000 FXUS65 KPSR 051000 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 300 AM MST Mon Dec 5 2022 .SYNOPSIS... Patchy dense fog will impact portions of southern and central Arizona this morning with localized very low visibilities making driving potentially hazardous. Another weak weather system moving through the region beginning Tuesday will bring chances for light showers, focused more over the higher terrain north and east of Phoenix Tuesday into early Wednesday. By Wednesday night into Thursday, a gradual drying trend will begin and last through the rest of the week, while temperatures trend slightly below normal through the upcoming weekend. && .DISCUSSION... Dense fog will be the primary forecast concern today as soggy conditions remain from the abundant rainfall that fell over the weekend over much of southern and central Arizona. The recipe for widespread fog is essentially present as high clouds have mostly exited to the east of the area, winds are light, and the boundary layer remains saturated to near saturated. Most observations around the area are reporting widespread light fog with pockets of dense fog focused in central Pinal County and other lower lying areas. It is doubtful the majority of the area will see dense fog, but given the conditions the area of dense fog is expected to become more expansive through just after sunrise. A Dense Fog Advisory covers all of southern Arizona through mid morning. A large scale positively tilted trough currently centered along the northern California coast will gradually shift southeastward over the next couple days, but drier air in the mid levels ahead of the system will allow some drying to occur within the boundary layer. Additionally, some high clouds are forecast to spread over much of the area tonight which will hamper another round of potential fog development. By Tuesday morning, energy from the weakening trough is expected to move eastward into our region providing at least minimal forced ascent for some isolated to scattered showers from Phoenix into the higher terrain north and east of Phoenix. Forecast 10-30% 6 hourly PoPs last through the first part of Wednesday before the system finally moves to our east by Wednesday evening. QPF amounts with this next batch of potential rain are light with upwards of around 0.10" in the northern and eastern foothills of Phoenix to around 0.25-0.40" in the Tonto National Forecast area. For later this week and through the upcoming weekend, model ensembles favor a drying westerly zonal flow across the Southwestern U.S., well south of the progressive wave pattern situated mainly over the Pacific NW and Southwestern Canada. However, due to the somewhat close proximity of the trough to our north, the air mass over our region will remain fairly cold. This will keep high temperatures mostly in the low to mid 60s, or slightly below normal for the entire period. Overnight temperatures will also become quite chilly once the boundary layer dries out enough with lows dropping into the 30s and 40s over the majority of the area starting Wednesday night. The NBM guidance shows the coldest days being Friday and Saturday with some minimal freeze potential in the typical coldest rural locations. Extended model guidance then shows the next potential weather system and precip chances sometime during the early to middle part of next week. && .AVIATION...Updated 0517Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: METARS around the Phoenix area this evening have a wide range of ceilings from LIFR to VFR. Locales in the East Valley are on the lower end of the range. Surface visibilities have a wide range as well from 4SM to 10SM. Mountain top obscurations are likely widespread. The ceilings will have hour to hour fluctuations for the next few hours with MVFR being quite common. Visibilities will generally trend downward the rest of the night with KPHX probably the slowest to do so. Anticipate low MVFR visibilities becoming common after 09Z with areas of IFR. In fact, there is a 20-40% chance of LIFR visibility between about 11Z-15Z at the TAF sites (KIWA most likely). The period with the lowest visibility will also be the lowest ceilings. Winds will remain light through the morning hours. Conditions are anticipated to begin improving after 16Z with more noticeable improvement by 17Z. Surface heating will likely generate some localized ceiling redevelopment in the afternoon (~BKN040) before thinning out again. Light westerly surface winds develop after 17Z before transitioning to light and variable favoring east. Southeast California/Southwest Arizona including KIPL and KBLH: Light surface winds will continue through the morning hours before more distinct west and southwest winds develop by midday Monday with gusts of 15-20kts. Clouds overall are expected to be limited to cirrus (increasing during the day Monday). There is some potential for fog/mist development at KBLH toward morning but anticipate visibilities will remain AOA 6SM. && .FIRE WEATHER... The current high moisture levels will gradually decrease through the week, but overall elevated RHs should prevail the entire period. MinRHs above 40% are expected through Wednesday before dropping to 20-30% by the weekend. A weak weather system passing through tonight into Tuesday will bring a 15-30% chance of wetting rains mainly in southern Gila County. Otherwise, expect continued drying conditions through the rest of the week with below normal temperatures and generally light winds. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...Dense Fog Advisory until 10 AM MST this morning for AZZ531>563. CA...None. && $$ DISCUSSION...Kuhlman AVIATION...AJ FIRE WEATHER...Kuhlman