Marine Weather and Tide Forecast for Sierra Vista, AZ

DISCUSSION
Sunny, breezy and warm is the most succinct way to describe the forecast. In fact, that's the one thing about our weather across Southeast Arizona during the month of May. While conditions are often sunny and warm, it is those same conditions that promote stronger winds to mix down to the surface because of the abundant daytime surface heating.

The upper pattern today impacting our forecast is defined by two main features. The first being a weak shearing trough of low pressure across northern New Mexico with a baggy trough axis extending across southern Arizona into the northern Baja. Still some stronger winds in the mid-levels holding onto the extreme SE corner of the state this afternoon, which should result in some afternoon breezes with gusts to 35 mph possible in Cochise county this afternoon.

The second feature is a strong upper low positioned along the coastline of British Columbia Canada this morning, moving SSE into the Pacific Northwest. The overall pattern will become amplified along the West Coast this weekend as this feature digs farther south and the upper ridge in the Eastern Pacific responds.
Initially we will see an increase in pressure gradients aloft Saturday with winds mixing down for a breezy day with southwest winds 15 to 20 mph with gusts to 30 mph. Although the main upper-low will only make it as far south as the Great Basin by 18/00Z Sunday afternoon, Southeast Arizona will reside on the southern periphery of this system with stronger mid-level flow (30-40 kts between 700-500 mb) expanding across our neck of the woods. These winds will mix down to the surface resulting in a windy day across the area, with southwest winds generally 20-30 mph with gusts 40-45 mph across the majority of the CWA
These winds would be strong enough to result in some patchy blowing dust Sunday afternoon. In addition, given the dry airmass in place with minimum relative humidity in the 7 to 15 percent range, we will experience critical fire weather conditions as well. The latest NBM 5.0 probability for near critical fire weather conditions (RHs<=15 pct and 10-m winds 20+ mph) remains between 30-60 percent Sunday across the majority of Southeast Arizona, with portions of southern Cochise between 60-90 percent. Given the increasing confidence with successive runs indicating the same thing, we have decided to issue a Red Flag Warning for fire weather zones 151/152/153/154 from 11 am MST Sunday morning until 11 pm MST Sunday evening.

Although the stronger winds should hold onto the areas east of Tucson Monday, we will see a slight increase in lower-level moisture. Dewpoints Sunday will range from the upper teens to mid 20s eventually increasing into the lower to mid 30s Monday.
This should help push minimum RH percentages back up into the mid to upper teens. I am a bit skeptical that areas east of Tucson will moisten up enough Monday to not result in another day of critical fire weather conditions, but at this juncture given the lower confidence, we will hold off on any fire weather product for Monday for another day or so.

AVIATION
Valid through 17/00Z. Mainly SKC through the valid period. SFC winds light and mainly SELY/SLY at 10 kts or less this morning, then aft 15/18Z becoming WLY/SWLY wind 8-15 kts with occasional gusts to 20-25 kts this afternoon. SFC winds diminish to 10 kts or less again aft 16/03Z and become SELY/SLY.
Aviation discussion not updated for TAF amendments.

FIRE WEATHER
Less wind today for Southeast Arizona with just a few afternoon breezes, especially across Cochise county.
Southwest winds will start to increase Saturday with 20-foot winds 15-20 mph with gusts up to 30 mph, and then ramp up even more Sunday into Monday to around 20-30 mph sustained and gusts 35-45 mph. The combination of these strong winds and continued dry conditions will result in near critical fire weather conditions Saturday and widespread critical fire weather conditions Sunday for the majority of Southeast Arizona, then near critical conditions again south and east of Tucson Monday.
We have issued a Red Flag Warning for fire weather zones 151/152/153/154 from 11 am MST Sunday morning until 11 pm MST Sunday evening.

Otherwise, high temperatures will be about 3 to 7 degrees above normal through Saturday with cooling to slightly below normal levels Sunday and Monday. Less winds thereafter for the middle of next week. Minimum relative humidity values into next week will generally be in the 6-16 percent range in the valleys and 10-20 percent in the mountains.

TWC WATCHES/WARNINGS/ADVISORIES
Red Flag Warning from 11 AM to 11 PM MST Sunday for AZZ151>154.