949 FXUS65 KPSR 061211 AFDPSRArea Forecast Discussion National Weather Service Phoenix AZ 511 AM MST Sat Sep 6 2025
.UPDATE...Updated Aviation Discussion.
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.KEY MESSAGES...
- Today will bring lingering chances for isolated showers and maybe a few weak thunderstorms before rain chances generally end starting Sunday.
- Slightly below normal temperatures this weekend will briefly warm back into the normal range early next week before dropping off again later next week.
- Localized Moderate Heat Risk is expected mainly across the south-central Arizona lower deserts during the first half of next week with highs as warm as 104 degrees.
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.SHORT TERM /Today through Sunday/... Drier air continues to work into the region from the west and northwest as a large Pacific low well west of the Pacific Northwest directs the dry mid level flow into Arizona. Despite the drying aloft, the lower levels (below 10K feet) are still quite moist with mixing ratios staying around 12 g/kg and surface dew points in the 60s. This moisture is still allowing for some elevated instability which will persist through at least this afternoon with an outside chance (10%) of a shower or weak storm this morning. Ample daytime heating today is expected to bring further convective potential this afternoon focused over higher terrain areas, but increasing subsidence aloft will act to limit the scope and intensity of any potential activity.
Going into Sunday, the Pacific low is forecast to deepen, amplifying the ridging over Arizona leading to further drying and essentially ending rain chances across the entire area. We can`t rule out a few stray high terrain showers Sunday afternoon, but little if any rainfall is expected. Temperatures this weekend will begin to warm as we see more sunshine, but the lingering boundary layer moisture and slowly rising heights aloft will keep the warming trend fairly muted. Forecast highs show readings from the mid to upper 90s in the Phoenix area today and near 100 degrees across the lower deserts of southeast California and southwest Arizona. Sunday should then bring highs in the upper 90s to around 100 degrees in the Phoenix area to around 100 degrees out west.
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.LONG TERM /Monday through Friday/... The main driver of our weather early next week will be the subtropical high centered just to our south, but the Pacific trough off the West Coast will continue to bring westerly dry flow into our region. H5 heights are forecast to peak early on Monday at 592-594dm before gradually lowering through the middle part of the week as the Pacific trough shifts closer to our region. The higher heights and thicknesses should boost daytime highs on Monday and Tuesday with highs anywhere from 100-105 degrees across the lower deserts. Overnight lows will also stay quite elevated, contributing to localized Moderate HeatRisk focused across the south-central Arizona lower deserts.
Ensemble guidance is in very good agreement bringing the Pacific low center into northern California next Tuesday, displacing the ridge that was over our region well to our southeast. H5 heights are likely to fall to between 584-588dm by Wednesday potentially staying in that range for a couple days late next week as the trough likely stalls out over Nevada before lifting to the northeast. This most likely scenario would continue to dry out the boundary layer with surface dew points dropping into the 30s in southeast California to the 40s in Arizona. Rain chances will stay near zero through at least the first half of next week with only a few members showing any slight rain chances at some point later next week. Temperatures will also react to the incoming trough with highs falling back into mid to upper 90s by around Wednesday or Thursday and overnight lows falling below 80 degrees areawide. It would not be surprising to see some low temperatures in the 60s across rural lower deserts and into the 50s over higher terrain areas. Lows within the Phoenix metro may eventually drop into the low to mid 70s at some point later next week.
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.AVIATION...Updated at 1211Z.
South Central Arizona including KPHX, KIWA, KSDL, and KDVT: Winds are expected to maintain a westerly component at KPHX this morning, while the other terminals will see west winds develop before noon today. An isolated shower/brief storm cannot be ruled out this morning in the Phoenix area, but confidence it too low for inclusion in the TAF. Should a storm develop in the vicinity of a terminal, brief erratic wind gusts under 30 kts, lightning, and a brief downpour will be the main impacts. Otherwise, showers and storms today are expected to stay north and east of the area. FEW to SCT cumulus around 6-8K ft AGL are expected through most of the TAF period.
Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation weather concerns are expected throughout the TAF period. KIPL will maintain a SE wind and KBLH will remain out of the S. Wind speeds will be around 5-10 kts through sunrise and then increase up to 8-13 kts with gusts to around 20 kts the rest of the day. Skies will be mostly clear during the morning and overnight hours, with FEW to SCT cumulus and high clouds in the afternoon and evening. There are a cluster of thunderstorms well north of KBLH, but this cluster is not expected to impact the terminal.
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.FIRE WEATHER... High pressure will gradually take hold across the region this weekend into early next week leading to drying conditions and diminishing rain chances. Today will again bring chances for isolated showers and a few thunderstorms, but less than a 10% chance for wetting rains. Rain chances will mostly come to an end beginning Sunday. Humidities will remain elevated this weekend before lowering early next week as MinRHs drop to below 30% Monday and 15-25% on Tuesday. Winds will continue to be light and favor diurnal patterns through early next week. Dry conditions with near zero rain chances and MinRHs back into the teens are then likely for the latter half of next week.
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.PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. &&
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SHORT TERM...Kuhlman LONG TERM...Kuhlman AVIATION...Benedict FIRE WEATHER...Kuhlman
NWS PSR Office Area Forecast Discussion