Area forecast discussion 
National Weather Service Denver/Boulder Colorado 
954 am MST sun Nov 23 2014 

issued at 931 am MST sun Nov 23 2014 

Not much snow falling in the high country right now. The north- 
northwesterly low level winds on the plains are beginning to pick 
up right now. Wind forecast in the gfe grids looks on track. Will 
make a few adjustments to sky and mountain probability of precipitation and blowing snow 
areas too. Nothing huge. However...will kill the highlights in 
north and Middle Park...and even if snow becomes likely again... 
highlight criteria amounts are not likely. 


Short term...(today through tonight ) 
issued at 359 am MST sun Nov 23 2014 

Strongest wave of moisture and energy is moving across the 
forecast area early this morning. There is a secondary wave noted 
in far northwest Colorado/northeast Utah/southwest Wyoming which 
will reach the forecast area later this morning. In between... 
there is slight drying so will see a temporary decrease in snow 
intensity across the mountains early this morning. On the 
plains...precipitation was blossoming on the Palmer Divide area 
and this area should continue to affect mainly areas south and 
east of Denver through early morning. There may be some 
redevelopment behind the main feature as large scale lift is still 
seen in the q-g fields this morning...but overall latest profiler 
data shows winds a slight westerly component just off the deck 
which would limit any precipitation redevelopment from Denver north. 
Could see a couple quick inches of snow accumulation due to 
intensity of precipitation on the Palmer Divide area...mainly above 5500 
feet where temperatures are cold enough. 

Otherwise...the precipitation on the plains will likely come to an 
end by middle morning as flow turns more north/northwest and some 
drying occurs behind first wave. Windy conditions will develop 
most areas and remain in place through the afternoon. With some 
sunshine returning and steep lapse rates...should see isolated 
showers redevelop this afternoon...mainly snow due to relatively 
low wet bulb zero heights. Again these would favor the Palmer 
Divide area. 

Mountain locations would also see a kick up of snow intensity with 
more of a convective scenario getting underway this afternoon. 
Those are expected to decrease in intensity this evening then as 
airmass stabilizes...only to have more widespread snow redevelop 
before daybreak Monday as another wave moves into the area in 
northwest flow aloft. Heaviest snow with this event occurred in 
the early morning hours...but impacts will remain in place through 
today and tonight and heavier snow expected again tomorrow so will 
leave warnings for the mountains and advisories in place for the 
High Mountain valleys. Generally look for another 2-4 inches 
today and another 2-4 tonight on average above 9000 feet. 

Finally...should see the wind increase again later tonight as 
mountain top stability profile becomes more favorable but still 
marginal with high country snow. The strongest winds with gusts 
in the 55-65 miles per hour range will remain in the higher elevations but 
areas right next to the foothills could see a few gusts into the 
30-50 miles per hour range. Surface gradients are a little weak so that 
should help the stronger winds stay up high. 

Long term...(monday through saturday) 
issued at 359 am MST sun Nov 23 2014 

Northwesterly flow aloft will remain over the area on Monday as weak 
disturbances embedded in the flow move quickly across. Moisture 
depth will improve in the mountains with favorable lapse rates and 
orographic component so should see periods of MDT to heavy snow through 
the day with considerable blowing snow. At lower elevations steep 
lapse rates will combine with abundant middle level moisture and passage 
of disturbance in the afternoon to allow for at least a slight chance of 
-shsn over northestern Colorado. Gusty north-northwest winds will continue as well. Highs 
temperatures will be a few degrees colder as readings stay in the upper 
30s to near 40. There could be a brief period of stronger winds 
in and near the foothills Monday morning which may get close to high 
wind criteria in the typical windy spots. 

By Monday night moisture will begin to decrease in the mountains with lapse 
rates begin to stabilize thus snowfall should begin to decrease 
however it will remain windy with areas of blowing snow. Although a 
mountain top stable layer will be present component along winds are only 
forecast to be in the 35 to 40 knots range so threat of high winds looks 
low at this time. On Tuesday moisture will increase once again in the 
mountains in northwesterly flow however lapse rates will be poor so additional 
snowfall will be on the light side. Once again will see areas of 
blowing snow. At lower elevations it will be dry with gusty west-northwest 
winds at times. 850-700 mb temperatures begin to rise which should allow 
for readings to rise back to seasonal normals. 

For Tuesday night into Wednesday persistent northwest flow aloft will continue 
with some moisture embedded in the flow. Although orographics will 
remain favorable lapse rates will continue poor which should limit 
accumulations in the mountains meanwhile latest data suggest an 
increasing threat for a high wind event for areas in and near the 
foothills Tuesday night into Wednesday morning as Strong Mountain wave develops and 
combines with decent low level pressure gradient. Component along 
winds are forecast to be at or above 65 kts by 12z Wednesday. As for temperatures with 
downslope low level flow increasing on Wednesday this may lead to much 
warmer highs especially alng the Front Range as readings approach 
60 degrees. Meanwhile further east over the plains readings may 
stay in the lower 50s near the Wyoming-NE border. 

By Thanksgiving day there is no agreement at all between the longer 
range models. The European model (ecmwf) has flip flopped back to its previous 
solution of a few days ago as it brings a cold front into northestern Colorado during 
the day. Meanwhile the GFS has strong downslope warming across northestern Colorado 
with the fnt staying way off the east of the area. To complicate 
matters even further the Gem and NOGAPS show a strong cold front moving into 
northestern Colorado by Thursday morning. As a result temperature guidance for Thursday is all 
over the place with highs ranging from the 20s to near 70 depending on 
which model you want to believe. In addition the Gem and NOGAPS 
show a strong upper level jet in northwesterly flow over the area which would 
enhance snow potential if the fnt comes in like they show. The 
European model (ecmwf) for now at least keeps the jet further to the north with precipitation 
staying out of the area. At this point will go with an in between 
solution until it becomes more clear what is going to transpire. 
Thus will keep a dry forecast with readings ranging from the middle 40s 
over the far northestern plains with 50s closer to the foothills. 

The same issues continue on Friday as the GFS has a flat upper level 
ridge over the area with highs in the 60s to near 70 over northestern Colorado 
along with dry conditions. Meanwhile the European model (ecmwf) has another surge of 
colder air moving into northestern Colorado with the upper level jet sagging over 
the area with a chance of snow. The Gem keeps the cold air over the 
areas as well but has no precipitation. Once again will just broadbrush the 
forecast for now. 


Aviation...(for the tafs through 18z Monday morning) 
issued at 931 am MST sun Nov 23 2014 

The north-northwesterly boundary layer flow was creating a bit of 
a Longmont anti-cyclone and some easterly component to the weak 
surface winds are dia earlier. To the north of the Airport...the 
atmosphere has mixed out as evident by the temperatures and 
north-northwesterly winds. This should get to dia by 18z. There 
are some high stratocumulus clouds around...about 070...but not a 
ceiling. Moisture profiles on most of the models do not suggest 
that there will be any ceiling issues at the big Airport. 


Bou watches/warnings/advisories... 
Winter Storm Warning until 5 PM MST Monday for coz031-033-034. 



short term...barjenbruch 
long term...rpk 

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