textproduct: NWS Phoenix

UPDATE

Updated Aviation Discussion.

KEY MESSAGES

- Well above normal temperatures will prevail across the entire region this weekend and into next week.

- Record setting highs and warm lows will be possible across the lower deserts including Phoenix today through Monday.

- Dry and tranquil weather will continue through next week.

SHORT TERM /TODAY THROUGH MONDAY/

An abnormally strong ridge of high pressure will continue to encompass the Desert Southwest this weekend and into early next week. Positive 500 mb height anomalies will overspread the entire forecast area, maxing out around 582-584 dam on Saturday and Sunday which is well above the 90th percentile of climatology for mid December. The strength of this ridge will result in surface temperatures reaching record breaking territory with lower desert highs in the upper 70s and lower 80s and lows in the mid 50s. Currently at Phoenix Sky Harbor there is a 90% chance of setting a new record high and 60% chance of a new record warm low on Sunday and around a 50-60% chance of reaching the record high on Monday. Yuma and El Centro could also set record highs and/or warm lows although the chances are slightly lower than Phoenix. The only sensible change in weather conditions across the state this weekend will be a slight increase in upper-level cloud cover, although this is expected to have little to no impact on temperatures.

LONG TERM /TUESDAY THROUGH NEXT FRIDAY/

Very little will change as far as the weather pattern is expected for next week with any weather systems staying across the northern tier states. The very weak shortwave trough cutting through the ridge later Monday into Tuesday should knock temperatures down a couple of degrees for Tuesday and Wednesday, but another ridge will already be rebuilding to our west. This next ridge should maintain H5 heights of 580-584dm over our region through the rest of next week with dry westerly flow persisting under generally clear skies. Depending on the strength of the ridge later next week, we may again see highs at or just over 80 degrees at some point later next week into the following weekend. Long range guidance is starting to allude to a potential pattern shift by around Christmas which may bring a larger trough farther to the south along the West Coast. If this were to occur, it could bring an end to our unseasonably warm and dry conditions.

AVIATION

Updated at 0500Z.

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 Saturday night under FEW-SCT high cirrus decks. Light winds (generally AOB 7 kts) will follow a familiar diurnal pattern, with extended periods of variability to nearly calm conditions, especially during diurnal transitions.

FIRE WEATHER

A strong ridge of high pressure will continue to bring unseasonably warm and dry conditions to the region through this weekend and into early next week. High temperatures in the upper 70s to the lower 80s will be common across the lower deserts, or around 10 to 15 degrees above daily normals. Winds will continue to follow typical diurnal trends with occasional afternoon breeziness across the AZ high terrain. Daily MinRHs will range between 20-25% while overnight recoveries run generally between 45-75%.

CLIMATE

Daily Record Highs

Phoenix ------- 12/12 79 (2010) 12/13 82 (2010) 12/14 78 (2010) 12/15 79 (1969)

PSR WATCHES/WARNINGS/ADVISORIES

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