textproduct: NWS Phoenix

UPDATE

00Z Aviation Discussion.

KEY MESSAGES

- Well above normal temperatures and dry conditions will persist across the region through the remainder of this week.

- A change in the weather pattern is expected during the latter half of next week potentially bringing precipitation chances and cooling temperatures.

SHORT TERM /TODAY THROUGH THURSDAY/

Current objective analysis reveals ridging building over the southwestern CONUS once again with northerly meridional flow stretching over our forecast area. Heights aloft at this time are comparable, and even slightly higher, to heights that were observed this time Monday. Typically, this would yield similar surface temps to what was observed yesterday when daily record highs were being exceeded for some locations. However, day-to-day MaxTs will actually drop a few degrees, likely due to a time lag from shallower heights that were seen with a passing disturbance, poor mixing, and cool northerly flow aloft. Nonetheless, temperatures this afternoon will continue their well-above-normal run as readings range 8-13 degrees above normal for the middle of December, which translates to highs in the middle 70s to lower 80s for lower desert locations. The higher end of the range will favor more western desert areas of SE California, where height anomalies will reach close to the 99th percentile due to their closer proximity to the warmest air near the ridge axis. Forecast conditions will not fluctuate much through the the middle part of the week as the ridge will stay the dominant feature. Dry conditions and warmer-than-normal temps will persist through Thursday.

LONG TERM /FRIDAY THROUGH MID NEXT WEEK/

Guidance continues to favor the center of the eastern Pacific ridge to 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 should allow for a bump in temperatures on Friday with the NBM showing highs mostly between 78-81 degrees. The progressive pattern across the northern tier states should then send another disturbance 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.

We should finally get a pattern change during the latter half of next week as guidance continues to show a deep Pacific trough setting up off the West Coast and the ridge gradually moving to over Texas. There is still a good deal of uncertainty with the evolution of the trough, but ensembles are quite consistent in showing moisture beginning to spread into our region from the southwest ahead of the trough by around next Wednesday. Precipitation chances may become possible also by Wednesday, but current forecast thinking is for the best precipitation chances to fall on Christmas Day or the day after. This potential weather system will most likely be on the warmer side resulting in high snow levels.

AVIATION

Updated at 2322Z.

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

No aviation weather concerns will exist through the TAF period. Wind speeds will remain light and diurnal with winds shifting out of the east by late this evening for the overnight period. At the southeast CA terminals, winds at KIPL will be primarily westerly with an easterly shift by late tomorrow morning going into the afternoon. While KBLH should eventually go NNW this evening with periods of VRB being common. Skies should remain mostly clear aside from a few passing high clouds.

FIRE WEATHER

Persistent high pressure across the region will result in warm and dry conditions all 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.