397 FXUS65 KPSR 032346 AFDPSRArea Forecast Discussion National Weather Service Phoenix AZ 446 PM MST Fri Oct 3 2025
.UPDATE...Updated Aviation Discussion.
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.KEY MESSAGES...
- Low pressure will brush the Desert Southwest today and bring a dry cold front through the region tomorrow morning leading to breezy to locally windy conditions and cooling temperatures heading into the weekend.
- A gradual warming trend will commence once again for the first half of next week.
- Increasing rain chances late next week into next weekend with at least a low chance for impactful flooding rainfall possible, but forecast confidence is still very low at this time.
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.SHORT TERM /TODAY THROUGH SUNDAY/... A low pressure circulation currently centered just south of Lake Tahoe, as seen on satellite, will push eastward over the next 24 hours and an associated dry cold front will drop down into southeast CA and AZ tonight and Saturday morning. With the base of the trough passing over the lower deserts and pressure packing, breezy to windy conditions can be expected today and again tomorrow primarily in eastern AZ. Today, widespread afternoon and evening wind gusts up to 20-30 mph are expected, with strongest gusts, up to 40-50 mph expected across parts of southeast CA, especially in Imperial County with mountain downsloping enhancements. The Wind Advisory in effect for western Imperial County has been expanded to now include the Imperial Valley for this evening through early-tonight. Latest HREF shows 50-70% probabilities for wind gusts greater than 40 mph in the Valley. These wind will be capable of generating localized dust channels that may briefly reduce visibility under 5 miles.
After reaching the middle 90s to around 100 degrees across the lower deserts today, temperatures will then cool by as much as 10 degrees by tomorrow afternoon, following the passage of the trough to the north and the dry surface cold front. Lower desert highs tomorrow are forecast to top out in the middle to upper 80s, around 5-7 degrees below normal. Highs will then be a degree or two warmer for Sunday. Dew point temperatures will also drop into the 30s tomorrow afternoon. This drier air will persist through the weekend and assist in some cooler mornings as well. Morning lows in the 60s are expected this weekend for most areas. Being in a desert, this may even feel a bit nippy for some people.
Isolated showers and storms are bubbling up in far eastern AZ this afternoon, east of San Carlos, and will remain isolated in this area and dissipate this evening. After this afternoon, with drier air moving in, most of, if not all of, AZ and SoCal will be cloud-free through this weekend.
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.LONG TERM /MONDAY THROUGH FRIDAY/... The highlight of the long term forecast is the potential for another high impact rain event with tropical influences late next week. Current Invest 99E off the southern coast of Mexico, in the eastern Pacific, is forecast to become a tropical storm within the next 24 hours and then slowly drift northwest through the middle of next week. Beyond this there is still a lot of uncertainty in what will unfold. The only couple of certainties there seems to be at this time is that there will be an increase in anomalous moisture into the Southwest U.S. and that the tropical cyclone will likely fall apart at sea as it moves closer to higher shear around the base of the lingering trough pattern over the northeastern Pacific and along the West Coast. One question is whether the remnants of the cyclone will turn and be pulled northeastward by the trough, stall and fizzle out, or turn westward further out to sea. While there is good confidence in anomalous moisture being pulled northward regardless, the remnants of the cyclone may still be needed to provide a source of lift in the region, as right now models are not showing too much in the was of instability late week and into the weekend and the coastal trough expected to remain coastal, which may limit dynamic forcing.
It is still worth talking about this, despite being a week or more out and low confidence/low probability, due to the potential high impact, especially after last week`s high impact flooding and winds. There are model solutions with high rainfall amounts for southern AZ and SoCal. Around 10-15% of global ensemble members have 1.5-2.5+ inches by the end of next weekend. The extreme members are driving up the ensemble means to the point where there are periods where the means are higher than 75th percentile of the full spread. The median (50th percentile) forecast rainfall amounts from the global ensembles and NBM is actually no rain with the latest runs. In addition to the large spread in rainfall forecast amounts, there is a lot of uncertainty in when rain will fall, or at least the best window for rain, but it is possible that the best window of opportunity for rain may not come until the coastal trough moves inland or a shortwave moves through the base of the trough, which may not even happen until the beginning of the following week. Ultimately, it is good to be aware of the potential for another high impact rain event in 6-12 day forecast.
Before getting to this window of potential rain, the weather will be pretty benign. Higher pressure is expected to nudge back into the region from the southeast early next week that will result high temperatures warming back to to a few degrees above normal by the middle of the week, with lower desert highs in the middle 90s. The morning lows will remain fairly cool and seasonal. Thursday onward, the temperature forecast become more uncertain, due to the uncertainty with the increasing rain chances.
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.AVIATION...Updated at 2346Z.
South Central Arizona including KPHX, KIWA, KSDL, and KDVT: Gusty west southwest winds into the early evening and lower than usual confidence on a full easterly wind shift overnight/early Saturday morning will be the only weather concerns under generally clear skies. Periodic gusts to around 20 kts will persist for the next few hours, then winds will relax and likely begin to exhibit periods of variability overnight. While a shift to east winds is possible at KPHX, confidence is low and speeds would be light (AOB 5 kts), so opted for prevailing VRB winds from 12-17Z. Prevailing SW/W winds AOB 10 kts will reestablish late Saturday morning and continue through the afternoon.
Southeast California/Southwest Arizona including KIPL and KBLH: Strong, gusty SW/W winds this evening will be the primary aviation concern under clear skies. Speeds will be stronger at KIPL, with gusts to 30-35 kts possible for a period. With these strong winds, some lofted dust/hazy conditions could briefly reduce visibilities to 5-6SM. Expect gusts to around 25-30 kts at KBLH. Gusts should subside late this evening or during the overnight hours and directions will tend to veer out of the northwest Saturday morning. Light NW winds generally AOB 8 kts will then prevail for much of the day Saturday.
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.FIRE WEATHER... Temperatures will start to cool out west today, but remain above normal across the central and eastern districts, with some south- central AZ lower desert locations seeing tripple digits again today. Further cooling is expected this weekend region wide, thanks to a dry cold front, with temperatures falling below normal. This cold front will bring breezy to locally windy conditions to the region. Gusts of 20-30 mph are expected across south-central and eastern AZ this afternoon and evening. Gusts in excess of 40 mph are possible across western Imperial County, otherwise gusts of 25-35 mph are expected across SE CA and SW AZ. The gusty winds will continue through early Saturday morning across SE CA and SW AZ. Gusty winds (20-25 mph) are expected Saturday afternoon and early evening across the eastern AZ higher terrain. MinRHs will be in the 15-25% range through the middle of next week, with overnight recoveries in the 30-60% range. Gradually warming temperatures and dry conditions are expected for the first half of next week. There is increasing chances for wetting rainfall by the end of next week, however, forecast confidence is low at this time. With the increasing rain chances MinRHs currently look to increase to 30-40% for the end of next week.
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.PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...Wind Advisory until 5 AM PDT Saturday for CAZ562.
Wind Advisory until midnight PDT tonight for CAZ566-567.
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SHORT TERM...Benedict LONG TERM...Benedict AVIATION...Whittock FIRE WEATHER...Berislavich
NWS PSR Office Area Forecast Discussion