textproduct: NWS Phoenix

UPDATE

18Z Aviation Discussion.

KEY MESSAGES

- Temperatures will remain largely unchanged, with a slight increase across southeast California and southwest Arizona during the middle of the week.

- Periods of breezy to locally windy conditions can be expected across south-central and southwestern Arizona through Monday with gusts reaching 20-35 mph.

- Dry weather with zero rain chances will persist through the upcoming week.

SHORT TERM /TODAY THROUGH MONDAY/

The overall synoptic pattern remains largely unchanged with high pressure stretching across the Desert Southwest and centered over southern Utah/northern Arizona and a trough centered over the Midwest. The high is expected to peak this morning around 591-593 dm before gradually weakening into tomorrow. With the high peaking this morning the increase pressure gradient, between this high and the low to the east, is also expected to peak this morning. Easterly/northeasterly winds of 20-35 mph with some occasional gusts upwards of 40 mph are expected to peak this morning then gradually decrease through the afternoon and early evening. The highest gusts are expected across the higher terrain to the east of Phoenix and across northern and western Yuma County. As mentioned previously, the pressure gradient will start to relax tomorrow as the high weakens and the low migrates eastward. However, there will still be some wind gusts of 20-30 mph across the region during the morning and afternoon hours. Peak gusts will be across the higher terrain to the east of Phoenix and southwest AZ.

Temperatures will be fairly similar to yesterday with afternoon highs above normal. High temperatures are forecasted to be in the mid to upper 90s across south-central AZ, the upper 90s to low 100s across SE CA and SW AZ, and in the 80s across the higher terrain areas. Morning lows will continue to be well above normal (7-12 degrees). Morning lows will be in the 70s to low 80s across the lower deserts and in the 60s across the higher terrain. As a result there will be widespread Minor Heat Risk with areas of Moderate Heat Risk, mainly across western Imperial County, Yuma County, and the Lower Colorado River Valley.

LONG TERM /TUESDAY THROUGH SATURDAY/

On Tuesday, the high pressure system will shift westward as a quasi- omega block pattern sets. There will be troughing across the eastern two-thirds of CONUS, a low pressure system in the Pacific, and the aforementioned high centered over the west Pacific Ocean/California coast. Forecast confidence is good that this pattern will hold through the majority of the week. This will result in temperatures remaining fairly steady across south- central AZ with afternoon highs in the 95-100 degree range across the lower deserts and ranging from the mid 80s to lower 90s across the higher terrain areas. The high across the coast of California looks to strengthen slightly resulting in a slight increase in temperatures for SE CA and SW AZ. As a result afternoon highs will be around 100-106 degrees across the lower deserts in SE CA and SW AZ on Wednesday and Thursday. With high pressure in place dry conditions with no chances for rain will continue.

The high pressure system is then expected to start to weaken by the end of the workweek with a trough moving into western CONUS this upcoming weekend. However, forecast confidence starts to decrease this upcoming weekend as the ensemble members differ on 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 to near to slightly above normal by this upcoming weekend. Additionally, dry conditions look to continue through at least Saturday, but this could change depending on when the aforementioned low moves into the region. 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, but since we're still a week out a lot could change. Stay tuned for updates.

AVIATION

Updated at 1735Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: The main aviation concern will be round of breezy conditions during the TAF period. Gusts today will be strongest during the afternoon, reaching upwards of 25-30 kt at times, but will be on a gradual downtrend through the day. Winds will remain relatively elevated overnight before gusts closer to 20-25 kt develop once again late Monday morning. These enhanced winds will have the potential to generate some lofted dust, but surface VIS reductions are not expected, though slantwise concerns may arise, especially as we get closer to sunset. LLWS shear may also present some operational challenges, but should remain below TAF criteria. Mostly clear skies will be present through the forecast window.

Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation concerns are expected over the next 24 hours. Winds will be favored out of the E/NE at each terminal through this afternoon before tilting back toward the NNE at KBLH and NW at KIPL by this evening. Clear skies will be common across the region through Monday morning.

FIRE WEATHER

Dry conditions with above normal temperatures will continue through the upcoming week. A slight increase in temperatures, into the 100-106 degree range is anticipated across the western districts during the middle of the workweek. MinRHs will mostly range from 15-25% over the western districts to 25-35% for the eastern districts with fair to good overnight recovery area-wide. A persistent breezy easterly gradient wind will continue through Monday. Expect winds to remain elevated around 8-12 mph with early morning and afternoon gusts up to 20-30 mph, with locally higher gusts of 35-40 mph possible, mainly across SW AZ and the eastern district. On Tuesday, winds will return to their more typical diurnal tendencies with only minor afternoon upslope gustiness in the afternoons.

PSR WATCHES/WARNINGS/ADVISORIES

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