The forecast details vary by site. Wunderground is forecasting a meager 3 inches with their “BestForecast” tool. AccuWeather is forecasting 4-8 inches. The National Weather Service is stepping out and forecasting 6-10 with a couple more on Friday. I’m sticking to my forecast from yesterday for “several inches.”
There are salient differences in all these forecasts and the models behind them. This morning the North American Mesoscale model shows the bulk of the storm hitting the eastern parts of Arizona, with Flagstaff expecting less than half an inch of water, or about 6 inches of snow.
The US Navy’s NoGAPs model shows the storm hitting more of the central part of the state with up to an inch of water, which could be a foot of snow.
The NAM model is a higher resolution model that takes into account more detail of time and place. The National Weather Service forecasting up to a foot of snow makes me wonder. Looking at their forecast discussion, I think the NWS is wondering to:
FORECAST CONFIDENCE…THE LATEST FORECAST MODEL RUNS CONTINUE TO BE FAIRLY CONSISTENT ON THE TRACK AND INTENSITY OF THIS LOW…HOWEVER THE PRECIPITATION AMOUNTS IN THE SAME MODEL RUNS HAVE A HIGH DEGREE OF VARIABILITY. WHILE OUR CONFIDENCE IN WIDESPREAD MEASURABLE PRECIPITATION IS HIGH…OUR CONFIDENCE IN THE AMOUNTS OF RAIN AND SNOW ARE ONLY FAIR AT THIS TIME. THIS MEANS WE SHOULD EXPECT SOME ADJUSTMENTS TO THE PRECIPITATION AMOUNTS AS THE TIME PERIOD GETS CLOSER.
So, I am sticking with my forecast for “several inches.” It’s going to snow, it will affect driving conditions. The NAM model shows the snowfall starting later in the evening on Thursday, and tapering off on Friday afternoon.