Area Forecast Discussion
Issued by NWS Phoenix, AZ
Issued by NWS Phoenix, AZ
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423 FXUS65 KPSR 231139 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 439 AM MST Sun Jun 23 2024 .UPDATE... 12Z Aviation Discussion. && .SYNOPSIS... Daily shower and thunderstorm chances will continue through early this week, with most activity confined to the higher terrain areas across southcentral Arizona. Cloudy conditions will persist through at least today, which will keep temperatures a few degrees cooler relative to the middle of this week, where highs will climb several degrees above normal. && .DISCUSSION... Mid to high level moisture and clouds continue to stream in from the southwest this morning, resulting in some scattered shower activity according to the latest MRMS radar returns. Specifically to southcentral Arizona, scattered showers are moving northeastward across Gila County, with a more solid area of showers moving into southern Maricopa County. Hi-res guidance suggest these showers, especially in southern Maricopa and western Pinal Counties to continue over the next several hours. After these showers dissipate, attention turns towards afternoon/evening convective activity once again. The highest chances again will be focused over higher terrain areas, as cloud cover will continue to be a limiting factor in potential/strength today as well as the mean mid-level flow turns more southwesterly. Further west across southwestern AZ and even into SE CA, less cloud coverage could spark a few showers and storms as the elevated moisture levels (and in turn more instability) will reach that region of the forecast area today. General expectations for showers/storms are around 30-40% (10-20%) for the higher terrain of southcentral AZ (southcentral & southwestern AZ as well as southeastern CA). HREF wind potential for 35+ mph for any outflows is much lower today, generally 10-30% centered across southcentral and southwestern AZ this afternoon and evening. Ridging/surface high pressure will continue to migrate westward going into tomorrow, continuing the downward trend for convective activity, mainly due to strengthening subsidence aloft from the building mid-level heights. This ridging feature will persist through the middle of the week, resulting in a warming trend, as mid-level heights hover in the 591-594 dam range. Widespread Moderate HeatRisk will persist during this period, while localized Major HeatRisk develop Tuesday through Thursday. While moisture levels will remain elevated during this period (general consensus is 1.75"-2.00" through Tuesday), thunderstorm chances will diminish, especially for lower desert locations beginning tomorrow. Thus, expect daily thunderstorm chances to reside mainly in the higher terrain areas of southcentral Arizona going through most of this week. Looking towards the extended period, ensemble clustering shows excellent agreement through at least Thursday, as a troughing feature moves into the Pacific Northwest. As this trough traverses across the Intermountain West going into this upcoming weekend, mid-level heights will fall by a few decameters, resulting in a slight cooling trend. More noticeable spread is seen in the clusters by this upcoming weekend, where there is some uncertainty in how quickly this trough exits the region and how quickly heights build in from the east again. This will affect if and how quickly temperatures may warm going through this upcoming weekend, as current NBM temperature spreads are around 5-8 degrees for the interquartile ranges for central Phoenix Saturday and Sunday. Ensembles continue to show elevated moisture levels during the extended period, thus while HeatRisk may remain mainly in the Moderate category, higher humidity levels should still be accounted for any outdoor plans during this period. && .AVIATION...Updated at 1130Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Latest area radars indicate a batch of light SHRA progressing nwd through south central AZ. These showers will likely weaken and dissipate after sunrise, but are expected to pass near KPHX and KIWA. No aviation impacts are anticipated. Winds will remain light out of the ESE this morning. Due to abundant cloud cover, there may be a slight delay in the onset of westerly flow this afternoon, but high-res guidance does indicate a WNW shift in wind direction by 20Z-21Z at the metro terminals. Convection this afternoon and evening is expected to remain outside of the Phoenix Metro area, but there could be outflow boundaries that emanate from distant storms which could cause a brief wind shift. Timing of any boundary is too uncertain to include mention in this forecast package. Abundant mid-high lvl clouds will persist through the forecast period. Southeast California/Southwest Arizona including KIPL and KBLH: VFR conditions will prevail at both terminals over the next 24 hrs. Winds will remain southerly at KBLH through much of the day with some afternoon breeziness anticipated. At KIPL, winds will be southeasterly through this afternoon before switching out of the WSW by sunset. A few isold storms may develop over/near the Kofa mountains which in turn could create temporary gusty conditions from the east/southeast at KBLH by late afternoon/early evening. SCT mid-high clouds will continue through the forecast period. && .FIRE WEATHER... Monsoonal moisture will continue to result in daily chances for shower and thunderstorm activity, with the best chances for activity across the higher terrain areas. With the elevated moisture in place, MinRH values through early this week will range between 35-45% across the far eastern districts to between 15-25% across the western districts before slowly drying into the middle to latter half of next week. Winds will follow their typical daily tendencies, with gusty outflows from any thunderstorm activity anticipated over the next several days. Temperatures through the weekend will average near to slightly above normal before increasing some heading into the middle of next week. Chances for wetting rains will generally remain around 15-25% for the higher terrain areas and 5-10% for the lower deserts of southcentral Arizona through tomorrow. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ DISCUSSION...Young AVIATION...Salerno FIRE WEATHER...Young/Lojero