Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 01/19/22

Area Forecast Discussion
National Weather Service Phoenix AZ
450 PM MST Tue Jan 18 2022 .UPDATE...Updated Aviation Discussion. && .SYNOPSIS... A weak weather system will continue to move through the region today and produce isolated light showers for a few more hours. Dry conditions along with near to slightly above normal temperatures will prevail during the latter half of the week. A weather system will bring a slight chance of showers and breezy conditions to the area over the weekend. && .DISCUSSION... The cutoff low that has resided off the coast of California for the past several days is now moving through Arizona as an open wave as it begins to be reabsorbed into the main flow. Water vapor satellite imagery show the low is now over northern Arizona and quickly moving east. Weak ascent from modest cyclonic vorticity advection and upper level jet support is allowing for a few showers to develop. So far these showers have been fairly meager with most locations seeing nothing, and just a few areas seeing a hundredth of an inch or two. ACARS soundings continue to show a very dry airmass below 850 hPa, which is further hindering any rain from reaching the surface. Overall, this should continue to be the case with showers winding down over the next few hours as the best forcing quickly heads east. This outcome is well supported by the HREF. Skies will clear out overnight. A second trailing shortwave will move into Arizona on Wednesday and temporarily amplify the back half of the departing trough resulting in reduced geopotential heights for one more day. Overall the effects will be minimal but HREF guidance is showing a few showers popping up in Gila County during the afternoon hours. NBM PoPs for Gila County increase to about 20% but remain below 5% for the rest of the CWA. The upper level high will quickly rebound behind this shortwave for Thursday with sunny skies expected. High temperatures will rise into the low 70s with NBM temperature probabilities showing an 80% chance of reaching 70F or higher in Phoenix by Thursday. The enhanced area of high pressure will be transitory, however, as yet another developing system dives south into Arizona Friday and Saturday. The system will strengthen and cut off from the mean flow on approach, but due to its inland and northerly trajectory it will be quite moisture starved. WPC cluster analysis shows that around 40% of the ensembles take the path of the low right over the CWA while the remaining 60% take it east. In general, clusters show that the western solution would offer a better chance of some precipitation, which conceptually makes sense. As of now, NBM PoPs are around 5-10% for south-central Arizona, and even lower for southeast California. Perhaps the bigger story with this system will be the wind potential. A strong area of high pressure will trail the weather system, inducing a robust northerly gradient Saturday and Sunday. A surge of gusty wind will result down the Colorado River and portions of southeast California. Some breezy conditions may also occur in the foothills north and east of Phoenix. ECWMF EFI shows values of 0.7 to 0.9, indicating a fairly unusual event for wind speeds. Ensembles diverge beyond this point with respect to whether an addition shortwave trough moves through the area or if strong ridging will return. Regardless, conditions will likely remain mostly dry with high temperatures remaining near seasonal norms. && .AVIATION...Updated 2345Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Minor weather systems will continue to move through the area. Isolated light showers from earlier today have moved out of the area along with a short-term decrease in cloud cover with FEW-SCT low-mid cloud decks from 7-18 kft. Mostly light winds AOB 7 kts following normal diurnal tendencies will continue along with periods of light and variable winds. BKN low cloud CIGS near 6 kft AGL will redevelop late in the evening before scattering out during mid-late Wed morning. Southeast California/Southwest Arizona including KIPL and KBLH: Mostly light to occasionally moderate winds are expected through much of the TAF period at both terminals. Winds to favor W-N components at KIPL, with winds at KBLH staying mostly NW-N. Partly cloudy skies with FEW V SCT low-mid and high cloud decks tonight and Wed morning will improve to clear to mostly clear skies by late Wed morning. && .FIRE WEATHER... Thursday through Monday: Dry conditions and near to slightly above normal temperatures are favored through the period. High pressure will dominate our weather for the beginning of the period before a weather system is expected to move into our area this weekend. As of now, this weather system looks to remain dry across our area, though it may result in increased breezy conditions this weekend, particularly for areas along and west of the Lower Colorado River Valley. Minimum RHs are expected to be around 15-30%, while maximum RHs are expected to be in the 30-60% range for most places through the period. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ DISCUSSION...Hodges/Smith AVIATION...Sawtelle FIRE WEATHER...Smith