It’s an early day today; I went on KXL this morning at 7:02am (early for me) to talk heat wave numbers. I have to admit though that I actually like heat waves. You get some meteorological excitement, such as some offshore flow, extreme temps…etc. But honestly, it’s sunny for the next 3-5 days…how tough of a weather forecasting day could that be? Heat waves in the Pacific Northwest are generally just a numbers game. So let’s talk numbers.
Looking at the 7am obs. it’s obvious the airmass is significantly warmer this morning. I only hit 63 for a low at my home at 1,000′ in a bit of a canyon. It feels like a Hawaiian morning. I see it only dipped into the upper 60s in the city. But unfortunately it’s going to get a lot hotter than Hawaii this afternoon. I’ll have to break down use the air conditioning today. Generally I don’t unless it gets above 95 in Portland. Even when it gets hot in the house (86 yesterday), by dark there is a 70 degree or cooler breeze blowing down the canyon into the wide open windows and doors…very efficient and quick cooling.
Highs: We hit 93 yesterday with weak onshore flow, but now I see the PDX-DLS gradient has switched to slightly easterly. So I figure about 7 degrees of warming takes us up to right around 100 degrees. Slightly more offshore flow and a warmer atmosphere awaits for Tuesday and Wednesday, so somewhere between 100 and 105 degrees for the next 3 afternoons should be a safe bet. Now I haven’t looked at any 12z model data yet (it’s ONLY 7:30am), but I did notice on the 00z data that we supposedly don’t get really significant surface easterly flow over us in this heat wave. I doubt we’ll even get east wind much out of the Gorge, let alone to I-205. Due to that I think the 105 number is high. IF we could get a sharper thermal trough west of the Cascades, then we could sure get close (or over) to the 107 degree record.
Lows: This part of the forecast is probably the biggest story. Looks like PDX might have dropped to about 67 this morning? MOS forecasts say the city only briefly drops below 70 the next few nights as well. Considering how warm it stayed this morning, and a hotter atmosphere/highs on the way, seems like those numbers are a bit low. More disturbing is our RPM which has done pretty well with heat wave temps recently. It shows lows only in the 70s the next two nights. Since we don’t have a dry east wind coming down into the city to get rid of the low level moisture (high dewpoints), it’ll be easier to keep the nighttime temps up. Remember that PDX’s all-time warm low is 74 degrees. I think we’ll be in the 70-74 degree range these next two nights…yuck! By the way, there were STILL air conditioners at a “big boxy store that sells tons of toilet paper” as of yesterday when I was there. So I would highly recommend putting out the $125 to get yourself one.
Okay, off to a morning bike ride…not a good day for an evening “between show” ride today!
Chief Meteorologist – Mark Nelsen