Tonight/Tomorrow Snow Outlook

December 28, 2010

Here is what I’m going with this evening (from our Facebook page this afternoon):

Steady rain changes to mainly heavy/wet snow after 8pm, could see brief sticking snow in the hills and east of I-205. Unlikely to affect traffic, except up around 1,000′ and far east side (Gresham, Estacada, Damascus, Camas, Battle Ground).
Snow showers off/on Wednesday……ZERO to TRACE accumulations.

This includes upper West Hills, Mt. Scott, hills around Gresham etc…
Rain changes to snow late this evening, could stick with a TRACE-1″ towards 10pm-Midnight. Then snow showers tomorrow with TRACE-1″ additional snowfall. No big traffic issues, but definitely so…me snow on roads for AM Commute up around 1,000′.

This includes highest spot or two in West Hills, Sandy, Northern Clark County Hills etc…
Rain to Snow later this evening…1-3″ on ground by daybreak. Snow showers with another TRACE-1″ during the day tomorrow. Total 1-4″. Above 1,500′ up to 5″ is possible.

But here’s a big issue.  Anything after midnight and through noon will be showery, so I could easily see one spot getting an inch near sea level, while 5 miles away the same elevation gets nothing!  Another reason not to go with the 500′, 750′, 800′ wording that seems to be so popular nowadays…

Chief Meteorologist Mark Nelsen

Tuesday AM Update

December 28, 2010

In a hurry this morning to get a few things done before heading to work…I can tell it’ll be a long day.  Three things pop out:

1.  Snow sometime after 7pm this evening to all areas above 1,000′, probably lower than that far east side of metro area.

Situation this evening is very similar to what occurred November 17th:  This should be fun to watch.

Steady, heavy precipitation as a wave passes by and colder air comes surging in at the surface from the northwest.  In fact no southerly wind but a light north-northwest wind.  Our RPM model shows a changeover to mostly snow in the air even at the lowest elevations, and sticking for sure on the hills.  In this pattern the foothills of the Cascades (and east Valley) are/is favored.  It may even stick in Gresham, Troudale, Camas, Estacada.  Less likely over in the Tualatin Valley as things dry out.  Prime time seems to be 7pm-Midnight.  I can already feel the news freakout…praying that it holds off until 9pm or so.

2.  Precipitation is very close Thursday morning, closer than in previous model runs…could be a dusting?

3.  GFS is swinging dry over the weekend like ECMWF now, we can leave the precipitation out of the forecast.

Chief Meteorologist Mark Nelsen