Marine Weather and Tide Forecast for South Tucson, AZ

KEY MESSAGES

1. Quiet Weather Pattern:

High pressure along the West Coast will result in above normal high temperatures and dry conditions through the middle of next week. No weather impacts are anticipated.

2. Weather System Late Next Week into Next Weekend (low-confidence):

A winter weather system is forecast to impact Southeast Arizona with valley rain and mountain snow late next week into next weekend. There is plenty of uncertainty amongst weather models, resulting in a low confidence on the strength and timing of this next system.

DISCUSSION
Weather conditions across Southeast Arizona remain quite nice for this time of year with seasonably-warm afternoon temperatures. These conditions will persist into the first half of next week as an amplified ridge of high pressure has established itself along the West Coast.

Numerical models have been somewhat confused the past several days on how to handle the strong trough of low pressure to the west of this feature in the Eastern Pacific was it moves east into the mean ridge along the West Coast. The latest 17/12Z ensemble members of the GEFS and ECMWF both have the southern portion of this feature split off into a cutoff-low near 28N/130W by 22/00Z Wednesday afternoon. The differences then become apparent as the operational 17/12Z GFS tries to grab hold of and then import a deep plume of sub-tropical moisture ahead of this feature into the Desert Southwest during the day Friday, with the upper-low tracking east into southern California by 24/12Z Saturday morning.
This scenario would bring a round of valley rain/high elevation mountain snow Friday, with another round of showers with better dynamics as the upper-low tracks thru Saturday. The timing of the upper-low is similar with the 17/12Z operational ECMWF, but it lacks the subtropical plume so the valley rain/mountain snow is more associated with the upper-low tracking thru during the day Saturday. These differences in timing and strength are still fairly significant. My hunch tells me that the ECMWF solution is more likely because it doesn't depend on the timing and location of the cutoff-low to grab onto that subtropical moisture. Cutoff- lows usually have a mind of their own, especially when encountering an amplified ridge.

AVIATION
Valid through 18/12Z. SKC thru 18/12Z Sunday morning, then SCT-BKN high cirrus clouds AOA 25k ft AGL. SFC wind less than 10 kts favoring a WLY/NWLY direction into the early evening hours, then ELY/NELY 8-13 kts aft 18/03Z. Aviation discussion not updated for TAF amendments.

FIRE WEATHER
High pressure aloft will result in above normal high temperatures and dry conditions through at least the middle of next week. 20-foot winds will be less than 15 mph and terrain driven.
Minimum RHs will be in the 12-20 percent at all elevations through Monday, with an increase of 5-10 percent across the eastern half of southeast Arizona Tuesday through Thursday of next week. A cutoff-low pressure system in the Eastern Pacific will then import a plume of sub-tropical moisture into the Desert Southwest late next week, resulting in an increase in Minimum RHs and a slight chance for valley rain and mountain snow across portions of Southeast Arizona next Friday into next weekend.

TWC WATCHES/WARNINGS/ADVISORIES
None.