South Tucson, AZ Weather

Synopsis

Dry conditions are expected across Southeast Arizona into Thursday. Showers and thunderstorms will return to the region late Thursday through next weekend, with the potential for heavy rainfall returning to the area Sunday. Afternoon high temperatures will be below normal today, warming to near to slightly above normal Monday through Thursday, then lowering back below normal Friday through next weekend.

Discussion

The primary role for a meteorologist is to spend countless hours investigating what the atmosphere will throw our way next, carefully determining its potential negative impacts, then crafting a method to express those thoughts and concerns to all those who may be impacted. Sometimes, it is easy to overlook that the best forecast may actually be one that encourages everyone to go outside, look-up, take in the scenery, and appreciate the beauty of Southeast Arizona and the weather that allows it to breathe.

The next few days will be gorgeous...which I would guess is no surprise given it is late October. Skies sunny to mostly sunny and afternoon temperatures generally be in the 80s...ranging from 3 to 6 degrees below normal today, warming to a few degrees above normal the first half of the upcoming week. Enjoy it, appreciate it.

The upper pattern today is defined by an upper-low over the northern half of Arizona and Utah, an upper low near the British Columbia coastline, and a strong upper-low in the Eastern Pacific near 33N/148W. The upper-low over AZ/UT will eject NE today/Monday as the trough in the Pacific Northwest amplifies and progresses inland across Washington and Oregon. Strong flow developing on the backside of this feature will first reinforce the Pacific Northwest trough, then produce a mean trough that helps weaken the closed circulation over the Eastern pacific and eventually allows this system to open into a progressive trough during the latter half of the week. This feature will weaken as it moves east, but southerly flow developing ahead of the trough should encourage a northward surge of tropical moisture, some of which may be associated with Hurricane Vance, through the Gulf of California and eventually into southwest Arizona Thursday and Friday. The 15/12Z GEFS was bullish with the moisture, with precipitable water values 2.0 to 2.5 standard deviations above climatological normal. This should result in scattered showers and thunderstorms for Southeast Arizona as early as Thursday night, but more likely Friday.

Elsewhere, additional shortwave energy reinforcing the mean trough over the Eastern Pacific late Friday into Saturday will close off another low near 30N/130W by 01/00Z Saturday afternoon before shifting east toward Arizona Sunday. This low will tap into a deep plume of subtropical moisture as it makes its way into Arizona with GEFS indicating PWATs in this plume 2.5 to 3.0 standard deviations above normal. Strong SWLY flow will likely focus the heaviest precipitation into the Mogollon Rim with the orographic lift, but the combination of anomalous moisture and increasing large-scale ascent may also support periods of heavy precipitation across Southeast Arizona Sunday into Monday. This is supported by the 25/13Z NBM, with a 30-50 percent probability of 48-hour pcpn amounts in excess of an inch Sunday and Monday, and even a 10-30% of exceeding 2 inches, particularly from Tucson northward.

At this time, it looks like Halloween may be the lull in storm activity in between these two distinct weather systems Friday and Sunday...but timing can change, and residual moisture and generalized instability may result in a low-end chance of showers none-the-less.

Aviation

Valid through 27/00Z. FEW-SCT clouds at 6k-9k ft AGL NE of KTUS thru 26/02Z, then clear skies/SKC conditions thru the remainder of the forecast period. SFC wind less than 12 kts thru the forecast period, favoring a WLY/NWLY direction during the afternoon/early evening hours and variable in direction at other times. Aviation discussion not updated for TAF amendments.

Fire Weather

Dry conditions are expected across Southeast Arizona into Thursday. Showers and thunderstorms will return to the region late Thursday through next weekend, with the potential for heavy rainfall returning to the area Sunday. Afternoon high temperatures will be below normal today, warming to near to slightly above normal Monday through Thursday, then lowering back below normal Friday through next weekend. 20-foot winds will generally be 15 mph or less through Thursday. Breezy to locally windy southwest winds will be possible next Sunday. Minimum RH values will be in the 25-35 percent range in the valleys today and higher in the mountains. Minimum RH values will then be in the 18-30 percent range Monday, 15-25 percent range Tuesday and Wednesday, increasing back above 40+ percent late this week into next weekend.