textproduct: NWS Phoenix

UPDATED...18Z Aviation Discussion

KEY MESSAGES

- Below normal temperatures will continue through the weekend before readings warm back closer to the seasonal average for the bulk of next week.

- Aside from a few showers mainly over the mountains of Arizona today, dry and tranquil weather conditions will grace the region through the middle of next week.

- A return to inclement weather with increased rainfall chances is possible towards the end of next week.

SHORT TERM /TODAY THROUGH SUNDAY/

Analysis early this morning showed a recently closed off low pressure system across the Southwest with a prominent vorticity center rounding the base of the low and moving east across SoCal with some light showers in Imperial County and southern Yuma County. This low will slowly track across AZ today through Sunday and exit through the Four Corners by Monday. As the cold-core pushes into AZ this afternoon it will be enough, combined with surface heating, to generate scattered showers and isolated storms across the northern AZ high terrain, including portions of Gila County. A few showers may also develop across Maricopa and Pinal Counties this afternoon as the vorticity center passes overhead, but with low mixing ratios around 4-6 g/kg any showers will likely be inconsequential and not lead to much in the way of rainfall. A brief thunderstorm cannot be completely ruled out as mid-level lapse rates increase to around 7 C/km, with chances better in the foothills north and northeast of Phoenix. Maybe even a cold-air funnel. H5 heights around 565-572 dam this weekend will keep temperatures 3-6 degrees below normal, with lower desert highs in the upper 70s to middle 80s and lows in the 50s to lower 60s. With light winds and the below normal temperatures it should be a comfortable Fall weekend.

LONG TERM /MONDAY THROUGH FRIDAY/

Gradually warming temperatures and overall tranquil weather is expected through at least the first half of the next workweek with quasi-zonal flow in the wake of the weekend low. An increase in H5 heights up to 579-582 dam by Monday will support the gradual warming of temperatures, with afternoon highs reaching the middle 80s and lows in the upper 50s to lower 60s across the lower deserts, which is right around normal for the time of year. Dry mostly clear skies will prevail under this pattern as well. Model uncertainty grows later next week as there are hints at some moisture return into the region from the southeast, then a potential atmospheric river approaching by next weekend. Either, or both of these moisture sources may eventually help to bring a return to rain chances at some point before the end of the month, but it is too early to have a good idea on timing and/or placement for any weather feature this far in advance.

AVIATION

Updated at 1720Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:

No major aviation concerns are expected during the TAF period. Winds will follow familiar diurnal trends with speeds generally aob 10 kt. A very isolated SHRA cannot be ruled out this afternoon, but chances of this occurring are 10% or less, so there is currently no mention on the TAFs. If VCSH do come to fruition, some brief erratic winds will be the main impact. SCT cloud decks, around 7-9 kft will be present through this evening before clear skies take over from there.

Southeast California/Southwest Arizona including KIPL and KBLH: No aviation concerns are expected over the next 24 hours. Winds will favor a W'rly component at KIPL, while KBLH will see N'rly flow tilt more to the west by this evening. Periodic windows of VRB conditions will be observed during the forecast window. Clear skies will be common through Sunday morning.

FIRE WEATHER

A low pressure system will linger across the region this weekend bringing light shower chances mainly to mountain areas today, but no wetting rainfall is expected. Minimum humidity levels will fall into a 25-50% range this afternoon and then dry heading into the start of the workweek, with minimum humidity falling closer to 15-35%. Overnight recoveries will remain good at 45-70% across the area. Overall quiet weather conditions are forecast Sunday through at least the first half of next week, with temperatures rebounding back into the normal range by Monday, and with light winds each day favoring typical diurnal tendencies. A shift in the weather pattern late next week and into next week may bring about cooler, wetter, and breezier conditions.

PSR WATCHES/WARNINGS/ADVISORIES

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