Cold Snap

October 28, 2006

Today’s models are increasingly insistent that a sharp (but brief) change towards colder weather is likely starting Sunday.  Temperatures at 5,000 feet (850 mb) are expected to drop to around -5 C (lower 20s in F) by Monday morning.  The NAM model is the coldest, with the GFS and ECMWF not quite as chilly.

As the cold front passes through Sunday morning, a brief round of light rain is possible.  The front is quite moisture-starved, so there may be locations that don’t record any measureable rain.  Later Sunday, colder air begins surging into the area from the north and northwest — you’ll notice the colder breeze (10-20 mph with higher gusts) in the afternoon and evening.  Sunday night could be the coldest night since last winter.  I expect PDX to drop into the mid 30s, with some upper 20s possible in the typical cold spots (Hillsboro, Forest Grove, Battle Ground, Scappoose).

The East Wind picks up Monday… and for the first time this fall, it should be a cold wind (past east wind events this month have been warm).  If the wind calms down Monday night, it could be very chilly… so we’ll have to see what the wind does as time gets closer before we’ll know how cold it might be.

East of the Cascades will be even colder — highs in the 40s and lows in the teens are likely Monday and Tuesday.

It looks like a significant pattern change will occur mid-late next week.  From cold and dry… to mild and wet.  Several days of rain are possible beginning Thursday… and strong south winds could buffet the coast as deep lows wind up offshore.

The "boring" weather season may indeed be behind us…

– Drew J

Weekend Update

October 27, 2006

Hi again…

A late post tonight, but this one should get us through the weekend.

Saturday looks to be a repeat of Friday, as the strong ridge continues its hold over the Northwest.  With the sunshine (after AM fog), we should easily reach the mid 60s again Saturday afternoon.

Everything changes Sunday.  A cold, but weak system drops out of the Northwest… allowing the coldest air of the season-to-date to plunge into the Northern Rockies and Northern Plains States.  Some of that chilly air will make it west of the Cascades… courtesy of the east wind that I expect will pick up Sunday night or Monday morning.  With the front’s passage Sunday, there is an opportunity for a little light rain… with the best chance of that happening in the morning.

How cold will the arriving cold air be?  I’m thinking low-mid 50s for highs Monday and Tuesday… and lows could be anywhere from 25 to 37 — depending on the wind.  Windy areas (such as Troutdale, PDX, and along the Cascade foothills) may not have a freeze… but valley locations where the wind dies down could have their first widespread hard freeze of the season early next week.

After Wednesday, the models are hinting that a pattern change towards mild and wet weather may be coming.  There is still no sign of any cold, wet storms that are necessary to start building the Cascade snowpack.  Bummer…

Enjoy the weekend… especially Saturday’s sunshine!

– Drew J

PS – Mark returns Monday… the day we move into our brand new weather center!!!  (But you won’t see it on TV for at least another week…)

End of the week Warmth?

October 25, 2006

Hello all… it’s been a while since I’ve had the blogging honor!

I read many of the comments in the previous post (yes, when Big Brother is on vacation, the Little Brother pays attention for him).  Some of you need a reminder to play nice… and thanks to some of you for saying that for me in your own comments.

On to the weather.  The big forecast dilemma over the next couple days is… does the ridge build enough to shift the storm track far enough north to keep clouds out of our sky?  At this point, I say yes.  Heights get into the 582 dm range Fri-Sat and thicknesses are quite high for this time of year (as are 850 mb temps).  With sunshine, high temperatures in the upper 60s shouldn’t be too tough.  Record highs this time of year are still in the low 70s… so 65-70 is totally in the realm of possibility.  Again, the fly in the ointment is high cloud cover.  We’ll see…

We’re entering the time of year when the fall rains should either be underway or just around the corner.  Not this year.  I don’t see any sign of a significant pattern shift to bring us a rainy pattern.  Perhaps later next week… but certainly not before.  Sorry skiers/snowboarders… patience may be required this fall.

– Drew J

One Post This Week

October 23, 2006

I’m taking time off Tuesday-Sunday and won’t be back until next Monday, so it’s possible there won’t be any posts the rest of the week.  That’s unless Drew decides to check in Wednesday, Thursday, or Friday.

Nice little cold front advancing towards the coastline at a pretty good clip this evening.  Should be over the metro area by 5am at the latest.  As someone on the earlier comments noted, it doesn’t have much moisture with it and the high clouds have pulled away from the low-level front.  So total rain here in the Western Valleys will likely only be .25-.50".  The coldest air of the season is following though.  An 850mb temp just below zero by Wednesday AM could bring snow down to just under 4000′, but there will be very little precip by that time.  At best expect a light dusting in the Cascades. 

