National Weather Service - Tucson 9:10 a.m. MST, Monday, Jan. 22, 2007
Synopsis ... A strong low pressure system will continue to bring a winter mix of weather to Southeast Arizona today. Locally heavy snowfall will continue with areas of fog and icy road conditions. The upper low pressure system will become stationary over Sonora, Mexico, by Tuesday ... with moisture lingering across the area through midweek. Dry conditions by the end of the week as high pressure aloft returns.
Discussion ... The upper low that has brought a winter mix of weather to Arizona was over Sonora, Mexico, this morning ... centered just southwest of Nogales. Spotty light snowfall was still being reported in the vicinity of this upper low across parts of central and eastern Pima (including Tucson) ... and Santa Cruz counties along with patchy fog and icy roads. Farther north of this low ... wrap around cloudiness and snow showers continued with heavy snow being reported in Safford. As the upper low drops farther south this afternoon ... this wrap around will shift southward bringing more scattered snow showers to areas that have cleared this morning. The main heavy snowfall threat had diminished but a winter mix of fog ... snow ... and some icy road conditions will continue today. Therefore ... will switch the heavy snow advisories and warnings over to a winter storm warning to cover the multiple hazards. This warning will replace the dense fog and frost warnings issued for parts of Pima and Santa Cruz counties. Refer to AWIPS header PHXWSWTWC or WMO header WWUS45.
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Information on preliminary snow accumulations so far can be found in various products ... but the primary ones will be issued under PHXRTPTWC ... PHXRTPAZ ... PHXPNSTWC. The heaviest snowfall reported so far this morning was at Hannagan Meadow in the White Mountains where 24 inches of new snow fell giving them a total of 32 inches on the ground. Safford area reported 6 to 9 inches already with heavy snowfall continuing.
The upper low will become somewhat stationary over Northern Mexico later today into at least Thursday. The position of the upper low will result in a chance of showers continuing across far Southeast Arizona ... mainly Cochise County this next couple of days. Otherwise ... areas farther west and north should see clearing later today with partly to mostly sunny skies Tuesday. Clearing skies will result in more sub-freezing temperatures on the lower deserts again tonight.
Aviation ... Expect low CIGS and VSBYS through the day at terminals. Current TAF and TWEBS adequately cover all significant weather at KTUS.
TWC watches/warnings/advisories ... Winter storm warning this afternoon all zones except 31.
