Area Forecast Discussion
Issued by NWS Tucson, AZ
Issued by NWS Tucson, AZ
543 FXUS65 KTWC 172149 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 249 PM MST Mon Jun 17 2024 .SYNOPSIS... After a mild decrease in temperatures today and Tuesday, high temperatures heat back up again Thursday and Friday. Moisture should begin to increase late this week which would bring the potential for thunderstorms late in the week into the weekend. && .DISCUSSION... In the upper levels, dry west to southwest flow remained as western CONUS troughing was sitting to the north. This unidirectional flow through the lower levels was also creating southwesterly surface breezes, with observed gusts of 15 to around 30 mph observed across southeastern Arizona at time of discussion. The story this week will be the reorientation of a southeastern CONUS high back towards the southwest CONUS by this weekend. This will act to bring heat risk back into the moderate to major categories Thursday and Friday, as well as turning mid to low level flow to the southeast. Anomalously warm Gulf of Mexico waters and a tropical disturbance should give a boost in moisture to the southeasterly air flow towards southeastern Arizona. Precipitable water values may begin to exceed 1 inches as early as Thursday (around a 30% chance around Tucson and 40-60% near the Arizona / New Mexico border) but becomes much more likely Friday into the weekend. The westward surge of moisture will also depend on daily convective activity from further east, so model run to run consistency is fairly low in precipitation chances each day. By Saturday, probabilities from the global ensembles for precipitable water values reaching 1.5 inches reach 15 to 35% across southeastern Arizona, indicative of impressive moisture for this time in June. The probabilities for surface dew points exceeding 55 degrees follow roughly the same trajectory. All this to say, probabilities for precipitation follow the trajectory of richer moisture, with highest chances following diurnal trends in the afternoon and evening hours. Going into the weekend, there isn`t a huge temperature change in the low level air mass but the forecast high temperatures become more uncertain due to the likelihood of convective activity. With the likelihood of excessive heat peaking Thursday and Friday, an Excessive Heat Watch has been issued with this shift. && .AVIATION...Valid through 19/00Z. SKC through the forecast period. Surface winds gusting 25 to 30 kts this afternoon become around 10 kts after 02Z then light after 06Z. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER... Temperatures are expected to heat back up by Thursday and Friday after the brief few degrees of cooling today and tomorrow. Through Wednesday expect minimum relative humidities of 5 to 9 percent in the lower elevations and 8 to 15 percent in the mountains, along with overnight recoveries between 25 to 40 percent. Afternoon breeziness out of the southwest can be expected through Wednesday with gusts to around 20 to 25 mph. Starting Thursday, surface winds turn to the south to southeast, which also begins to open the door for increasing mid-level moisture. Chances for mainly dry thunderstorms east of Tucson arrive on Thursday and then as far west as Tucson by Friday. && .TWC WATCHES/WARNINGS/ADVISORIES... Excessive Heat Watch from Thursday morning through Friday evening for AZZ501>506. && $$ Public...Edwards Aviation...Edwards Fire Weather....Edwards Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson