729 FXUS65 KTWC 012043 AFDTWC Area Forecast Discussion National Weather Service Tucson AZ 143 PM MST Thu Feb 1 2024 .SYNOPSIS...A winter storm moving in will spread colder temperatures and precipitation across the area tonight through Friday night. The cool temperatures will linger through the weekend before warming up again early next week. Then stormy weather is again expected the middle to the end of next week. && .DISCUSSION...Mostly sunny skies from Tucson westward early this afternoon with mostly sunny to partly cloudy skies east of Tucson as a cumulus field has developed. Latest observations indicate gusty south to southwesterly winds across the entire forecast area with a few spots seeing gusts in the 35 to 40 mph range. Looking upstream, the main frontal band that's associated with the trough that is moving in tonight is currently located across southern California. Latest hi-res model guidance is in good agreement on the timing of the front as it shifts east and moves through the forecast area tonight into Friday morning. Most locales will have a solid 6 hour or so period of widespread valley rain and mountain snow as the frontal band pushes through. Current timing for this is around 10 pm to 5 am in Tucson, a little earlier to the west and later to the east. Following the frontal band, precipitation will become more showery/convective in nature during the day Friday. Thus, while it will be considerably cooler, remaining breezy and mostly cloudy, it will not be raining all day Friday. A rumble of thunder also can't be ruled out tonight through Friday. QPF values in the valleys remain relatively unchanged for tonight through Friday, mainly in the 0.25" to 0.75" range with locally higher amounts up to around 1 inch possible. Meanwhile, for the mountains, liquid equivalent amounts will be 1 to 2 inches as the higher terrain will be aided by strong orographic lift along the front. These higher QPF values in the mountains, especially from Tucson northeastward have resulted in an upward bump in corresponding snow amounts. Latest most likely snow amounts for the Catalinas/Rincons, Mount Graham and the White Mountains are 12 to 18 inches above 8000 feet and 8 to 16 inches above 7000 feet. Therefore, these locales have been upgraded to a Winter Storm Warning. For the southern mountains including the Santa Ritas, Huachucas and Chiricahuas, where snow amounts will be a bit lower, a Winter Weather Advisory has been issued above 6500 feet for 6 to 12 inches of snow. A few showers will linger into Saturday, mainly across Graham and Greenlee Counties. The rest of southeast Arizona should generally remain dry but continued cool as highs top out in the upper 50s in Tucson. Dry conditions and warming conditions Sunday and Monday as shortwave ridging moves through and heights aloft increase ahead of the next trough. Latest ensembles are showing this next system moving in as early as Tuesday afternoon and continuing through Wednesday. This will bring our region another round of valley rain and mountain snow along with a return to cooler temperatures on Wednesday. && .AVIATION...Valid through 03/00Z. SCT-BKN clouds around 7-10k ft MSL from KTUS eastward this afternoon. Then frontal clouds advancing from the west late this afternoon becoming BKN-OVC 9-12k ft MSL with BKN-OVC layers above and widespread SHRA, mountain SHSN developing, reaching KTUS/KOLS around 02/05Z and KDUG around 02/09Z. After 02/04Z local MVFR CIGS and VSBYS with mountain obscuration in clouds and precipitation. SHRA/Mountain SHSN then becomes more hit in and miss in nature aft 02/15Z through the end of the forecast period. SFC winds SWLY 15-25 kts with gusts 30-40 kts, becoming WLY and diminishing to 10-20 kts aft 02/12Z. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Continued warm and windy this afternoon in advance of a storm system that will bring precipitation tonight through Friday night and colder temperatures tonight through the weekend. Expect 20 foot wind speeds 15-20 mph this afternoon into Friday with local gusts 30+ mph. Then after a break in the weather later this weekend into the early part of next week, another storm system will impact Arizona late Tuesday into Wednesday with a possible followup system late next week. && .TWC WATCHES/WARNINGS/ADVISORIES... Winter Storm Warning from 8 PM this evening to 11 PM MST Friday for AZZ510-511-514. Winter Weather Advisory from 8 PM this evening to 11 PM MST Friday for AZZ512-513. && $$ Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson