Winter and Spring in The Forecast

Today was a wonderful late winter/early spring day with temps in the mid-upper 50s around the metro area; a bit warmer than average.  Tomorrow and Tuesday morning winter takes a run at us again, then it’s on to our warmest weather so far this season for later in the week.  The Spring “roller-coaster” is beginning…

For tomorrow we’ve got a very sharp cold front on the coastline at daybreak, heading through the Portland area maybe 10am or so, then east of the Cascades through the afternoon.  When I say “sharp”, I mean snow levels around 6,000′ ahead of it and as low as 1,000′ right behind it in the heaviest precipitation.  This is one of those unusual “anafronts”, which leads to much of the precipitation on the cold side of the front.  These can sometimes lead to unusually low snow levels behind the cold front due to steady, heavy precipitation for a few hours (or maybe just an hour or two tomorrow).  I remember several of these have brought sticking snow to Boring, Sandy, and Corbett when we had expected the snow level to be well above 2,000′.  One was maybe Halloween 1994 or 1995, or maybe it was 1996, but it was definitely Halloween night…  Memory is fading…  That will happen midday to early afternoon tomorrow, not the best timing in early March, but something to keep an eye on.  If you live anywhere east of Gresham, watch for “chunky rain” after 11am or so!

Then a very cold upper-level trough sweeps through the Pacific Northwest tomorrow night and early Thursday morning.  850mb temps look to be around -9 deg C.  That’s cold enough to get sticking snow to sea level at night; however almost all of the precipitation is gone by that time.  Models have been trying to produce a cluster of showers that come south in the late night hours tomorrow night.  The MM5-NAM and WRF-GFS have this idea.  Our RPM (at least at 00z) does not.  Regardless, no models are showing any sort of heavy precipitation, so I don’t see how anyone could get more than an inch, but anyone could see a dusting to sea level tomorrow night and the Tuesday morning commute could see slippery spots.  The good news is that we quickly dry out.  It’ll be melting quickly after sunrise anyway and then it’s on to a mostly sunny Tuesday afternoon with highs in the mid 40s.

 

Beyond Tuesday, nice upper level ridging pops up later Wednesday through Friday.  Take a look at that 500mb chart for Thursday afternoon:

Looks nice doesn’t it?  We NEVER saw this kind of ridging through last March, so this is a big improvement, hopefully a sign of a more reasonable spring to come?  We’ll see.  850mb temps rise up to around +6 to +10.  It’s time to pull out the March Magic Chart!  The warm season must be approaching since I only use these March-September.  It says somewhere into the low-mid 60s with offshore flow.  That would be why we have a 62 & 64 in the forecast.  Hopefully that’s not a warm bias; the 00z GFS is flattening the ridge more rapidly Friday, so 64 might be high.

00z GFS ensemble chart here: 

You can see near or above average temps from Thursday through Sunday, then a bit cooler as a large, cold upper level trough sits in the eastern Pacific.  If you take all 16 days, it appears about “average” to me.

Chief Meteorologist Mark Nelsen

37 Responses to Winter and Spring in The Forecast

  1. B1900 Pilot says:

    Pea sized hail coming down just as the front is passing over. ( I’m in Bethany area of Washington County. ) Pretty impressive for a frontal passage, usually you see hail with thunderstorms behind the front.

  2. pappoose in scappoose says:

    Tower temps should be fun to watch for a day or two.

    http://www.wrh.noaa.gov/pqr/tower_temps/tower_temps.php?&units=F

    • mark says:

      Back-edge of the moisture should cross the metro area in about two hours (2 pm-ish). Too bad the towers info is delayed by at least two hours of so, because they should drop rapidly after the front passes…

    • pappoose in scappoose says:

      Just watched a forecast for a 200ft snow level! Need to get the tree climbing gear ready. Hahaah!

  3. SnowedIn - North Plains says:

    Bring on the anafront.

