March 2019 Weather Discussion in the PNW

[Cloud]

00z 3km NAM shows things drying out fairly quickly behind the front tonight but does show a band moving through the Central Sound tomorrow morning.

 

Is this PSCZ? Not sure if CZ are typically modeled?

[TT-SEA]

Here in the northwest we warm up after cold fronts and cool down after warm fronts, dogs walk people and we wear hats on our feet.

You seem sensitive about this. But you know what I am saying is completely true.

 

I have two sons who watch the ski conditions like a hawk here and I am intimately aware of how it works.

[Deweydog]

OK.

 

Point is... its not uncommon for it to warm up here after a cold front passage. That is just a fact of life in this area.

He’s being a contrarian pill. No when to say when.

[TacomaWaWx]

Well I hope we see a little more snow tonight,looks like there’s a decent chance but things are looking promising for a pattern change and some warmer weather finally...it’s literally been below average temps here since February 2nd. Hopefully some cool thunderstorms or interesting weather happens (August 2015 windstorm was awesome) this summer but looking forward to a couple months of sunshine again also.

[TT-SEA]

Is this PSCZ? Not sure if CZ are typically modeled?

 

 

Not a c-zone.  

 

Cold, instability showers rotating around a ULL.

 

But this time it will be cold enough for those showers to be in the form of snow.  

[Phil]

True. Probably depends on trajectory of incoming system too.

 

But warming up after a cold front passage is still very common here.

 

Same with Snoqualmie Pass. My son hates that... they get tons of powdery snow and then the cold front comes through and it turns to rain and ruins the powder. <_>

Are you talking about a brief warm up after the front itself mixes out an inversion, or surface temperatures actually warming for a prolonged period of time due to compressional heating? If the airmass change is modest (IE: it’s more of a dry front than a cold front) then it would be common in many places for surface temps to warm. At least initially.

 

In my area, most cold fronts (even intense ones) will produce an initial temperature spike due to downsloping off the mountains and the pressure surge itself deepening the mixing layer, before the cold advection overwhelms it.

 

Often times (especially in the Fall/Spring) it takes an entire day for the cold advection to overwhelm the downslope warming, in which case it’s often extremely windy, and will be one of the few occasions where the dewpoints tank low enough to be a fire hazard.

 

But the cold eventually wins, when its present.

[Jesse]

He’s being a contrarian pill. 

 

I'd think both you and Tim would be pretty good at spotting those.

 

But yeah not really. I never said it doesn't happen sometimes, but its also not as overwhelmingly common as he's making it sound. Point out where I'm wrong. I would say a majority of our cold fronts feature cooling temperatures/airmasses behind them. Of course there can be setups where there is a surface cold layer that gets scoured out by the mixing, but I would say that is less common than our traditional fronts with a switch from southerly surface flow to NWrly.

[snow_wizard]

Is this PSCZ? Not sure if CZ are typically modeled?

 

Nope.  It appears it's going to be a cluster of showers that will hook around the south end of the Olympics.  I looked very deeply into this and the flow trajectory and temperature profile look excellent for the 3am to 9am period for something good to happen.  During the evening 700mb temps are going to plunge which will get rid of this drizzle crap some places are seeing right now.  Besides that thicknesses and 850mb temps will also fall.  This thing has decent potential.

[TT-SEA]

Are you talking about a brief warm up after the front itself mixes out an inversion, or surface temperatures actually warming for a prolonged period of time due to compressional heating? If the airmass change is modest (IE: it’s more of a dry front than a cold front) then it would be common in many places for surface temps to warm.

 

In my area, most cold fronts (even intense ones) will produce an initial temperature spike due to downsloping off the mountains and the pressure surge itself deepening the mixing layer, before the cold advection overwhelms it.

 

Often times (especially in the Fall/Spring) it takes an entire day for the cold advection to overwhelm the downslope warming, in which case it’s often extremely windy, and will be one of the few occasions where the dewpoints tank low enough to be a fire hazard.

 

The results sound very similar... but the cause is completely different.

 

We often get continental air ahead of a storm or cold front... and then we are flooded with maritime air when the flow switches behind the storm or front.  

 

This does not happen in the warm season.   Cold fronts almost always bring in colder air immediately... because air coming in from the ocean is going to be colder than the antecedent air mass in the summer. 

[HighlandExperience]

Nope. It appears it's going to be a cluster of showers that will hook around the south end of the Olympics. I looked very deeply into this and the flow trajectory and temperature profile look excellent for the 3am to 9am period for something good to happen. During the evening 700mb temps are going to plunge which will get rid of this drizzle crap some places are seeing right now. Besides that thicknesses and 850mb temps will also fall. This thing has decent potential.

