textproduct: NWS Phoenix

UPDATE

Updated Aviation Discussion

KEY MESSAGES

- Isolated showers and storms will remain possible mostly over the high terrain east northeast of the Greater Phoenix Area through the remainder of the afternoon.

- A pronounced warming and drying trend is expected over the next several days as a weather system departs the Desert Southwest and high pressure takes hold along the West Coast, leading to triple digits highs across the lower deserts as early as Friday.

SHORT TERM /TODAY THROUGH THURSDAY/

An expansive cumulus field covered the entire forecast area early this afternoon, with better vertical development over the eastern half of the state, where modest instability (100-250 J/kg MLCAPE from RAP analysis) is present. This has resulted in spotty showers and storms forming over the mountains east of Phoenix and more notably along/downstream of the Mogollon Rim. An upper level low continues to draw nearer to the area and is currently spinning over SoCal, bringing abundant cooler air aloft to aid in the development of the cumulus across the region. Breezy conditions continue today, as regional pressure gradients remain strong, particularly across portions of Eastern AZ. Widespread gusts to between 15-30 mph have been observed this afternoon, with locally stronger gusts in the typically prone western/southwestern portion of Imperial County (30- 40 mph). An increase in westerly winds may occur around/after sunrise for the southwest corner of Imperial County, with gusts flirting near Advisory level for a few hours, but generally localized to gaps in the terrain and just downstream of prominent terrain features.

The main energy from the low will exit to the northeast on Wednesday and will be absorbed by another larger scale trough that will encompass most of the central and eastern CONUS. Meanwhile, a trailing piece of energy is expected to become cutoff from the main jet stream and form a new upper-level low across northern Sonora as a ridge of high pressure builds across the west coast. This feature will continue to gradually progress eastward through northern Sonora through Thursday with no sensible weather impacts expected for our region. As 500 mb height fields steadily rise with the building ridge over the west coast, temperatures will be on a rapid warming trend, warming into the middle 80s on Wednesday to middle 90s on Thursday across the lower deserts.

LONG TERM /FRIDAY THROUGH MONDAY/

The main story heading into the long term period will be a prolonged heat episode that will materialize as triple digit highs will be in place for several days. As the aforementioned ridge continues to gradually build across the western CONUS, temperatures will continue to gradually warm with lower desert highs reaching the low 100s as early as Friday with widespread highs in the low to mid 100s continuing through the weekend. Heading into early next week, ensembles show the ridge intensifying a bit more as 500 mb height fields near 590dm. This will result in additional warming, with the latest NBM showing widespread lower desert highs in the mid to upper 100s. With temperatures heating up into the triple digits by the end of the week and beyond, widespread Moderate HeatRisk will be in place across most of the area. Thus, any vulnerable communities and those participating in outdoor activities will need to take the necessary heat precautions to avoid any heat- related illnesses.

AVIATION

Updated at 0515Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No major aviation concerns are expected during the TAF period under mostly clear skies. Winds will resume their light and diurnal trends, with a later than usual switch to the E/SE tonight ahead of a quick return back to W'rly flow by the late morning hours. Some occasional gusts will be possible during Wednesday afternoon but should only reach into the mid-teens.

Dependent on smoke generation by the wildfire in Buckeye, W-SW winds Wednesday afternoon may pull more smoke into central portions of Phoenix and could impact slantwise visibility, especially during the afternoon and evening timeframe.

Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation concerns are expected during the next 24 hours. Outside of periods of variability, winds should favor a W/SW'rly component during the forecasting window. Mostly clear skies will dominate the region through Wednesday evening.

FIRE WEATHER

Below normal temperatures will prevail today and Wednesday across the region as readings across the lower deserts will top out in the upper 70s today and middle 80s Wednesday. Isolated showers and storms remain possible through this afternoon, particularly across the higher terrain areas east of Phoenix. Breezy conditions will continue for today with afternoon/early evening gusts peaking at 15-30 mph and locally higher in Western Imperial County. MinRHs for this afternoon will remain elevated with values bottoming out between 20-40%. Lighter winds as well as much warmer temperatures and lower humidities are then forecast for the latter half of the week and beyond as high pressure builds back into our region. Although conditions for critical fire weather will not be met, single digit MinRHs this weekend will combine with well above normal temperatures (triple digit highs for the lower deserts) and typical upslope breeziness with gusts 15-25 mph to produce some areas of elevated fire danger.

PSR WATCHES/WARNINGS/ADVISORIES

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