Hot Summer Weather Later This Week

July 8, 2018

9pm Sunday

Today was warmer with highs well into the 80s west of the Cascades.  Meanwhile scorching hot weather continues east of the Cascades.  Everyone east side was in the 90s.

We have a relatively strong marine push in progress this evening.  Check out the visible satellite image showing clouds already moving over the Coast Range:

CODGOES16-local-Portland.truecolor.20180709.030223-over=map-bars=none

So tomorrow and Tuesday will be cooler with highs right around the average for mid-July…80 or so.

What changes the 2nd half of the week?  A huge/sprawling upper-level ridge will be covering about 3/4 of the USA by Thursday…

m500za_f096_bg_NA

notice the 588dm heights covering a huge chunk of the USA at that time?  Notice also that much of North America is seeming higher than normal heights.  That’s something I notice continues well beyond the 7 day period in all the models.  A sustained period of unusually high atmospheric heights instead of a big sharp ridge of high pressure with a downstream trough.  What does that mean?  Models for the next two weeks seem to show a continuously warm/hot period as opposed to a huge heat wave followed by cooling, then more heat.

So how hot could it get over the next week?  Record highs are all 101 or higher beginning Wednesday.  Plus I don’t see a thermal trough west of the Cascades with its easterly wind, so I doubt we get to 100 degrees.  That said, both Wednesday and Thursday the GFS & ECMWF show no onshore flow with gradients flat through the Columbia River Gorge.  850mb temps reach +18 Wednesday (over Salem) and +21-23 Thursday.  That 23 is the ECMWF and its ensembles support the number.  So I forecast 90/98 for Portland Wednesday/Thursday; not record-breaking but the 98 would be the hottest we’ve seen so far this year.  A very weak marine push and 850mb temps down around +19 to +20 Thursday through Sunday means highs retreat to around 90 or just above.

With such a strong/flat upper-level ridge over us, thunderstorm moisture seems to be pretty well suppressed to the south much of the next two weeks.  This is the driest ECMWF precip meteogram I’ve ever seen:

KPDX_2018070812_eps24_precip_360

Enjoy the next two days and then try to stay cool later in the week…

Chief Meteorologist Mark Nelsen


A Very Warm 4th of July On The Way

July 3, 2018

6pm Tuesday

The weather shouldn’t affect your 4th of July plans Wednesday, but it’ll be one of the warmer Independence Days of the past 20 years.  High temperatures will reach well into the 80s.  Gusty east wind during the morning/midday in the Gorge, Cascades, & east metro means extreme fire danger so be careful with those fireworks!

Today was just about a perfect day with a few patchy low clouds breaking up to sunshine across NW Oregon and SW Washington.  It’s about as normal as it gets this time of year with a high temperature around 77-78 in the metro area.

Of course tomorrow is the 4th of July so let’s take a look at the numbers:

Mark IndependenceDayHistory2

Notice that we average a wet fourth once every 4 years.  Yet we’ve seen only one with measurable rain since 1999!  1998 & 1999 featured cool/showery days, but since that time only 2008 saw just .01″ of rain.  My kids, in high school, have never seen a wet Independence Day!  The past few years…

Mark IndependenceDayHistory3

We’ve seen a very cool airmass drop through the northern Rockies and eastern side of OR/WA the past 36 hours.  Timberline only had a high of 39…on July 2nd!  That cool airmass plus mainly clear skies last night led to a chilly morning.  I saw lots of 40s around the metro area and Eugene’s low of 38 was the coldest on record for the month of July.  I see a few spots had a light frost in Central Oregon too.  That includes Sisters & Prineville with Madras, Bend, & Redmond quite close to that 32 degree mark.

The airmass is warming right now and that peaks tomorrow afternoon before a weak upper-level low approaches the region at the end of the week.  One interesting twist tomorrow is a brief surge of easterly wind over the Cascades and through the Gorge from later tonight through about midday.  In fact gusts at Vista House will likely reach at least 40 mph during the morning hours.  By the way, if you’re headed out there the old highway closes in Corbett area from around 10am-Noon for a parade.  Obviously the combo of dry east wind + very warm temps means even higher fire danger through the early afternoon hours.  Easterly offshore wind plus 850mb temps around +17 by afternoon typically means a high in the lower 90s this time of year.  But tomorrow we’ll see lots of high clouds during the daytime, and that should keep highs in the 80s.  Regardless, it’s going to be a toasty 4th.  But the benefit is that temperatures will be comfortable for fireworks after sunset

Independence Day Fireworks Forecast

Beyond tomorrow, a summer weather pattern continues as we head deeper into July.  The hot ridge establishing itself across the Rockies and 4 Corners region the next few days seems to stay just far enough east to keep real hot stuff away from Western Oregon and Washington.  But temperatures will generally remain above normal for the next 7-10 days.  Note the ECMWF ensemble forecast for highs in Portland the next two weeks:

KPDX_2018070312_eps_min_max_15

Some ups and downs, but the trend is for summer heat to set in next week.  Rain?  Forget about it, unless we get marine drizzle of some sort (like yesterday).  The 2 week ensemble forecast from the ECMWF:

KPDX_2018070312_eps24_precip_360

Only 4 ensemble members show .10″ rain ANYTIME in the next two weeks…that’s mid-summer dry weather.

Have a safe Independence Day!

Chief Meteorologist Mark Nelsen

 

 


Nice Start To July

July 1, 2018

10pm Sunday…

It’s REALLY slow weatherwise so I’ve been having some weather blog writer’s block.  Or possibly just a bit lazy as summer rolls on…

Take a look back at June, which nationwide was much warmer than average, including about half of the Pacific Northwest.

conus_mtd_t2max_anom_2018

Portland looked like this

JuneTempCalendar

We saw 4 days at/above 90…most in that warm period mid-month.  Most interesting to me is that it’s the 4th consecutive warm June.  I’ve ALMOST forgotten about those terrible cold/wet June months when my garden just didn’t want to grow (2010, 2011, 2012).

It was another dry month of course, unless you happened to be right under one of those thundershowers late-month.

JuneRainCalendar

We’ve see less than 1.5″ since the middle of April!

MarkDrySpellsJune

Only one other time in Portland history has it been even close to this dry.  That was late spring-early summer 2015.  Of course that turned into a terrible fire season with the Canyon Creek fire around John Day and numerous massive fires up in Washington.  We’ll hope for some cool spells with a few showers at times over the next 8 weeks to keep things under control this year.

The weather pattern is interesting over the next 7 days with upper-level ridging developing over the central USA.  That’s where the extreme heat will be.  This is the 500mb map for Thursday:

500vty_f108_bg_NA

We’ll be on the far western periphery of that ridge, which allows weak systems to bring occasional onshore flow at times.  Over the past 5 days I’ve noticed a trend of models trying to push that ridge right over the West Coast and then backing off and keeping it farther east.   We’ll see if that continues.

For now, it looks like we have a great weather pattern in general for this first week of July.  No real heat, thunderstorms, or cool/wet weather.  Enjoy!

Chief Meteorologist Mark Nelsen