Some Snow?

Snapshot Ahh, the good times are back this evening with some good heavy rain showers in spots (right over Steve Pierce's home).  And now we have the possibility of snow to low elevations tomorrow night and Thursday.  I just had the studs taken off my
"snow car", luckily it's a 4 wheel drive that'll do fine in a few inches of snow!  For tonight…more showers.  For tomorrow…more showers.  A nice slug of moisture to our southwest keeps the showers going overnight.  It still looks like the heaviest precipitation will be from the Columbia River south. 

     Then a sharp cold front moves into Northwest Oregon tomorrow afternoon.  This is the leading edge of a very cold maritime polar airmass.  Arctic air is already beginning to spill out of British Columbia between Vancouver Island and the Queen Charlotte Islands.  So we get an upper-level low and a surface low spinning up near Northern Vancouver Island later tomorrow.  These both pass overhead Thursday.  00z models all seem to be in agreement now on the movement.  The surface low comes inland around Astoria as it fills Thursday morning.  It's a really cold airmass!  850mb temps are somewhere around -8 to -9 deg. C.  That's usually cold enough to get snow to sea level if you can get rid of a mixing wind.  We still have a light southerly flow up the Willamette Valley tomorrow evening and Thursday because the low is staying farther north, but it's not exactly a raging south wind.  Heavy precipitation intensity always helps in these situations, or is sometimes the key factor to getting snow to low elevations.  With the westerly flow, the areas west of I-5 may have lighter precip.  In general I don't see a ton of heavy showers.  The steadiest precipitation should be in that 4am-10am time period Thursday…then we dry out in the afternoon (and warm up of course). 

Put these all together and this is what I get:  I think it'll be tough to get significant snow (>1") here in the lowest elevations of Portland, but all of us should see at least a dusting in the morning Thursday.  I'd say 1-3"+ snow is a done deal at/above 1,000' anywhere in our region, and anywhere in SW Washington north of Vancouver.  The Coast is a big question mark…there's no reason we shouldn't be able to get snow to the beaches, unless the southerly breezy from Astoria south kills it for you folks.  We have 24 more hours to keep digesting information for this little event too.

Beyond Thursday, pretty quiet.  A new upper level trough develops offshore Saturday through Monday.  There are some deep surface lows that linger way out over the Pacific, but they aren't really going anywhere in a hurry, so they aren't a high wind threat for us…Mark Nelsen

13 Responses to Some Snow?

  1. Sandi (Wilsonville) says:

    Heavy rain shower going through. I can see blue sky off in the distance, but wind picked up and rain really coming down now.

  2. William Johnson says:

    here in Astoria 11:20 am 46 degrees A heavy Rain shower band from megler bridge all the way south as far as i can see winds are gusting quite well. Bill from Astoria oregon

  3. Tetraforce (2009-2010 The 1949-50 snow year equailvent) says:

    Do you have any weather equipment at all? William?

  4. Mike from Orchards says:

    Yah, the 12Z run does seem to shut down the windstorm excitement but it still bears watching….
    0.62″ rain here yesterday…..greatest 1 day total since Jan 1st. The mountains are getting much needed snow.
    46.2F currently…few showers around….0.03″ rain since midnight

  5. stevied (North Portland) says:

    Low tomorrow morning looks a tad further north than shown last night and also a tad warmer for PDX. Also, seems to be a bit less precip than shown last night as well. All that seems to point toward a 500-1000ft snow level for right around PDX.
    http://www.atmos.washington.edu/mm5rt/data/2009022512/images_d2/slp.30.0000.gif

  6. Andrew Johnson (Silverton) says:

    I think Astoria stands a decent shot of at least seeing some flakes. Currently light rain and 46 here in the mid-valley.

  7. Ian *Longview* says:

    so should longview expect anything significant? i know there have been several times this winter we have been bullseyed, and get nothing much while everyone else got good snow.
    is mark referring to the “rest of SW WA” as the hilly areas around kelso and longview, or the valley floor here in longview as well?

  8. Tetraforce (2009-2010 The 1949-50 snow year equailvent) says:

    47.3F and 0.75 of rain up from 0.47. I’ll erase my gauge now.