  4. W7ENK says:

    Sadly, this is the most confident they’ve sounded about snow in about three years…

    http://inws.wrh.noaa.gov/weather/alertinfo/5185524

    Where was this in January, or last January, or the January before???

    Should we believe it this time?

    • W7ENK says:

      One thing I see working against our favor for STICKING snow tonight is yesterday’s warmth. I saw this happen many a time down in Klamath Falls — where one day would be sunny and warm, the next would be snowy — the ground spent all day soaking up the warmth from all that solar energy. Granted, it didn’t go all that deep, but yesterday was one of the warmest days we’ve had so far this year — certainly one of the nicest! I could still feel that energy radiating off things this morning, particularly solid surfaces like brick and asphalt. In the direct sun like yesterday’s, the ambient air temperature might reach 60 degrees (or so), but the temperature of the ground itself (particularly darker surfaces like asphalt) probably topped 90 degrees. It will take more energy from melting snowfall to essentially suck out that heat and cool those surfaces down below freezing than it normally would in the dead of winter, or even had it been cloudy yesterday. So, while the air temperature may drop to 31 with considerable snowfall, the latent heat still remaining in the ground will keep melting anything that falls until it’s completely pulled out, which could take a while. How annoying! So the question now becomes, how long will it take for any remaining latent heat to dissipate, and can that happen before the snowfall ends?

      It would be nice…

    • Sandi (Wilsonville) says:

      With the rain coming in now, wouldn’t that cool things down a bit?

    • o.c.paul says:

      I noticed the high angle of the sun yesterday too. No good for snow.

    • Dave in South Salem (500') says:

      I guess I should be happy we barely saw the sun…

    • W7ENK says:

      Yes, the rain will help cool the ground, but not below freezing.

      High sun angle, and duration — the sun is up for nearly 11-1/2 hours right now. Roughly two weeks from the Equinox!

      FWIW, today is the “Solstitial opposite” of October 7th. Imagine getting snow here on October 7th?

      That’s a term I admittedly made up (YEARS ago) that we should probably include in the Fox 12 Weather Blog Glossary:

      Solstitial Opposite — A comparative date on the opposite side of the Solstice; either one.

      Example: March 5, 2012 |§| October 7, 2012

      March 5 to June 21 (the Summer Solstice) = 108 days.

      June 21 + 108 days = October 7.

      Solar declination (variable δ☉) — or the sun’s angle in the sky in reference to the Equator — is equal, and the sun is above the horizon for approximately the same amount of time on both dates, therefore the sun’s influence (Insolation) on the Earth’s surface at any latitude should be the same on both dates.*

      *Granted, this does not factor in the roughly 6-week (±2) seasonal lag in mean temperatures for any given location.

      I’m sure someone smarter that I can surely invent some formula, an equation or an expression, to derive this more accurately… I suck at math!

    • Karl Bonner says:

      I’d use the term “declination twin” to describe the date on the opposite “side” of the year (spring vs fall) when the sun angle is the same. So March 5 and October 7 are declination twins…

  5. pappoose in scappoose says:

    I’m all in for a inch of snow!

    NATIONAL WEATHER SERVICE PORTLAND OR
    329 AM PST MON MAR 5 2012

    MUCH COLDER AIR WILL ADVECT INTO THE REGION DURING THE EVENING AND OVERNIGHT. BY 10 PM SNOW LEVELS IN THE NORTH WILL BE NEAR THE VALLEY
    FLOOR…BUT THE BIG QUESTION IS HOW MUCH MOISTURE AND SHOWERS WILL THERE BE. THE 06Z NAM AND GFS BOTH SHOW A SHORT WAVE DROPPING DOWN
    THE BACK SIDE OF THE TROUGH OVER NORTHWEST OREGON AND SOUTHWEST WASHINGTON FRONT 06Z TO 12Z. THE MODELS SHOW LIMITED MOISTURE WITH
    THIS SHORTWAVE WHICH COULD PRODUCE A DUSTING TO 1 INCH THE LOWLANDS. MY CONCERN IS THAT THE AIR MASS IS SO COLD THAT IT IS PICKING UP
    CONSIDERABLE MOISTURE OVER THE WATER. THIS CAN BE SEEN IN THE IR IMAGERY WITH A GOOD ORGANIZED BAND OF SHOWERS OFF NORTHERN VANCOUVER
    ISLAND EARLY THIS MORNING. THERE IS ABOUT A 40 PERCENT CHANCE THAT MORE SIGNIFICANT SNOW COULD OCCUR WITH THIS FEATURE…FOR NOW WILL GO
    WITH THE 1 INCH AMOUNTS…WATCH HOW THE SHORTWAVE DEVELOPS THIS EVENING AND BE PREPARED TO MAKE ADJUSTMENTS IF NEEDED.

