Update on Snow.

As many of you heard already there is a chance of snow tonight and tomorrow.

Now this evening the chance of sticking snow is very low, however tonight around 11pm a cold front will come through and bring the snow levels down to about 500-1000ft 

The Image below shows the placement of the cold front at 4:30pm

What to expect:

Now-11pm:

• Rain/snow turning to all rain
• Breezy winds becoming southerly

 

11pm-11am:

• Rain/Snow showers becoming all Snow
• Accumulations will stay mostly above 500ft
• Accumulations below 500ft will be brief and only a trace -1 inch

12pm +

• Snow showers will become rain/snow showers
• T'storms will be possible as the air will be unstable

Long range:

In the long range models are in disagreement just look at the ensembles below some say warm weather other say it will stay cool 

My forecast:

Thanks for reading

-Michael 

A Snowy Update

I'm sure most if not all have already seen some snow mixing in with rain today but its not over yet.

Info on snow:

• Everyone will see snowflakes.
• Best chance for snow will be tonight and Sunday morning
• Spotty accumulations of a trace to1 inch
• Accumulating snow will mostly stay above 500ft
• Daytime highs 40-45
• Sun breaks will melt any accumulated snow below 1000ft
• Sunday evening moisture dissipates and leaves us dry
• Monday will be cool and dry

Tuesday:

Now Tuesday morning models are not all in agreement on the position of a low but if that low does come far enough south then we would get an offshore flow which would give us a snow to rain transition.

The image below is the 12z WRF-GFS on Tuesday morning

Notice how the wind barbs circled in red are pointed offshore that indicated wind blowing from the east.

The image below is an explanation of the setup that we will have.

Now is this does setup right we could get 1-2inches of snow then rain. But if the low tracks farther north then we will get south winds and rain.

My forecast:

Thanks for reading

-Michael 

Too Warm in the Lowlands for Snow.

As I mentioned in the last post a trough of cold air is going to arrive over us this weekend.

Saturday the 25th

Now earlier this week models were supporting temperatures cold enough for snow down to sea level. however over the past few days models have warmed that cold air just slightly but enough to not give us snow.

The image below is the WRF-GFS cross section forecast

The dotted purple line is 32 degrees or freezing  the solid blue line represents 1000ft, notice how the dotted line barely goes below the 1000ft mark.

Also when the coldest air arrives in Monday the air dries out and we have no precip.

   So what will we see? 

• Snow levels 1000-1500ft
• Possible rain/snow mix in showers Sunday night
• NO ACCUMULATING SNOW in the valleys.
• Scattered cold rain showers
• Cold but dry Monday morning

My forecast:

Colder Weather Pattern with a Possibility of Snow?

For the past few weeks we have been in a relatively warm and quiet weather pattern. Starting next week end a cold trough from the north will drop down and bring us cold air.

Now models are still disagreeing on exactly how cold the air will be but most are in agreement that it will be between -6 to -8c at 850mb (5000ft) over our area. now in the middle of winter -8c at 850mb will give you snow however during this time of year we would need about -9c to produce snow with an onshore flow.

2 Problems for snow:

1. Onshore flow: 

The image below explains how onshore flow is a problem for snow.

2. Its the end of February:

At the end of February the sun angle is higher which gives us warmer temperatures. 

Bottom line:

• Snow level will be most likely be around 1000ft.
• Best chance of brief accumulation at the valley floor would be Sunday morning.
• Any accumulation would be spotty and brief. 
• this is one week away and it could change.

My forecast:

Thanks for reading 

-Michael

One Last Grasp of Winter.

As I explained in my last post that after we enter March our chances of lowland snow/arctic blast decreases dramatically.

However winter has decided to attempt to visit us one last time. 

Saturday-Monday (18th-20th):

 A trough of low pressure will arrive over our area and allow some cold air to seep into our region (shown below). Now this cold air will lower the 850 mb (5,000ft) temps down to about -6c which means the snow levels will be 1,000 ft to 1,500ft. Now the snow levels being up there does not rule out the chance of a rain/snow mix down to almost sea level in the heavier showers. 

The image below is the 18z GFS ensembles showing the trough over our area on Saturday. 

Tuesday-Thursday(21st-23rd):

A ridge of high pressure will build just to the west of us and give us drippy conditions.

The image below shows the 12z WRF-GFS showing the setup.

Notice how the high pressure gives us an onshore flow. Now what does an onshore flow do? Well it usually gives us lots of low clouds, fog, or drizzle. This is also known as a "Dirty Ridge" 

Saturday+ (25th+):

Models are now starting to agree on that a trough of low pressure will drop down over us and drop snow levels down to 500-1500ft. However how low the snow level goes will depend on where the upper level high will be located.

The image below is the 12z Euro ensembles showing the trough bringing cold air to our region.

My forecast:

Timberline Forecast via NWS:

Friday: Snow, mainly after 10am. High near 34. Southwest wind between 17 and 21 mph, with gusts as high as 31 mph. Chance of precipitation is 90%. New snow accumulation of 2 to 4 inches possible. 

Friday Night: Snow showers. Low around 19. Breezy, with a west southwest wind around 25 mph, with gusts as high as 40 mph. Chance of precipitation is 100%. New snow accumulation of 5 to 9 inches possible. 

