04/13/09 FCST: WA/OR

[Keith Mullen]

Looks like the makings of a decent Cold Core set-up today and early this evening primarily within the Puget Sound region of Washington along the PSCZ and possibly along the Portland Columbia river gap.

Upper trough barrelling through today into tonight should bring 500mb temps to or below -35C.

LI's around -2. Lapse Rates at 8C or greater through mid levels. With surface based winds remaining from the W and SW throughout the day. Up here, that last part is rare to see with the above parameters.

With enough clearing and some heating up, there is the potential for SBCAPE at or slightly above 500jk.

Convective temps should need to barely break the 40 degree mark & with a few sunbreaks & a good position on the PSCZ this will not be a problem.

Again, best bets N of Tacoma & S of Everett as shortwaves eject thru the area late afternoon - fizzling out late afternoon as winds shift & area scoured out in evening.

 

[Rocky Rascovich]

I love these types of set ups! If I were there, I would be taking off and heading up to between Woodinville, Monroe, Arlington and on east towards to Cascades around Sultan. Would love to intercept some of the heavier convective cells that would harbour not only heavy rain, graupel (maybe even pea to marble sized hail) but the chance that some of these cells may push the snow level down to 500 feet above sea level, all that with the ever elusive bolts of lightning and claps of thunder that is a rarity in these parts. Even Queen Anne Hill will likely see a slushy accumulation possible. Another area I would target is up toward Mount Rainier around Longmire for some blinding, convective snow bursts.

Out of curiosity, just how late as snow been observed in the Seattle area? I know this is not that uncommon for mid April, but this surely doesn't happen every year.

 

[Keith Mullen]

Snow

Snow heavy enough for accumulation is generally fairly rare here. Some years go by without even trace - then there is this year - had 2 feet of snow on the ground at my house, hasn't been seen in 50+ years. Feb & Mar are generally the best bet to see snow on the ground in So. Sound. April is not unheard of in past records.

Queen Anne through Woodinville is not a bad bet. Personally I think Sultan or higher upslope would be a messy bust unless winds shift stronger from the west v. Southwest. The Enumclaw/Black Diamond area and a hair N/NW should probably fire up good if the localized winds there push out of the S/SW. If our temps break 50 - it should be quite interesting out there.

Why am I stuck in the office today???

 

[Keith Mullen]

12:45 PDT

A couple cells are starting to pop up around Portland / Kelso. One cell firing up between Seattle & Tacoma. Temps currently around 43-45F at surface. Upper temps should plummet shortly with the passing. Still a ways to go before anything of true interest fires up.

Concerned about the lack of heating due to overcast skies, as well as the directional shear being near straight-line at the present.

My confidence is low, to say the least, for anywhere other than the PSCZ & upper Willamette Valley. If the surface temps surprise me and reach 50 in the lower South Sound, we will have something.

To those near the PSCZ & Portland area, enjoy. I'll keep a watch going.

UPDATE: 12:50 PDT

Not worth starting a NOW: just yet, BUT aforementioned cell approaching Enumclaw/Maple valley producing about 1/2" hail at the moment 12:50PDT.