Raging East Winds.... And Another Wintery Event?

Hey everyone... Well it's the early morning hours of the second day of 2013 and our weather (at least on the east side of town) is and has been active. My snow forecast was on point for some areas (even underdone!) and in others it busted a bit. SW Washington, particularly parts of Vancouver and points North were the winners with this, 2 inches was about the max but road conditions were affected, so I feel like the forecast did pretty well as the low pressure system pivoted and allowed for steady precip over a small area. It was a well modeled event!

Onto our current situation... The east wind is howling with a pressure gradient of -10mb from Troutdale to The Dalles. Here's what the NWS said about gradients that high in their AFD..

IN ANY EVENT...A KTTD-KDLS GRADIENT OF -10 MB IS A TRIGGER POINT FOR

HIGH WIND WARNING CONCERNS. ANOTHER RULE-OF-THUMB IS THE 7-8 MPH PER
MB FOR MAXIMUM GUSTS. THUS...70-80 MPH GUSTS SEEM REASONABLE IN
THE EXIT REGION OF THE GORGE AND THE NOTORIOUS WIND-PRONE SPOTS JUST
ABOVE THE GORGE. FOR INSTANCE...EXPECT GUSTS OF 90 TO 100 MPH AT THE
VISTA HOUSE DURING THE PEAK PERIOD...

Both a high wind warning for the Western Gorge and a Wind Advisory for the East Metro are currently in affect.. In reference to the previously mentioned gradient, here's what it's currently looking like.

Latest models put the gradient at its peak this morning around -11 to -12, so it will intensify. Crown point has seen multiple 80mph gusts, and several Troutdale locations are approaching 60. Also seeing close to 50 around here (NW Gresham) and wind has become much more sustained in the last hour or so. I fully expect a gradient around -12mb, which should yield the following gusts...

Crown Point 90-100mph (100+ on the stairs)

West Gorge (Areas under High Wind Warning) 65-80mph

East metro (Gresham, Wood Village, Troutdale, Fairview, East Portland) 55-70mph

All in all, if you live east of 205, good luck sleeping... 

Now onto our other point of interest with this forecast... When we have east winds of this strength, the first weather system following it is a tricky forecast, and this is no different. We have a very small area of low level cold air with a steep temperature inversion currently. As this system moves in Thursday morning, there should be a melting layer (column of above freezing temps) followed by a freezing layer (column of sub freezing temps) below it. This is why I believe Freezing Rain, rather than Snow will be an issue. Here's a 4km sounding (Dew Point in Green, Temp in Red) for my location on Thursday morning...

Notice the large disparity in Temp/Dewpoint around the 700mb level on down? This should allow for very nice evaporative cooling with such dry air, and normally would aid snow... But with the inversion visible on this sounding (warmer at 850-900mb than surface) the precip will likely thaw in the atmosphere , and if it hits as modeled in the morning, will refreeze on the ground icing everything over. I expect the NWS to issue either a ZR advisory or a Winter Weather Advisory or both... I will post more about that tomorrow as data becomes available.

An active start to 2012 !
Josh

New Year's Eve Snow?

Hey everyone, it is COLD this morning. Temps across the area are down into the 20’s, and that’s not the only interesting development in our weather on this New Year’s Eve... A splitting low pressure system is just offshore, one which was previously modeled to give us little or no moisture. The trend recently however has been for SLIGHTLY more moisture, as evidenced by this morning.  This is the current radar image is of 7:45 AM, with plenty of shower activity offshore, side-by-side with a zoomed 36km image from the 00z WRF-GFS model. Notice the discrepancy in moisture? Curious to see how 12z looks (which is running right now)

Tonight is another tricky portion of the forecast... The aforementioned WRF continues to show slightly increasing moisture for this afternoon, and with a temp/dp spread that we will have due to the cold dry east wind, along with moderate cloud cover holding temps down all day, this would presumably fall as snow. Here is last night’s 00z 4km WRF-GFS moisture image for 4pm this afternoon.
It shows modest moisture (.2-.5”) but as I’ve shown, it MAY be underdone. As more model data and OBS come available, as I will pass on any thoughts to you. I currently think at the most we could see a quick inch or a dusting, but I may amend that later. Keep it right here for the latest
-Josh Gardner



UPDATE: 12z model data is in and showing some very interesting developments. As I mentioned before the trend had been for more precip, and 12z did not disappoint in that regard. The ‎12z WRF 4km for 4pm this afternoon is wetter than previous runs... Steady light precip for 2-3 hours...

