textproduct: NWS Phoenix

UPDATE

12Z Aviation Discussion.

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 may bring scattered showers and a few isolated thunderstorms with the best area of focus across southeast Arizona.

SHORT TERM /TODAY THROUGH WEDNESDAY/

The quiet weather will continue today under dry westerly flow. However, a slight bump in upper level heights compared to yesterday will provide a boost to temperatures as daytime highs rise into the mid 80s today. Additionally, a Pacific weather system roughly 900 miles west of southern California will gradually strengthen and start to make more eastward progress today into Wednesday. Farther to the south, a modestly strong sub-tropical jet will begin to drift northward connecting with the Pacific disturbance. The northward push of the jet will also help to usher in a good amount of upper level moisture and clouds by tonight and likely through Wednesday. Despite the increase in clouds over at least southern and eastern Arizona on Wednesday, temperatures should rise another 2-3 degrees with the warmest spots potentially reaching 90 degrees.

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 1111Z.

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 aob 10 kts. Skies will be mostly clear in the early morning hours but 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. W-NW winds will continue to prevail at KIPL. At KBLH NW winds will give way to S-SW winds by this afternoon. Wind speeds have relaxed and will remain aob 10 kts, with mostly clear skies through the morning hours with increasing high clouds anticipated throughout the TAF period.

FIRE WEATHER

Dry conditions along with warming temperatures will be observed through Wednesday. Winds will remain fairly light following diurnal trends. MinRH values will drop further reaching 10-15% both today and Wednesday. Overnight recoveries will also become generally poor by Tuesday night/Wednesday morning as values decrease toward 25-40%. A weather system is then forecast to move just to south of the region centered on Thursday leading to increased RH and chances for rain focused more toward southeast Arizona.

PSR WATCHES/WARNINGS/ADVISORIES

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