Forecasters have been having difficulty getting a good idea of how the storm will develop because of large inconsistencies in our forecast models. A small difference in storm's track and speed can be the difference between just a few inches of snow and several inches of snow in many spots.
So NOAA is sending a plane out over the Pacific Ocean to drop some weather instruments where the storm is developing in an effort to get some better weather data -- much like what they do to get better data on hurricanes when they threaten in the Atlantic Ocean and Gulf of Mexico.
Our Tuesday night storm is currently still in its development stage in the ocean waters north of Hawaii. Models are having a difficult time determining if and how the storm will phase with a storm bringing arctic air out the Aleutian Islands of Alaska into the Gulf of Alaska.
How that combination plays out will determine the storm's eventual strength, path and, in turn, just how much snow we get around here.
But it's not just the Northwest that had NOAA concerned. The model errors are also playing a part in some frayed nerves in the central and eastern U.S., where models have indicated potential snowstorms for them too, while other model forecasts keep the cold air bottled up in Canada.
Forecast models work by initially taking all of the weather observations across the globe -- including weather stations, weather balloons, satellite images, ship reports, pilot reports, radar data - and then applying all the math we know about the atmosphere to simulate how the weather will evolve from that point.
Over the ocean, that data is a bit more sparse and more prone to error. Their hope was to get more precise data of what's going on in that storm right now so the models have better starting data to base their calculations.
The goal was to get the data in time for the forecast models' 4 p.m. (PST) run but in checking the models late Sunday evening, there was still a wide range of differences.
These flights are not unheard of. A couple of years ago NOAA flew some flights from Anchorage to Honolulu to monitor some storms and they've done it in years' prior as well.
As for the forecast, right now general idea is for potential for 4-8 inches of snow regionwide Tuesday night into Wednesday as a "blend" of what the forecast models show now, and then a changeover to rain sometime Wednesday and staying warm and mild for the rest of the week.
Sunday evening update
The model runs generated Sunday evening still had a wide range of opinions. One (the "GFS") has 4-8" of snow falling between roughly 7am and 1 p.m. on Wednesday, followed by a period of heavy rain and strong gusty winds of 30-35 mph with temperatures warming rapidly into the 40s .
Another American model (the "NAM") had the storm coming in much further south into central Oregon, keeping the Seattle area colder but also less snowy.
The European model keeps the snow around longer, but gradually warms us up. Its solution would make a snowier picture for the Northwest.
It looks like we'll just have to wait until the storm draws closer and develops more before the models will come to a closer consensus.
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