Marine Weather and Tide Forecast for Casas Adobes, AZ

DISCUSSION
The upper pattern today is defined a trough of low pressure across the Intermountain West/Northern Plains with a low center over Wyoming, a second trough west of California centered near 35N/129W and a dampening ridge of high pressure over the SERN states with a high center over ERN TX/WRN LA. In the lower-to-middle levels of the atmosphere (850 to 700mb), there is an weak trough moving into southwest Arizona from the northern Baja Mexico.

The latest GOES precipitable water imagery indicated that the weak lower-level feature has imported some moisture into Southeast Arizona from the SW. Precipitable water values between 0.80 to 1.00 inches extend across Pima/SE Pinal and Santa Cruz counties, with lower values between 0.65 and 0.80 inches east of Tucson.
As this feature ejects across southern Arizona today, we should have enough lower-level moisture convergence to support a weak shower to develop across south-central Arizona. I still wouldn't expect anything strong given the shortwave ridging occuring in the middle to upper levels, but since the sub-cloud layer is dry, we may see some gusty/breezy winds to 35 mph accompany the light shower downdrafts.

Monday, both of the upper troughs continue to track east with one centered over the upper Midwest and the other along the central California coastline. An amplified shortwave ridge building between these two features into north-central Mexico will result in a southerly flow across Sonora/Chihuahua MX. This will draw deeper moisture starting Monday. The bulk of the moisture will advect into New Mexico and far eastern portions of Arizona Tuesday and Wednesday. The best deformation aloft/lift between the upper trough to our west and the subtropical ridge to our east will occur over New Mexico. However, there appears to be a westward expansion of this area of lift into our neck of the woods. This should increase the potential for heavy rainfall across Southeast Arizona from Tucson east on both Tuesday and Wednesday. In fact, the latest NBM suggests there is a 10 percent chance of rainfall totals greater than 1.25 inches along the Arizona/New Mexico border between 12Z Tuesday and 12Z Wednesday.

The NHC still identifies an area 350 miles south of Manzanillo Mexico (Invest 99E) with conditions conducive for it to become a tropical depression or storm within the next day or so. There is still a ton of uncertainty with the forecast track and strength of this feature. In a general sense, it will work its way northwest to a location west of the tip of the Baja between 200-240 hours. My intuition tells me that we will see a broad ridge develop over northwest Mexico that will block the deeper moisture and force it to track farther west where moisture eventually shears out to the NE across the Desert Southwest. We will see...there is a lot of time to monitor its development.

AVIATION
Valid through 22/00Z. SCT-BKN clouds 8k-11k feet with a 5-15% chance for -SHRA through 21/02Z, then SCT-BKN high clouds AOA 20k ft AGL overnight through 21/18Z, then SCT-BKN clouds 8k-11k feet with a slight chance for -SHRA/-TSRA.
Although localized wind gusts to 30 kts will be possible near storms today, SFC winds will be light and under 12 kts through the forecast period. Surface wind direction west to northwest in the afternoon, otherwise terrain driven. Aviation discussion not updated for TAF amendments.

FIRE WEATHER
A modest increase in moisture today will bring minimum relative humidity values up to 20-30 percent in the lower elevations and above 30 percent in the mountains. An isolated shower can't be ruled out this afternoon with the potential for a gusty downburst wind to 35 mph. Moisture values will increase 10-20+ percent, especially in Graham, Greenlee, and Cochise counties, Tuesday through the end of the week.
Chances for showers and thunderstorms will also arrive daily with this moisture increase. Gusty and erratic winds will accompany any thunderstorms.

TWC WATCHES/WARNINGS/ADVISORIES
None.