CALGARY I wonder what today might have been with a little more surface moisture. As it stands, we don t have enough. Evapotranspiration (moisture being pulled out of the soil) is a large helping hand for storm development, which sits in the cards for today as a weak trough piles through. Showers across southern Alberta will range from periodically heavy (up to 10 millimetres) to a light sprinkling. The median across this span is two to three millimetres. As far as storm energy is concerned, the metric for that (convective available potential energy, or CAPE) is rather low; just 500 J/Kg (of energy per mass of air). CAPE isn t considered large until you push above 1500 J/Kg, and isn t into a greater extremity until you hit 2500 J/Kg.
CALGARY In meteorology, there can be good and bad in just about every set of circumstances; outdoor enthusiasts love the sun and certainly don t mind that April fell short of seasonal average precipitation (while simultaneously cursing that we were above seasonal on snowfall, all the same!) That data s below: How badly do we need that rain? Pretty badly. Here s the data from Agroclimate Canada: This means that from a period starting from meteorological fall (Sep 1, 2020) to present day, conditions are quite a bit drier than usual, and flat-out arid east of Edmonton. This to say nothing of our fire ban picture:
CALGARY A warm day in Calgary without some form of an asterisk is still not in the cards. The high pressure ridge aloft is going to settle into zonal flow (a direct west-to-east motion) across the Rockies today, opening the south end of the province to strong westerly wind. Gusts in Calgary could top the 60 km/h range; that on top of temperatures in the low 20s (within four degrees of the record!). This weekend we re looking at an upper trough driving in limited amounts of rainfall. First off, our quantitative precipitation forecast (QPF) is showing exceptionally low rainfall amounts. Secondly, our dry air will entrain a lot of ground-bound moisture – it ll act like a giant, airy sponge, absorbing water on the way down.
CALGARY Today and tomorrow, we re into – and out of – a high pressure rise. Today the wind is a little gentler as we re directly beneath the ridge, and tomorrow it ll pick up as the ridge falls away and returns us to seasonal temps. Until then, this ridge of high pressure is going to pump us to the 20s! The standard drawback continues, in that this will keep the landscape dry and ramp up the fire advisories. Our weekend is shaping for some light showers, but the key word is light. We are a ways off from the sort of saturation our lawns could surely use right now, with between two to three millimetres Saturday, and barely a single millimetre of rain Sunday. That s nowhere near enough. Here s a look at the Agroclimate Percent of Average Precipitation:
CALGARY The only major shake-up from yesterday s projected conditions is (once again) ongoing reductions in the expected rainfall this weekend. Initially, we were focused on getting 10-15 millimetres of rain, beginning midday Saturday and carrying forward into Sunday. Now, we ll be lucky for scattered showers on Saturday, with Sunday largely clear. This bodes well for many outdoorsy-types, but not so well for farmers, gardeners and, quite possibly, firefighters. We re into a ridge of high pressure tomorrow and Friday, which builds up our wind to the 40s or 50s with a westerly component. When that high pressure fully cycles in, we re looking straight at the 20 C region here in Calgary.