The State of the Atmosphere: Sunday, October 18th, 2020

Subscribe to Weather5280Don't get left out in the cold, subscribe to Weather5280!

A cold front moved through last night around 9pm and thank goodness! While it won't deliver any appreciable moisture to Northern Colorado, the wind shift, cooler temperatures, increased humidity, and even some light drizzle all will help make today an altogether different day for fire fighting along the Front Range than what we saw with Saturday's explosive fire growth.

Temperatures dropped into the 20s and 30s across Northeast Colorado Sunday morning, with relative humidity values from 90 to 100% at most stations around 9 am, including those near the CalWood Fire north of Boulder.

As of Sunday morning the CalWood Fire was estimated to have burned over 8,000 acres since it began on Saturday, and is reported to have burned "several" homes and structures as well. The map below shows the current fire perimeter, as well as active evacuation and pre-evacuation zones. You can find an interactive version of this map here.

Last night's wind shift will help fire fighters tremendously with their efforts today. Winds are now out of the east which will stop the eastward progression of the fire, and even work to push the fire back on itself today. Still, for those in the area PLEASE be prepared to evacuate if asked as we are by no means out of the woods with this fire yet.

The week ahead
Today's chilly weather will be short-lived, as milder weather returns for the start of the work week and will stick with us as least through Wednesday. Highs across the region will be in the 40s and 50s today, then climb back into the 60s and 70s Monday. The warmest day of the week looks to come Wednesday, where highs in Denver could approach 80°F before our next cold front arrives.

Lows will be cool but not cold, at least through Wednesday night. For the Denver area we should see lows in the mid 30s for this time of year, but Monday night through Wednesday night we'll see lows in the 40s across the metro area.

Once we get beyond Wednesday, the last days of the month may feature more below average temperatures than above as we watch several troughs drop out of the Northwest and move through our region.

The first is likely to arrive Thursday, and at this point it looks like it'll provide little more than a bit of a temperature drop from Wednesday's warmth.

Another front moves through for Friday which could cool us into the 40s for highs, and perhaps even provide some better light shower chances to Northern Colorado than these other fronts have managed.

Yet another trough may arrive later in the weekend/early next week which at times (no, not consistently) has looked like it could deliver a bit more of a meaningful winter blast to the Northern Mountains and Northeast Plains of Colorado. Let us hope, but very little confidence in this possibility just yet. Below is a look at the European ensemble temperature forecast, with a clear cooling trend later in the week and next weekend –– but plenty of uncertainty in just HOW cold we'll get.

The same is true for precipitation chances as well. In the chart below you see no greens showing up until Friday or so, then quite a few GEFS ensemble members suggesting a wetter/more unsettled period arrives. Each block indicates a 6 hour precipitation total for each of the 30 (y axis) ensemble members. While more greens are showing up, even some dark ones for the Saturday night - Monday timeframe, there are is still a lot of variation between the members, including some that remain mostly dry:

Since we are in such dire need for moisture, let's look at some probabilities for the next 15 days from the European model as there are some signs of hope. Much of this is from next weekend's potential system, as well as some ensemble members sniffing out one more short wave after that before the end of the month.

First, probabilities for 0.5" of liquid between now and November 1st. IF this comes to fruition, great news for areas hardest hit by fires right now:  

For snow, here are the probabilities for 3" of snow or more over the next 15 days. Let it be so!

Plenty to watch over the next week, even if our persistent pattern would suggest one should not get their hopes up just yet.

Happy average first measurable snowfall date for Denver! Look for our Winter Outlook 2020-2021 to be released this week! Stay warm out there today and go away fires.