conditions, cooler temperatures, and possibly some higher terrain rain chances.

AVIATION

Updated at 1740Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No major aviation concerns are expected through the TAF period. Winds will follow typical diurnal tendencies, with speeds below 10 kts. High clouds will progressively thicken throughout the period to SCT-BKN.

Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation concerns are expected through the TAF period. Expect periods of light and variable throughout the afternoon with W-NW winds continuing to prevail throughout the rest of the forecast period at KIPL. At KBLH S-SE winds expected this afternoon shifting W-NW by this evening with periods of light and variable. Wind speeds have relaxed and will remain below 10 kts, with mostly clear skies this afternoon and increasing high clouds anticipated later this evening.

FIRE WEATHER

Dry conditions along with warming temperatures will be observed through Wednesday. Winds will remain fairly light, following diurnal trends, with a few afternoon gusts to around 20 mph primarily across southern Gila County. A weather system will bring increasing rain chances Thursday with the best chances remaining south and east of Phoenix. However, chances for wetting rainfall will be low around 10% or less. MinRH values will be around 8-15% Wednesday before increasing to 15-20% on Thursday. Overnight MaxRH values will generally range between 25-40% through midweek. Gusty winds are expected to increase this weekend into early next week, which could lead to elevated fire weather conditions in some areas.

PSR WATCHES/WARNINGS/ADVISORIES

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