429 FXUS65 KTWC 152231 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 330 PM MST Sun Sep 15 2019 .SYNOPSIS...Scattered thunderstorms east of Tucson ending early this evening. Scattered showers and thunderstorms develop again Monday and continue into Monday evening before dissipating. Markedly less thunderstorm activity beginning Tuesday and prevailing into next weekend. The best coverage of showers and thunderstorms should occur Thursday. Seasonably warm daytime temperatures this week. && .DISCUSSION...Isolated showers and thunderstorms were occurring at this time across portions of Greenlee/Graham/Cochise Counties east of Tucson. Other isolated showers/tstms have occurred during the past hour near the International border southwest of Tucson. Expect any remaining showers/tstms the rest of this afternoon to remain east to south of Tucson, and either dissipate or move eastward into southwest New Mexico around or shortly after sunset. Dry conditions to occur later tonight and into Monday morning. Southwesterly flow aloft Monday to prevail ahead of a deepening upper trough over the Pacific Northwest. Have noted several Univ of AZ WRF solutions to favor a north-to-south oriented band of showers/ tstms to develop Monday afternoon west of Tucson. These showers/tstms are then progged to move northeastward and encroach upon the Tucson metro area Monday evening before dissipating. Global scale models suggest more widespread coverage of showers/tstms to occur Monday afternoon and evening before ending late Monday night. At any rate, the official forecast continues with scattered showers/ tstms across much of this forecast area late Monday morning into Monday evening. Expect any remaining showers/tstms to dissipate by daybreak Tuesday. A low amplitude upper trough should exist Tuesday across the western CONUS. There appears to be enough residual moisture to justify isolated showers/tstms from Tucson eastward/ southward with dry conditions elsewhere. Any showers/tstms Wednesday should be limited to mountains across eastern sections. There were fairly distinct differences between the 15/12Z GFS/GEFS and ECMWF/EPS regarding the potential for showers/tstms across this forecast area on Thursday. The GFS/GEFS was markedly more robust with precip potential, likely due to the northward import of subtropical moisture into the area. However, the ECMWF/EPS shunted the bulk of this deeper moisture plume further east into the southern Rockies. Per coordination with neighboring WFO`s, have maintained isolated showers/tstms Thursday east to south of Tucson. Thereafter, the GFS/GEFS and ECMWF/EPS were quite similar with depicting a light-to-moderate generally westerly flow aloft regime to prevail across the area Friday into next Sunday. As a result, expect mostly dry conditions across much of southeast Arizona Friday into next Sunday with isolated afternoon/evening showers/ tstms confined mainly across the White Mountains. Daytime high temperatures during this forecast package can generally be characterized to average within a few degrees of seasonal normals depending upon location. && .AVIATION...Valid through 17/00Z. Isolated SHRA/TSRA mainly east of KTUS continuing into the early evening, with cloud bases around 8k-12k ft MSL. TSRA/SHRA redevelop tomorrow afternoon and areal coverage will extend across much of the forecast area. SFC winds remain less than 12 kts through the period, favoring a WLY-NWLY direction during the afternoon both today and tomorrow. Stronger gusts will be possible around TSRA. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Expect showers and thunderstorms Monday afternoon and evening across much of southeast Arizona. A drying trend then occurs on Tuesday, which continues through the remainder of the week. However, isolated mountain storms will still be possible during the usual afternoon/evening timeframe. Light terrain driven winds generally persist, except for breezier conditions on Thursday afternoon across western Pima County. && .TWC WATCHES/WARNINGS/ADVISORIES...none. && $$ Francis/Howlett Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson
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