And then here's the 4km snow model for the same time.. Trace-1" across the entire metro area.

Now Snowing Across the Area

Well rain has turned to snow now across much of the area, as the precip is doing a good job cooling down the atmosphere, and temps are dropping at the surface. Here in Gresham, down to 34.0 and still some precip moving across the area. Here are the current Tower Temps and Radar... I will update this as conditions change..

Christmas Eve Eve Update

Happy Holidays everyone. Interesting setup for this afternoon/tonight that has developed basically out of thin air... Seems like that's how it works around here. Anyway there is a low pressure "shortwave" swinging over the reigon this afternoon and areas east of the Cascades are getting pounded with snow. But will any of that make it westside? That's where the surprise comes in... Colder air is wrapping around the low, and temps are dropping across the area (specifically east metro). Now here's where it's interesting... According to the 12z WRF, (another update will be forthcoming following all 18z model data) by 5-7pm 925 mb temps are projected to drop to at or below 0c. Steady precip during that same time MAY allow for cooling of the atmopshere and for snow levels to drop rapidly this afternoon. I'm going to update this in the next hour or so, but here's the 12z WRF images I referenced... 

12z WRF-GFS 4km Precip Map for 4pm

12z WRF-GFS 4km 925mb Temps for 4pm. Notice the light easterly flow as well

Potential for Overrunning Snow Late Tuesday into Wednesday...

SNOW or RAIN?

There is a POTENTIAL for decent snowfall tonight, but everything needs to line up just right (like always!)... The setup is due to the cold air we already have in place, and an approaching warm front, this front will eventually raise snow levels well off the valley floor, but when it does will be crucial to snowfall in the PDX metro. The most important thing we're currently seeing is a slight offshore gradient (meaning winds are not coming off the ocean but towards them). This is what gives us our east wind... ANY, and I mean ANY sort of east wind tonight will make a dramatic difference in snow chances. It is forecast to get up to a healthy gradient of -4 to -5 from The Dalles to Troutdale, which in the east metro may provide some slightly breezy east wind for a few hours, enough to hold onto the cold for that much longer, and with the approaching warm front that could be all we need. Below is the image that I'm referring to, it can be a bit confusing but it is read from right to left, the red and blue plots mark pressure at Troutdale and The Dalles respectively, as you can see in the last couple of hours the gradient has switched to offshore...

Now the front I'm talking about is just now pushing showers into the coast range, with the heavier precip forecasted for 2-4am... This is the time period to watch for the possibility of some decent snowfall, but like I said, it all comes down to how strong this cold air and offshore flow can hold on..

As you can see this setup is about as borderline as it gets... But if the factors line up right we may get a few hours of good snow out of it.. Ill leave you for now with both the Short Term portion of tonights AFD, as well as the Winter Weather Advisory that goes into effect at 2am

SHORT TERM...RADAR IMAGERY SHOWS SHOWERS HAVE BEEN TAPERING OFF THIS
EVENING. A COLD AIRMASS OVER THE AREA COMBINED WITH RADIATION COOLING
HAS RESULTED IN COLD TEMPERATURES ACROSS THE REGION. SURFACE
OBSERVATIONS INDICATE THE FREEZING LEVEL IS NEAR 1000 FEET THIS
EVENING. SNOW OR A MIX OF RAIN AND SNOW SHOWERS WILL CONTINUE TO
DECREASE TONIGHT.

SATELLITE IMAGERY SHOWS AN APPROACHING WARM FRONT AROUND 150 MILES
OFF THE OREGON COAST. THE LANGLEY HILL RADAR IMAGERY IS JUST SHOWING
RAIN OR VIRGA AHEAD OF THE FRONT AROUND 70 MILES OFFSHORE OF THE
WASHINGTON OREGON BORDER. WARMER AIR WILL EVENTUALLY MOVE INTO THE
AREA AND RISE SNOW LEVELS...BUT NOT LIKELY WITH THE INITIAL BAND OF
PRECIPITATION.

