Weather Lookup

Synopsis

Scattered showers will be possible this afternoon, increasing in coverage from tucson west this evening as a weather system approaches. Sunday into monday morning as the weather system moves through showers become widespread, with heavy rainfall at times and embedded thunderstorms. A flood watch is in effect for all of southeast arizona from 11 PM saturday through 5 AM monday. Expect dry conditions tuesday into friday.

Discussion

Scattered showers have been ongoing this morning and afternoon as moisture begins to stream in as part of an atmospheric river ahead of a pacific low. Rainfall amounts have been relatively light, generally 0.01"-0.4" with no lightning. Instability is fairly limited, but can't rule out a lightning strike or two this afternoon while the sun is up. Hi-res guidance has struggled with this shower activity, but expect it to continue on and off through the afternoon.

Precipitable water will continue to increase this evening and overnight ranging from 1.6" in western pima county to 1.25" along the az/nm border by sunday morning. The pacific low will dig south this evening and overnight, then move inland sunday. This will lead to widespread moderate to heavy showers with embedded thunderstorms tonight into monday.

Over the past couple model cycles hi-res guidance shows a first wave of moderate showers this evening and part of the overnight hours from tucson westward. Shower activity is expected to increase west of tucson between 4-6 PM then increase in coverage through the evening. General rainfall totals through midnight look to be 0.25"-0.75". Sunday morning showers will likely still mainly be from tucson west then increase in coverage to the east late morning into the afternoon as the core of the trough moves through arizona. A strong jet associated with the low will aid shower and thunderstorm development. Heavy rainfall leading to flash flooding and wash/river flooding will be the main threats. However the jet will also help create an environment conducive to strong to maybe even severe wind gusts in stronger thunderstorms. SPC has southeast arizona in a marginal risk for severe weather sunday. However the main limiting factor in this will be instability which may be lacking, at least in arizona. Better instability will be in place over new mexico. Regardless convection within the widespread showers will likely be responsible for the heaviest rainfall rates. Activity is expected to decrease from west to east sunday night into monday. A flood watch is in effect from 11 PM this evening through 5 AM monday. QPF hasn't fluctuated by much over the past 12-24 hours with pinal county, northern graham and greenlee counties, and the sky islands north of i-10 expected to see the heaviest rain. The refs shows the catalinas, pinalenos, and white mountains having a 20-60 percent chance to see 3+ inches through monday morning. Below is a look at the expected totals and high/low end totals.

-expected: valleys 0.50"-1.75", mountains 1"-3+"

-low end (9 in 10 chance): valleys 0.25"-1.25", mountains 0.50"-1.5" -high end (1 in 10 chance): valleys 1.75"-3.25", mountains 2"-4" locally higher

With the expected rain on sunday into early monday we will see a response in area rivers, creeks, and washes across SE az. See hydrology section below for further details.

Monday morning will see lingering showers, but no significant rainfall is expected. In the wake of the trough, brief ridging will be in place through tuesday. Then a couple shortwaves moves through the region during the latter half of the work week. The atmosphere dries out fairly quickly monday leading to dry conditions for the work week. High temperatures will be 4-7 degrees below normal through the work week.

Aviation

Valid through 02/00Z. Expect intermittent MVFR cigs at all terminals through the forecast period with brief IFR cigs possible at kdug and kols tonight through the end of the forecast period. Scattered -shra will be possible at kols and ktus through 01/00Z, then more numerous shra with slight chc -tsra mainly from ktus/kols westward through the overnight hours. Shra and isolated tsra increase eastward encompassing all terminals after 01/15Z. Vis down to 1-2 miles will be possible in shra or tsra. Sfc winds mainly sely/sly 5-10 KTS thru sunday morning becoming swly 12-20 KTS and gusts 25-30 KTS after 01/18Z. Near stronger tsra wind gusts of 30-40 KTS will be possible on sunday. Aviation discussion not updated for taf amendments.

Fire Weather

Scattered showers this afternoon then precipitation chances increase tonight with widespread showers and isolated thunderstorms sunday into monday. Moderate intensity rainfall with pockets of heavy rain is expected sunday into sunday night. The heaviest rain will be over the higher terrain. Afternoon high temperatures will lower below normal through the forecast period. Breezy to locally windy southwest winds expected sunday, turning northwest monday. Minimum rh levels values into early next week will be 40+ percent.

Hydrology

As mentioned in the discussion section above, with the expected moderate to heavy rain on sunday into early monday we will see a response in the area rivers, creeks and washes across SE az. There is the potential for significant rises on the san francisco river, blue river, gila river, eagle creek, and sabino creek with minor to major flood stages possible. This will continue to be evaluated over the next day and through the event.

Climate

Below is a listing of probability of exceedance of 36-hour rainfall totals from 5 PM saturday oct 31 to 5 AM monday nov 2.

Chance of seeing more than 1" 2" 3" tucson 76% 52% 4% marana 82% 55% 5% mount lemmon 100% 88% 55% ajo 67% 19% 2% picacho peak 95% 56% 4% oracle 96% 63% 19% hannagan meadow 100% 94% 63% safford 65% 28% 3% clifton 89% 46% 9% willcox 52% 4% 0% douglas 27% 3% 0% sierra vista 44% 4% 0% nogales 68% 26% 3% tucson rainfall records october 31st: 0.44" in 1926 november 1st: 0.42" in 1987 november (one-day): 2.09" on november 22, 1931