textproduct: NWS Phoenix

UPDATE

Updated 12Z Aviation Discussion.

KEY MESSAGES

- Above normal temperatures with afternoon highs in the nineties will be common through much of the upcoming week as high pressure prevails over the area.

- A weak weather system will traverse the region today, providing slightly cooler temperatures and chances for scattered showers and isolated thunderstorms with activity mainly confined to the Arizona high terrain.

- Another stronger weather system is likely to affect the region late this week into next weekend, leading to breezy conditions, cooling temperatures, and the potential for increasing rain chances across portions of the area.

SHORT TERM /Today through Wednesday/

Upper level water vapor satellite imagery and objective analysis early this morning shows a high pressure system centered over the Four Corners Region and a shortwave trough just off the coast of southern CA. Similar to the past couple of mornings an easterly wind surge is expected during the mid to late morning hours mainly across the higher terrain areas east of Phoenix and across the lower elevations of eastern Maricopa and NW Pinal Counties. Gusts in the 25-35 mph range are expected across the higher terrain areas and in the 15-25 mph range across the lower elevation areas.

The aforementioned shortwave trough will quickly traverse the region today. PWAT values will increase across the region today from both the increased easterly winds this morning and the shortwave will also bring a little bit of moisture with it as it moves through the region today. This increase in moisture will be sufficient enough to generate some scattered showers and isolated storms across the AZ higher terrain in northern and eastern AZ. This increase in moisture will not be enough to generate any shower or storm chances across the lower deserts as there will be too much dry air to overcome. However, this disturbance will bring an abundance of mid and high level clouds that could result in areas of occasional virga across the lower deserts. Additionally, this abundance of cloud cover will result in cooler temperatures (around 5-7 degrees cooler than yesterday) across south-central AZ. Temperatures will remain similar to yesterday across SE CA and SW AZ as the thicker clouds will already be exiting those areas by the afternoon hours. So, temperatures this afternoon look to top out in the lower 90s across SE CA and SW AZ, in the mid to upper 80s to around 90 degrees across south-central AZ, and in the lower 80s to lower 80s across the higher terrain areas to the east of Phoenix.

By Tuesday the weak shortwave trough will be east of our region with high pressure starting to build back in over the Desert Southwest. With the disturbance to the east and high pressure in place drier air will filter back into the region. As a result, skies will be mostly clear with warming temperatures Tuesday and Wednesday. Temperatures will rebound into the low to mid 90s (mid to upper 80s) across the lower deserts (higher terrain), which is around 10 degrees above normal for this time of year. The high pressure looks to peak on Wednesday, with H5 heights around 576-579 dm.

LONG TERM /Thursday through Sunday/

High pressure will continue to encompass the region on Thursday resulting in continued dry conditions and well above normal temperatures. Temperatures Thursday will be similar to Wednesday with afternoon highs in the low to mid 90s (mid to upper 80s) across the lower deserts (higher terrain), which is around 10 degrees above normal.

By the end of the workweek and this weekend ensembles continue to point towards a pattern change for our region. Ensembles show a closed low pressure system moving onshore of central CA on Friday, which will result in heights starting to lower across AZ. Ensembles show H5 heights going from 576-579 dm on Thursday to 573-576 dm on Friday. With lowering heights, temperatures will also start to cool, with afternoon high temperatures falling into the upper 80s to low 90s (low to mid 80s) across the lower deserts (higher terrain). The low pressure system looks to weaken as it moves onshore this weekend and eventually get wrapped up into a trough digging out of the Pacific NW and eventually slowly progress eastward into our region by the end of the weekend. However, there remains a decent amount of uncertainty within the ensemble members in the exact track and strength of this system as it moves on shore. If the system is stronger and deeper than precipitation chances will increase across the region as the system will bring in more moisture. However, if the system is weaker and shallower than precipitation chances may be confined to the higher terrain areas. Additionally this system could bring breezy conditions to the region. Either way temperatures will decrease and look to fall back into the 80s (upper 60s to mid 70s) across the lower deserts (higher terrain) this weekend. Temperatures on Sunday look to fall back to near to even slightly below normal.

AVIATION

Updated at 1121Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: Lingering gusty conditions will be the main aviation concern through the morning hours. Gusts between 15-25 kts can be expected through this morning before relaxing heading into the afternoon hours. Even once gusts relax sustained winds will still hover near 10 kts at KPHX and KIWA, and become more light and VRB at KSDL and KDVT. Wind directions will continue to predominately favor easterly flow, but virga and any light showers may create sudden wind shifts between 17-23Z. SCT-BKN mid to high level clouds are expected through this evening then quickly moving out of the area by the end of the TAF period.

Southeast California/Southwest Arizona including KIPL and KBLH:

No major aviation concerns through the TAF period. Westerly winds will persist at KIPL and at KBLH NW'rly winds will become VRB for most of the period before settling out of the west by late this evening. Wind speeds are expected to mostly stay aob 10 kts at both terminals. SCT- BKN mid to high level clouds will remain through most of the period, before quickly filtering out by this evening into the over night hours.

FIRE WEATHER

Generally dry weather and above normal temperatures will persist during the upcoming work week. MinRHs will be in the 10-20% range across the lower deserts today and in the 20-40% range across the higher terrain areas. Lower RH values return for the remainder of the workweek with minRH falling to 10-20% region wide. Overnight recoveries will be good to excellent overnight tonight (40-60% across lower elevations and 60-100% across the higher terrain). Overnight recoveries then fall to 25-60% for the remainder of the workweek. The increase in moisture today will result in some scattered showers and isolated thunderstorm chances across the higher terrain in northern and eastern AZ this afternoon. Elevated winds are once again expected during the mid and late morning hours today with gusts of 25-35 mph possible across the higher terrain and 15-25 mph possible across the lower deserts in eastern Maricopa and NW Pinal Counties. Lighter winds are then expected for the remainder of the workweek. This weekend a weather system will start to move into the region bringing breezy conditions, chances for precipitation, and cooler temperatures to the region.

PSR WATCHES/WARNINGS/ADVISORIES

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