April Ending Cold & Wet

April 28, 2011

There is a good chance we’ll set the all-time April rainfall record within the next 24 hours here in Portland.  As of 9pm we’ve received 5.04″ rainfall this month, the 3rd wettest of all time.  The record is 5.26″ set in April 1993.  Of course that means we need less than .25″ rain to break the record.  There is one more surge of showers coming through later tonight and tomorrow morning.  That needs to produce the needed rain since we really dry out tomorrow afternoon and showers on Saturday look very sparse.

Along with the rain moving through the area this afternoon/evening, it was a really cold airmass.  Widespread snow has been seen above about 1,000′ with sticking just above that elevation.  Had a report of 3/4″ east of Corbett at 1,800′.  That’s just totally inappropriate for April 28th…oh, and you can add in 10-12″ fresh powder at Timberline and Meadows in the past 24 hours.

The reason for the low elevation snow this afternoon was a nice shortwave curling inland, clearly seen in satellite and radar imagery.  The solid cloud shield and rain did keep the thunderstorms away though.  We really need the sunbreaks to get the big hail and thunder action this time of year.

It appears that this will probably be the final really cold airmass of the season (sticking snow down below 2,000′) since models show a significantly warmer patter beginning on…May1st (Sunday).  It may not be totally dry next week, especially on Monday, but we should see the longest period of 60+ temps so far this season and mainly dry weather.  We get upper level ridging Sunday, a weak system moving through the ridge Monday, then the ridge returns with higher upper-level heights and warmer 850mb temps Tuesday-Thursday.  We pushed the forecast highs Wednesday-Thursday into the mid 70s due to those 850mb temps around +10.  Record highs are around 90, but you’d need 850 mb temps up around +20 with east wind for that.

Chief Meteorologist Mark Nelsen