366 FXUS65 KPSR 141742 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 1042 AM MST Tue Jan 14 2025 .UPDATE... Updated Aviation && .SYNOPSIS... The below normal temperatures and freezing overnight lows will not last much longer as readings return to normal on Wednesday and even briefly warm to above normal areawide on Thursday. A mostly dry weather system is then expected to push through the region late Thursday into Friday bringing slight chances for precipitation over the eastern Arizona higher terrain. This system will also cool temperatures back to normal beginning Friday before even colder air settles into the region over the coming weekend. && .DISCUSSION... The chilly and very dry air mass in place over the region is again bringing freezing to near freezing temperatures over much of the south-central Arizona lower deserts this morning. The broad upper level trough largely responsible for this air mass will begin to break down later today into Wednesday, while a Pacific ridge currently coming onshore into the Pacific Northwest before shifting southeastward into our region. This ridge will quickly raise heights over our region tonight into Wednesday leading to a decent warm-up with highs around 70 degrees Wednesday and even into the lower 70s for the Phoenix area on Thursday. At the same time the ridge is moving into our region over the next couple of days, a cut-off low will be spinning off the coast of southern California. The latest guidance has somewhat reversed course with this cut-off low with it now looking a bit stronger as it is likely to track east northeastward through our region later Thursday into Friday. As a result, forecast moisture levels have improved some over the southeastern 1/3 of Arizona with PWATs peaking around normal in the Phoenix area to 125% of normal across far eastern Arizona. Despite the slightly stronger system and marginally better moisture, nearly all of this moisture will be above 10K feet with forecast soundings showing an inverted V structure and surface dew points at most reaching into the mid 20s. Latest NBM PoPs still seem too high, so we continue to dial back PoPs some with only virga showers/sprinkles expected in the south- central lower deserts to at most some slight shower activity with less than 0.05" QPF in the higher terrain. Some cooling will also be realized as the system passes through the region with highs dropping back to around normal starting Friday. Once the cut-off low exits east of our region during the latter half of Friday, our pattern will return back to what we have experienced over the past week. An even colder arctic air mass is forecast to dive southward down the Plains into much of the Eastern CONUS this weekend with some of this cold air likely filtering southwestward over the Rockies into our region. We very well could see very similar temperatures later this weekend into early next week like we just experienced over the last couple of days. The NBM does show some low end PoP chances this weekend mainly focused over eastern Arizona, but this is likely overdone as any shortwaves that drop into or just past our region will be coming directly out of the north and should be quite moisture starved. && .AVIATION...Updated at 1731Z. South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No major weather issues will exist through Wednesday under clear skies. Primarily east winds, aob 10kts, will prevail well into the afternoon hours though some directional variability may exist tomorrow morning. Otherwise, confidence is moderate that a brief period of light W/NW winds will develop this afternoon before reverting back to an easterly fetch by mid evening. Southeast California/Southwest Arizona including KIPL and KBLH: No significant weather concerns will exist through Wednesday morning under clear skies. W/NW winds will be preferred through most of the period for both terminals. KIPL is expected to see a west shift by tonight and KBLH`s current gusts are expected to relax by early this afternoon but maintain wind speeds around 8-12kts. && .FIRE WEATHER... Temperatures will gradually warm to slightly above normal over the next few days as a dry air mass remains in place. Elevated northerly winds will also continue across much of the western districts through Wednesday with gusts up to around 25 mph. For the eastern districts, expect higher terrain breeziness with gusts of 20-25 mph mainly focused more during the morning hours through Wednesday. MinRHs will continue to be between 10-15% over the lower deserts to around 20% in higher terrain areas. A mostly dry weather system later this week is likely to marginally raise humidities Thursday into Friday, but little to no precipitation is expected while winds remain fairly light. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ DISCUSSION...Kuhlman AVIATION...Ryan FIRE WEATHER...Kuhlman