textproduct: NWS Phoenix

KEY MESSAGES

- Dry and tranquil weather conditions with well above normal temperatures will prevail across the region through early next week.

- A more unsettled weather pattern is likely to develop later next week with cooler temperatures and increased precipitation chances

SHORT TERM /TODAY THROUGH SATURDAY/

The latest objective analysis shows a strong upper-level ridge situated off the northern Baja Peninsula. Under the influence of the ridge, the dry and tranquil weather pattern that is been in place now for the last several days will continue. Afternoon high temperatures will continue to run a good 10-15 degrees above normal for mid-December standards as readings will top out in the upper 70s to around 80 degrees this afternoon and once again on Saturday across the lower deserts.

LONG TERM /SUNDAY THROUGH LATE NEXT WEEK/

Upper-level ridging will continue to dominate the overall weather pattern across the Desert Southwest through the first half of next week, continuing the dry and tranquil conditions. Temperatures will continue to remain unseasonably warm as afternoon highs top out in the upper 70s to around 80 degrees across the lower deserts. There continues to be a high probability (>70% chance) of Phoenix at least tying to even breaking daily record highs both on Sunday and Monday according to the latest NBM.

A more unsettled weather pattern then is likely to ensue heading towards the middle and latter portion of next week as the upper- level ridge shifts eastward into the southern Plains, allowing a deep trough to build just off the west coast. The deterministic and ensemble model suite continue to diverge significantly on the overall strength and positioning of the trough as it deepens off the west coast, leading to a low confidence forecast heading towards the latter portion of next week. Abundant moisture is likely to spread northeastward from the subtropical Pacific into the region from late Tuesday into Wednesday, with both the EPS and GEFS showing PWATs rising above 200% of normal. Guidance is showing a lead shortwave out ahead of the main trough moving through the Great Basin, which combined with the moisture that will be in place, could generate shower activity across portions of the region during the day on Wednesday. Precipitation chances after Wednesday will then be dependent on the overall strength and positioning of the main trough off the west coast as it eventually migrates inland. With more abundant cloud cover and potential precipitation as well as the decreasing heights aloft, temperatures are likely to cool down later next week by about 5-10 degrees from the readings earlier in the week but still remain above normal.

AVIATION

Updated at 0455Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT; and Southeast California/Southwest Arizona including KIPL and KBLH:

No weather concerns will exist through Friday night under periods of high cirrus decks. Wind speeds will remain light with only subtle diurnal/nocturnal directional shifts. An easterly direction will be favored around the Phoenix metro while a NW direction will be preferred over SE California. Extended periods of nearly calm conditions will be common.

FIRE WEATHER

High pressure across the region will continue to promote dry and tranquil weather as well as unseasonably warm temperatures, 10 to 15 degrees above normal, into early next week. Winds will generally be light under 15 mph. Afternoon MinRHs will range between 20-30% with good overnight recoveries of 40-70%. A more unsettled pattern in form of cooler temperatures and increased precipitation chances is likely later next week.

PSR WATCHES/WARNINGS/ADVISORIES

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