A Soaker Today, but Summer Preview 2.0 Ahead

May 8, 2014

10:45pm Thursday…

What a gray and wet day, with the biggest downpours this evening.  For some reason it decided to really pour while I was making a “donut run” for the kids; what a good father, willing to risk TV makeup and wet hair just for the kiddos.  At least I think so.

Here are the rain totals as of 10pm…

PLOT_Rain_Metro_Autoplot

Colder air moving in aloft tomorrow along with sunbreaks points to hail and possible thundershowers tomorrow.  Take a look at the WRF-GFS depiction of CAPE (Convective Available Potential Energy) for tomorrow afternoon.

mcape.33.0000

When you see numbers above 300 or so west of the Cascades that’s always good.  Up around 800 or more is “big time” thunderstorms for us.  “Big Time” in this case means more than one flash every 5 minutes of course…

So tomorrow (Friday) should be an active weather day as a cold pool of air in the upper atmosphere passes overhead.  It’ll be shifting to our south quickly on Saturday, thus a much better day with just partly cloudy skies and a few sprinkles or a shower.

Beginning Sunday, an upper-level ridge builds over the West Coast for the 2nd time this month.  That means another period of much warmer than normal temps and abundant sunshine.  Basically another preview of summer for a few days.

How warm is it going to get?  The 12z GFS and 12z ECMWF were in excellent agreement; here are their ensemble charts:

tseries_850t_000-360_Portland tseries_850t_000-384_Portland

Both show 850mb temps around +10 over us by Monday afternoon, and +15 to +18 for Wednesday and Thursday afternoons.  Low level flow turns offshore Tuesday and Wednesday, with flatter flow (depending on the model) Thursday.  Pretty good agreement on these models and most of their ensembles, so I went for some mid-upper 80s in the 7 Day forecast.

The 00z GFS has come in significantly cooler, although still very nice, the middle of next week.  Even the ensembles are a little cooler so if the ECMWF follows suit we’ll need to lower our 7 day forecast temps by 5 degrees or so.  Here is the fresh 00z chart:

tseries_850t_000-384_Portland (1)

We’re definitely headed for a dry period, check out the 12z ECMWF meteogram showing no rain after Saturday afternoon for the following 8+ days:

KPDX_2014050812_dx_240

So enjoy the rain because we’re headed back into a dry pattern for a while.

By the way, last night I showed this hail graphic on the 10pm newscast:

MarkHail_FactsOregon

I was curious how large hail has been in our viewing area in the past.  I do clearly remember the July 9, 1995 supercell thunderstorm event in north-central Oregon.  Once in a great while we have seen quarter size hail west of the Cascades, but the main action happens east of the Cascades. Almost every summer we hear of golf ball size hail at least once somewhere over there.  But it’s been 16 years (1998) since larger sizes have been documented as you see in the graphic.

Chief Meteorologist Mark Nelsen