Forecast Discussion
675 FXUS65 KTWC 202122 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 222 PM MST Mon Jan 20 2025 .SYNOPSIS... A dry system will bring breezy to windy conditions tonight through tomorrow along with a colder temperatures through Wednesday morning. Highs warm to near seasonable then above normal through the remainder of the week and into the weekend. A stronger system may arrive late this weekend or early next week, bringing colder temperatures, breezy conditions, and chances for precipitation. && .DISCUSSION... Active flow aloft in the periphery of a central-eastern CONUS trough will bring a shortwave through the desert southwest this evening through Tuesday. A pressure gradient will tighten overnight, turning winds from the northwest this evening to the east to southeast by early Tuesday morning. Unseasonably cold air will drop in with this shortwave, bringing chilly conditions Tuesday and Wednesday mornings with below normal highs on Tuesday. An overlap of the tightened pressure gradient and increased mid- level winds will occur Tuesday morning, which is when the opportunity for strong gusty winds in areas open to easterly flow is maximized. In most areas (especially sheltered locations), breezy winds of 15-20 mph with gusts to 30 mph are likely through much of Tuesday. On the higher end, namely exposed elevated ridges and some locations open to east winds, gusts to around 45 mph, with a few high elevation ridges potentially exceeding 50 mph are likely. High- resolution ensemble modeling is highlighting the difference in wind strength well between higher terrain and more sheltered locations. As mid- level winds diminish with the exiting shortwave Tuesday afternoon, the highest wind gust potential will likely begin to taper off starting late Tuesday morning. Cold air with morning wind chills will arrive with this shortwave tonight. As windy conditions will have a dampening effect on the diurnal cycle, it remains a bit uncertain how cold temperatures will get tonight. Low to mid 30s are forecast in Tucson and westward with lows in the 20s in valleys south and east. Wind chill values in eastern locations may drop into the teens if there is enough of an overlap between breezy winds and dropping temperatures, but again the floor of this potential is uncertain. Greater chances for colder morning lows will arrive Wednesday with southeastern Arizona on the back side of the trough and winds having diminished. Sub-freezing temperatures are very likely across most of southeastern Arizona outside of far western Pima County (though a few exposed higher elevation locations, such as the Catalina foothills area, may still see a lingering easterly breeze that keeps temperatures a bit warmer). Sheltered locations in Tucson and west should see lows drop into the 20s, with lows in valleys eastward down to the lower teens. Mid-level height rises behind the exiting shortwave will see temperatures quickly jump through the second half of the week. By Friday, above normal highs in the 60s in eastern valleys and 70s Tucson westward are likely. Looking towards the end of this coming weekend, most guidance is in good agreement with a shortwave dropping south through the west coast and deepening over the desert southwest. The amplitude and placement however have moderate inconsistencies, leading to uncertainty in precipitation potential/timing. Some solutions produce a more progressive trough which brings precipitation chances as early as late Saturday, while others close the low northwest of the area and delay any potential into early next week. This provides similar uncertainty in temperature trends and wind potential, however colder temperatures arriving again late this weekend or early next week is a reasonable outcome. && .AVIATION... Generally starting SKC with increasing cirrus AOA 20k feet through the forecast period. Northwest winds this afternoon become northerly then east to southeasterly through tonight. Wind speeds generally 11-18 kts with gusts 20-25 kts through 21/12Z, then increasing to 14-22 kts with gusts up to 35 kts through the morning. Winds gradually diminish through Tuesday evening. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER... A dry system moves through the region tonight and tomorrow, bringing cooler temperatures and windy conditions. Brief periods of near critical fire weather conditions possible tomorrow. Winds shift from the northwest this evening to the east- southeast through Wednesday morning. Gusty east to southeast winds are likely in areas exposed to that wind direction, especially late tonight through Tuesday morning. Exposed ridge tops and areas open to easterly flow may see gusts as high as 40-50 mph. Winds then gradually diminish through Tuesday evening. Minimum relative humidities in the valleys will be 8-14 percent through tomorrow, then 5-10 percent through the remainder of the week. Mountain minimum humidities in the 7-14 percent range through the week. && .TWC WATCHES/WARNINGS/ADVISORIES... None. && $$ Public...Edwards Aviation...Edwards Fire Weather....Edwards Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson
NWS TWC Office Area Forecast Discussion