textproduct: NWS Phoenix

Update

06Z Aviation Discussion

SYNOPSIS

A broad trough of low pressure over the western U.S. will keep temperatures below normal and bring chances for light showers to the region through Friday. Scattered rain showers will progress through the area this afternoon and evening with the better chances for measurable rainfall confined to the foothills and higher terrain NE of Phoenix. Another round of showers will be possible across the high terrain of southcentral AZ on Friday. Temperatures through the end of the week will remain well-below normal before a warming trend takes shape starting this weekend.

DISCUSSION

Latest visible satellite and radar imagery depicts a band of showers which is now progressing through southcentral AZ. This band is associated with an upper-level disturbance that is now rotating through the Great Basin. The majority of this shower activity is expected to remain over N Maricopa County this afternoon and portions of the Phoenix Metro area could receive a few hundredths of an inch of rainfall. There is also enough instability aloft (ML CAPE values around 100-150 J/kg) for a few isolated lightning strikes or pea sized hail with this activity as it continues to progress ewd over the next several hrs. Winds will also remain gusty through this evening as momentum transport from any shower brings stronger winds aloft to the sfc. Any lingering showers should diminish after sunset with a quiet night anticipated thereafter. Lows will fall into the 40s to around 50 degrees with a few high elevation locations such as Globe/Miami and western Joshua Tree getting down to the upper 30s overnight.

Temperatures will warm by a few degrees on Thursday and Friday, but are still expected to remain well-below seasonal normals with highs only reaching the upper 60s to lower 70s both days. On Friday, the upper-lvl trough over the western CONUS will continue to deepen with 500 mb hghts becoming closed off over AZ. This closed low will pass directly over the forecast area resulting in additional large scale lift. Scattered showers will again be possible Friday afternoon and evening, however this activity will be mainly confined to the higher terrain areas north and east of Phoenix. We will begin to see a warming and drying trend through this weekend as the trough of low pressure begins to weaken and a ridge builds in over the E Pacific. Highs are expected to rise into the mid to upper 70s by Saturday and return to normal levels in the upper 70s to lower 80s by Sunday.

Ensembles members and deterministic guidance is in good agreement that ridging over the E Pacific will continue to build eastward into the Desert Southwest early next week. This will promote rising temperatures with highs topping out around 90 degrees as early as Tuesday. By the middle to latter half of next week, hghts aloft will are forecast to increase even further, boosting temperatures to well- above normal levels. In fact, there is a good probability that by the latter half of the week many of the lower deserts communities will observe the first triple digit highs of the year.

AVIATION

Updated at 0548Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No aviation concerns are expected during the TAF period. Winds will resume their typical diurnal trends with speeds generally aob 10 kts. Low clouds will stick around through Thursday evening with the lowest bases generally aoa 6k ft. Guidance points towards the potential for more shower activity Thursday afternoon, but as of now, chances are far too low to include mention of any VCSH in the TAFs. However, if these showers due come to fruition, gusty winds, reduced visibility, and CIGs below 6k ft will be possible.

Southeast California/Southwest Arizona including KIPL and KBLH: No aviation concerns are expected over the next 24 hours. Winds at IPL will gradually relax but remain out of the W through Thursday afternoon and evening. AT BLH, SW winds will eventually become more variable, with calm conditions at times. Low cumulus will be observed through the forecast, with bases around 8-9k ft. Guidance points towards the potential for more shower activity Thursday afternoon, but as of now, chances are far too low to include mention of any VCSH in the TAFs. However, if these showers due come to fruition, gusty winds, and brief periods of reduced visibility will be possible, but CIGs should remain above MVFR thresholds.

FIRE WEATHER

Scattered showers and isolated thunderstorms will be possible through this evening. The strongest cells will be capable of producing gusty, erratic winds up to 25-35 mph and a few lightning strikes. Chances for wetting rainfall will remain low around 10-30% with only a few locations receiving measurable rainfall. Another chance for light showers will arrive on Friday with this activity expected to remain confined to the foothills and higher terrain areas NE of Phoenix. MinRHs will range from 20-30% areawide on Thursday and between 10-25% from Friday through the weekend. Winds should remain light with the exception of some afternoon gustiness across the western districts and AZ high terrain. Well- below normal temperatures are anticipated through the end of the week before a gradual warming trend takes shape beginning this weekend.

PSR WATCHES/WARNINGS/ADVISORIES

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