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Forecast Discussion:
I'll post this early, since precipitation should start in the next 4-6 hours...
Yet another (less windy or cold) storm is on its way. There is a giant trough in the middle of the country giving us northwest flow aloft (upper level winds coming from a northwest direction) (Figure 1). Ripples (called short waves (also Figure 1)) that travel down this flow can bring cold surface air in (a cold front -Figure 2) and, when there is moisture, create some snow by lifting the moist air via the front and up-slope (from the east-ish direction) surface air flow.
This is the situation tonight into Thursday am (though moisture is limited). The surface front will pass Longmont around 11 pm tonight and make it to Castle Rock (the PD communities) around 4 am. My snow forecast and timing for selected cities is:
FC: 1/2 to 2" Wed 8 pm to Thur 10 am
BE: 1-2" Wed 10 pm to Thurs 11 am
LM: 1-2" Wed 10 pm to Thurs 11 am ** Us! **
BO: 2-4" Wed 10 pm to Thurs 1 pm
EP: 3-5" Wed 6 pm to Sat 3 am
DN: 2-4" Wed 8 pm to Thur 1 pm
PD: communities 2-4" Wed 9 pm to Thur 2 pm
(Note: if 'banding' sets up, some folks will see a surprise greater amount of snow.)
There are winter weather advisories for the higher mountains, but nothing along I-25 presently. Looking further out - there is a chance of a low-land flurry/dusting Friday night then a wetter/snowier/stronger storm is on the horizon for Monday.
The GFS (Figure 3) is still bullish north of and through Denver with 3-4 inches of snow around town. The NAM (Figure 4) has us pretty snowy with 2.5 to 3.5 inches of snow. The forecasters at weather5280.com put us in the Trace - 3 inch zone with banding potential nearby that could greatly increase snow for a minority of the region (Figure 5).
The longer range forecast:
A ripple north of Colorado may kick off some snow flurries Friday pm. We warm to just under and just over 50°F for the weekend - then watch a Sunday pm to Monday storm set up (that isn't looking as significant as it did a few days ago) - Figure 6.
