785 FXUS65 KPSR 082344 AAA AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 444 PM MST Thu Apr 8 2021 .UPDATE... Updated Aviation Discussion. .SYNOPSIS... With high pressure remaining situated over the region, high temperatures will hover around 10 degrees above average through the weekend. This area of high pressure will also ensure widespread dry weather with no realistic chance of rain. Breezy afternoon conditions will be common with some chance of enhanced winds during the middle of next week as a weather disturbance slides north of the area. This disturbance may also allow temperatures to cool somewhat closer to the seasonal average eventually next week. && .DISCUSSION... Early this afternoon, the SW Conus was trapped between a northern stream shortwave digging into the central Rockies/high plains and a subtropical ridge retrograding into the eastern Pacific. While soundings show subtle height falls and cooing aloft, compressional heating ahead of a decaying front was yielding temperatures near to slightly warmer than Wednesday. In addition, the increased pressure gradient was supporting stronger wind gusts though the gradient was already beginning to relax. As is typical this time of year, the strongest winds will be experienced near downsloping terrain features in the far western CWA. Conceivably, a few mountain rotors could descend into the Imperial Valley, but the preponderance of evidence indicates wind speeds remaining below advisory criteria. The entire western hemispheric pattern will remain blocked through at least the middle of next week resulting in an extended persistence type forecast. Mean longwave troughing will be preferred through much of the central/eastern Conus while high amplitude ridging becomes anchored near each coastline. Ensemble spreads is quite narrow with excellent confidence WNW flow and H5 heights in a 576-580dm range will settle over the region through the beginning of next week. High temperatures around 10F above normal should be common equating to lower elevation communities reaching into the lower/middle 90s. A reconfiguration of the large scale pattern will begin early next week as the upstream Pacific blocking retrogrades poleward merges with another ridge center over eastern Canada. As this merger occurs, negative height anomalies trapped equatorward of the northern ridge will also retrograde over much of the north-central United States and Great Basin. Ensemble means show this general progression, however WPC cluster analysis shows that there is still uncertainty with respect to where the deepest negative height anomalies will materialize. In general, clusters align along model physics packages with the GEFS membership more sheared and dampened with the wave structure while EPS members heavily lean towards a deeper, more blocked, retrogressive wave structure. As is usual, CMC ensembles are far more dispersive covering a wider range of outcomes. In spite of this pattern uncertainty, given the northerly continental flow, it can easily be assumed that the atmosphere will be quite dry with very little potential for precipitation. Ensemble solutions where the negative height anomalies focus further to the west and south are naturally much cooler and windier heading through the middle of next week. While the ensemble mean partially washes out the signal, feel given the predominant hemispheric blocking pattern, a slower, deeper, and more cutoff PV anomaly would be more preferred. At this point, it does appear likely that lower elevation temperatures will finally cool into the 80s at some point beyond the middle of the week, albeit probably staying around the seasonal normal. && .AVIATION...Updated at 2344Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Current gusty westerly winds to persist into the early evening hours, then gradually diminish and become more nw-ly later this evening/overnight as a weather disturbance passes well to the north into the central Rockies. A later-than-normal onset of easterly drainage winds is expected as well (towards daybreak). More typical westerly winds can be expected to return Friday afternoon, with lighter westerly winds persisting into Friday evening. Mainly CLR skies can be expected through the TAF period, with just some high cirrus decks aoa 25k feet passing overhead from time-to-time. Southeast California/Southwest Arizona including KIPL and KBLH: Pressure gradient will tighten across southeastern California in response to a trough moving through northern Arizona. Westerly gusts as high as 25-30 are expected to continue at KIPL/KBLH, before subsiding overnight. There also is a slight chance of moderate visibility reductions due to localized blowing dust. Lighter westerly winds can be expected during the day on Friday at KIPL while winds at KBLH become more northerly. Mainly CLR skies can be expected through the TAF period, with just some high cirrus decks aoa 25k feet passing overhead from time-to-time. && .FIRE WEATHER... Sunday through Thursday: Temperatures will only slowly cool through next week with readings around 10 degrees above the seasonal average early in the week falling to only about 5 degrees warmer than normal. Typical spring breeziness during the afternoons will be common with the favored upslope areas experiencing the strongest gusts. Somewhat stronger winds will be possible by the middle of next week potentially yielding a period of elevated fire danger. Dry conditions will also prevail through the week with afternoon minimum humidity values falling to near 10% while overnight recovery will be poor only bouncing back to a 20-40% range. Overall, conditions will be quite favorable for prescribed burning operations much of the week. && .SPOTTER INFORMATION STATEMENT... Spotters should follow standard reporting procedures. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ DISCUSSION...MO/Hodges AVIATION...percha/Hirsch FIRE WEATHER...MO