February Weather in the Pacific Northwest

[SilverFallsAndrew]

Looks like a record low for PDX this morning.

 

Good timing for some cold high temps today too. Clear now but clouds look to move back in by late morning.

 

Record low?! Wow some major low hanging fruit. Score one for the 21st Century!

[SilverFallsAndrew]

GFS trending toward the NAM. A shot of snow PDX to Eugene.

 

I like Friday evening for a couple inches in the Seattle area. 

[snow_wizard]

I'm almost wondering if some places could have freezing high temps today.  Really cold this morning, thicknesses falling during the day, and rapidly increasing clouds.  Looks like it dropped to 23 here this morning.

[Perturbed Member]

PDX NWS

 

GFS remains the fastest model in sending the upper shortwave and
surface low south of the area Thu. Past experience with these types
of weak surface lows that form in response to the cold air and warm
water interaction, is that a slightly slower movement and
dissolution like that seen in the NAM may be the way to go. As such,
will be a little slower to to bring an end to the showers Thu,
although by evening still expect to be able to relegate pops to the
Cascades.

[snow_wizard]

GFS shows all snow for Tacoma northward now on Friday.  Trending colder on each run with that feature.

[snow_wizard]

The GFS has finally shaken off it's anti snow thoughts for Seattle.  MUCH better.

[HighlandExperience]

The GFS has finally shaken off it's anti snow thoughts for Seattle. MUCH better.

Still skeptical

[snow_wizard]

Still skeptical

 

I'm thinking we will probably see something with today's system.  Looks a bit different than yesterday's.

[SilverFallsAndrew]

Down to 24 at PDX. Impressive.

[SilverFallsAndrew]

That trough early next week could produce some lowland snow...Looks a lot like the March 5-6 trough last year.

[MossMan]

GFS shows all snow for Tacoma northward now on Friday. Trending colder on each run with that feature.

Friday might just be what people in a widespread area have been hoping for! At 19 degrees with clouds lowering, going to be a cold day!

[Frontal Snowsquall]

12z RGEM/RDPS showing a nice burst of moisture Thursday morning southern PDX Metro. The exact placement of where the heaviest moisture will be is still TBD but I think somebody will get a nice pounding. As for snowfall amounts, I'm leaning towards what the NAM-3km said.

 

http://maps3.pivotalweather.com/maps/models/rdps/2018022112/036/sn10_acc.us_nw.png

[BLI snowman]

24 or 23 for a low at PDX, perfectly respectable. Breaks a record from 1955.

 

Models still insistent on a clear start for Friday as well, so decent chance we can add (subtract) to these lows.

[MossMan]

That trough early next week could produce some lowland snow...Looks a lot like the March 5-6 trough last year.

I got a little on 3/6/17!

[Perturbed Member]

12z GEM is better for everyone tonight.

[MR.SNOWMIZER]

Precip is going to arrive sooner again it would appear.

[snow_wizard]

Amazing how this cold snap just keeps giving us these reinforcing shots of cold air.  It was originally expected highs would rebound to the low 40s after just a few days.  Now we have a legit shot at highs below 40 for at least 6 consecutive days.  I'm trying to respect the impressiveness of this cold snap in spite of the snow problems so far.

[SilverFallsAndrew]

Seems like pretty good consensus for at least 1-2" across most of W. Oregon. 

 

Also the daily climate report says PDX had 4.2" yesterday. 

[snow_wizard]

Precip is going to arrive sooner again it would appear.

 

Looks like it might stay cold enough for snow to accumulate even during the warmest part of the day this time.  This appears it will be the coldest disturbance of the entire series at this point.

[SilverFallsAndrew]

Some absolutely beautiful pics from Air 12 this morning over a snow covered PDX metro.

[VancouverIslandSouth]

Look like we may eke out our first sub-freezing high of the winter. Also the coldest low so far, falling down to 27.5F last night. Thick clouds moved in this morning and it's currently stuck around 28.5F, throw a bit of afternoon snow into the mix and things could get interesting. I wasn't expecting such a cold airmass today, heights are headed back down to around 515dm with -11C at the 850mb level.

[VancouverIslandSouth]

Precip is going to arrive sooner again it would appear.

 

Probably starts as virga, the air is still pretty dry.

[wxmet]

NAM 12z 12km looks good and is backed by the 3km. Let’s hope the Sound doesn’t get shadowed.

[TT-SEA]

NAM 12z 12km looks good and is backed by the 3km. Let’s hope the Sound doesn’t get shadowed.

 

It will not be a shadowing problem... it will be an offshore flow problem for the Seattle area.

[TT-SEA]

The projected radar loop on the HRRR model is usually too aggressive in a offshore flow situations.     I have seen many times when it shows precip over us but it is not actually reaching the ground.   I have come to expect it.   

