Weekend Outlook & ECMWF Weekly Maps

May 15, 2015

11:30pm Friday…

A thick marine layer west of the Cascades sticks around tomorrow, giving us another gloomy day with a few sprinkles.  If you want sun head east of the Cascades.

Sunday the onshore flow weakens dramatically.

7 Day

Monday is an interesting day as a weak thermal (warm) surface trough develops right over us.  Not really an east wind situation, but the effect on temperature should be dramatic regardless.  We might end up around 80 degrees Monday.  The other reason Monday is interesting is because some models show a lot of CAPE and below zero lifted index along with the thermal trough.  A very unstable atmosphere.  That plus easterly upper-level flow and increasing precipitable water screams “THUNDER POSSIBLE” to me.  We’ll see how models develop the situation as we get closer.

These maps are actually from the ECMWF 32 day run two nights ago…sorry, a little slow.

500za_week1_bg_NA

500za_week2_bg_NA

500za_week3_bg_NA

500za_week4_bg_NA

They show upper-level heights rising to a bit above normal over the Pacific Northwest over the next month.  Supposedly the pattern of cool troughs moving in to our south will end; which has been very unusual for May.  This tells me we still don’t have any long cold/wet period coming up, at least west of the Cascades.  Rainfall is still a bit below normal here in Portland at mid-month.  We could end up with a drier than normal May.

Chief Meteorologist Mark Nelsen