Saturday: Snow showers. High near 21. Wind chill values as low as zero. Windy, with a west wind between 26 and 30 mph, with gusts as high as 48 mph. Chance of precipitation is 100%. New snow accumulation of 6 to 10 inches possible. 

Saturday Night: Snow showers. Low around 16. Breezy, with a west wind between 20 and 28 mph, with gusts as high as 45 mph. Chance of precipitation is 100%. New snow accumulation of 5 to 9 inches possible. 

Sunday: Snow likely, mainly before 10am. Mostly cloudy, with a high near 26. Chance of precipitation is 70%. New snow accumulation of 1 to 2 inches possible. 

Sunday Night: Snow likely. Mostly cloudy, with a low around 20. Chance of precipitation is 60%. New snow accumulation of less than a half inch possible. 

Washington's Birthday: A chance of snow showers. Mostly cloudy, with a high near 30. 

Monday Night: A chance of snow. Mostly cloudy, with a low around 22. 

Thanks for reading

-Michael  

Is Winter Over?

Well the answer on the calendar is no, but meteorologically it might be over, let me explain.

Here in the Pacific Northwest our winter usually ends after about February 25-28. In March our chances of an arctic outbreak or any lowland snow dramatically decrease, however mountain snow and wind events are still possible. You might be thinking so what, its only the 2nd week of February.

Here  is why I think our lowland winter is over.

Currently we have a big ridge of high pressure sitting just to the west of us causing the storm track (jet stream) to go over us and giving us mild temps. 

Now here is an image of the 18z GFS ensemble mean 500mb heights at hour 288 (2/23/12)

Notice the ridge of high pressure is still sitting there almost 2 weeks from now.

However there is only one last chance of winter that models are hinting at.

The image below is the 18z GFS ensemble mean 500mb heights at hour 324 (2/25/12) 

Notice how the ridge moves to the northwest allowing the cold air to seep in.

Now if this does not happen then our winter is over for the lowlands.

My forecast:

Timberline Forecast via NWS:

Sunday: Increasing clouds, with a high near 32. West wind between 5 and 8 mph. 

Sunday Night: Snow likely. Cloudy, with a low around 23. West southwest wind between 5 and 8 mph. Chance of precipitation is 70%. New snow accumulation of 1 to 3 inches possible. 

Monday: Snow showers likely, mainly before 4pm. Cloudy, with a high near 24. Northwest wind around 8 mph. Chance of precipitation is 70%. New snow accumulation of 1 to 3 inches possible. 

Monday Night: A 30 percent chance of snow showers, mainly before 10pm. Cloudy, with a low around 22. North northwest wind between 6 and 8 mph. Little or no snow accumulation expected. 

Tuesday: A 30 percent chance of snow, mainly after 10am. Mostly cloudy, with a high near 26. Little or no snow accumulation expected. 

Tuesday Night: A 40 percent chance of snow showers. Mostly cloudy, with a low around 21. Little or no snow accumulation expected. 

Wednesday: A chance of snow showers. Partly sunny, with a high near 28. 

Wednesday Night: A slight chance of snow showers. Mostly cloudy, with a low around 27.

Thanks for reading

-Michael

Micro-climates and a Small Pattern Change

This weekend was just gorgeous! Some locations have even received their first 60 degree day on Sunday.

   Now what has been causing this beautiful weather? This is being caused by a big upper level high sitting just to the east of us driving all the weather systems around us.

The image below shows the upper level high making the storm track bend around and over our region. 

I'm pretty sure all of you have felt that east wind out there. The east wind is being caused by low level high being bottled up against the cascades in the Hood River Valley. Winds gusted at crown point up to 77 mph on Friday and are still gusting up to 70 mph today(Monday). However Pressure gradients are still slowly climbing creating some very strong wind ( gusts 50-60) near the gorge.
Micro-climates:

Now this east wind is causing micro-climates, and a very noticeable one is in the Battle Ground/Hockinson area.

To show you this micro-climate, this image shows the temperatures at 12:00 am Monday.

  Notice how the temps outside the red circle are considerably warmer by about 17 degrees in places.

Now What causes this Micro-climate? This is caused my Larch Mt. and Silver Star Mt. Blocking the east wind. You can really well see how the wind is blocked on this WRF-GFS run

Pattern change:

Models are now mostly agreeing on a small pattern change starting tomorrow night due to the upper level high deteriorating. now this pattern change will be more wet than it has been but not a complete washout.  

My forecast:

Timberline Forecast:

Tuesday: Partly sunny, with a high near 34. South southeast wind between 13 and 17 mph, with gusts as high as 29 mph. 

Tuesday Night: A 20 percent chance of snow after 10pm. Mostly cloudy, with a low around 23. South wind 8 to 10 mph becoming west. 

Wednesday: A 20 percent chance of snow. Partly sunny, with a high near 35. West wind between 8 and 10 mph. 

Wednesday Night: Partly cloudy, with a low around 26. West wind between 3 and 10 mph. 

Thursday: Mostly sunny, with a high near 41. 

Thursday Night: Mostly cloudy, with a low around 25. 

Friday: A slight chance of snow. Mostly cloudy, with a high near 38. 

Friday Night: A chance of snow. Mostly cloudy, with a low around 25. 
Saturday: A chance of snow showers. Mostly cloudy, with a high near 34.  

Thanks for reading

-Michael