  6. Kyle says:

    One thing intresting about this storm is not only is it coming from The Bearing Sea but there is VERY little south wind to this system unlike the last one where the S wind was like an Energizer Bunny. It always kept going and going and going and going……………

    Right now it already is 40F here and the storm hasn’t even started with the forecast of snow being pulled lower all day Mark is likely going to have to do a major operation on his 7-cast.

    Is spring coming? NO! At least not for a long shot and this is just the beginning of a weird spring which will only prove the 5 year trend we have been having on weird springs.

  7. Ryan says:

    It’s gonna snow

  8. bgb41 says:

    3/4/2012 Oregon (All) Temperature Summary

    Warmest:
    High:70 at DW7799 Heppner(2103 ft) & AC7WN Hermiston(497 ft)
    Low: 45 at NEWPRT Cape Foul(1024 ft)

    Coldest:
    High:36 at Timberline Lodge(7001 ft)
    Low: 8 at CRAZYMAN FLAT (6100 ft )

    Largest Diurnal Change: 47 degrees
    KLAMATH BASIN NW (64/17 ) (4200 ft )
    CHRISTMAS VALLEY (63/16) (4360 ft)

  9. Karl Bonner says:

    Let the wishcasting begin for a significant snow tomorrow night, followed by UPPER 60s for Thursday and Friday in The Dalles!

  10. pappoose in scappoose says:

    I really like unusually low snow levels for a hour or two!

    • W7ENK says:

      I don’t. They usually only bring “significantly higher accumulations of strong to severe disappointment”. 😦

    • pappoose in scappoose says:

      Usually is the key word here. We must be always on guard for the unusual event!

    • pappoose in scappoose says:

      AREA FORECAST DISCUSSION
      NATIONAL WEATHER SERVICE PORTLAND OR
      825 PM PST SUN MAR 4 2012

      MODELS ARE IN GOOD AGREEMENT IN SHOWING QUITE A COLD AIR MASS TO QUICKLY MOVE THROUGH MON NIGHT AND TUE. 1000-500 MB THICKNESS VALUES
      ON THE ORDER OF THE 516-519 DM ARE DEPICTED BY 12Z TUE…WITH H8 TEMPS BOTTOMING OUT FROM -8 TO -10 DEG C…WHICH SHOULD BE PLENTY
      COLD FOR SNOW TO REACH VALLEY FLOORS. AT ISSUE THOUGH IS HOW MUCH…IF ANY…PRECIPITATION FALLS MON NIGHT INTO TUE. MODELS DO
      DEPICT SOME LOW LEVEL MOISTURE STILL…ESP MON NIGHT WHEN LOW LEVEL FLOW IS STILL OUT OF THE NW. OVER WATER TRAJECTORIES THOUGH ARE ON
      THE SHORT SIDE…BECOMING MORE SO TUE…SO PROBABLY THE BEST CHANCES
      FOR SNOW IN THE LOWLANDS WILL COME LATE MON NIGHT WHEN MOISTURE LOOKS
      BEST AND A VORT MAX/TROUGH AXIS PUSHES THROUGH.

  11. W7ENK says:

    It’s a very confusing time for Mother Nature…

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