Area Forecast Discussion

SYNOPSIS

Modest mid-level moisture will result in a chance of mainly dry storms/thunderstorms this afternoon near the White Mountains. Otherwise, warm and dry for much of the week and into the weekend. Breezy conditions are anticipated for the second half of the week into this weekend, resulting in near critical fire weather conditions east of Tucson Wednesday through the weekend.

DISCUSSION

There is just enough moisture 0.4 to 0.7 inches of precipitable water for showers/thunderstorms to form in the White Mountains and cumulus clouds around the rest of the Sky Islands late this morning and early afternoon. These showers/thunderstorms will stick around through the early evening hours. There is not much in the way of rainfall totals with these storms, making the greatest impacts lightning along with gusty and erratic outflow winds.

Looking ahead for the rest of the week, the feature to look out for is the cut off low that is currently in the Pacific Ocean off the coast of Northern California/Southern Oregon. This system will pass to the north of us Wednesday into Thursday, translating to breezy west to southwest winds each afternoon.

As this first low pressure passes through, high pressure forms behind it in the Gulf of Alaska/British Columbia, Canada. As the high pressure builds, a second area of low pressure forms in the Pacific, keeping the upper level overhead in a dry southwest flow. To the south in Mexico, weak high pressure begins to build, increasing the pressure gradient. This will keep the elevated southwest/west winds through the weekend, bringing near critical fire weather conditions (more in the fire weather section). The models are in fair agreement with this overall pattern, however there are slight differences in depth/strength of this low pressure and high pressure. These differences translate to how strong our afternoon winds could be, with the ECMWF having stronger winds/gusts with the deeper low and stronger high pressure and GFS ensemble having slightly less strong winds thanks to the broader low pressure and weaker high pressure. Overall, breezy winds will be the main weather story for much of the upcoming week.

AVIATION

Valid through 22/00Z. SCT 10-15k ft AGL development of 8-12k ft AGL clouds to the NE of KTUS (including the terminal at KSAD) in the afternoon through 21/02Z. After 21/02Z, increasing high clouds AOA 20k ft AGL from the southwest through the rest of the valid period. SFC winds SWLY/WLY 10-14 kts with occasional gusts to 20 kts into the early evening thru 21/03Z then again aft 21/18Z thru the end of the period. Otherwise, SFC winds remain under 10 kts and terrain driven. Aviation discussion not updated for TAF amendments.

FIRE WEATHER

There is a modest increase in mid-level moisture near the White mounatins that has resulted in mainly dry storms/thunderstorms this late morning and is expected to continue this afternoon with gusty and erratic outflow winds possible near the downdrafts. Minimum RHs will generally be 10-15 percent in the valleys and 15-25 percent in mountains today, decreasing to the single digits to mid teens areawide by mid- week. Otherwise, passing systems to the north this week will keep Southeast Arizona dry, but breezy the second half of the week into next weekend. There is a 50-70 percent probability that areas Tucson eastward will reach elevated to near critical fire weather conditions Wednesday through the weekend.

TWC WATCHES / WARNINGS / ADVISORIES

None.