479 FXUS65 KTWC 092056 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 156 PM MST Tue Oct 9 2018 .SYNOPSIS...It is expected to remain dry Wednesday through much of Thursday with warmer, but still cooler than normal temperatures. Increasing moisture from tropical system Sergio and a Pacific storm system will bring showers and thunderstorms to much of the region Thursday night into the weekend. && .DISCUSSION...A few decorative cumulus clouds were about the area this afternoon with a shower or two over the White mountains. This convective activity will shut down around or shortly after sunset this evening with skies clearing, setting us up for another cool night. Wednesday morning low temperatures will be similar to what they were this morning with a few low 30s possible in the coldest areas of Cochise, Graham and Greenlee counties. Wednesday we will be under the influence of dry westerly flow as we transition from post trough to pre-Sergio/next trough. Highs will warm about 6 degrees from today which is still cooler than average. Temperatures will be similar Thursday with cloud cover on the increase in advance of the next weather system to head our way. We should squeak out another dry day with deep moisture holding off until Thursday night and Friday. Current trends for Sergio are to take its remains just south of the state as it passes by Friday and Friday night. Given that the heavy rainfall with these systems is generally concentrated very near the core of the system (even when decayed) small shifts in the path result in significant differences in total rainfall amounts over any given location. The greatest threat for heavy rains continues to be over the SE corner of the state at this time with the absolute heaviest of the system remaining over Mexico. For this afternoon's update I adjusted our QPF down a touch mainly across central and western parts of the forecast area. Beyond that, models continue to struggle a bit with the closed low that looks to impact the area potentially well into next week in some fashion. Cutoff upper lows that are still fairly close to the main westerlies are difficult to deal with and I would expect to see plenty of shifting around in the models over the next several days. Suffice to say current solutions and many ensemble members have this low in the area through Friday, October 19th. If that comes to pass the below normal temperatures will continue with a threat of showers here and there at times through the entire period of time. && .AVIATION...Valid through 11/00Z. Isolated -SHRA/-TSRA NE of KSAD until 10/01z. Otherwise SCT clouds around 10k ft AGL until 10/04z then CLR overnight into Wed morning. Few clouds 10k ft AGL Wednesday afternoon E of KTUS. Surface wind until 10/01z wly/nwly 8-15 kts with gusts near 20 kts. Surface wind variable in direction mainly less than 12 kts rest of valid period. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...A few showers until early this evening across the White Mountains. Otherwise, dry conditions are expected into Thursday with daytime temperatures remaining several degrees below normal. Increasing moisture associated with tropical system Sergio is expected to result in showers and thunderstorms late Thursday night through Saturday. 20-foot winds will be terrain driven and generally less than 15 mph much of this week. && .TWC WATCHES/WARNINGS/ADVISORIES... None. && $$ PUBLIC...Cerniglia AVIATION....99 FIRE WEATHER...99 Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson