Sunday, February 27, 2011

Snow Tomorrow Morning? Windstorm on Wednesday?

Folks...I don't want to cry wolf about this...but if you take the current model output literally, we will have a significant lowland snow event after midnight tonight. What gets me nervous is that my colleagues in the National Weather Service are not mentioning the possibility at all in their forecast or discussion.

Here is the 24-h snowfall map for the period ending 4PM Monday.

Wow. The mountains get 2-3 feet of snow and the Puget Sound and SW WA lowlands get several inches. There would be precipitation shadowing west and north of Seattle. I should also note that the Weather Channel automated system is also going for early morning snow.

The previous run has only scattered, light snow showers. Here it is. So we don't have run to run consistently...which tells us that there is real uncertainty here.


The temperatures are marginal for snow later this evening, but the last model run suggests that a heavy precipitation rate will drive the snow level down to sea level in many locations. This kind of situation is called a diabatic snow event...since the melting of snow is an important source of the cool (diabatic is term for such an effect). A tricky forecast since it depends on getting the intensity of the precipitation correct...something we are not that good at.

YES, there is uncertainty with this event. If the last run is wrong and the precipitation is lighter all the lowlands will get is rain. Anyway, just be aware of the possibility. If this happens the commute tomorrow will be a zoo. If tonight's run has it, I would be prepared.

Want more weather fun? The models have a major windstorm coming in on Wednesday. And there was snow today in Los Angeles and several inches around Tucson.

23 comments:

Kevin said...

Hi Cliff,

Maybe worth mentioning that we have had 6+ inches overnight and this morning at 1050ft on Chuckanut Mountain, just south of Bellingham. Our neighbors near the top of the mountain (1500ft) have had nearly a foot. Still a winter wonderland up here, even while we can see the lowlands turning green again.

Just goes to show that a few hundred feet difference in elevation can make.....

Urbancowgrrl said...

We just got home from Phoenix yesterday afternoon and a woman on the plane was talking about how sunny and warm it was in Tuscon last week. In Phoenix it was in the upper-60's. Now snow in Phoenix would really be something - has that ever happened?

iphonesteve79 said...

I saw that model run too and I got very concerned. Lets see what the NWS says in their afternoon forecast. Just going on that model run, they would need to issue a Winter Storm Watch for tonight! haha Let's See what happens...

Donna & Chris said...

The NWS is mentioning some possibility of snow tonight and tomorrow. I think those of us who live in Seattle proper are wary of any real snow actually falling at this point. But it is so cold and nasty!

Wx Enthusiast said...

Both the NAM and the GFS have been very consistent for the past couple days in bringing snow all the way to the southeast part of Lake Washington (as shown on the model output you displayed from last night) even if not around the rest of the lowlands. That would include here in the Newcastle area, it seems. Most times it has been between 2-4 inches, but of course this morning it was more like 6-12. Any thoughts on this.

Dreaming in Waves said...

Whew, so excited for both possibilities, especially that low which seems to be deeper on each run and although it has shifted north in the latest GFS output, earlier runs had it going into Southern Oregon so I'm not counting out anything but regardless, that would be a MAJOR wind event, no doubt about it *keeps fingers crossed, buys rabbit foot and dedicates windstorm shrine*

lhsouthern said...

i can't tell if chehalis is being spared or not.

and if there is a windstorm, would it be in the traditional windstorm prone areas or all over western washington?

Andy said...

ESRL HRRR and RR are both going for snow right now in the amount of a couple inches... They were similarly off in terms of the Seattle snow as UW-WRF in placing the convergence zone during the Wed-Thurs event, but the utter and complete slamming of the mountains seems a given at this point (hence the NWS published avalanche warning). If the convergence zone sets up as forecast this time, though, I'll be skiing in to UW from 19th and 52nd in the morning.