  9. HIO Phil (Punxsutawney) elevation 189' says:

    Rob, the gradients look a bit too easterly here for good winds. An impressive low though as shown on your links and right on the 130 line. Really interesting place for a wintertime low to form and then come north. I had to look at your first link twice to realize it’s placement.
    That’s a pretty dead zone down there most of the year, but the subtropical jet has been active down that way in the last week.
    Oh, we can’t have a windstorm until Sunday as I predicted last Sept that we wouldn’t have any major south windstorms this winter through February, and I don’t really think we have have.

  10. Rob "Wrath" - Elevation 300' -Far S.E. Portland- says:

    The Wind cast model has a swath of hurricane force/high winds along and just offshore the southern Oregon/northern California coast. IF the low were to get inside of 130W toward 128W that could pull high winds inland….
    Definitely worth keeping an eye on.
    Good night all.

  11. Rob "Wrath" - Elevation 300' -Far S.E. Portland- says:

    Okay, I know all of the talk and hoopla tonight is about possible snow, but I see something on the 00z WRF-GFS that REALLY catches my eye and what I have to say IMO is a serious major wind storm threat? Quite amazing setup *potentially*
    Okay the area of interest is projected to develop Friday 28th 4:00 PM near roughly 134.3 W, 29.7 N.
    http://www.atmos.washington.edu/mm5rt/data/2009022500/images_d1/slp.72.0000.gif
    Moving ahead….
    12 hours later Saturday 4:00 AM the low is now 994mb and rapidly developing. It is now near 130.9 W, 36 N.
    http://www.atmos.washington.edu/mm5rt/data/2009022500/images_d1/slp.84.0000.gif
    12 hours later Saturday 4:00 PM the low is deepening to 975mb near 130.4 W, 44 N.
    http://www.atmos.washington.edu/mm5rt/data/2009022500/images_d1/slp.96.0000.gif
    12 hours later Sunday 4:00 AM the low is reaching its peak around 965mb near 130.4 W, 46.6 N.
    http://www.atmos.washington.edu/mm5rt/data/2009022500/images_d1/slp.108.0000.gif
    *My Thoughts*
    The Gulf of Alaska trough digs very favorably so any systems that develop are likely to rough the trough well south of 40 N. This low is moving very quickly and deepening rapidly. It is shown to hug the 130 W line remaining largely out of harms way, but this needs to be watched extremely closely. Its origins are practically down near the South Pacific Ocean around 15 N, so it will be a warm core low which may make it more dangerous.
    Any thoughts?

  12. Jon 500' stevenson, Wa (the gorge) says:

    anyone have any thoughts for the gorge? more or less snow?

  13. Marc (NE Orchards) says:

    Love this winter

Some Snow?

Snapshot Ahh, the good times are back this evening with some good heavy rain showers in spots (right over Steve Pierce's home).  And now we have the possibility of snow to low elevations tomorrow night and Thursday.  I just had the studs taken off my
"snow car", luckily it's a 4 wheel drive that'll do fine in a few inches of snow!  For tonight…more showers.  For tomorrow…more showers.  A nice slug of moisture to our southwest keeps the showers going overnight.  It still looks like the heaviest precipitation will be from the Columbia River south. 

     Then a sharp cold front moves into Northwest Oregon tomorrow afternoon.  This is the leading edge of a very cold maritime polar airmass.  Arctic air is already beginning to spill out of British Columbia between Vancouver Island and the Queen Charlotte Islands.  So we get an upper-level low and a surface low spinning up near Northern Vancouver Island later tomorrow.  These both pass overhead Thursday.  00z models all seem to be in agreement now on the movement.  The surface low comes inland around Astoria as it fills Thursday morning.  It's a really cold airmass!  850mb temps are somewhere around -8 to -9 deg. C.  That's usually cold enough to get snow to sea level if you can get rid of a mixing wind.  We still have a light southerly flow up the Willamette Valley tomorrow evening and Thursday because the low is staying farther north, but it's not exactly a raging south wind.  Heavy precipitation intensity always helps in these situations, or is sometimes the key factor to getting snow to low elevations.  With the westerly flow, the areas west of I-5 may have lighter precip.  In general I don't see a ton of heavy showers.  The steadiest precipitation should be in that 4am-10am time period Thursday…then we dry out in the afternoon (and warm up of course). 

