ANOTHER SNOW EVENT TUESDAY?
Many residents from Salem, Oregon north to Vancouver, Washington woke up to snow in the air Saturday morning and continuing throughout the day Saturday. My thoughts from earlier in the week pretty much played out as forecast. Actually, the snow fell a bit lower than I was thinking, with snow sticking down to about 900ft and nearly all locations seeing snow in the air down to sea level. Now my eyes are turning to what looks to be a very interesting set up for this coming Tuesday into Wednesday. It is getting late in the winter season so these forecasts are a little harder to pin down. So, here goes.
System #1 is passing by right now and will exit the area on Sunday. In its wake is an area of drier and colder air will slide down over the Pac NW Sunday night. You can see thicknesses drop to about 520dm at 1000-500mb Sunday afternoon through Monday morning in this image below:
Overnight lows on Monday morning will be below freezing in most areas west of the Cascades, outside of the coast line. Then on Tuesday, another very cold system comes down the BC coast right over the Pac NW. This system appears to be as cold or even colder than the one that just went through the region this weekend. Here is the 925mb temperature forecast from the U of W WRF for Tuesday morning. This is cold enough for snow in the northern end of the valley from Portland north into SW Washington and on north towards Seattle:
Then the center of the upper level (500mb) trough moves right over Portland on Wednesday morning along with a surface low in nearly the same position as the upper level trough:
By 7am Wednesday, 925mb temperatures have warmed a bit, but are still cold enough to support snow to some very low elevations:
Here is the WRF sounding forecast for Tuesday morning as the overrunning precipitation begins. That my friends is VERY close to sea level snow. This image looks even better for PDX snow than today’s snow event did :
Finally, the WRF snowcast shows more snow in the 24 hours surrounding Tuesday and Wednesday than it did for this weekend. Again, areas from Portland north could be under the gun for snow:
So, to sum it all up —
500mb trough of 522dm directly over Portland Tuesday morning.
Overrunning precip coming in at the coldest time of the day.
1000-500mb thicknesses remain about 525dm through Wednesday.
925mb temps below -4C as precip begins.
Those are good ingredients for a little snow in Portland and points north on Tuesday. The track of the surface low will play a MAJOR role in what if any snow Portland gets Tuesday. If the low stays to the north, it will be a brief shot of snow followed by a warm up. If the low stays just south and remains weak (as models have trended) Portland could be in for more snow than even currently modeled. Caution — this is just one model run, but I have noticed a distinct trend colder with the Tuesday system over the past 36-48 hours on the models. This will need to be watched closely over the next 24-48 hours to see what the models have in store for future runs. I will update here as needed.
Finally, don’t forget about the great weather meeting we have planned next Tuesday in Portland. The topic is “Summertime Lightning Forecasting” and is hosted by KPTV and the Oregon Chapter of the American Meteorological Society (AMS). Our guest speaker will be Meteorologist John Saltenberger. This is going to be a really informational meeting. You can see all of the details at: http://www.ametsoc.org/chapters/oregon. Hope to see some of you there!
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