EASTERLY WINDS EAST OF THE CASCADES WILL PUSH MUCH COLDER AIR FROM
EASTERN OREGON THROUGH THE GORGE BEFORE THE ARRIVAL OF
PRECIPITATION...AND CAN EXPECT A GOOD DOSE OF SNOW FOR THE GORGE AND
UPPER HOOD RIVER VALLEY LATE TONIGHT INTO WEDNESDAY MORNING. SOME OF
THIS COLDER AIR WILL SPILL INTO THE NORTHERN WILLAMETTE VALLEY AND
SUPPORT THE POSSIBILITY FOR SNOW IN THE INTERIOR LOW LANDS AS WELL.

THERE IS FAIR CONFIDENCE THAT SNOW WILL IMPACT MUCH OF THE AREA
BEFORE THE WARM FRONT BRINGS WARMER AIR BUT THERE IS LESS CONFIDENCE
IN THE AMOUNT OF SNOW.PRECIPITATION LOOKS FAIRLY LIGHT WITH THE
INITIAL SLUG OF MOISTURE WHICH SHOULD LIMIT ACCUMULATING SNOW. HAVE
MAINTAINED THE CURRENT FORECAST OF HAVING LIGHT SNOW
DEVELOPING AFTER 3 AM...BUT NOT REALLY ACCUMULATING UNTIL AFTER 5 AM.
THE INTERIOR LOWLANDS SHOULD HAVE ALL SNOW EARLY WED
AM...TRANSITIONING TO SLEET AND THEN RAIN AND SNOW BETWEEN 7 AM AND 9
AM...THEN JUST RAIN. 1 TO 2 INCHES GENERALLY EXPECTED WITH A FEW
AREAS GETTING UP TO 3 INCHES. BUT IN CENTRAL AND SOUTH WILLAMETTE
VALLEY...ESPECIALLY FROM SALEM SOUTHWARD...THE WARM AIR ARRIVAL
SHOULD LIMIT SNOW AMOUNTS TO LESS THAN 1 INCH.

Winter Weather Advisory
URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE PORTLAND OR
307 PM PST TUE DEC 18 2012

ORZ005-006-WAZ022-039-191400-
/O.CON.KPQR.WW.Y.0033.121219T1000Z-121219T1800Z/
LOWER COLUMBIA-GREATER PORTLAND METRO AREA-I-
5 CORRIDOR IN COWLITZ COUNTY-GREATER VANCOUVER AREA-
INCLUDING THE CITIES OF...ST. HELENS...HILLSBORO...PORTLAND...
OREGON CITY...GRESHAM...TROUTDALE...LONGVIEW...KELSO...
VANCOUVER...BATTLE GROUND...CAMAS...WASHOUGAL
307 PM PST TUE DEC 18 2012

...WINTER WEATHER ADVISORY REMAINS IN EFFECT FROM 2 AM TO 10 AM
PST WEDNESDAY FOR THE NORTH WILLAMETTE VALLEY...CLARK COUNTY AND
THE I5 CORRIDOR...

A WINTER WEATHER ADVISORY FOR SNOW REMAINS IN EFFECT FROM 2 AM TO
10 AM PST WEDNESDAY.

THE NATIONAL WEATHER SERVICE IN PORTLAND HAS ISSUED A WINTER
WEATHER ADVISORY FOR SNOW...WHICH IS IN EFFECT FROM 2 AM TO 10 AM
PST WEDNESDAY.

* TONIGHT...MORE WIDESPREAD ACCUMULATING SNOW WILL DEVELOP LATE
  TONIGHT. GENERALLY...1 TO 2 INCHES OF SNOW ARE LIKELY FOR LATE
  TONIGHT AND WEDNESDAY. HOWEVER...A FEW LOCATIONS TOWARDS EASTERN
  CLARK COUNTY AND THE WEST HILLS MAY SEE 2 TO 3 INCHES.

* SNOW LEVELS TODAY...WILL LOWER TO NEAR VALLEY FLOOR LATER
  TONIGHT INTO EARLY WEDNESDAY MORNING. SNOW LEVEL WILL RISE TO
  2500 FEET QUICKLY WEDNESDAY MORNING.

Snow Updates... Monday PM - Tuesday AM

Lowland Snow 

12/17-12/18

Dusting of Snow in Oregon City
(via Jeff Raetz)

(8:40pm) Snow is now falling across parts of the metro area, as temps at the lower elevations are hovering around 35, with locations at or around 1000' hitting 32. The cold air over our area following last night's wind is allowing for only limited moisture, and most showers will be spotty. Perfect example is from just a few miles south in Oregon City (550'), a quick hitting shower produced a dusting. Lets take a look at the current radar and KPTV tower temps, which give us a good idea of where the freezing level is across Portland

These are the tower temps as of 7:00pm, the freezing level is hovering around 1000 feet, but freezing level and snow level, can differ greatly. That's why the forecast for tonight, while the likeliest locations for sticking snow are 500-1000' and up, anywhere could see a trace-1".

