Area Forecast Discussion
Issued by NWS Phoenix, AZ
Issued by NWS Phoenix, AZ
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009 FXUS65 KPSR 271758 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 1058 AM MST Thu Jun 27 2024 .UPDATE...Updated 18z Aviation Discussion. && .SYNOPSIS... A period of drying conditions will carry through the end of the week with rain chances decreasing to near zero across south-central Arizona by Friday. Moisture and subsequent rain chances begin to increase again by Sunday, likely lasting through the middle of next week. Above normal temperatures will persist through at least early next week with lower desert highs approaching or exceeding 110 degrees, especially in some of the typically hotter locales. && .DISCUSSION... The impacts of drier air filtering in from the west were very apparent yesterday with the overall lack of convection across most of Arizona. The center of the ridge has shifted westward over the past 24 hours, now positioned over northern Sonora and this is helping to increase subsidence into southern Arizona. For the rest of today and through Friday, the ridge will begin to weaken while also gradually recentering itself again to our east. At the same time, a trough passing across the northern tier states will bring some slight influences into our region by reinforcing the westerly flow aloft. Additional drying is forecast through Friday, especially in the mid-levels with boundary layer moisture only drying very slightly. Due to the continued drying and subsidence aloft, only minimal shower and thunderstorm chances are expected over the higher terrain in far eastern Arizona. Temperatures will remain a few degrees above normal for the rest of the week, but still below excessive heat levels as heights aloft are kept in check with the passing trough. The pattern will begin to shift beginning Saturday as the ridge becomes fully centered over the Southern Plains and quickly restrengthens. The strengthening of the ridge is expected to modestly impact our region as our heights aloft are forecast to temporarily rise, adding a degree of warming on Saturday and another on Sunday. This should push daytime highs into a 108-113 degree range on Saturday right before we see a strong moisture push out of the southeast Saturday night into Sunday. Models are in fairly good agreement showing an easterly wave tracking across Mexico Friday into Saturday reaching northern Sonora Saturday evening. This should bring enhanced convection to our southeast on Saturday with subsequent outflows and mid-level gravity waves spreading northwestward into south-central Arizona by Sunday morning. As of now, NBM PoPs are fairly low (5-10%) Saturday night/Sunday morning into south-central Arizona, but it would not be surprising to see some nocturnal elevated convection due to the advancing higher moisture and increasingly unstable air mass. Moisture advection is likely to persist through much of Sunday as PWATs likely increase to 1.5-1.75" over much of southern Arizona, allowing for building instability. NBM forecast temperatures are also quite hot for Sunday due to the increased heights aloft, despite the increased dew points with highs mostly between 109-114 degrees. Sunday is likely to be the worst day for heat across the area, especially when taking into account the humidity, but only a few small localized areas reach into the Major HeatRisk category at the moment. There are indications Sunday evening could see some good chances for convection (potentially strong) working into south-central Arizona from the southeast, or at the very least strong outflow winds and blowing dust. A southeasterly steering flow will be present to help push any convection near Tucson toward the Phoenix area, but it will likely still have to contend with some weak CIN over the lower deserts. This will definitely be something to watch over the next few days. For the first half of next week, guidance all point toward keeping good monsoon moisture in place across much of southern Arizona. As the ridge center stays well to our east and another center develops well off the coast of California, we may end up seeing some influence from an extension of an upper level trough that sets up over the Northern Rockies into the Great Basin. The lack of any strong subsidence aloft in this scenario would likely result in at least one other busy monsoon convective day at some point early next week. Temperatures should also cool off slightly during the first half of next week, but NBM forecast temperatures are still on average a few degrees above normal most days. Looking at the latter half of next week, ensemble guidance generally agrees bringing in a strong ridge off the California coast into the Great Basin area. As of now, this would likely lead to a period of northerly drying flow into our region around next Thursday/Friday and hotter temperatures. && .AVIATION...Updated at 1750Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: No major aviation weather concerns expected through the TAF period. Winds through the evening and at least through the first part of the overnight period will be out of the west with sustained speeds aob 12 kts. Gusts this afternoon through early this evening could occasionally peak at 20-25 kts before subsiding later in the evening and overnight. Winds early Friday morning will likely be light and variable to briefly switching out of the east before switching back out of the west by the mid to late morning hours. FEW to occasionally SCT mid to high-level clouds expected through the period. Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation concerns under mostly clear skies expected through the TAF period. At KIPL, winds will be out of the southeast through this afternoon before switching out of the west this evening. At KBLH, winds are expected to fluctuate between the south to southwest. Wind gusts this afternoon through this evening in excess of 20 kts will be common at both sites. && .FIRE WEATHER... Drier conditions will continue to spread across the region from the west through Friday, lowering humidities and essentially ending rain chances across all areas except for far eastern Arizona. MinRHs will lower into the teens across the majority of the lower deserts starting today to 25-30% over higher terrain areas. Afternoon breeziness will be common today and Friday with gusts reaching to or just over 20 mph in many locations. The dry conditions with virtually no chances for rain should persist through Saturday before moisture returns Sunday, increasing humidities and potentially bringing back chances for thunderstorms across south-central and eastern Arizona. Temperatures through the period are expected to average several degrees above normal. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ DISCUSSION...Kuhlman AVIATION...Lojero FIRE WEATHER...Kuhlman