Put these all together and this is what I get:  I think it'll be tough to get significant snow (>1") here in the lowest elevations of Portland, but all of us should see at least a dusting in the morning Thursday.  I'd say 1-3"+ snow is a done deal at/above 1,000' anywhere in our region, and anywhere in SW Washington north of Vancouver.  The Coast is a big question mark…there's no reason we shouldn't be able to get snow to the beaches, unless the southerly breezy from Astoria south kills it for you folks.  We have 24 more hours to keep digesting information for this little event too.

Beyond Thursday, pretty quiet.  A new upper level trough develops offshore Saturday through Monday.  There are some deep surface lows that linger way out over the Pacific, but they aren't really going anywhere in a hurry, so they aren't a high wind threat for us…Mark Nelsen

13 Responses to Some Snow?

  1. Sandi (Wilsonville) says:

    Heavy rain shower going through. I can see blue sky off in the distance, but wind picked up and rain really coming down now.

  2. William Johnson says:

    no i dont tetraforce wished i did so i knew everything here from rainfall to wind speeds to temps. bill

  3. Tetraforce (2009-2010 The 1949-50 snow year equailvent) says:

    Do you have any weather equipment at all? William?

  4. William Johnson says:

    thanks tetraforce
    So far what we got out here in Astoria is off and on heavy showers the wind picked up for a while was a lil gusty now just cloudy and breezy when i got up at 6 am it was 48 degrees now its dropped to 45 acording to fox 12s desktop weather bug even the weather channel desk top weatherbug is reading the same temp so i agree it seems a lil colder. bill

  5. Rob "Wrath" - Elevation 300' -Far S.E. Portland- says:

    12z WRF-GFS still shows the low developing unusually far to our south. It is also now shown to move inside of 130 W. However it only deepens to near 982mb and it stops its momentum about parallel with Astoria before moving off to the west as it dumbbells around another area of low pressure.
    *My thoughts*
    The mere fact models are becoming to consistently show the low developing down near the South Pacific is extraordinary and the fact models continue to show a due N-S trajectory like this is reason to keep a close eye on things. Also a scenario of the low rotating around another low means a secondary low could shoot around the base of the trough carved out aligning it much more favorably inside 128 W and on a conducive SSW-NNE trajectory.
    We’ll just have to wait and see how this all plays out over the next 24-36 hours.

  6. Jethro / South of Canby says:

    12z NCEP-GFS still showing good snow possibilities for tomorrow: http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/12/images/gfs_ten_024l.gif
    But it’s showing Saturday’s low weaker and farther offshore: http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/12/images/gfs_ten_090l.gif

  7. William Johnson says:

    Whats the probability that Astoria will see snow?

  8. Tetraforce (2009-2010 The 1949-50 snow year equailvent) says:

    Guhood night.

  9. HIO Phil (Punxsutawney) elevation 189' says:

    Rob, the gradients look a bit too easterly here for good winds. An impressive low though as shown on your links and right on the 130 line. Really interesting place for a wintertime low to form and then come north. I had to look at your first link twice to realize it’s placement.
    That’s a pretty dead zone down there most of the year, but the subtropical jet has been active down that way in the last week.
    Oh, we can’t have a windstorm until Sunday as I predicted last Sept that we wouldn’t have any major south windstorms this winter through February, and I don’t really think we have have.

  10. Mike from Orchards says:

    Snow would be fun, but the low forecasted to meander up/off the coast on the 28th might be something we can have fun with, too. Earlier model runs showed it wandering quite a bit but the latest (00Z) run shows a little “less” meandering than previously. This “baby” needs to get inside of 130° W and travel NNE, although so far, this appears to not be the case.
    http://www.atmos.washington.edu/mm5rt/data/2009022500/images_d2/slp.111.0000.gif
    46.9F…….0.60″ rain so far today (which is more here for a 24hr period then any day the first week of January)

  11. Rob "Wrath" - Elevation 300' -Far S.E. Portland- says:

    The Gulf of Alaska trough digs very favorably so any systems that develop are likely to round* the trough well south of 40 N.

