Mallow Posted February 22, 2011 Share Posted February 22, 2011 This is a very interesting late-season event. For Portland, most of the snow is falling with onshore flow. That is very uncommon. The reason it's progged to work out this time is that the very cold airmass in southern BC (north of the low) will be continuously and vigorously pulled over the ocean and around to the south side of the slow-moving low. This can be illustrated with the following three images, 24 hours apart: http://www.atmos.washington.edu/mm5rt/data/2011022200/load.cgi?images_d2/slp.30.0000.gif http://www.atmos.washington.edu/mm5rt/data/2011022200/load.cgi?images_d2/slp.54.0000.gif http://www.atmos.washington.edu/mm5rt/data/2011022200/load.cgi?images_d2/slp.78.0000.gif Notice 925mb temperatures are generally forecast to be near or below about -2C. 850mb temperatures are expected to drop below -8C Wednesday evening and remain there: http://www.atmos.washington.edu/~ovens/loops/wxloop.cgi?mm5d2_850t+2011022200//84/3 Temperatures at 500mb are very cold starting Wed afternoon, too, getting down to around -40C by Thursday: http://www.atmos.washington.edu/~ovens/loops/wxloop.cgi?mm5d2_500t+2011022200//84/3 So with those kinds of temperatures, surface temperatures MUST be below freezing, right? Not according to the WRF. The WRF says afternoon sunshine will push temperatures above 40F on Wednesday and Thursday afternoons (even mid 40s Thursday): http://www.atmos.washington.edu/mm5rt/data/2011022200/images_d3/wa_tsfc.48.0000.gif http://www.atmos.washington.edu/mm5rt/data/2011022200/images_d3/wa_tsfc.69.0000.gif You can imagine the kinds of lapse rates that are forecast. But why imagine? Check out this skew-T: http://www.atmos.washington.edu/mm5rt/rt/sound_gen/scripts/tmp_images/sounding.90159069.gif You'll note that the wet-bulb supports snow to the surface, even with the warm temperatures. So any precip would be snow regardless of the modeled highs. The moist-adiabatic lapse rate is almost as steep as the dry-adiabatic lapse rate once you get above the LFC in this case, but there is some spotty CAPE: http://www.atmos.washington.edu/~ovens/loops/wxloop.cgi?mm5d2_mcape+2011022200//84/3 A few of my own thoughts... - Showers will be too numerous on Wed and Thu to allow for long enough sunbreaks for highs to poke up to the 40s - Showers will be convective in nature, with organized bands of showers associated with weak vortmaxes rotating in from time to time - Steady and/or moderate-heavy showers will all be snow from Wednesday on. Light showers/drizzle could be rain Wednesday afternoon. - Plenty of melting is possible Wednesday afternoon if there's any accumulation in the morning. Likewise, but to a lesser extent, on Thursday afternoon. Starting Thursday evening, whatever falls and whatever is still left on the ground will be frozen and preserved quite well through Friday and probably Saturday. - Breakdown of periods of snow and possible amounts at the lowest elevations: ... - Tuesday night and Wednesday morning (T - 2") ... - Wednesday during the day (T - 1") ... - Wednesday night and Thursday morning (2 - 3") ... - Thursday during the day (1 - 2") ... - Thursday night and Friday morning (T - 2") ... - Friday during the day (T - 1") - Most likely totals: 3 - 5" Link to comment Share on other sites More sharing options...
icebreaker5221 Posted February 22, 2011 Share Posted February 22, 2011 I hope you get crushed Mallow! You deserve it, especially during a Nina Link to comment Share on other sites More sharing options...
tacoman25 Posted February 22, 2011 Share Posted February 22, 2011 Right now, I'd say Portland's best period for accumulating snow will be 3 am to 3 pm Thursday. For Seattle, the best period will probably be 3 pm Wednesday to 3 am Thursday. Portland area: 3-6" total accumulations (5-10" above 500') Seattle area: 4-8" total accumulations (6-12" above 500') Easily the best region-wide snowstorm since Dec 2008. Link to comment Share on other sites More sharing options...
Mallow Posted February 22, 2011 Author Share Posted February 22, 2011 Just to get things kicked off, we had a brief graupel shower just now. Didn't even look that impressive on radar: http://radblast-mi.wunderground.com/cgi-bin/radar/WUNIDS_map?station=RTX&brand=wui&num=12&delay=15&type=N0R&frame=0&scale=0.396&noclutter=0&t=1254093153&lat=45.4387&lon=-122.5828&label=Mallow%27s+Apartment&showstorms=0&map.x=400&map.y=240¢erx=374¢ery=191&transx=-26&transy=-49&showlabels=1&severe=0&rainsnow=0&lightning=0&smooth=0 Link to comment Share on other sites More sharing options...
