Area Forecast Discussion
Issued by NWS Phoenix, AZ
Issued by NWS Phoenix, AZ
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191 FXUS65 KPSR 050531 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 1031 PM MST Tue Jun 4 2024 .UPDATE...Updated 06Z Aviation Discussion. && .SYNOPSIS... One more day of near to slightly above normal temperatures will precede a warming trend that will bring the hottest temperatures of the year through the rest of the week, with some spots at risk of breaking daily high temperature records and warm low records. Cooler, but still hot, temperatures are expected going through this weekend, with moisture levels rising. && .DISCUSSION... The hottest temperatures of the year so far are expected during the second half of this week, including potential record high and record warm low temperatures, as strong high pressure builds over the region. Lower desert highs will reach and exceed 110F widespread Thursday and Friday, as well as potentially on Wednesday and Saturday in some localized areas like Downtown Phoenix. Morning lows will be quite warm for this time of year, reaching the upper 70s to middle 80s. These hot temperatures will lead to widespread Major HeatRisk Thursday and Friday and high-end Moderate to isolated Major risk on Wednesday. An Excessive Heat Warning remains in effect for most lower desert and valley areas of AZ and CA. There is potential for the warning to be extended through Saturday as forecast temperatures are not too dissimilar to Wednesday. However, there is still uncertainty at this time as there may be increased cloud cover over the area late this week into this weekend as mid and upper level moisture increase over the area down stream of a weak Pacific low. .PREVIOUS DISCUSSION... Mid-level heights will build in excess of 591 dam Wednesday through Friday, resulting in temperatures warming significantly during this period. HeatRisk will reach the Major category for large portions of the region, with the hottest temperatures anticipated for Thursday and Friday. As a result, Excessive Heat Warnings remain in effect for most of the forecast area during this period. Probabilistically, chances for peak highs of 115+ are highest Thursday and Friday around 10-30% across the lower deserts. Heading into the weekend, ensembles continue to trend the weak troughing feature hanging off the Baja Peninsula weaker and slower moving, thus the cooling trend is becoming more muted for Saturday. However, the temperatures likely (>75% chance) will cool enough to not warrant an extension of the Excessive Heat Warnings through Saturday at this point, as increasing clouds will moderate temperatures a few degrees. Moisture advection with this troughing feature continues to trend drier for Friday due to the slower progression, with the highest PWAT levels now for Saturday at around 0.75-0.90". Subsequently, the higher PoP potential now resides for Saturday, with higher terrain areas generally around 10-20%. However, the very dry low levels will mute most of the potential for accumulating rains for any showers or storms that develop. Dry lightning could be a risk with this regime due to the rarity of thunderstorms for this time of year and very dry conditions, so will have to keep an eye on how storm chances trend going through the week (chances currently no higher than 5-10% for the higher terrain). As the weak troughing feature progresses across the region going into early next week, temperatures are expected to remain slightly above normal due to sub-590 dam heights and persistent mid to upper level cloud coverage. Ensembles show very subtle differences in the mid-levels through this weekend, which could result in some shifting towards higher or lower shower/storm potential. However, most solutions lean towards the lesser chances at this point. Going into early next week, ensembles are more uncertain on how amplified the pattern will become, specifically another troughing feature in the eastern Pacific well offshore of the Baja Peninsula. Should a strong trough develop, upstream ridging would likewise be stronger, precluding another warming trend going into the middle of next week. Ensemble clusters are split pretty evenly between a stronger or weaker trough forming during this period, thus uncertainty remains decently high, at least for how hot temperatures may trend through the middle of next week. && .AVIATION...Updated at 0530Z. South-Central Arizona including KPHX, KIWA, KSDL, KDVT; and Southeast California/Southwest Arizona including KIPL and KBLH: Winds will follow their typical diurnal tendencies with speeds aob 10 kt. There may be some occasional gusts tomorrow afternoon and early evening up to around 15 kt. Mainly clear skies will prevail through the TAF period. && .FIRE WEATHER... Seasonably warm temperatures will continue through today, ahead of a strong warming trend through the rest of the week, where temperatures will soar between 110-115F for highs through Friday. MinRH values will continue to run between 5-10% across the majority of the area through the rest of the week, while overnight recoveries will continue to range from poor to fair at around 25-40% over the eastern districts to 35-50% over the western districts. Winds will remain fairly light following diurnal tendencies with periodic afternoon gusts of 15-20 mph. While humidities will improve by a few percentage points by this weekend due to a weak disturbance advecting moisture into the region, a low end chance (5-10%) of some isolated thunderstorms over the Arizona higher terrain may result in a non-zero dry lightning threat Friday and/or Saturday. && .CLIMATE... Record high temperatures: Date Phoenix Yuma El Centro ---- ------- ---- --------- June 5 113 in 2016 115 in 1957 114 in 2016 June 6 111 in 2016 114 in 1928 113 in 2002 June 7 115 in 1985 116 in 1985 113 in 1985 && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...Excessive Heat Warning from 10 AM Wednesday to 8 PM MST Friday for AZZ530>556-559>562. CA...Excessive Heat Warning from 10 AM Wednesday to 8 PM PDT Friday for CAZ561-563-566-567-569-570. && $$ DISCUSSION...Benedict PREVIOUS DISCUSSION...Young AVIATION...Berislavich FIRE WEATHER...Young CLIMATE...18