  12. Steve Pierce (Vancouver, WA.) says:

    SPECIAL WEATHER STATEMENT
    NATIONAL WEATHER SERVICE PORTLAND OR
    945 PM PST TUE FEB 24 2009
    …SNOW LEVELS TO PLUMMET LATE WEDNESDAY NIGHT AND THURSDAY…
    SNOW LEVELS WILL FALL RAPIDLY LATE WEDNESDAY NIGHT AND THURSDAY
    MORNING AS A COLD UPPER LEVEL ORIGINATING OVER BRITISH COLUMBIA
    DROPS SOUTH DOWN THE WASHINGTON COAST. BASED ON THE EXPECTED TRACK
    OF THE LOW AND ITS SHORT OVER WATER TRAJECTORY THIS SYSTEM HAS THE
    POTENTIAL TO BRING LOW ELEVATION SNOW TO AREAS OF SOUTHWEST
    WASHINGTON AND NORTHWEST OREGON.
    THE CORE OF THE UPPER LEVEL LOW WILL SWING INLAND OVER THE
    SOUTHWEST WASHINGTON THURSDAY MORNING BRINGING THE COLDEST POOL
    OF AIR ALOFT OVER THE SOUTHWEST WASHINGTON AND NORTHWEST OREGON
    COAST AND COAST RANGE. THIS COLD AIR ALOFT WILL PRODUCE A VERY
    UNSTABLE AIRMASS STRENGTHENING SHOWERS AND GIVING THESE SECTIONS
    OF THE COAST THE BEST CHANCES FOR SIGNIFICANT SNOW ACCUMULATIONS
    AT OR NEAR SEA LEVEL. FURTHER SOUTH ALONG THE CENTRAL OREGON COAST
    PRECIPITATION WILL MORE LIKELY BE A MIX OF RAIN AND SNOW WITH
    ACCUMULATIONS LIMITED TO ABOVE A SNOW LEVEL OF 50O TO 1000 FEET.
    FURTHER INLAND SNOW LEVELS BETWEEN 2500 FT NORTH AND 3500 FT
    SOUTH ON WEDNESDAY WILL DROP TO 1000 OR 2000 FT WEDNESDAY NIGHT.
    AS THE LOW SWINGS INLAND THURSDAY MORNING THE COLDEST AIR AND
    LOWEST ELEVATIONS SNOW SHOWERS WILL ALSO SPREAD INLAND OVER
    SOUTHWEST WASHINGTON…THE WESTERN COLUMBIA RIVER GORGE AND HOOD
    RIVER VALLEY.
    THE VANCOUVER AND PORTLAND METRO AREAS WILL BE ON THE SOUTHERN
    EXTENT OF THE LOW LEVEL SNOW POTENTIAL AND SHOULD SEE MOST
    ACCUMULATIONS CONFINED TO HILLS ABOVE 500 FT. SNOW LEVELS AROUND
    1000 FT WILL SPREAD FURTHER SOUTH LATER IN THE DAY THURSDAY
    DROPPING TO AROUND 500 FT THURSDAY NIGHT. THE SHOWERS HOWEVER WILL
    TAPER OFF RAPIDLY ONCE THE UPPER LOW CROSSES EAST OF THE CASCADES
    LATE THURSDAY AFTERNOON TO BE REPLACED BY A BUILDING UPPER LEVEL
    RIDGE THURSDAY NIGHT…THEREFORE ANY ACCUMULATIONS IN THE LOWLANDS
    OF THE CENTRAL AND SOUTHERN WILLAMETTE VALLEY SHOULD BE MINIMAL.

  13. kcteach says:

    Problem for sticking snow is that the temp is in the 40’s for the 24 hours prior to the possible start of the snowflakes. Even though it shows the possibility of >.4, the ground may be too warm UNLESS the rate of precip is high enough. Also, precip shows to shut off as temp drops. Not as smart as the rest of you, but that’s what my untrained eyes see

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