textproduct: NWS Phoenix

UPDATE

Updated 06Z Aviation Discussion.

KEY MESSAGES

- A pair of weather systems moving through the region today and tomorrow will bring rain chances back to the region and cool temperatures to near to below normal.

- Sunday and Monday will be warm and dry before another weather disturbance brings occasional rain chances and cooling temperatures back to the Desert Southwest by Tuesday.

- Another weather system could move through the region at the end of next week that will help keep temperatures below normal.

SHORT TERM /TODAY THROUGH SATURDAY/

A shortwave trough is currently centered over SE CA/NW Mexico and is moving into SW AZ as of early this afternoon. Out ahead of the shortwave trough is a broken line of showers and a few embedded thunderstorms, stretching from Wickenburg down to Tucson. These showers have formed along the front and there is some low level frontogenesis, as seen on the SPC mesoanalysis, helping the showers along. These showers will continue to move northeastwards as the trough progresses eastward through the evening. There was a lot more lightning activity earlier today when the activity was in SW AZ where there was some more instability (around 500 J/kg). However, there is some CIN (-25 J/kg) over south-central AZ, including the Phoenix Metro, so most of the activity is now just shower activity as it has moved away from the instability. This activity should push northeast of the Phoenix Metro by early this evening and then will be confined to the higher terrain areas. PWATs are only around 0.8- 1.0", so minimal accumulations are expected with most locations seeing less than 0.10" with some isolated locations seeing up to 0.25".

Tomorrow, a secondary shortwave will move through the region. This shortwave is currently situated over the central CA and will quickly progress eastward, moving through northern AZ tomorrow. This shortwave will be weaker and will be further north. As a result isolated to scattered rain chances will be confined to the higher terrain and foothills north and east of Phoenix. Best chances will be during the overnight hours tonight and morning hours tomorrow with dry conditions returning by tomorrow evening. PWATs will be around 0.6-0.8" and there will be little to no instability. Therefore, rainfall accumulations will be light and generally around 0.10" or less.

Some wind gusts of 20-30 mph are expected through the evening and overnight hours. Highest gusts will be associated with the rain showers moving through central AZ and across SE CA. Higher gusts of 30-40 mph are possible across portions of SE CA, particularly the usual windy spot of the SW corner of Imperial County. Additionally, as a result of these two shortwave troughs temperatures will be on a decline. Afternoon high temperatures will be in the upper 70s to low 80s across SE CA and SW AZ. An abundance of cloud cover, and the rain currently moving through central AZ, will keep high temperatures in the low to mid 70s across the south-central AZ lower deserts. Matter of fact, areas across south-central AZ likely already reached their afternoon high temperature prior to the rain moving through. Across the higher terrain temperatures will be in the 60s. With the secondary shortwave and additional cloud cover tomorrow, temperatures will cool even more. With highs in the mid to upper 70s across SE CA and SW AZ, in the low 70s across south- central AZ, and in the 50s to mid 60s across the higher terrain areas.

LONG TERM /SUNDAY THROUGH WEDNESDAY/

Sunday will be a down day for shower activity with a brief period of shortwave ridging and some slight dry air advection from the northwest. This will lead to considerably less clouds, virtually no rain chances and temperatures climbing back into the upper 70s by Monday. Models remain in good agreement that another northern Pacific waves will continue to be ejected southeastward toward the U.S. West Coast starting early next week. Currently models suggest the next potential system reaching the California coast early Monday before reaching our region Monday night into Tuesday, where additional rain chances will return to the forecast with NBM PoPs peaking between 50-80% in south-central AZ and the higher terrain areas, however this far out this may need to be adjusted based of how the track of this low progresses. By Wednesday models are pointing towards yet again another low system, however larger discrepancies between models are evident for this system. Due to this confidence is low for rain chances by mid to late next week as things are too inconsistent at this time.

Despite if these next systems bring rain to the region or not, a more significant cooling trend can be counted on by the middle of the week as these series of weather systems move in from the northwest. They will likely usher in a cooler air mass with afternoon highs trending more towards the upper 60s to low 70s, the higher or lower end of this range largely being dependent on the depth and position of the systems.

AVIATION

Updated at 0455Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: Extended periods of SCT to BKN clouds down to 3500-6000 ft AGL will be the primary aviation weather impact through Saturday. Spotty light showers may also develop Saturday morning through midday (10% chance), but activity will mostly focus just north and east of the terminals. E-SE winds will prevail through Saturday morning with speeds mostly below 10 kts. Winds will then shift W-SW at all terminals around 18-20Z Saturday and then back E in the evening.

Southeast California/Southwest Arizona including KIPL and KBLH: West winds will prevail through most of the period at KIPL, while winds at KBLH will vary between SSE and SW. Sustained speeds will remain elevated, around 8-13 kts, through tonight at both terminals. Minor LLWS may develop as surface winds subside Saturday morning, but shear magnitudes are expected to stay below TAF threshold. Lighter wind speeds (5-10 kts) and less gustiness is expected Saturday. SCT clouds down to 5K ft AGL are expected at both terminals most of Saturday. Otherwise FEW to SCT mid and high clouds will continue to pass over the area.

FIRE WEATHER

Multiple weather systems are expected to move through the region over the next week bringing multiple chances for showers and a few storms to the area. One weather system is currently moving through central AZ this afternoon and a secondary one will move through tomorrow. Tomorrow's rain chances will be confined to the foothills and higher terrain areas north and east of Phoenix. In addition to the rain chances, these systems will cool temperatures off below normal. Dry conditions and warmer temperatures are then expected Sunday and Monday before another weather system moves through the region on Tuesday. A fourth weather system is then possible by the end of next week. These systems will bring additional rain chances to the region and cool temperatures back below normal. MinRHs will be around 30-60% through next week, with excellent overnight recovery. Occasional wind gusts of 20-30 mph will continue through tomorrow afternoon, with the highest gusts associated with any shower activity and across the western districts. By tomorrow night, winds will return to their light and diurnal patterns, with another period of gusty winds expected with the weather system on Tuesday.

HYDROLOGY

Gila: A Flood Warning remains in effect from Painted Rock Dam through the Dateland area through at least early next week due to water released from the dam. Water release levels have now risen to 3000 cfs and are expected to remain at this release level through the next several days. This will have the potential to flood farm fields and low-water crossings along the river downstream from the dam.

PSR WATCHES/WARNINGS/ADVISORIES

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