Andy

Model run links: http://rapidrefresh.noaa.gov/hrrrconus/displayMap.cgi?keys=hrrr:&runtime=2011022720&plot_type=acsnw_t1sfc&fcst=15&time_inc=60&num_times=16&model=hrrr&ptitle=HRRR%20Model%20Fields&maxFcstLen=15&domain=t1&adtfn=1&wjet=1

http://rapidrefresh.noaa.gov/RR/displayMap.cgi?keys=rr:&runtime=2011022721&plot_type=acsnw_q1sfc&fcst=12&time_inc=60&num_times=19&model=rr&ptitle=RR%20Model%20Fields&maxFcstLen=18&domain=q1&adtfn=1&wjet=1

emilyadi said...

Urbancowgrrl-I'm from Phoenix and can remember if snowing a few times in my life, although it never stuck. I do recall it sticking a few years ago in Tucson as well.

windlover said...

The NWS afternoon update is making the wind event on Wednesday sound like it will be confined to the usualy high wind areas...mainly the coast and admiralty inlet areas.


Is there any chance of "major" winds over all of western Washington...or will it just be a normal, breezy day?

larchitech said...

The streets were white when we got up and it snowed most of the morning here in Olympia. We just got in from walking the dog and there were ice pellets in the rain. It doesn't seem like it would take much to go back to snow at this point.

Upupaepops said...

I have never seen the precip maps that lit up with gold.

rainycity1 said...

rain mixed with snow here in W. Seattle... don't know if it will last, though.

Cyndy said...

OK, for all weather wonks pining for a REAL snow event: this, via the 10 yr. old daughter of a friend. Drop an ice cube in the loo and wear your PJs backwards, guaranteed to increase any predicted snow X10. I'm personally not above a little magical thinking if there's even the slightest chance that I might be able to stay home from work in the morning and bake blueberry muffins instead.

trav said...

I like snow, and I like changeable weather (beats non-stop rain) - but I'm ready for spring. This stuff can stop any day now, as far as I'm concerned.

Darn you La NiƱa!!

a progressive crank said...

Will we see a Cliff Mass NowCast™ in the small hours? It's raining pretty hard in 98115 and it feels colder than the thermometer says, for sure. Just what we need, a snow day on the first day back after a week break.

HarrisonCZ7 said...

Very interesting. NWS still not talking about anything like that model is showing. Evenings runs will be telling. Come Friday, I wonder what % of normal our snowpack will be? Certainly looking better.

climo man said...

It`s hard to bite on a model that was initialized back at 4AM local time.Let us know what the 00Z run says as soon as it comes out!(Although it could be semi-obsolete at issuance,the way conditions are rapidly changing.)
By the way there was no snow officially recorded in LA today.( Maybe up in the mountains somewhere.)I think that you fell victim to the media hype.The upper low that moved down the west coast the past few days was pretty much a bust,as most of the coldest air and instability stayed well offshore.However, the front associated with it did produce some rather heavy snow in some Sierra foothill areas,but this was not unprecedented.
Urbancowgrrl: Phoenix has had measurable snowfall (one inch or less in each occurence) at least three times (1939,1937,and earlier).But I don`t believe any has occurred in modern times, although I`m not 100% certain.

frantzy said...

In this case, I don't think you'd be "crying wolf"...wouldn't you be yelling, "the sky is falling"?

Ferdi said...

That storm on Wednesday is the most interesting feature of the latest models. Looks intense and aimed at the Northwest interior. Sunday could see a repeat performance. Tides not exceptionally high this week but could see some minor coastal flooding.

Andy said...

Looks like the RR and HRRR are now backing off of the lowland snow threat... the convergence zone that set up in the earlier solutions is no longer present. Guess no skiing into work for me.

Andy

Jeff said...

In Haller Lake area I've got rain and about 2 degrees C @ 20:38.

william said...

Personally I don't see it happening for the Oak Harbor area... main reason? we are in the rain shadow of the olympic mountains. Everywhere else in Wester Washington today saw a lot of rain. We saw nothing except a hint of the sun midday. Second, I just don't see the temp dropping 8 degrees to freezing with a southern wind blowing (which is why we saw the temps warm up today). Now im not saying Mr. Mass is an idiot... there's probably truth to his knowledge and what the models are saying... i just don't see it happening especially here in Oak Harbor.