Area Forecast Discussion
Issued by NWS Phoenix, AZ
Issued by NWS Phoenix, AZ
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220 FXUS65 KPSR 242059 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 159 PM MST Fri May 24 2024 .SYNOPSIS... A weak area of low pressure will move over the region during the front half of the weekend, resulting in a quick relative cooldown and breezy to locally windy conditions. The strongest gusts will be focused over southeast California this afternoon and evening, with more widespread breeziness developing again on Saturday. Temperatures will quickly warm up into the triple digits by the end of the Memorial Day Weekend, with further warming into the start of the next work week. && .DISCUSSION... Atmospheric analysis reveals quasi-zonal flow over our forecast area, with a weak shortwave trough just west of the California Coast. Before negative height anomalies associated with this system move onshore, temperatures today will hover around what we have seen over the past several days. Afternoon highs will continue to run in the middle and upper 90s across the lower deserts, which is right at normal for this time of year. Although this disturbance is not expected to move over our area until late tonight/early Saturday morning, its influence will be felt across portions of the Desert Southwest as early as this afternoon/evening as breezy to locally windy conditions begin to develop. The strongest winds will focus over parts of SE California, where gusts 30-40 mph will be common. HREF guidance continues to show high probabilities (>80%) of winds exceeding 40 mph over parts of the Imperial Valley, resulting in a Wind Advisory being posted for this area that will be in effect this afternoon through the evening hours. Elsewhere across southwestern and south-central Arizona, peak gusts will generally range between 20-30 mph, with isolated higher gusts around the Colorado River Valley and enhanced terrain features. Once the aforementioned trough moves onshore, regional heights aloft will decrease as cooler air begins to spread over our forecast area. Afternoon highs on Saturday, as a result, are forecasted to range between the upper 80s to lower 90s, a good 5-10 degrees below normal for this time of year. Enhanced flow aloft will likely yield breezy conditions across Arizona again on Saturday, with the highest gusts focused over high-terrain areas. However, the wind forecast has become a bit murkier since yesterday. The NBM favors gusts near 30-35 mph over Gila County, while the newest HREF guidance has gust only reaching near 25 mph over the same areas. This disagreement appears to stem from some models having the strongest flow aloft occurring before the hours of peak mixing, limiting the transfer of the highest momentum winds down to the surface. Nonetheless, it would not be surprising to see wind gusts range somewhere in between these two ensemble forecasts, with gusts ranging between 25-30 mph, with the occasional gust near 35 mph. Peak gusts of 20-25 mph can be expected across the lower elevations of south-central and southwestern Arizona. Familiar terrain-driven winds will push gusts for parts of SE California towards 30-35 mph once again on Saturday afternoon/evening, but winds should remain below advisory-levels. Future guidance remains in excellent agreement regarding a developing amplified ridging pattern in the wake of the previously discussed trough. Heights aloft will quickly rise through the latter portion of the weekend, resulting in a quick rebound of day-to-day temperatures. Daytime highs by Sunday will be back in the middle to upper 90s across the lower deserts before rising further into the triple digits for many areas by Memorial Day. Projections show the ridge continuing to amplify into the next work week, leading to further warming. Widespread 100-105 degree temperatures are forecasted by Tuesday, with similar conditions expected once again on Wednesday. This pattern will promote tranquil and very dry conditions, yielding near-zero rain chances for the next several days and likely through the end of the month, barring any significant changes to ensembles guidance in the near future. && .AVIATION...Updated at 1800Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: VFR conditions are anticipated through the forecast period. SE-SSW crosswinds, particularly at KPHX, will continue for a 3-4 hr period before winds ultimately shift out of the WSW by 20Z-21Z. Intermittent gusts up to 20-25 kts can be expected this afternoon through early this evening. Winds will then subside later this evening before eventually becoming easterly during the overnight hours. Despite a few passing high clouds, skies should remain mostly clear. Southeast California/Southwest Arizona including KIPL and KBLH: The main aviation concerns will be strong, gusty winds developing at both terminals this afternoon and evening. Westerly flow will become established at KIPL late this morning while winds remain southerly at KBLH. Gusts around 25-30 kts will become common at both terminals by this afternoon. Stronger sundowner winds are anticipated at KIPL after 00Z with gusts increasing to around 35 kts at at times. Some of the stronger gusts may loft dust, which could lead to temporary slantwise and surface visibility reductions. FEW-SCT passing high clouds will move over the region throughout the period. && .FIRE WEATHER... Elevated fire weather conditions will exist today and Saturday over parts of the western districts and high terrain of the eastern districts as a weak system helps to generate breezy to locally windy conditions. Strongest winds (35-45 mph peak gusts) will be focused over the western districts and enhanced terrain areas, with 20-30 mph gusts expected elsewhere. MinRH values during this timeframe will increase slightly from 10-15% today, to 10-20% Saturday. Overnight recoveries will be fair tonight and Saturday night at around 30-50% and locally higher in high terrain locations. Hot and dry conditions will persist beyond Saturday, with generally lighter winds speeds and typical afternoon breeziness each day. Daily highs will reach the century mark in many lower desert locations by Monday and values generally top out between 100-105 through the middle of next week. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...Wind Advisory from 4 PM this afternoon to 9 AM PDT Saturday for CAZ562. Wind Advisory from 4 PM this afternoon to 11 PM PDT this evening for CAZ563-566-567. && $$ DISCUSSION...RW AVIATION...Young/Salerno FIRE WEATHER...Whittock/RW