Mallow Posted February 23, 2011 Author Share Posted February 23, 2011 I'm ready: URGENT - WINTER WEATHER MESSAGENATIONAL WEATHER SERVICE PORTLAND OR 327 PM PST TUE FEB 22 2011 ...SIGNIFICANT LOW ELEVATION SNOWFALL EXPECTED LATE WEDNESDAY THROUGH FRIDAY MORNING... .UNSEASONABLY COLD WEATHER FOR LATE FEBRUARY IS CAUSING THE SNOW LEVEL TO FALL TO THE LOWER ELEVATIONS OF THE CASCADE FOOTHILLS AND COAST RANGE OF SOUTHWEST WASHINGTON AND NORTHWEST OREGON TODAY. AS MUCH COLDER AIR MOVES INTO THE REGION WEDNESDAY AND THURSDAY...ACCUMULATING SNOW WILL BECOME LIKELY DOWN TO THE BEACHES AND VALLEY FLOOR LATER WEDNESDAY THROUGH THURSDAY. BY THE END OF THE WEEK...SNOWFALL ACCUMULATIONS IN THE CASCADES WILL BE MEASURED IN FEET. ORZ001-005-006-009-WAZ021>023-039-231400- /O.UPG.KPQR.WS.A.0003.110223T2000Z-110225T0000Z/ /O.EXB.KPQR.WS.W.0003.110223T1400Z-110225T0600Z/ NORTH OREGON COAST-LOWER COLUMBIA-GREATER PORTLAND METRO AREA- WESTERN COLUMBIA RIVER GORGE-SOUTH WASHINGTON COAST-I- 5 CORRIDOR IN COWLITZ COUNTY-GREATER VANCOUVER AREA- INCLUDING THE CITIES OF...ASTORIA...CANNON BEACH...TILLAMOOK... NETARTS...PACIFIC CITY...ST. HELENS...HILLSBORO...PORTLAND... OREGON CITY...GRESHAM...TROUTDALE...HOOD RIVER...CASCADE LOCKS... MULTNOMAH FALLS...CORBETT...RAYMOND...LONG BEACH... CAPE DISAPPOINTMENT...LONGVIEW...KELSO...STEVENSON...SKAMANIA... VANCOUVER...BATTLE GROUND...CAMAS...WASHOUGAL 327 PM PST TUE FEB 22 2011 ...WINTER STORM WARNING IN EFFECT FROM 6 AM WEDNESDAY TO 10 PM PST THURSDAY FOR THE COAST...COLUMBIA RIVER GORGE AND LOWLANDS OF SOUTHWEST WASHINGTON AND NORTHWEST OREGON...INCLUDING THE PORTLAND AND VANCOUVER METRO AREA... THE NATIONAL WEATHER SERVICE IN PORTLAND HAS ISSUED A WINTER STORM WARNING FOR SNOW...WHICH IS IN EFFECT FROM 6 AM WEDNESDAY TO 10 PM PST THURSDAY. THIS REPLACES THE WINTER STORM WATCH THAT WAS PREVIOUSLY IN EFFECT. * TIMING...SOME LIGHT ACCUMULATING SNOW WILL BE POSSIBLE IN THE HIGHER ELEVATIONS EARLY TOMORROW MORNING...WITH HEAVIER SNOW BEGINNING LATER WEDNESDAY AND CONTINUING INTO THURSDAY. * ACCUMULATION/SNOW LEVELS...A TRACE UP TO 3 INCHES OF SNOW ARE POSSIBLE EARLY WEDNESDAY MORNING IN THE HIGHER TERRAIN. TWO TO 4 INCHES ARE EXPECTED LATER WEDNESDAY THROUGH THURSDAY RIGHT DOWN TO THE VALLEY FLOOR. GENERAL STORM TOTALS OF 2 TO 5 INCHES ARE EXPECTED FOR THE COAST AND LOWLANDS BY THURSDAY EVENING. SOME LOCAL ACCUMULATIONS OF 6 TO 10 INCHES IS POSSIBLE MAINLY IN THE HIGHER HILLS...ESPECIALLY WHERE THE VALLEY MEETS THE CASCADE FOOTHILLS AND IN THE GORGE NEAR CASCADE LOCKS. * IMPACTS...ROADWAYS MAY BECOME ICY AND SNOW COVERED... RESULTING IN SLICK DRIVING CONDITIONS. THIS MAY SIGNIFICANTLY IMPACT THE COMMUTE BOTH WEDNESDAY AND THURSDAY. PRECAUTIONARY/PREPAREDNESS ACTIONS... A WINTER STORM WARNING FOR HEAVY SNOW MEANS SEVERE WINTER WEATHER CONDITIONS ARE EXPECTED OR OCCURRING. SIGNIFICANT AMOUNTS OF SNOW ARE FORECAST THAT WILL MAKE TRAVEL DANGEROUS. ONLY TRAVEL IN AN EMERGENCY. IF YOU MUST TRAVEL...KEEP AN EXTRA FLASHLIGHT... FOOD...AND WATER IN YOUR VEHICLE IN CASE OF AN EMERGENCY. && $$ Link to comment Share on other sites More sharing options...
