Snowstorm in rockies tonight and friday

[PTPatrick]

Okay I am new to the Denver area. I have been looking at the last few forecast and at this point the NWS is saying that the snow levels will be down to 6000 ft late friday. I am aware that at high elevations snow does not recquire the 540 thickness line, in fact, during this storm, the line is supposed to be in canada. The GFS is actually saying that on friday afternoon to saturday morning there could be prolonged upslope...which if GFS is right could mean up to 2 ft of snow in higher elevations in and east of the divide and 1-2 ft in the foot hills. Now the foothills are 6000-8000 ft. I guess, what I am trying to figure out is how they determine the snow levels. I mean I was in the mountains on this past weekend and it was snowing(quite heavily) at 40 degrees. The forecast in denver for saturday night is 38...so what are the chances that snow levels can drop to 5280 ft?
I need to some info from folks that understand snow levels...seeing as I come from below sea level

Here are some excerpts from the Denver/boulder disco:

LONG TERM DISCUSSION...GENERAL AGREEMENT ON THE UPSTREAM SYSTEM BUT
MANY DILEMMAS IN THE DETAILS. JET STREAK IS SCREAMING ACROSS BRITISH
COLUMBIA AND APPEARS TO BE COMING QUICKER THAN PREVIOUSLY EXPECTED.
THIS IS REFLECTED IN BOTH NAM AND GFS...BUT THEY DO DIFFERENT
THINGS. BOTH HAVE A LEADING WAVE ASSOCIATED WITH THE BC JET STREAK
WITH A TRAILING WAVE ABOUT 24 HOURS LATER...THIS HAS BEEN SHOWN FOR
A LONG TIME. BOTH ARE MORE INTENSE WITH THE JET WHICH IS OBVIOUSLY
GOOD. NAM PUTS THE EMPHASIS ON THE FIRST JET STREAK BRINGING STRONG
LIFT OVER THU NIGHT INTO FRI...DEVELOPING A DEEP LOW EAST OF US WITH
DOWNSLOPE WINDS. SO THIS SOLUTION IS FASTER AND COLDER BUT WITH A
LIMITED PERIOD OF PRECIPITATION EVERYWHERE. 12Z GFS ON THE OTHER
HAND IS AT LEAST 12 HOURS SLOWER WITH THE FIRST JET STREAK AND NOT
AS SHARP RESULTING IN MORE COLD AIR DUMPING INTO THE SECOND PART OF
THE SYSTEM AND BETTER DEVELOPMENT WITH THAT. THIS PRODUCES A SLOWER
NET MOVEMENT OF THE TROUGH...AND ALLOW FOR BOTH A LONGER PERIOD OF
PRECIPITATION AND SOME UPSLOPE ALONG THE FRONT RANGE. IN FACT...GFS
PRODUCES TWO FEET OF SNOW ON THE DIVIDE AND 10-20 INCHES OF SNOW IN
THE FOOTHILLS OF BOULDER AND LARIMER COUNTIES. LOTS OF TREPIDATION
ABOUT EXPECTING THE UPSLOPE...PLUS WARM AIR AND GROUND...BUT THIS
NEEDS TO BE WATCHED. GIVEN THE PROGRESSION OF THE JET STREAK ON THE
WATER VAPOR PICTURES...I TEND TO BUY THE NAM ON THE SPEED AND
INTESITY OF THE FIRST PART...BUT THERE WILL BE A STRONG JET
PERSISTING UPSTREAM OF THAT AS WELL. SO I WILL COMPROMISE A BIT AND
PUT UP A WINTER STORM WATCH FOR HIGH MOUNTAINS AND EASTERN
FOOTHILLS. TIMING OF THIS IS A COMPROMISE AS WELL...BUT WILL HIT THE
MOST LIKELY PERIOD. ONE CONSENSUS IS A BIT COOLER THAN WE HAVE
FORECAST...SO WILL INTRODUCE A SNOW LEVEL DOWN TO AROUND 6000 FEET
SATURDAY MORNING. NAM SOLUTION IS MARGINAL FOR A WATCH IN THE HIGH
MOUNTAINS...GFS WOULD REQUIRE ONE FOR THE FOOTHILLS AND POSSIBLY
DOUGLAS COUNTY AND NORTH/MIDDLE PARKS.

12-24 HOUR DISCREPANCY IN THE CLEARING/DRYING AS WELL...THIS IS
ALREADY COMPROMISED AND WILL LEAVE ALONE. DROPPED TEMPS SUN A BIT.
FOR MON THROUGH WED...PREFER A FLATTER FLOW WHICH WILL PROBABLY BE
DRY...BUT LOW MOUNTAIN POPS APPROPRIATE.


ANd the 54 hr GFS:
http://www.nco.ncep.noaa.gov/pmb/nwprod ... p_060m.gif

[bob rulz]

I wouldn't be too surprised if snow fell in Denver under those conditions. And are you sure it was only 40 degrees when the snow fell? I guess it's possible, but it's rare. I think it could have something to do with the high elevation...I think that has something to do with at what temperatures snow can fall. Also, the higher the temperature it is when it snows, the bigger the snowflakes usually are, and it can still snow pretty hard. However, it wouldn't be accumulating at that temperature, but it could still be falling. 40 degrees seems a little high, though.

Anyway, don't be surprised if you see snow falling in Denver, but don't put any bets on it.

However, I don't know anything about how they determine snow levels. Perhaps someone with more knowledge about this could help you with that.

[PTPatrick]

Yeah...I am fairly certain that the temp was around 40... When i first noticed the flakes my car thermometer was around 42, then it dropped to 40. Stayed there as the snow was falling for the most part, toward the end 15 min later, dropped to 38. I can only say that snow was melting as it hit the ground...the only place it was accumulating was on the glacier I was hiking around. Nor did it really feel that cold. Definately didnt feel like 32 outside. I was probably near 13000 ft, so yeah, that would make a big difference. I have heard that at that elevation the snow literally drops the temp as it falls. I have heard that flakes have fallen at around 45, but the temp rapidly dropped(like in 15 min, from 45 to mid 30's.