Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 02/20/22

Area Forecast Discussion
National Weather Service Phoenix AZ
1238 PM MST Sat Feb 19 2022 .SYNOPSIS... Very warm temperatures and dry conditions will continue through Sunday. Highs this weekend will reach the upper 70s to low 80s across the lower deserts. More unsettled weather is likely starting early next week with a weather system bringing increased winds, cooler temperatures, and a chance of rain. Snow levels will decrease leading to a risk of high elevation snow showers as well. && .DISCUSSION... High pressure remains in control over the desert southwest with clear skies and light winds for most locations today. The airmass has warmed considerably compared to yesterday, with surface-700 mb temperatures roughly 2-5C warmer according to the latest ACARS soundings. This will lead to increased surface high temperatures today with the NBM showing readings mostly in the 75-82 F range. The probability of reaching 80 F has increased to around 40% for Phoenix. With the synoptic height pattern remaining relatively unchanged into Sunday, temperatures are forecast to be similar to, if not a few degrees warmer. However, Sunday is expected to be cloudier, with high clouds streaming in from the compact low working its way down the west coast. This could slightly insulate morning temperatures and inhibit daytime solar heating. Conditions will begin to deteriorate heading into next week in response to the previously mentioned cut off low ejecting inland over Arizona. This feature will be filling in on approach and will be quite moisture starved in the lower levels, leading to essentially no risk of precipitation. However, cloud cover will thicken and lower, which will result in high temperatures dropping 5-10 F from Sunday`s readings. Global ensembles continue to come into better agreement with respect to the pattern evolution Tuesday through Thursday, as a second and much colder trough digs into the region. As it does so it will absorb the remnants of the compact cut off low and partially phase the northern and southern jet streams. This should put Arizona in a favorable location for dynamically induced lift and will help to compensate for what is otherwise a fairly dry system. Forecast PWAT will only be around 0.5-0.6" at the peak. This system will have multiple impacts. Considering the wind potential, this will focus on Tuesday and Wednesday. A robust west to southwest oriented pressure gradient will significantly increase the wind speed. Winds at all lower levels will be anomalous, but particularly so above 850 hPa. ECMWF EFI is highlighting widespread values of 0.6 to 0.8, with values approaching 1 just north of the CWA for the higher elevation areas. SOT values have increased since yesterday, indicating a greater fraction of the ensemble members forecasting a more unusualwind event may occur. As of now, the potential exists for wind gusts of 25-35 mph across most of the lower deserts, with higher values possible near Imperial and the high terrain areas. Another impact of this system will be the rapid decrease of temperature and anomalously cool conditions beginning Wednesday. 500mb heights will fall into the mid 540s under the coolest portion of the trough, with 850 mb temperatures decreasing to around -1C. This will be enough to knock highs down into the upper 50s to near 60F in the valleys, with low temperatures in the mid 30s to near 40F. Some typically cooler areas away from the city center may locally observe frost or freeze conditions. Precipitation is also expected with this storm. WPC clusters now show a robust signal for mostly dry weather except for Tuesday night through Thursday morning, when PoPs rise considerably. The odds of at least some measurable precipitation is near 60-70% for Phoenix now, with a 25-35% chance for southeast California and southwest Arizona. NBM probabilities show about a 25% chance of exceeding a quarter inch in the Phoenix area. A few sporadic ensemble members maintain the possibility of heavier totals, but this seems unlikely for now. It won`t just be rain with this storm system, snow is also possible for some locations. Snow levels will decline to 3000-4000` on Wednesday, suggesting that a transition to snow may occur for portions of JTNP and Gila County. Totals are not expected to be heavy, but the highest elevation locations may see a few inches. Towards the tail end of next week WPC clusters are in good agreement that storm conditions will diminish, but less certain with respect to how this happens. Roughly half of solutions bring a return of the ridge, with the other half showing some variation of weak troughing returning. None of these cases result in much precipitation. && .AVIATION...Updated at 1705Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT; and Southeast California/Southwest Arizona including KIPL and KBLH: No significant weather issues will exist through Sunday afternoon with only a modest increase in cirrus decks late in the period. Winds in the Phoenix area will maintain an easterly direction much longer than usual this afternoon, only briefly obtaining a light west to northwest drift during the early evening. A W/NW component will be preferred at SE CA terminals for the bulk of the period though variability will be common. For the vast majority of the time, wind speeds will remain below 10kt. && .FIRE WEATHER... Monday through Friday: A weather system will approach and move through the region during the early through middle of the week, cooling temperatures back to normal Monday and then several degrees below normal into the middle part of the week. This system will also lead to increased winds during the first half of the week, with 30-40 mph gusts anticipated for many areas. Precipitation chances increase beginning as early as Tuesday, with the best chances in South- Central AZ Wednesday into Thursday. There will also be potential for accumulating snow at higher elevations like Joshua Tree NP and southern Gila county. Minimum humidities increase into a 20-30% range by Tuesday with overnight recoveries through the middle of the week upwards of 60- 80%. Drier air returns through Thursday and into the end of the week, as minimum humidities fall back to around 10-20%. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ Visit us on Facebook, Twitter, and at DISCUSSION...Hodges/Benedict AVIATION...18 FIRE WEATHER...Benedict