ksstormhunter Posted February 23, 2011 Share Posted February 23, 2011 We are tracking 2-4" for the Ft. Lewis areas, looking on the high side on this though, 4" is a good possiblity for us here. Link to comment Share on other sites More sharing options...
LizardMafia Posted February 23, 2011 Share Posted February 23, 2011 I'm happy for you guys, I know it's been quite the disappointment of a winter for snowfall west of the cascades this year.. Link to comment Share on other sites More sharing options...
tacoman25 Posted February 23, 2011 Share Posted February 23, 2011 Right now, I'd say Portland's best period for accumulating snow will be 3 am to 3 pm Thursday. For Seattle, the best period will probably be 3 pm Wednesday to 3 am Thursday. Portland area: 3-6" total accumulations (5-10" above 500') Seattle area: 4-8" total accumulations (6-12" above 500') Easily the best region-wide snowstorm since Dec 2008. Still like this call, just push everything back about 3-4 hours. Link to comment Share on other sites More sharing options...
Mallow Posted February 24, 2011 Author Share Posted February 24, 2011 So far, no more than a dusting. But showers tonight have been all snow. Just a degree or two of cooling and it will stick to everything, which should be easily achievable. How many showers can we get? In the meantime, looks like a couple decent cells (thundersnow?) arriving on the coast right now. Link to comment Share on other sites More sharing options...
Mallow Posted February 24, 2011 Author Share Posted February 24, 2011 I'm up to about a half inch, but prospects for much more aren't too great. Link to comment Share on other sites More sharing options...
Mallow Posted February 24, 2011 Author Share Posted February 24, 2011 Dumping right now. We're up to about 0.8" on the cars, now. Big agglomerations of dendrites and needles. Link to comment Share on other sites More sharing options...
Mallow Posted February 24, 2011 Author Share Posted February 24, 2011 I'm basically up to an inch total after this shower is done. Link to comment Share on other sites More sharing options...
Mallow Posted February 28, 2011 Author Share Posted February 28, 2011 Want snowy? I got your snowy right here: These webcams should be impressive tomorrow morning... Timberline Lodge: http://www.fsvisimages.com/fstemplate.aspx?site=moho2 Government Camp: http://www.tripcheck.com/roadcams/cams/GovernmentCamp_pid624.jpg?0.4167959129906057 Link to comment Share on other sites More sharing options...
Mallow Posted February 28, 2011 Author Share Posted February 28, 2011 Also, although we missed out on most of the snow, Portland did set several records. The 34F on 2/25 was a record lowest high temperature for the date. The 33F on 2/26 was, likewise. The 18F on 2/26 was not only a record low for the date, but the latest 18F or lower temperature on record. To top it off, we had 3 highs in the 30s and 3 lows in the 10s and 20s in a row. That's a very impressive feat for PDX for so late in the winter. The high of 34F on 2/25 came with complete wall-to-wall sunshine (thanks to very cold, steady east winds out of the Gorge), and I don't believe there is any comparable day so late in the season. Link to comment Share on other sites More sharing options...
Mallow Posted February 28, 2011 Author Share Posted February 28, 2011 These webcams should be impressive tomorrow morning... Timberline Lodge: http://www.fsvisimages.com/fstemplate.aspx?site=moho2 Government Camp: http://www.tripcheck.com/roadcams/cams/GovernmentCamp_pid624.jpg?0.4167959129906057 Bump. Link to comment Share on other sites More sharing options...
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