A somewhat flat ridge follows Wednesday-Sunday for mainly dry weather again.  I’m assuming we get some southerly surface wind Friday or Saturday to push temperatures back up to or near 70 degrees. 

Long range models continue to be all over the place with very little continuity between models and even within model runs themselves.  Some show troughing moving inland Monday and beyond, but others split the trough and keep most offshore.  Roll the dice!…Mark

Update – 7:30pm.  Upon closer inspection of models, including our own RPM model here…looks more like .10" west metro to .25" east metro with the incoming cold front…a pretty dry one.  Hope it’s not a sign of the winter to come!

Windy Saturday

October 20, 2006

As you folks have discussed in great detail in the last post, it was a fun meeting today at OMSI.  Nice to meet a few of you too.  Those of you that did make it discovered one of the secrets of TV…everyone looks the same size don’t they?  Short people look taller than they are and tall folks look shorter.  People always tell me "I thought you were shorter!".

Okay, on to weather.  I see at 9pm the PDX-DLS pressure gradient (through the Gorge), just turned negative.  Easterly flow is beginning now and will increase to 6-8 millibars by midday tomorrow.  Peak gusts to 50 mph are likely at the west end of the Gorge.  Of course we do have a moist atmosphere in place over the metro area.  So with the east wind not arriving for most areas until after daybreak, we’re set up a for a thin layer of dense fog overnight.

The wind dies quickly on Sunday as we switch to onshore flow again.  A weak wave moving by starts that up pretty quickly.  A much stronger shortwave carves out a brief, but cold trough for midweek.  This should be our coldest airmass so far this fall season…500-1000mb thicknesses fall to around 532 dm Wednesday morning, which brings snow showers down to around 3000′ or a little lower. 

Models after that point are ALL over the place, so who knows what happens later next week.  We’ll save that for the weekend crew…Mark

Quiet Evening

October 19, 2006

Pretty calm conditions tonight on our side of the mountains.  Radar at 8:30pm shows now showers left over, although plenty of clouds behind today’s cold front.  Not exactly a strong front since the temperature didn’t even drop behind it.  A vort max is moving south across Eastern Washington with a few lightning strikes right now east of Spokane and just northeast of the Tri-Cities.  Tremendous pressure gradient across the eastside too.  I see ELN (Ellensburg) just gusted over 50 mph…strong even for them.
Slow clearing tomorrow, then it’s off to strong offshore flow Saturday, no change in that since last night.

The last 10 days have been very rough with respect to model reliability.  Looks like ridge won’t last long as a trough comes swinging through here Tuesday and Wednesday.  Still seems a bit hard to believe, considering ridging was looking more likely 24 hours ago.  But I’ll put rain back in the forecast, plus a cool trough in the last week of October will be pretty chilly.  Highs in the low-mid 50’s are likely.

I hope to see a few of you at the meeting tomorrow.  It’s always a chaotic meeting because you want to talk to lots of different folks that you only see once or twice a year, but you only have a short time to chat before and after the meeting…Mark

9:45pm note:  00z models are even worse!  Either a ridge or cold trough next week…flip a coin!

Early Rain

October 18, 2006

Junk2_1The first person to call me (and whine) was Shauna Parsons this morning, it went something like this:  "Mark, I’m sitting here IN THE RAIN at the Pumpkin Patch…I THOUGHT it was going to be a dry day with morning fog?".  What she really meant was: "You fool!  Can’t you ever get it right?  You dishonor our First, Live, Local newscast with your forecast for today."

But now of course it’s old news that this evening’s rain showed up about 12 hours early.  It was light…only about .05" at PDX, but enough to keep the high temperature about 6 degrees below where I expected it to be.

Easier forecast for later tonight and tomorrow as a healthy cold front slides over the top of the building upper-level ridge and into the Northwest.  Heaviest rain should be around midday (like Sunday’s system).  It might even dry quite a bit towards sunrise.

Then it’s on to ridging…surface high builds to our north Friday, gradually clearing us out.  Then a switch to strong offshore flow Saturday & Sunday.  This will be the first "winterlike" east wind event in the Gorge.  MM5-UW clearly shows a closed surface high developing Saturday afternoon and Sunday in the Columbia Basin.  About 8 millibars gradient from DLS-PDX should give us gusts to 50 mph in the Gorge and 35 mph in the metro area.  It also means a beautiful weekend.  I have NO idea why another station in town is calling for a rainy day Sunday.

Long range maps are still all over the place, but there seems to be a tendency for either ridging or split-flow near the West Coast.  With that uncertainty, I’ve left rain or significant clouds out of the forecast early next week.  Of course last week at this time I thought all of THIS week would be sunny too.

Don’t forget the Winter Weather Meeting coming up Friday at OMSI (10am-Noon and open to the public).  It’s free and you’ll get to meet lots of other weather friends (geeks).  But please, no weather gang fights alright?