textproduct: NWS Phoenix

KEY MESSAGES

- Cooler temperatures, but still remaining 10 degrees above normal, can be expected through midweek.

- A dry weather system will bring locally windy conditions on Thursday and Friday, while also briefly dropping temperatures more into the near normal range.

- There is potential for a stalled out weather system near our region this weekend into early week to bring a round of precipitation early next week.

SHORT TERM /TODAY THROUGH WEDNESDAY/

The latest water vapor satellite imagery as well as objective analysis show a weakening shortwave trough moving through the central Rockies with the associated trough axis extending southwestward through the Desert Southwest. A lingering pressure gradient on the back side of the trough will result in some northerly breezes, mainly along the Lower Colorado River Valley, through this afternoon with peak gusts of 20-30 mph. With a cooler air mass in place, afternoon high temperatures will be noticeably cooler compared to the record warmth observed since late last week as readings are expected to top out in the mid 80s across most of the lower desert communities. Heading into Wednesday, a transient upper-level ridge will pass through the region out ahead of the next troughing feature from the Pacific Northwest that will influence the weather pattern heading towards the latter half of the week. The ridge will result in tranquil weather with light winds and temperatures similar to today.

LONG TERM /THURSDAY THROUGH MONDAY/

Model guidance is starting to come into better agreement with the incoming system later this week, but there are still some unknowns with its evolution, how long it will stick around, and whether or not rain chances will be in our future. Guidance seems to have come to a good consensus with the initial development of an upper low just to our north late Thursday before a second piece of energy dives southward into the base of the trough on Friday. The first piece of energy will not impact our region, but strong height falls associated with the trough will help to bring another breezy to windy day on Thursday while highs temperatures also drop just below 80 degrees. Model uncertainty increases once the second piece of energy drops into the trough on Friday. However, there is at least good consensus for this feature to cause a new upper low to develop somewhere to our southwest by Friday night into Saturday before likely becoming cut off from the main flow.

Dry conditions will persist across our region late this week into the weekend as the disturbances will contain little to no moisture as they briefly pass through or brush by our region. NBM guidance has been trending cooler for at least Friday with highs now potentially only topping out in the lower 70s to around 75 degrees. Uncertainty in the position of the cut-off low this weekend is impacting the potential range for our forecast temperatures, but they should at least bounce back into the 80s if the low moves far enough to our southwest.

Models are suggesting a quick deepening of the low this weekend as well as it stalling out somewhere near or just west of Baja. The eventual strength of the low and how long it stalls out will likely determine how much moisture can get entrained into the system and whether or not the moisture will get transported into our region. Model trends over the past couple of days have been leaning toward a higher probability of at least some modest moisture advecting into the area Sunday into Monday. This in turn has led to an increasing number of ensemble members pointing at some mainly light QPF into the region, focused more across the southeastern 1/3 of Arizona. NBM PoPs have risen with the latest run, but chances max out at 20% across the south-central Arizona lower deserts to 40% over the eastern Arizona high terrain. Another couple of days of model runs will hopefully result in decreasing model uncertainty.

AVIATION

Updated at 1720Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No aviation concerns expected during the TAF period. Winds will follow typical diurnal trends with windows of variability during directional shifts. Clear skies will give way to SCT-BKN high clouds during the latter half of the forecast.

Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation concerns are expected during the next 24 hours. N'rly winds will prevail at each terminal before directions tilt back toward the W/NW after sunset. Clear skies this afternoon will become SCT-BKN early tonight as high clouds stream over the region.

FIRE WEATHER

Temperatures will cool today, but remain well above normal as a dry weather system passes by to the north. Winds will also be lighter today except for northerly gusty winds up to 25 mph across southeast California and the Lower CO River Valley. Overall light winds are anticipated for Wednesday. MinRHs will continue to range between 10-15% areawide, followed by fair overnight recoveries commonly between 30-50%. Another dry weather system later this week should again bring widespread breezy conditions by Thursday while dropping highs mostly into the mid to upper 70s.

PSR WATCHES/WARNINGS/ADVISORIES

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