FXUS65 KTWC 211037

AFDTWC



Area Forecast Discussion

National Weather Service Tucson AZ

337 AM MST Mon Sep 21 2026



.SYNOPSIS...



A modest increase in moisture will bring partly

cloudy skies with a slight chance of a weak shower this

afternoon and early this evening. Moisture will continue to  

increase after today bringing daily chances for showers and 

thunderstorms through much of the week.



&&



.DISCUSSION...



Today, an upper low will move into central-southern California

while a downstream shortwave ridge exits southeastern Arizona to

give way to southwesterly flow. Satellite derived moisture

values aren't terribly impressive this morning with

precipitable water at 0.8-1 inches, however with the trough

nearby a slight chance of a shower or thunderstorm is in the 

forecast this afternoon mainly east of central Pinal/Pima 

through the New Mexico border. Moisture is expected to advect 

north out of Mexico tonight as low-mid level flow turns 

southerly, which will keep a slight chance of a shower in the 

forecast through the night. 



Tuesday through Thursday will see upper level troughing persist

over southern California and northern Baja, while a southerly 

stream of moisture continues, mainly focused over New Mexico 

with central Pima on the western periphery. Precipitable water 

should increase to 1-1.25 inches in this area and combined with

persistent upper level support, shower/thunderstorm chances 

will increase to 30-60 percent in eastern areas of the state.. 



Precipitation chances lower a bit Friday into the weekend as the

upper level wave finally exits the region. Confidence in any one

forecast solution in this period going forward deteriorates

as ensemble models disagree on the flow pattern as well as the 

potential influence of Tropical Storm Polo currently off the 

southwestern Mexico coast. At this moment the forecast favors 

just low end rain chances through early next week with most 

ensemble members keeping tropical activity away from the region 

through mid-week next week.



&&



.AVIATION...Valid through 22/12Z.



Mainly SKC through the morning. SCT-BKN 8k-11k ft ceilings after

21/18Z with 10-20 percent chance of a -SHRA/-TSRA. Slight chance

of -SHRA through the night but with lower confidence. Surface

wind west/southwest 6-11 kts this afternoon and early evening, 

otherwise light and terrain driven. Aviation discussion not

updated for TAF amendments.



&&



.FIRE WEATHER...



Minimum relative humidity 20-30 percent in the lower elevations

and 30-40 percent in the mountains today, increasing further for

the remainder of the week especially across Graham, Greenlee,

and Cochise counties. Chances for showers and thunderstorms will

also arrive daily Tuesday onwards with this moisture increase. 

Gusty and erratic winds will accompany any thunderstorms.



&&



.TWC WATCHES/WARNINGS/ADVISORIES...

None.



&&



$$



DISCUSSION...Edwards

AVIATION...Edwards

FIRE WEATHER...Edwards



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