textproduct: NWS Phoenix

UPDATE

Updated Aviation

KEY MESSAGES

- Well above normal temperatures and dry conditions will persist across the region into at least early next week.

- A change in the weather pattern is expected later next week potentially bringing precipitation chances and cooler temperatures.

SHORT TERM /TODAY THROUGH THURSDAY/

Conditions across the southwestern CONUS remain quiet as unseasonably strong high pressure continues to sit over the region. Over the Great Basin, a low-amplitude shortwave is helping to keep our ridge relatively flat and heights a bit suppressed compared to yesterday. Nonetheless, 500mb heights remain around the 90th percentile for this time of year, owing to the amount of warm air currently over the forecast area. This will translate to a continuation of surface temperatures running around 10 degrees above normal for the middle of December. Lower desert highs this afternoon will range in the middle to upper 70s, with areas in and around the Imperial Valley getting close to 80 degrees once again. With little fluctuation in the day-to-day forecast, similar afternoon highs can be expected for Thursday.

LONG TERM /FRIDAY THROUGH MID NEXT WEEK/

After the northern U.S. trough exits into the Plains States on Thursday, the center of the eastern Pacific ridge will move closer to our region late Thursday into Friday with H5 heights peaking over the Desert Southwest between 585-587dm early on Friday. This peak in heights will help to boost temperatures starting Friday with the NBM showing highs mostly between 78-81 degrees. The progressive pattern across the northern tier states will then send another trough across the Pacific Northwest/Northern Rockies later on Friday into Saturday which should flatten the ridge slightly and lower heights more into a 582-584dm range on Saturday. This back and forth of slightly rising and lowering of heights looks to continue through early next week with Monday showing another temporary bump in heights. Overall, this will continue to allow for the unseasonably warm temperatures to last into at least early next week with readings staying near 15 degrees above normal.

The latter half of next week should bring a pattern change with models showing decent agreement of a deep Pacific trough setting up off the West Coast and the ridge gradually moving to the east. There is still uncertainty with the evolution of the trough and its strength, but ensembles are quite consistent in showing decent moisture beginning to spread into our region from the southwest ahead of the trough by around next Wednesday. Precipitation chances may become possible at some point later next week, but confidence remains quite low for the timing. The weather system is expected to be quite warm, so any precipitation across the area should fall as rain.

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 Thursday night under occasional high cirrus decks. Wind speeds will remain extremely light with an easterly component favored and only a temporally limited west wind shift mid afternoon through early evening in the Phoenix metro. Winds across SE California will favor a general NW direction. Extended periods of nearly calm conditions will be common.

FIRE WEATHER

Persistent high pressure across the region will result in warm and dry conditions into early next week. Highs in the upper 70s to the lower 80s will be common across the lower deserts, or 10 to 15 degrees above daily normals. Winds will overall be light and follow familiar diurnal patterns. MinRHs will range from 15-25% while overnight recoveries will generally remain fair up to 40-70%.

PSR WATCHES/WARNINGS/ADVISORIES

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