There is HOPE for Halloween Evening! Dry For Some

October 28, 2015

A glimmer of good news is starting to emerge from our numerical weather models for Halloween evening!

As far as I recall, we have not had a “washout” (pouring rain) during the critical Trick-or-Treat time since at least 2001.  That’s when I started taking my kids; in fact I never went candy collecting with the kids in anything other than a sprinkle.  I do remember a washout with strong wind and rain in 1994 and then it turned to snow in Sandy behind the front that year.

All that really matters is the 5pm to 8pm period that evening.  For anyone under age 10 it’s pretty much over by that time.  So it’s not like we need the whole day dry.

A cold front will be traversing north to south across our viewing area from afternoon through the evening.  Under the front it’ll be pouring anywhere from the Cascades west.  What has changed is that models seem to be speeding up the movement a bit, which means the steady/heavy rain will likely come to an abrupt end first up north and eventually late in the evening farther south.

Take a look at the 12z ECMWF 6 hour rain forecast from 11am to 5pm Saturday:

ecm_11ato5p

That means the total ENDING at 5pm.  This says the heaviest rain is just arriving in the metro area around 4-5pm.  Now the 5pm-11pm total:

ecm_5pto11p

During that period a lot of rain from Portland to Albany (and along the north-central coastline).  But notice there is very little rain from about Tillamook north along the coast and north of Portland.  The current run of this model says the little kids will be in great shape on the far north coast and north of the metro area; wet elsewhere.  The previous run of this same model was a bit farther north (by about 20 miles), so the trend is a bit faster…very good.

How about another model…the GFS?  Even better news.  Here’s the 5pm-11pm rainfall:

gfs_5pto11p

Look at that!  Pretty much dry from Pacific City north along the coast and north of Woodburn along I-5.  This run says the main rain has finished by 5pm, especially west and north metro areas.  Very good.

The UW’s model (WRF-GFS), which is based of the GFS model shows something similar:

wrf_5to8pm

Mainly dry once the main cold frontal band passes by overhead.

To summarize:

If model trends continue, kids in the metro area could again escape with a mainly dry Halloween or at least just showers.  There is a better chance for dry conditions the farther north you go.  Salem and Albany still look wet for now.

It’s still 3 days away so it’ll be perfectly normal to see some movement in that main rain band forecast as we get closer.

Stay tuned!

MarkPromoHalloween

Chief Meteorologist Mark Nelsen