While welcome, the dry start to March we’re seeing in 2020 isn’t that unusual. For the last four years, March has typically started dry and the snow has fallen later in the month.
April tends to follow a slightly more random pattern, with snow developing throughout the month.
What’s common to both early spring months, however, is the strong possibility of late month snow so enjoy your flying early in these months!
As an IFR pilot based at BJC, I tend to find myself longing for actual IMC sometimes! It seems as though it’s VFR all the time, and when it’s not, there are unfavorable conditions for icing.
As a pilot looking for actual IFR at KBJC, statistically the most likely time to find it is in the early mornings of late spring or early summer where nearly 1/3rd of our days are likely to start with IMC.
The great news for VFR pilots is that the heart of the summer is unlikely to see much IMC – but it is possible to catch a lot of afternoon thunderstorms!
Having flown into and out of KBJC hundreds of times, I’ve never been able to put my finger on which runways, 12LR or 30LR, get used more frequently. My intuition suggests that our dominant winds seem to be from the west, so therefore 30LR would see more action.
As it turns out, that’s true, but not by as much as I would have thought! Over the past four years, 30LR is in use roughly 60% of the time compared to 12LR which is in use about 40% of the time.
But that’s not the whole story! It turns out that both time of day and time of year greatly impact the winds we see at KBJC and, by extension, the runways we’re likely to find in use.
During the mornings and early afternoon in the summer, we’re about 70% likely to depart and land on 30LR. Conversely, late afternoons and evenings in winter yield about a 70% chance to land and takeoff on 12LR.
As a pilot in CO, I often think of the crosswinds to expect when landing at KBJC. As can be seen from the tables below, they vary greatly by season and time of day. But a good rule of thumb is that around 90% of the time you’re most likely to encounter crosswinds of 10 knots or less.
The stronger crosswinds, those of 11 knots or greater in this model, do appear but not very frequently. Those are most likely to occur in early afternoon in the Spring and Winter.
One question I’ve always wondered about flying from KBJC is: Are summer afternoons really the windiest time to fly?
Thanks to some historical METAR data, I’ve been able to answer that question.
In short, no. After looking at the past three years of METAR data between 8AM and 8PM (local) it appears the summer winds are relatively more mild than the spring winds. In particular, March.
March is unique in its wind pattern as it builds early and maintains its strength throughout the the day. This is in contrast to more typical patterns of light winds in the morning and then building throughout the day.
In fact, to become a proficient flyer in the prevailing winds we see at KBJC, it looks like there is no better time than March to get out and fly.
