textproduct: NWS Phoenix

KEY MESSAGES

- Breezy to locally windy conditions can be expected this morning through the early afternoon across south-central and southwestern Arizona with gusts reaching 20 to 35 mph.

- Above normal temperatures with minimal day to day changes will exist through the start of the week as afternoon highs reach 97 to 103 degrees across the lower deserts.

- An Extreme Heat Watch remains in effect for portions of southeast California and southwest Arizona on Wednesday and Thursday as temperatures warm to near record levels.

- Dry weather with zero rain chances will persist through Saturday with isolated shower and storm chances returning to the high terrain in eastern Arizona on Sunday. .

SHORT TERM /TODAY THROUGH TUESDAY/

The overall synoptic pattern remains fairly similar to the past couple of days with broad high pressure situated over the Desert Southwest with it centered over southern Utah. The strong E-W pressure gradient remains in place across southern AZ, although it has relaxed slightly from yesterday. Wind gusts of 20-35 mph are anticipated from this morning through the early afternoon with speeds lowering through the rest of the afternoon and evening as the pressure gradient relaxes further. Similar to the past couple of days, the highest gusts will be across SW AZ and the higher terrain to the east of Phoenix. Temperatures today will be similar to those of yesterday with morning lows in the 70s to low 80s across the lower deserts and in the 60s to low 70s across the higher terrain. Afternoon high temperatures will be in the upper 90s to around 100 degrees across south-central AZ, in the upper 90s to low 100s across SE CA and SW AZ, and in the 80s to low 90s across the higher terrain areas. This will result in widespread Minor HeatRisk with areas of Moderate HeatRisk across SE CA and SW AZ.

Heading into Tuesday the high will start to breakdown and flatten out while also shifting the mid-level flow to be out of the west/northwest instead of out of the east/southeast. Despite these mid-level flow changes it will not be noticed at the surface. In fact, temperatures are forecasted to either be the same as Monday or 1-2 degrees warmer resulting in a similar HeatRisk outlook across the region as on Monday. Additionally, despite the more relaxed pressure gradient, there still may be some occasional breezy conditions Tuesday morning. Mainly across the higher terrain east of Phoenix and portions of SW AZ. Gusts will only be around 15-25 mph. With high pressure in place early this week, dry conditions with no chances for rain will continue.

LONG TERM /WEDNESDAY THROUGH SATURDAY/

By Wednesday, a quasi-omega block will develop with a high pressure system developing near/over the southern California coast and a low pressure system over the Pacific and another low pressure system draped across the eastern two-thirds of CONUS. Forecast confidence is good that this pattern will hold through Thursday before it starts to break down. The high will strengthen slightly on Wednesday, to around 591 dm across SoCal with H5 heights around 587- 590 dm across southern AZ and SE CA. This will result in temperatures increasing slightly, with Wednesday and Thursday forecasted to be the hottest days of the week. Afternoon high temperatures are forecasted to be in the 100-108 degree range across SE CA and SW AZ and in the 98-102 degree range across the lower deserts of south-central AZ. The afternoon high temperatures in the higher terrain areas in eastern Arizona will be in the mid 80s to mid 90s. The combination of these high temperatures and low temperatures around 10 degrees above normal will result in ares of Moderate to Major HeatRisk, especially across SE CA and SW AZ. In fact, temperatures will be near record levels in El Centro, CA and Yuma, AZ. As a result, the Extreme Heat Watch continues for portions of western Imperial County, including the Imperial Valley, and the Yuma area for Wednesday and Thursday. With high pressure in place dry conditions are expected to persist with no chances for rain, except for near the White Mtns Wednesday with a weak shortwave moving through the Four Corners.

The high pressure to the west is then expected to start to weaken by the end of the workweek and into the weekend with a trough moving into western CONUS this upcoming weekend. However, forecast confidence decreases considerably by the end of the weekend and start of the following week as the ensemble spread is large with respect to the timing of the high weakening and moving out of the region and the trough moving in. The ensembles also disagree on the strength of the trough for this upcoming weekend. Either way temperatures are expected to gradually decrease back toward normal by the end of this weekend and beginning of next week. Additionally, dry conditions look to continue through at least Saturday, with slight chances for isolated showers and storms returning to the high terrain of eastern Arizona on Sunday. But, this could change depending on the evolution of troughing during the weekend. Right now better chances for rain look to arrive by the beginning of next week, with the best chances across the higher terrain in eastern AZ. Stay tuned for updates.

AVIATION

Updated at 0505Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: With clear skies persisting, the main weather concern through Monday night will be frequently gusty east winds. Confidence is very good that a few gusts will affect the PHX metro overnight with the atmosphere not completely decoupled and sustained speeds near 10kt. As a result, LLWS conditions should be limited to the most sheltered aerodromes before widespread 20-25kt easterly gusts sweep across the entire area mid morning through mid afternoon. Gusts will abate early/mid afternoon, though an easterly component will prevail the entire TAF period.

Southeast California/Southwest Arizona including KIPL and KBLH: No weather concerns will exist through Monday night under clear skies. Confidence is very good that wind directions will oscillate between a daytime E/NE component and overnight N/NW trajectory with speeds occasionally reaching 10-12kt.

FIRE WEATHER

Expect easterly winds to remain elevated around 8-15 mph with early morning and afternoon gusts up to 20-35 mph. The highest gusts will be across SW AZ and the eastern district. Winds will return to their more typical light diurnal tendencies on Tuesday with only minor morning and afternoon upslope gustiness. These lighter winds may only last a few days before gusty easterly gradient winds develop again by Friday. Dry conditions with above normal temperatures will continue through the majority of the upcoming week, with slight chances for showers and storms returning to the higher terrain across eastern AZ on Sunday. A slight increase in temperatures, into the 101-106 degree range is anticipated across southeast CA and southwest AZ Wednesday and Thursday. MinRHs will mostly range from 15-25% across the western districts to 20-35% across eastern districts with fair to good overnight recovery (35- 60%) area-wide. No wetting rain expected through the next 7 days.

PSR WATCHES/WARNINGS/ADVISORIES

AZ...Extreme Heat Watch from Wednesday morning through Thursday evening for AZZ532.

CA...Extreme Heat Watch from Wednesday morning through Thursday evening for CAZ566-567.