Area Forecast Discussion
Issued by NWS Phoenix, AZ
Issued by NWS Phoenix, AZ
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455 FXUS65 KPSR 080458 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 958 PM MST Fri Jun 7 2024 .UPDATE... 06Z Aviation Discussion. && .SYNOPSIS... Continued high pressure over the region will lead to well above normal high temperatures again this afternoon. As a result, Excessive Heat Warnings remain in effect through this evening. A weak disturbance will pass over the Desert Southwest this weekend, leading to increased cloud cover and slightly cooler temperatures into early next week. Temperatures heat up again for the middle of next week as high pressure builds over the region. && .DISCUSSION... A weak upper level low has remained nearly stationary off the Baja Peninsula for the last 24 hours, with a broad ridge downstream over the Southwest US, allowing for continued southerly to southeasterly flow over southern AZ. As abundant mid-level moisture was already present over the region, convective activity began quite early today over the high terrain of eastern AZ and western New Mexico. Very low (less than 10%) chances for an isolated dry thunderstorm remain over eastern Gila County through the remainder of today. The aforementioned ridging in place overhead will continue to bring us temperatures in excess of 110 degrees for some lower desert locations this afternoon. Pockets of Major Heatrisk coinciding with these hotter locations still remain today, and so Excessive Heat Warnings will continue to be in effect through 8 pm MST this evening. Over the next 24-36 hours, the cutoff low that has been sitting west of the Baja Peninsula will move northward and eventually cross into southern AZ. As this is a relatively weak disturbance at this point, 500 mb heights are expected to decrease on the order of 1-3 dam over South-Central AZ, and so surface temperatures will cool by only a few degrees tomorrow (highs ranging from 105-110 in the lower deserts). As a result of the slight cooldown tomorrow, HeatRisk will drop into the Moderate category. However, those planning outdoor recreation during the weekend should continue to practice heat safety measures, i.e., stay hydrated, seek shade or air conditioned places, and take frequent breaks during physical activity. High temperatures on Sunday and Monday drop to the low-to-mid 100s across the lower deserts, with ensemble mean 500 mb heights generally ranging from 585-588 dam late this weekend into early next week over the region. WPC cluster analysis continues to depict good agreement between global ensembles with respect to the upper level flow evolution. A shortwave trough approaches the West Coast late Saturday into Sunday and becomes a closed low by Monday. Ensembles still continue to show uncertainties in terms of the overall position/strength of the closed low as it meanders offshore near the latitude of the international border through the middle of next week, which will dictate the positioning of ridging downstream over the Southwestern US. Due to the proximity of the closed low, high temperatures will likely be greater over the South-Central AZ deserts than over Southeast CA. If a stronger ridge does indeed develop over the area, another round of excessive heat with highs of 110+ degrees will become more likely in the Tuesday-Thursday timeframe. && .AVIATION...Updated at 0500Z. South-Central Arizona including KPHX, KIWA, KSDL, KDVT; and Southeast California/Southwest Arizona including KIPL and KBLH: No aviation concerns are anticipated through the TAF period. Winds will follow typical diurnal tendencies with speeds generally aob 10 kts outside of occasional gusts up to 20-25 kts, mainly at the southeast California terminals tomorrow afternoon. Winds should shift out of the ESE at KPHX and KIWA by 08Z-09Z tonight and slowly veer back out of the WSW by 21Z-22Z tomorrow afternoon. High clouds will remain FEW overnight before becoming SCT at 25 kft over the region early tomorrow morning. && .FIRE WEATHER... Hot and seasonably dry conditions will continue to support a high fire danger across the area during the next several days. Isolated thunderstorms developing over the White Mountains, Mogollon Rim, and in the far eastern districts later today could lead to an increased risk of lightning-related fire starts, however, the chances of dry thunder across the far eastern districts remains below 10 percent. Another day of excessive heat is forecast across most of the lower deserts with highs near 110 degrees before a gradual cooldown over the weekend. Winds during the next several days will continue to favor diurnal tendencies with sustained speeds remaining below 15 mph along with occasional afternoon breeziness upwards of 20-25 mph. MinRHs through next week will hover at around 10% with poor to fair overnight recoveries of around 20-40%. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ DISCUSSION...Whittock AVIATION...Salerno FIRE WEATHER...Lojero