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FXUS65 KTWC 042045 AFDTWC

Area Forecast Discussion National Weather Service Tucson AZ 145 PM MST Sat May 4 2024

SYNOPSIS
Sunny, warm and dry through the weekend. A dry weather system will bring windy conditions on Sunday, along with the possibility of some blowing dust. Cooler Monday, then temperatures warm up the remainder of next week with continued afternoon breezes.

DISCUSSION
A Pacific storm system off the southern Oregon coast will move southeast into the Great Basin on Sunday and then east into the plains on Monday. This system will bring breezy to windy conditions across southeast Arizona on Sunday. Expect southwest winds of 15-30 mph and gusts to 35-45 mph from late Sunday morning through Sunday evening. Wind speeds will be just below wind advisory criteria, so no wind headlines for Sunday. However, wind speeds will exceed critical fire weather thresholds, so have elected to upgrade the Fire Weather Watch to a Red Flag Warning. The Red Flag Warning will be in effect from 11 am MST through 7 pm MST Sunday. I could have gotten a little fancy with the Red Flag Warning and left out far western Pima County (most likely just below criteria), but this would split up Fire Weather Zone 150 with 2/3's of the zone still in the warning, and therefore, elected against this approach. The same could have been said for elevations above 7.5k feet, where fuels may not quite be as available to burn. At the end of the day, with the wind speeds involved, if a fire start does occur it will spread rapidly and be difficult to control. Blowing dust will also be concern on Sunday, especially in the favored areas along I-10 between Willcox and San Simon and from Red Rock northward.

On the back side of the system Monday, high temperatures will lower 5-7 degrees (versus highs Sunday) and top out 2-4 degrees below normal. Still breezy, but below wind advisory/fire weather thresholds. Expect west winds of 15-20 mph and gusts to around 30 mph across portions of Cochise, Graham and Greenlee counties and lower wind speeds further west.

Tuesday and Wednesday, high temperatures warm back up to 1-3 degrees above normal. Wind speeds pick back up during the afternoon and early evening hours, especially to the east of Tucson. Cochise, Graham and Greenlee counties will be near critical fire weather thresholds. Something to keep an eye on going forward.

Thursday and Friday, highs continue to be 1-3 degrees above normal, with typical May afternoon breezy conditions due to strong surface heating.

AVIATION
Valid through 06/00Z.
Clear skies/SKC conditions thru much of the forecast cycle, with just a FEW clouds AOA 20k ft AGL at times. SFC wind SWLY/WLY at 10- 16 kts and gusts up to 24 kts thru 05/02Z, with the strongest SFC wind east of KTUS in the vicinity of KDUG and KALK. SFC wind less than 12 kts and variable in direction between 05/02Z and 05/15Z.
Increasing SFC wind after 05/15Z, with SWLY SFC wind at 17-25 kts and gusts up to 40 kts between 05/18Z and 06/00Z. Aviation discussion not updated for TAF amendments.

FIRE WEATHER
High temperatures will be 2-5 degrees above normal through Sunday and then within a couple of degrees of normal next week. 20-ft winds will generally be 10-20 mph today. A dry weather system will move to our north on Sunday, resulting in windy southwest winds of 15-30 mph and gusts between 35-45 mph across most of southeast Arizona. Breezy winds during the afternoon and early evening hours then persist much of next week, especially to the east of Tucson. Min RHs values in the valleys will be in the single digits to lower teens, with values generally in the teens for the mountains.

On Sunday, the combination of strong and gusty southwest winds, low relative humidity levels and a high fire danger rating will result in critical fire weather conditions from the late morning through early evening hours for most of southeast Arizona. A Red Flag Warning has been issued for all of southeast Arizona from 11 am to 7 pm MST Sunday.

TWC WATCHES/WARNINGS/ADVISORIES
Red Flag Warning from 11 am to 7 pm MST Sunday for AZZ150>154.

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