Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
402 FXUS65 KTWC 172225 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 325 PM MST Tue Sep 17 2024 .SYNOPSIS...Breezy and dry conditions with temperatures a few degrees cooler than normal through the work week. Temperatures are forecast to warm above normal again late this weekend. && .DISCUSSION...The upper air pattern this afternoon was characterized by a deep trough centered over the Great Salt Lake as a secondary reinforcing trough makes its way into the Pacific Northwest. The remaining influence of the primary trough will gradually exit the area this afternoon and evening leaving noticeably cooler and drier air in its wake along with continued breezy southwest winds. In fact, high temperatures this afternoon will be around 3 to 6 degrees below normal. Low and mid-level moisture has begun to scour out from west to east across western and central Pima County with a tight precipitable water gradient moving into eastern Pima County this afternoon. Just enough moisture remains for scattered plumpy Cumulus clouds to continue thriving to the east of the gradient across southeast Arizona. As remaining moisture continues to get scoured and shunted to the south and east, precipitation chances will remain low heading into next week. The secondary trough will approach the area Friday into Saturday reinforcing cooler and drier conditions across the forecast area. Morning lows will start to dip into the 50s over normally colder eastern/southern valleys, and low to mid 60s in and north/west of Tucson. Ensemble height anomalies return to near to above normal Sunday onwards, leading to an above normal temperature forecast into next week. && .AVIATION...Valid through 19/00Z. SCT-BKN clouds 6-9k feet this afternoon gradually decreasing in coverage after sunset. Surface winds SWLY at 10 to 15 kts with gusts to 25 kts. Winds become light and terrain driven after 18/03Z. Tomorrow, mostly SKC conditions through the valid forecast period. Southwest winds pick up again after 18/17Z with speeds of 8 to 12 kts with gusts to around 20 kts. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Crossing low pressure this afternoon and evening will continue to bring in dry air, breezy winds, and temperatures 3 to 6 degrees below normal. Breezy southwest winds will continue this afternoon with speeds of 12 to 18 mph and localized gusts to 30 mph. Lingering moisture will keep minimum relative humidities from falling off too quickly this afternoon, but valley locations are forecast to fall to the 15 to 20 percent range this week and 10 to 15 percent as temperatures warm again this weekend. Winds will be breezy each day before diminishing by the weekend. && .TWC WATCHES/WARNINGS/ADVISORIES...None. && $$ Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson