000 FXUS65 KPSR 101747 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ Issued by National Weather Service Tucson AZ 1047 AM MST Wed Aug 10 2022 .UPDATE... Updated 18z Aviation section. && .SYNOPSIS... Elevated chances for showers and thunderstorms will continue the rest of the week and into next week, with slightly higher potential Friday through Sunday. Occasionally heavy rainfall, localized flash flooding, gusty winds and localized blowing dust will be possible. High temperatures will remain below to near normal through the forecast period. && .DISCUSSION... Another August night with nocturnal convection is upon us. A close study of GOES-18 imagery of the middle and upper water vapor channels reveals a pronounced circulation passing near Nogales this morning. It emanated from the mid level shear axis/frontal boundary in place draped across southern New Mexico/Texas and on up toward the Ohio River Valley. This westward traveling wave is encountering pockets of conditionally unstable parcels (per SPC OA and verified with PHX ACARS sounding data) near the 700 mb layer with around 500 J/kg of energy. Various 00Z CAMs have latched on to this and generate some continued but decreasing convection into Maricopa/Pinal Counties through 12Z, though intensity is not very high in-line with CAPE values. Shear is also marginal at best (10-15 kt). Given trends and less than favorable environment, will cancel FA.A at this time. While some heavy rain is still possible, the potential (10%) does not remain high enough to warrant the watch. At the synoptic scale, we still have the mid level high anchored well to our northeast, near Cheyenne, WY, and a well defined mid- level low off the northern California coast. A 700 mb front extends in a large arc from MI-TX-UT. The Desert SW is caught in the warm/moist sector ahead of the CA low and on the southern periphery of the high, where a plume of anomalously high PWAT values extend all the way into Washington. Over the next few days, the low will lift toward Vancouver and weaken while the high drifts to the southeast. This will essentially result in little day-to-day change for our forecast area through Friday. Deep ESE flow will remain entrenched with continued MCVs and other perturbations shearing off the mid-level front drifting westward and across our forecast area in a high moisture environment with modest instability. Thus rain chances will remain elevated. Latest HREF data do suggest a strong signal for outflow winds across Pinal County this afternoon (70% chance of 30+ kt) but sporadic elsewhere. Something else to watch for the following days will be if any substantial PV anomalies develop and drift just off the northern Baja coast by the end of the week. Toward the weekend, as the larger systems reposition, there are indications that the meridional flow within the moisture plume will increase. Should any PV anomalies be sitting off the US/MEX coast near San Diego, they would be apt to be ingested by this enhanced flow and carried northward, enhancing the convective potential across our western CWA this weekend and possible lingering into early next week. While the bulk of EPS data support a more typical albeit wet monsoon pattern, the EPS EFI continues to suggest that there is a low end potential (5%) for significant rains across our western CWA during this period. Meanwhile, as the high shifts southeast this will push the mid-level front further into NM and AZ, increasing shear and potentially enhancing mountain convection that spills into lower elevations. Uncalibrated EPS data show a broad area of 20-30% probability for 1/2"+ rain across our Arizona zones Sat/Sun though calibrated and fuller NBM data bring that down a bit (10-20%). Regardless, there is the potential for convection to be a bit more active and focused perhaps as early as Friday and continuing through the weekend. Temperatures will continue to run near or below normal through the forecast period, highly dependent of course on convective activity and remnant cloud cover. Yesterday is a good example where cloud cover earlier in the day helped keep KPHX somewhat cool with a high of 98F which was below the NBM 25th percentile forecast. Temperature uncertainty increases the next several days and will be highest Sunday, decreasing slightly thereafter. HeatRisk will likely continue in the Low category across our AZ zones with Moderate into SE CA. && .AVIATION...Updated 1747Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Main aviation weather concern will be the potential for thunderstorm activity and associated outflow winds to affect the terminals later this evening. In the meantime, conditions will remain tranquil through the late afternoon with east to southeast winds predominating through most of the morning hours followed by a westerly shift by the late morning into the early afternoon hours. Speeds will generally remain aob 10 kts. Thereafter, will be monitoring the potential for thunderstorm activity and associated outflows, mostly predominating from the east-southeast, affecting the area terminals between 02-04Z. However models are also showing an outflow from the north that could briefly impact terminals on the northern edge of the Phoenix metro around 01Z. At this time, there is a 50% probability of winds exceeding 30 kts with any surging outflows. Southeast California/Southwest Arizona including KIPL and KBLH: KIPL: Southeasterly winds aob 10 kts will predominate. An isolated afternoon thunderstorm cannot be ruled out in the vicinity, however, confidence is too low at this time to mention in TAF package. KBLH: Mostly southerly winds aob 10 kts will prevail through the period. A round of thunderstorms originating from La Paz County may affect the terminal this afternoon and perhaps again in the early evening. && .FIRE WEATHER... A humid airmass will remain in place through the forecast period, yielding elevated afternoon RH values and good overnight recovery. Chances for wetting rains will continue for most areas almost daily. Winds for the most part will remain light, with the exception of thunderstorm outflows generating stronger gusts. The fire danger threat is expected to remain low for the foreseeable future. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ DISCUSSION...Iniguez AVIATION...Lojero/Hardin FIRE WEATHER...Iniguez