Sunrise 5:44 AM   Sunset 7:08 PM Moonrise 9:13 PM   Moonset 6:31 AM

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FXUS65 KPSR 251152 AFDPSR

Area Forecast Discussion National Weather Service Phoenix AZ 452 AM MST Thu Apr 25 2024

UPDATE
Updated 12z Aviation Discussion...

SYNOPSIS
Multiple areas of low pressure will traverse the Desert Southwest over the next several days, resulting in cooler-than- normal temperatures through at least Saturday. These systems will help generate persistent breezy to locally windy conditions while increasing rainfall potential for some areas. We quickly warm back up to start next wee as high pressure build over the region.

DISCUSSION
The ridge that parked over the region during the past several days has now pushed off toward the Central Plains while a weak area of low pressure advances off the eastern Pacific. This trough will quickly move over our forecast during the next 24 hours, providing us with much cooler temperatures, continued breezy to locally windy conditions, and even chances of rain for southwestern Arizona.
Afternoon highs today will be 15-20 degrees cooler compared to where we were to start the week, with readings only expected to reach into the lower and middle 80s across the lower deserts. Areas of southeast California will once again see enhanced winds with peak gusts around 30-35 mph this afternoon, though a few advisory-level gusts (40+ mph) are likely again (60-80%) across the Imperial Valley and areas around the Salton Sea. Although coverage of these enhanced gusts will be more limited to what was seen yesterday, a Wind Advisory has been posted for these areas for this afternoon and evening regardless in addition to the Advisory that remains in effect for southwestern Imperial County through early Saturday.

Even with relatively limited moisture flux over the region associated with this trough, showers, with some even containing some lightning, have been observed over parts of southwestern Arizona early this morning, which was hinted at by the CAMs over the last day. Hi- res guidance shows these showers persisting as far as the late morning hours, mainly across La Paz County, but a light shower or two over northern Yuma and western Maricopa Counties would not be surprising. Any totals with these showers will be light, amounting to generally less than .10".

This initial system will quickly eject out of the region by late today into early Friday, but a trailing more potent low will file in behind it, helping to keep conditions cooler and unsettled through the end of the week. Temperatures Friday afternoon are forecasted to be, once again, in the lower to middle 80s across the lower deserts, a good 5 degrees or so below normal for this time of year. Recent model runs have become more consistent regarding the timing of this system, with the base of the trough pushing over the region by Friday afternoon and evening. This timing favors the generation of more breezy to locally windy conditions this afternoon, but with this disturbance being deeper than its predecessor, gusts will be stronger and more widespread compared to today. Gusts greater than 40 mph are likely (>90% chance) to return across parts of southeastern California, which has prompted the issuance of another Wind Advisory for much of Imperial County and the area around Joshua Tree NP. However, advisory-level winds will not be limited to those areas alone, as there is high confidence in seeing similar gusts across portions of the south- central Arizona high terrain, resulting in a Wind Advisory being posted for parts of eastern Maricopa and Pinal Counties, as well as southern Gila County. Winds elsewhere should remain below the advisory threshold, but gusts between 25-35 mph will be common across the remainder of the region. These enhanced winds will be capable of producing areas of blowing dust, especially out in Imperial County, leading to potentially hazardous travel conditions at times due to reduced visibilities.

With better kinematic forcing and moisture flux associated with this secondary system, rain chances continue to be shown for parts of our forecast areas for late Friday into early Saturday, with the best chances (30-40%) over northern Maricopa and southern Gila Counties.
Elsewhere across the lower deserts of Maricopa and Pinal Counties, rain chances have dropped slightly, but PoPs around 10-20% remain.
Rainfall amounts with this round of potential rainfall would again be on the light side, ranging from 0.01"-0.10", with those higher totals favored over high terrain areas.

One more day of unseasonably cool conditions, with some residual breeziness, will occur on Saturday as the aforementioned system begins ejecting out of the region. Forecasted conditions across the lower deserts Saturday call for highs in the low to middle 80s, with widespread gusts between 20-30 mph. From there, after the trough has fully cleared the Desert Southwest, high pressure will begin to fill in, leading temperatures on a warming trend as we head into the start of next week. Temperatures will quickly rise to the middle and upper 80s for much of the region by Sunday before rising further into the lower 90s by Monday and then into the mid and upper 90s by Tuesday.

AVIATION
Updated at 1150Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Current east to southeast winds will gradually veer out of the west to southwest by the mid to late morning hours. A few hours of southerly winds are likely during the transition. Otherwise, speeds by late this morning through the afternoon will pick up once again with gusts up to 20 kts, before subsiding after sunset.
SCT mid-level clouds of around 15 kft will persist into early this morning, becoming FEW by later this morning with bases slightly lowering to 9-12 kft.

Southeast California/Southwest Arizona including KIPL and KBLH: West winds will persist at KIPL while southwesterly winds will persist at KBLH through much of the day. Speeds will once again be elevated, especially heading into this afternoon and evening with gusts upwards of 20-25 kts at KBLH and up to 30-35 kts at KIPL.
Winds are expected to gradually subside by the late evening hours.
Skies will remain mostly clear throughout the period.

FIRE WEATHER
Multiple areas of low pressure will traverse the region over the next several day, helping to cool temperatures and producing daily occurrences of breezy to locally windy conditions. However, due to the cooler-than-normal temperatures and rising RH levels, fire danger will remain limited through the start of this weekend.
MinRH values will range between 20-30%, with good to excellent overnight recoveries expected. Increasing moisture levels will also yield chances (~30%) for wetting rain across the high terrain of the eastern districts late Friday into early Saturday.
Dry and hot conditions return by the start of next week.

PSR WATCHES/WARNINGS/ADVISORIES
AZ...Wind Advisory from 2 PM Friday to midnight MST Friday night for AZZ557-558.

CA...Wind Advisory from 2 PM Friday to midnight PDT Friday night for CAZ560-563-565>567.

Wind Advisory until midnight PDT Friday night for CAZ562.

Wind Advisory from 3 PM this afternoon to midnight PDT tonight for CAZ563-566-567.

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