 

This is the current radar image as of 8:55 pm. As you can see, showers are scattered in nature, and will continue to be that way throughout the night. Shower activity, if it were to increase would likely be from midnight to sunrise (per the NWS). Please add all reports of snow, temps, etc in the comments. and I will be updating this throughout the night.

(12:21 am) It is currently looking like my original forecast will be right, showers are very spotty and temps at lower elevations (below 500') are still above freezing (around 35 F)... Places in the hills have seen some accumulations, and continue to expect that throughout the night. The reason we're not cooling off and more despite cold air aloft is the light southerly wind in the area. This ALWAYS prevents snow at the lowest elevations, as it keeps it just warm enough. Due to that ice in the am will not be a huge problem, but it may be spotty and could be slick as you go up in elevation or in the typical cold pockets. I will be breifly updating this when I check again...

(1:41 am) ALOT more shower activity picking up out offshore and into the coast range, most impressive radar returns of the night. I'm expecting around 2:30-4:00am to be our best shot at snow nearly anywhere, as these showers seem strong enough to pull the snow level down the extra bit needed. As you can see below, precip is really picking up to our west, so I wouldn't rule out a quick trace-inch anywhere 

(4:06 AM) Pretty good wet snow falling right now here, radar continues to look good and the temp is down to 34.0.. Nothing sticking yet but it will at this rate. Higher hills likely have snow on the ground now

Storm Update

Sunday, December 16, 2012
11:20 P.M.

10:30 pm PST Sun 16 Dec 2012 - West Coast 4km NWS water vapor satellite

Hello all, this is Charlie Phillips posting on behalf of Josh Gardner. I'm not from Rip City, but I am from Jet City, and the weather we are experiencing up here is similar to what you guys are getting down there.

However, there is one significant difference. Portland will be significantly windier than Seattle for the rest of tonight into Monday morning. Although it's a little hard to tell on the satellite picture, the center of the low pressure system is actually further south than even the models predicted. It's expected to roar ashore around Destruction Island on the Washington Coast and then head over Seattle as it makes its way eastward. Since the pressure gradients at the center of the storm are relatively light, Seattle will see light winds at first, and then stronger winds as the low passes through and Seattle feels the wrath of the bent-back occlusion of the cyclone, or, as some like to call it, the "poisonous tail." Portland will be under the influence of a larger pressure gradient and will see higher winds. This won't be anything like the Hanukkah Eve Storm of 2006 even for Portland, but it will be the windiest storm to strike the Willamette Valley so far this autumn/winter. The coast will get pummeled with 25 foot waves and sustained storm force winds of 40-50 knots, with occasional gusts to 60 knots. I would not be surprised if a few of the isolated headlands, such as Cape Blanco, Mt. Hebo, or Naselle Ridge, see a triple-digit gust from this storm.

This storm is also bringing gobs of snow to the Cascades. In fact, a blizzard warning is in effect for the central Washington Cascades down all the way to southern Oregon. The snowiest locations, like Mt. Rainier, Mt. Baker, and Mt. Hood, could receive up to three feet of snow from this storm. There will also be very strong winds on the ridges, which should come as no surprise. The Northwest Avalanche Control Center is actually forecasting 70-90 mph winds at 9,000 feet in the southern Washington Cascades. I can't think of any reason you would like to be up there, unless you REALLY like flying kites.

But you shouldn't just stay out of the highest mountains in the Cascades; you should stay out of the passes too.

It's hard to see in this picture, but Snoqualmie Pass has compact snow and ice on the ground with blizzard conditions outside. Great for skiers... I'm definitely looking forward to going up this week... but not so great for travelers. The pass is closed in several places due to collisions, so it might be better to wait a day to travel over the pass.

I love having these "triple threat" (rain, wind, snow) storms come through the area. It's just what I needed, and it couldn't have come at a better time. It's definitely an early Christmas present for us weather geeks!

Stay safe, warm, and happy. :)
Charlie Phillips
charliesweatherforecasts.blogspot.com
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