Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
912 FXUS65 KTWC 170922 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 222 AM MST Tue Sep 17 2024 .SYNOPSIS... A few isolated showers and thunderstorms this morning diminish in coverage by the late morning hours. Breezy, dry, and a few degrees cooler than normal through the work week. Temperatures are forecast to warm above normal again late this weekend. && .DISCUSSION... In the upper levels this morning, a deep trough was centered over Nevada into far southern California, while a jet streak was ejecting through the base of trough into Arizona and Utah. While low to mid level moisture remained over southeastern Arizona, a precipitable water gradient evident on the GOES TPW product was advancing eastward this morning into central Pima county. The eastward dry air push associated with the southwesterly flow of the trough will effectively cut off precipitation chances by late this morning, though coverage has already been diminished by the top- down moisture erosion ongoing over the previous couple days. As for sensible weather this morning, early cloud cover should gradually erode after sunrise as the deepening boundary layer mixes down dry air. Any lingering shower or thunderstorm chances will shrink from south to northeast, with some final activity possible in northern Graham and Greenlee counties into the early afternoon hours. The tightened pressure gradient aloft and unidirectional flow to the surface will promote breezy southwest winds with gusts to around 30 mph during the day today. The crossing jet streak and associated frontal passage will also bring high temperatures to 3 to 5 degrees below normal this afternoon. Temperatures remain a few degrees below normal through the work week under persistent western CONUS troughing. That should allow for morning lows to fall into the 50s over normally colder eastern/southern valleys, and low to mid 60s in and north/west of Tucson. A shortwave will likely cross Arizona on Saturday, though weaker and more open than the early week version. Moisture return looks unimpressive which keeps the forecast dry. Ensemble height anomalies return to near to above normal Sunday onwards, leading to an above normal temperature forecast into next week. && .AVIATION...Valid through 18/12Z. Clouds generally SCT-BKN 4k-8k feet this morning, decreasing in coverage after sunrise. Isolated showers and thunderstorms this morning follow the same trend, with a few lingering near and north of KSAD late morning. Surface winds expected to increase to 10 to 15 kts with gusts to 25 kts and become southwesterly today. Winds become light and terrain driven after 18/03Z. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER... Crossing low pressure today brings in dry air, breezy winds, and temperatures 3 to 5 degrees below normal. Winds are expected to become southwesterly and increase to 12 to 18 mph with gusts to 30 mph. Lingering moisture keeps minimum relative humidities from falling too quickly today, 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. && $$ Public...Edwards Aviation...Edwards Fire Weather....Edwards Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson