960 FXUS65 KTWC 220418 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 918 PM MST Sun Jul 21 2019 .SYNOPSIS...Ample moisture and favorable flow will result in scattered to numerous thunderstorms Monday afternoon into Monday night. Blowing dust due to thunderstorm gusts may occur Monday afternoon and evening. Scattered showers and thunderstorms to continue Tuesday into next weekend. && .DISCUSSION...Plenty of activity this evening with Pima county, namely the Tohono O`odham Nation, taking the brunt of it with several severe warned storms thanks to capes in excess of 3000 j/kg. That activity has moved east of the area and we even noted a small MCV within the dying convection. There was plenty of water with some of the storms as noted by the rapid rise on the Vamori Wash. I`m sure at least some water was flowing in a few other washes in central and western Pima county as well. We will need to keep that in mind tomorrow evening when convection moves into that area. At this time the activity over southern Arizona should be very limited for the rest of the night with most of the action remaining across northern Mexico. I made some adjustments to the grids tonight into Monday to account for current and expected conditions, mainly less activity tonight and more tomorrow. Actually tomorrow looks to be the most active day by far this season and I tweaked on pops, winds and temps for the afternoon and evening hours. Should be an interesting afternoon and evening! && .AVIATION...Valid through 23/06Z. Isolated -SHRA may continue southeast to southwest of KTUS late tonight into early Monday morning. Then scattered to numerous TSRA/SHRA expected Monday afternoon into Monday night. Brief wind gusts to 45-55 kts with the stronger TSRA. SCT-BKN cloud decks mainly 10k-15k ft MSL, except MFVR cigs and vis with storms and brief IFR conditions possible Monday afternoon with local mountain obscuration. Surface wind light and variable overnight becoming westerly 5-15 kts Monday afternoon. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Expect scattered to numerous thunderstorms Monday afternoon into Monday night. Adequate moisture will then persist Tuesday into next weekend for scattered mainly afternoon and evening thunderstorms. Gusty outflow winds expected near thunderstorms. 20-foot winds generally from the northwest under 15 mph but will transition to be out of the east to southeast Monday morning. Lowest minimum humidity is under 15 pct in the Gila River Valley today. Relative humidity unlikely to be under 20 percent anywhere for the rest of the week. && .PREV DISCUSSION... /issued 315 PM MST Sun Jul 21 2019/ Our large scale pattern is shaping up nicely with a strong ridge over the desert southwest and the high center consolidating near the 4-corners region to start the week. The surge we were discussing yesterday continues to increase in intensity with 12-20kts now up to 6k feet on the KYUX Vad Wind Profile. Surface dew points are up 5 to 15 degrees across the board with upper 50s and 60s pushing through Santa Cruz and Pima counties. Probably maintaining precipitable water values in the 1.5 inch range from Tucson westward, with up to 1.75 inches south of the border and 1.3 inches in eastern areas. Our main area of focus this afternoon is in the deeper moisture areas with a weak convergent area from northern Sonora through Santa Cruz county and the Tohono O`Odham Nation. Deeper moisture will continue to push into the area from the south tonight as we set up an easterly steering flow under the high. Tomorrow looks like our first widespread thunderstorm outbreak of the season. SREF plumes have ML CAPE around 1200 to 1500 tomorrow afternoon with HREF ensembles surface based CAPE in excess of 1500 J/kg. Effective vertical wind shear between 25 and 30 kts. UA WRF forecasts respond accordingly tomorrow with strong and organized thunderstorm development through the afternoon (and are doing well today). Perfect set-up for organized easterly outflow and blowing dust issues into the lower deserts. As mentioned before, Tuesday would likely be a recovery day if the Monday forecast works out. We`ll see on that. We will still have plenty of boundary layer moisture to recycle the second half of next week, but are unlikely to maintain a deep fetch of moisture with an easterly component to our mid level flow periodically drying out (with limited Gulf of Mexico influence). However, with the high center finally in a position where it wobbles back and forth overhead to northwest to northeast of us, the overall trend will be better with up days and down days. && .TWC WATCHES/WARNINGS/ADVISORIES... None. && $$ PUBLIC...Cerniglia/Meyer AVIATION....Cerniglia FIRE WEATHER...Pawlak Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson
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