Perfect time for snow to fall. Might be the last of the season

[Jesse]

Perfect time for snow to fall. Might be the last of the season

 

I feel like we've all been saying that for weeks now.

[TT-SEA]

I feel like we've all been saying that for weeks now.

 

 

Becomes more likely with each passing day.    

[snow_wizard]

I'd think both you and Tim would be pretty good at spotting those.

 

But yeah not really. I never said it doesn't happen sometimes, but its also not as overwhelmingly common as he's making it sound. Point out where I'm wrong. I would say a majority of our cold fronts feature cooling temperatures/airmasses behind them. Of course there can be setups where there is a surface cold layer that gets scoured out by the mixing, but I would say that is less common than our traditional fronts with a switch from southerly surface flow to NWrly.

 

Tim is right that the surface often warms behind fronts like this.  We are lucky this time that mid level temps are rapidly cooling and we will avoid that for the most part.  I think a lot of the fronts that bring warming are occluded fronts as opposed to true cold fronts.

[Jesse]

Becomes more likely with each passing day.    

 

So does "This might be my last day on this planet"

[Requiem]

Tim is right that the surface often warms behind fronts like this. We are lucky this time that mid level temps are rapidly cooling and we will avoid that for the most part. I think a lot of the fronts that bring warming are occluded fronts as opposed to true cold fronts.

I know PDX isn’t your forte, but any thoughts for us down here in regards to snow showers tonight?

[MossMan]

Just finished shoveling the pad in front of the garage.

Very light snow still falling. 32.2.

[Jesse]

Tim is right that the surface often warms behind fronts like this.  We are lucky this time that mid level temps are rapidly cooling and we will avoid that for the most part.  I think a lot of the fronts that bring warming are occluded fronts as opposed to true cold fronts.

 

I never said he wasn't. Not once. Just that it's not our most common type of surface reaction to a cold front. He seems to be playing it up to Phil to underscore how wacky our climate is or something.

[TT-SEA]

So does "This might be my last day on this planet"

 

 

So does our impending death.  

[snow_wizard]

Perfect time for snow to fall. Might be the last of the season

 

Looks like early Friday morning has a solid shot also.  Until this cold wave actually ends we will probably continue to see opportunities.  Right now it appears another week of below normal temps.  I think I said that two weeks ago, and one week ago....

[TT-SEA]

I never said he wasn't. Not once. Just that it's not our most common type of surface reaction to a cold front.

 

 

It seems like its probably half the time in my area during the cold season.    But almost never happens in the warm season.   So I guess that means it happens about 25% of the time here.    But its not uncommon.  

[snow_wizard]

Just finished shoveling the pad in front of the garage.

Very light snow still falling. 32.2.

 

I'm jelly.  I hope it looks like that here tomorrow morning!

[Jesse]

So does our impending death.  

 

ANd so does us dyeing

[Jesse]

It seems like its probably half the time in my area during the cold season.    But almost never happens in the warm season.   So I guess that means it happens about 25% of the time here.    But its not uncommon.  

 

GLAD WE WERE ABLE TO IRON THAT OUT

[Bryant]

Light snow continues, but looks to come to an end shortly. Received 2" of fresh snow today, with higher amounts on pre existing snow surfaces, bringing the seasonal total to 20" IMBY. Maybe a little more snow from passing showers? We'll see.

[Jesse]

Light snow continues, but looks to come to an end shortly. Received 2" of fresh snow today, with higher amounts on pre existing snow surfaces, bringing the seasonal total to 20" IMBY. Maybe a little more snow from passing showers? We'll see.

 

Even though I'm pretty sure you're happy right now I still read this in an angry voice. Habit I suppose.

[TT-SEA]

Tim is right that the surface often warms behind fronts like this.  We are lucky this time that mid level temps are rapidly cooling and we will avoid that for the most part.  I think a lot of the fronts that bring warming are occluded fronts as opposed to true cold fronts.

 

 

I see OLM is still at 36 with SSW 9.

 

This is definitely not warmer maritime air rushing in tonight.   

[snow_wizard]

I know PDX isn’t your forte, but any thoughts for us down here in regards to snow showers tonight?

 

My gut feeling is you may have a better shot tomorrow night.  Certainly possible you could score late tonight though.

[Phil]

The results sound very similar... but the cause is completely different.

 

We often get continental air ahead of a storm or cold front... and then we are flooded with maritime air when the flow switches behind the storm or front.

