Tucson, AZ 85751 Weather

Synopsis

Temperatures at or slightly above normal today through Thursday, then cooler than normal Friday into the upcoming weekend. An unsettled weather pattern will be around this week with daily chances of shower and thunderstorms with Wednesday afternoon through Thursday having the best chances area wide with localized heavy rainfall

Discussion

Infrared satellite imagery this morning showed clear to partly cloudy skies across the area. Water vapor imagery showed tail end of upper trof moving through the 4-corners with ridging pushing in from the southwest. Moisture remains in place across the area and with surface dewpoints in the upper 50s to lower 60s this afternoon, widely scattered showers and thunderstorms will develop mainly north and east of Tucson.

To our west is our next significant weather maker with satellite imagery showing the upper low about 450 miles west of San Francisco as of 230 am. This system will continue to move to S-SE over the next 48 hours and then move inland Wednesday night and become negatively tilted on Thursday while lifting to the E-NE. Southerly flow out ahead of this system will keep higher than normal moisture values across the region. On Wednesday there is an increased risk of severe thunderstorms, especially north of Tucson where SPC has this area painted in slight risk. Heavy rain is the other risk, especially northeast of Tucson where WPC Excessive Rainfall Outlook has this area painted as slight risk for flash flooding.

Thursday looks like it will be the more impactful day as the upper trof becomes negatively tilted. Heavy rain and flash flooding threat continues, especially Pinal, Graham and Greenlee counties while the severe threat is minimized a bit due to cloud cover. WPC Excessive Rainfall outlook has areas NE of Tucson painted in slight risk, while on the severe side, most of the area has a marginal risk with this possibly being upgraded over the next 48 hours.

The heaviest rainfall is expected to occur across Pinal, Graham and Greenlee counties where 48 hour NBM probabilities, ending Thursday night, off greater than 1.50" being 25-85% chance and greater than 2" being 20-60% chance. With that said and in coordination with WFOs Phoenix and Flagstaff, a Flood Watch was issued Pinal, Graham and Greenlee counties has various time frames but mainly from late Wednesday morning until late Thursday night. Overall QPF for Wed/Thu range from less 0.10" far west areas to over 1" across Greenlee, Graham and eastern Pinal counties with higher totals in the mountains due to upsloping.

Drier air moves in for Friday, though some lingering showers possible near the NM border, which could linger into the weekend as well.

Temperatures through Thursday will be at or slightly above normal, then cooler than normal Friday into the upcoming weekend. Latest NBM has possible first freeze of the season at the highest elevations of the White Mountains.

Aviation

Valid thru 21/12Z. SCT-BKN 8k-10k ft AGL. ISOLD -SHRA/-TSRA mainly NE of KTUS from 20/19Z thru end of valid period. SFC winds ELY/SELY at 5-15 kts with gusty winds psbl near -TSRA. Aviation discussion not updated for TAF amendments.

Fire Weather

Temperatures at or slightly above normal through Thursday, then cooler than normal Friday into the upcoming weekend. Wind speeds mostly less than 15 mph this week except for Thursday with southwest winds around 15 to 20 mph. Minimum relative humidity remains above 25-40 percent through most of the week with most days seeing anywhere from a 20-80 percent chance of showers with embedded thunderstorms at times as an unsettled pattern continues.