textproduct: NWS Phoenix

UPDATE

Updated Aviation Discussion

KEY MESSAGES

- Scattered light showers will continue across central and eastern AZ through early this evening before departing east of the area.

- Patchy fog may develop across the lower deserts overnight into early Monday morning.

- Dry and tranquil weather returns for this upcoming workweek with temperatures warming near to slightly above normal.

SHORT TERM /TODAY THROUGH MONDAY/

Latest satellite wv imagery and 500 mb streamline analysis depicts the deep cutoff low pressure system that brought widespread rain to our forecast area is now departing into the Four Corners region. Subsidence on the back side of the departing upper-low has allowed for clearing skies across western AZ and southeast CA, however southcentral AZ is still holding onto abundant low level moisture and cloud cover which has kept temperatures in the low to mid 60s. These temperatures are around 5-8 degrees below average for late November. Besides a low chance for a pop up shower this afternoon, rain chances will come to an end across the entire forecast area by this evening. Model guidance including most HREF members are indicating near sfc saturation across portions of the lower deserts tomorrow morning which could result in the development of patchy fog in low lying areas and river valleys. There could also be pockets of denser fog with visibilities falling below 1SM at times. Drivers should exercise caution when encountering lower visibilities during the morning commute.

By Monday afternoon, the low pressure system will continue to lift into the Central Plains, resulting in a return of dry and tranquil conditions with mostly clear skies across the Desert Southwest. Heights aloft will rise slightly in response to a building ridge over the eastern Pacific. These rising 500 mb heights will promote slightly warmer temperatures with afternoon highs ranging from the upper 60s to low 70s across the lower deserts, and the low to mid 60s across the higher terrain.

LONG TERM /TUESDAY THROUGH SATURDAY/

Global ensemble members continue to be in great agreement that heights aloft will steadily rise through the workweek rising to a 582-585 dm range by the end of the workweek. These rising heights aloft will continue to promote dry and tranquil conditions through the week along with a gradual warming trend. Temperatures will return to near normal on Tuesday and then go slightly above normal by the end of the workweek. Afternoon high temperatures on Tuesday will range from the low to mid 70s across the lower deserts and from the mid to upper 60s across the higher terrain. Then, by the end of the workweek highs will be in the mid to upper 70s across the lower deserts and in the upper 60s to low 70s across the higher terrain. Morning lows will go from the mid 40s to low 50s on Tuesday to the upper 40s to mid 50s by the end of the workweek across the lower deserts. For the higher terrain, morning lows will go from the low 40s on Tuesday to the mid to upper 40s by the end of the workweek.

By next weekend, global ensemble members start to differ on the overall synoptic pattern. They all show a deep trough traversing the region by some point either during the weekend or early the following week, but they differ on the exact timing. They are in good agreement that the trough will be moving down into our region from the Pacific NW and not move down along the eastern Pacific Ocean and then move inland like this last low pressure system did. With this trough looking like it will not be coming from the Pacific Ocean the system won't be bringing a lot of moisture to the region. PWATs currently look to only rise to a 0.5-0.7" range. This may be enough to squeeze out some light rain showers across the higher terrain, however, it likely won't be enough to produce showers across the lower deserts. With this system around a week out and emsemble members in some disagreement things can change, so be sure to keep checking back for updates.

AVIATION

Updated at 2350Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: The main aviation concern in the near term will be lingering low CIGs through this evening. Cloud coverage will gradually decrease through early tonight but lingering VFR CIGs may lead to some slantwise VIS issues on approach. By early Monday morning, there are signs of potential FG development that would result in reduced VIS. KIWA looks to be the most likely terminal to see operational impacts, therefore a TEMPO group has been introduced in the TAF, but KPHX cannot be completely omitted from the discussion of reduced VIS. However, confidence is lower so any mention of BR/FG has been left out of the TAF at this time. Winds over the duration of the period will be light with extended periods of VRB to calm conditions.

Southeast California/Southwest Arizona including KIPL and KBLH: The main aviation concerns during the period will BR/FG development early Monday morning. With increasing confidence regarding potential operational impacts, TEMPO groups have been added to each TAF, with the greatest impacts (1SM VIS) highlight at KIPL. Winds will be light with extended periods of VRB to calm conditions.

FIRE WEATHER

Below normal temperatures are expected to continue through Monday before rising back to near to slightly above normal by the middle of this week. The low pressure system which brought abundant wetting rainfall to the region will continue to depart north and east of AZ through tonight, allowing shower activity to come to and end and bringing dry tranquil weather back to the forecast area. MinRHs will range from 40-60% with excellent overnight recovery of 80-100% through Monday. Drier air will filter into the region by the middle of the week with MinRHs bottoming out around 25-35% by Wednesday and Thursday. Despite a few upslope gusts in the teens to lower 20 mph range, winds will remain light and follow normal diurnal patterns.

PSR WATCHES/WARNINGS/ADVISORIES

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