 

This does not happen in the warm season. Cold fronts almost always bring in colder air immediately... because air coming in from the ocean is going to be colder than the antecedent air mass in the summer.

Oh, I see what you’re saying. That sounds more like a maritime front (IE: cool/moist advection instead of cold/dry advection).

 

Very different than a classical cold front. That combination of cool + moist advection is quite rare away from the West Coast and New England. I’m not sure I’ve ever experienced it.

[snow_wizard]

The new GFS is sticking to it's guns.  A well organzied batch of showers early tomorrow morning here.  It has been very consistent on this.

[Jesse]

Oh, I see what you’re saying. That sounds more like a maritime front (IE: cool/moist advection instead of cold/dry advection).

 

Very different than a classical cold front. That combination of cool + moist advection is quite rare away from the West Coast and New England. I’m not sure I’ve ever experienced it.

 

Ohhhhhh. That’s right, you guys live right by the largest body of water in the world. I always forget, darnit.

[Bryant]

Even though I'm pretty sure you're happy right now I still read this in an angry voice. Habit I suppose.

Lol, I do that all the time. I could complain about this winter in some regards if I really wanted to (especially the amount of time spent with non accumulating snow falling), but overall it was an enjoyable winter.

 

Cruising around the neighborhood with Brennan on his quad and sledding the streets around here made this winter memorable for sure.

[Phil]

Ohhhhhh. That’s right, you guys live right by the largest body of water in the world. I always forget, darnit.

I thought when Tim said “cold front”, he was talking about a backdoor cold front and downsloping in his backyard or something, considering the fact he was lecturing me about it just yesterday.

 

I’m not familiar with maritime cold fronts, dude. I’ve never experienced one.

[Andrew.]

Doesn't it suck to be in Multnomah county though? Seems the property taxes are kind of gross.

 

I'm looking for property that is 1000ft or higher but probably needs to be WA county. I can't believe I'm even thinking of making potential property investment decisions based on snow prospects. All non weather geeks think I'm a total loony.

I'm actually Washington county thank god, just barely into it, but still a Portland address. It's technically unincorporated Washington county. I had no interest in being in multnomah county haha.

 

And I'm right there with you. The snow prospects of the property where right up there with location and house type. This is actually close to the lowest I wanted to go, but so far its turned out to be a great spot and can really tell the difference during these marginal setups. The snow line has been roughly 100 feet below me multiple times this winter.

[TT-SEA]

I thought when Tim said “cold front”, he was talking about a backdoor cold front and downsloping in his backyard or something, considering he was lecturing me about it just yesterday.

 

I’m not familiar with maritime cold fronts, dude. I’ve never experienced one.

Colder 850mb temps behind a cold front from the west... but not uncommon for surface temps to rise here with the switch from continental to maritime air after the frontal passage.

[Jesse]

I thought when Tim said “cold front”, he was talking about a backdoor cold front and downsloping in his backyard or something, considering the fact he was lecturing me about it just yesterday.

 

I’m not familiar with maritime cold fronts, dude. I’ve never experienced one.

All jokes aside, even our cold fronts moving off the ocean often feature dropping dewpoints and function like “traditional” cold fronts. But we can also get marine intrusions that moderate continental air masses in both the summer and winter. It’s never linear. Depends on many factors, and thus there are a lot of diverse setups.

[Phil]

All jokes aside, even our cold fronts moving off the ocean often feature dropping dewpoints. It’s never linear. Depends on many factors, and thus there are a lot of diverse setups.

In that case it’s an actual cold front, and the airmass would probably not produce any warming of the surface boundary layer over land unless there was an inversion present. Coming off the ocean it would be hard for there to be sufficient dry air advection/boundary layer deepening for that.

[GHweatherChris]

Good lord

[Geos]

The new GFS is sticking to it's guns.  A well organzied batch of showers early tomorrow morning here.  It has been very consistent on this.

 

Rush hour is going to be a challenge I'm thinking.

[Jesse]

In that case it’s an actual cold front, and the airmass would probably not produce any warming of the surface boundary layer over land unless there was an inversion present. Coming off the ocean it would be hard for there to be sufficient dry air advection/boundary layer deepening for that.

Yes, the situations Tim is speaking of ususally involve inversions getting mixed out.

[Phil]

Colder 850mb temps behind a cold front from the west... but not uncommon for surface temps to rise here with the switch from continental to maritime air after the frontal passage.

Why would that be?

 

Eroding of the inversion/low level cold bleeding through the terrain? Dry air advection? Boundary layer deepening via the aforementioned and dynamic overturning?

 

Edit: Jesse answered my question.