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Forecast Discussion:
3 p.m. Update:
A little more snow will be added to the snow pack, but the snow amounts are going to start tapering off before 6 p.m. The HRRR in Figure 1 update shows about 1 more inch possible overnight.
End 3pm Update.
I won't bury the lead; the NWS has issued a Winter Weather Advisory:
...WINTER WEATHER ADVISORY IN EFFECT FROM MIDNIGHT TONIGHT TO4 PM MST SUNDAY...
* WHAT...Snow expected. Snow accumulations of 3 to 6 inches
expected by late Sunday afternoon.
* WHERE...Boulder and the western suburbs of Denver, Denver and
Castle Rock.
* WHEN...Snow will develop by midnight tonight and be heaviest
Sunday morning. Lighter snow will likely continue into Sunday
evening.
* ADDITIONAL DETAILS...Plan on slippery road conditions.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
A Winter Weather Advisory for snow means periods of snow will
cause primarily travel difficulties. Expect snow covered roads
and limited visibilities, and use caution while driving.
The latest road conditions for the state you are calling from can
be obtained by calling 5 1 1.
The early morning weather map for Sunday shows the real cold air still coming down with the first front far to the south (Figure 1). The snow is just getting underway along the Front Range. The deep upper level trough (red line(s) in Figure 2) are passing by Monday a.m.
The weatherunderground.com shows precipitation chances starting to pick up around 11 a.m Saturday and really getting going around 6 a.m. Sunday. The snowfall chances drop off around 8 p.m. Sunday, but some precipitation could keep falling through noon Monday now and then (Figure 3).
The National Weather Service (NWS), in their statement above, puts 3-6 inches down just to our west, Boulder and the foothills, but also over Denver.
Figure 4, the GFS now has us in the 2-3" zone.
Figure 5 is the GFS again (same model) but pulled out to include the Plains through Monday PM.
Figure 6 is the NAM model over this region. We get heavier amounts 3-5" fall around Longmont in this model.
Figure 7 is the WRF model goes even higher with 4-7" over us.
BUT weather5280 forecasters only give Longmont about 1-3". (You can read their discussion here: https://www.weather5280.com/blog/2018/11/10/after-a-mild-saturday-a-cold-veterans-day-with-a-chance-of-snow/).
My forecast is for 2-4" (a bit heavier than weather5280) due to the plentiful cold air (2+ days below freezing) and vigorous upper level support, along with the expected duration of the event.
The longer range forecast:
Figure 3, again, shows us staying below freezing (especially if there is a good snow pack) until midday Tuesday. Things remain dry until a small system comes in Friday morning. More on that later!
