The figure above indicates the forecasted high in orange (with error bar denoting the range of ensemble forecast members), average high for this time of year in orange (dashed line), forecasted low in blue (with error bar), average low this time of year in blue (dashed line), and forecasted wind speed in purple. Note that the wind speed forecast is sustained wind (not gusts), and it is based on only one model (not an ensemble).
A strong, cold low pressure system will develop for the next two days along the West Coast amid a strong northerly jet stream aloft that is exceeding 120 knots at its core. The low pressure system is forecast to cut off and become centered over Southern California by Wednesday morning, then shift eastward across Arizona on Wednesday and Thursday. Cutoff low pressure systems are notoriously difficult to forecast. Moreover, the precise location where the low develops will determine how much moisture will be tapped and how much lifting will result over the Prescott area. The center of the storm will likely be just south of Prescott as it shifts eastward which may reduce the amount of upslope lifting over the mountains. Nevertheless, there is a good chance we will see snow showers from late Tuesday night to Thursday (possibly mixed with rain on Tuesday night to Wednesday morning). All of the forecast models are indicating snow accumulation from this storm, but there is tremendous uncertainty in the snow amounts with anywhere from 0.5” up to 11” predicted for the Prescott Airport. The most likely snowfall total for the airport is about 4”, with higher snowfall totals to be expected for the city of Prescott and especially in the mountains around Prescott. The National Weather Service is indicating 4”-8” of snow above 5,000’ elevation and a total of 5.4”of snow forecast for downtown Prescott (http://www.wrh.noaa.gov/FXC/wxstory.php?wfo=fgz) and over a foot of wind-driven snow over south-facing mountain slopes.
The heaviest snow accumulations are expected to occur during the day on Wednesday (New Year’s Eve), tapering off to light snow showers Wednesday evening to Thursday. If these forecasts are accurate, travel on New Year’s Eve could be difficult, with icy or snow-packed roads and periods of low visibility due to falling and/or blowing snow.
Met Mail is an unofficial weather discussion and forecast transmitted once or twice a week via e-mail by the Embry-Riddle Department of Meteorology (http://meteo.pr.erau.edu/). Embry-Riddle offers an undergraduate bachelor-of-science degree program in Applied Meteorology. Please spread the word to all potential qualified candidates!
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Official National Weather Service forecast