 

Its not even doing that for tonight...

 

[wxmet]

It will not be a shadowing problem... it will be an offshore flow problem for the Seattle area.

Yes it will be a shadowing problem consider the flow will be coming from the west mean Seattle would be on the leeward side. Please take a look at the low level winds on the models during the time of the event.

[MR.SNOWMIZER]

Yes it will be a shadowing problem consider the flow will be coming from the west mean Seattle would be on the leeward side. Please take a look at the low level winds on the models during the time of the event.

That is not shadowing. Tim is talking about the drying effect. If the storm was coming from the east then it would be a shadow issue.

[TT-SEA]

Yes it will be a shadowing problem consider the flow will be coming from the west mean Seattle would be on the leeward side. Please take a look at the low level winds on the models during the time of the event.

 

Shadowing typically occurs in a strong onshore flow situation where the Olympics block the precip while my area is pounded.

 

This is not that situation at all.  My area will be even less likely to see measurable snow than Seattle.  

[Frontal Snowsquall]

12z UKMET tomorrow morning at 4am. Starting to get a good consensus of what track the low will take.

 

http://img.meteocentre.com/models/ukmet_amer_12/GZ_D5_PN_024_0000.gif

http://img.meteocentre.com/models/ukmet_amer_12/P1_GZ_D5_PN_024_0000.gif

[wxmet]

Both of you are conflating two things (and contradicting each other) between the track of the low and the actual flow coming onshore from the low which will be from the west. Being on the leeward side of a mountain is the definition of rain shadowing. Take a look at the NAM.

[Guest Dome Buster]

I just don't see how this thing takes until 11 pm to start precipitating based on the visible satellite. Am I seeing this wrong? Looks like the cloud shield is rapidly approaching and fox12 says sunny today. Hmmm

[TT-SEA]

Both of you are conflating two things (and contradicting each other) between the track of the low and the actual flow coming onshore from the low which will be from the west. Being on the leeward side of a mountain is the definition of rain shadowing. Take a look at the NAM.

 

You just not correct here.   This is the 00Z ECMWF at 10 p.m. tonight when the low is passing to the west of Seattle and when the bulk of the precip is occurring in WA.

 

The flow is offshore.   If anything... there could be an upslope component in Seattle as they are closer to the Olympics.    But it looks like the offshore flow is just too dry and strong.

 

[Perturbed Member]

12z UKMET tomorrow morning at 4am. Starting to get a good consensus of what track the low will take.

 

http://img.meteocentre.com/models/ukmet_amer_12/GZ_D5_PN_024_0000.gif

http://img.meteocentre.com/models/ukmet_amer_12/P1_GZ_D5_PN_024_0000.gif

 

Looks ideal for PDX area. I'll be thrilled with even an inch of snow at this point. 

[TT-SEA]

Got down to 19 degrees here earlier this morning... coldest low of the season so far.

 

Wow... only got down to 26 in North Bend and at the station up near my house.   Might be a little east wind already at home.  

[wxmet]

You just not correct here. This is the 00Z ECMWF at 10 p.m. tonight when the low is passing to the west of Seattle and when the bulk of the precip is occurring in WA.

 

The flow is offshore. If anything... there could be an upslope component in Seattle as they are closer to the Olympics. But it looks like the offshore flow is just too dry and strong.

 

It convenient to pick the frame of the 00z when the low is already south of the area lol. Of course, at that time, the flow of offshore.

[ShawniganLake]

Gfs looks cold throughout.

[TT-SEA]

It convenient to pick the frame of the 00z when the low is already south of the area lol. Of course, at that time, the flow of offshore.

 

That is when the precip is happening... there will not be 'shadowing' tonight.    The low would have to be east of the Cascades for that to happen.   There might be some SW flow ahead of the low but when the main event is occurring there will be easterly flow across the Seattle area.   

 

Shadowing does not occur when the low is west of Seattle and sliding south.   It just doesn't.  

[TT-SEA]

Seattle is more likely to see snow than my house in the foothills near North Bend.    That is exact opposite scenario for shadowing in the Seattle area.

[MR.SNOWMIZER]

The end of next week is looking interesting on the 12z GFS.

[wxmet]

That is when the precip is happening... there will not be 'shadowing' tonight. The low would have to be east of the Cascades for that to happen. There might be some SW flow ahead of the low but when the main event is occurring there will be easterly flow across the Seattle area.

 

Shadowing does not occur when the low is west of Seattle and sliding south. It just doesn't.

I disagree. There will be shadowing at some point with the low north of the area and the flow coming on shore. You are again confusing the track of the low with the actual flow as the low slides south. Precip is happening because at that point the flow is on the windward side of the Olympics as the slow slides to the south but even with that the available moisture is departing the area.