Pressure Difference: 0.15 in (Boulder-Eagle)
Granger’s Weather wisdom:
NBR—is a weather station above launch on the ridge.
High winds aloft—if the winds aloft over Denver at 9,000′ or 12,000′ are more than 20 knots, flying on the front range can be hazardous. “2318” means 230 degrees at 18 knots. When the inversion breaks, rotor and strong, turbulent winds descend! Check the winds above Boulder to warn you of approach.
Front Range Pressure Difference.This is the difference in barometric pressure between Boulder and Eagle Airports. These weather stations are at the same altitude and opposite sides of the divide. Although there are other factors, the lower the front range pressure at Boulder airport becomes, the more likely west or tail winds become at our flying areas on the front range. A pressure difference reading in the range -.18 — -.30″ assures us of west winds!
Shifting winds—You will experience shifting winds—-from the North and then from the South—before they become catabatic or downslope winds.
A “lee trough” is one and the same thing as a “dynamic trough”. According to the AMS Glossary, it is “A pressure trough formed on the lee side of a mountain range in situations where the wind is blowing with a substantial component across the mountain ridge; often seen on United States weather maps east of the Rocky Mountains and can be formed either as a result of the adiabatic compression of sinking air on the “lee” side of a mountain range, or through cyclogenesis resulting from “the horizontal convergence associated with vertical stretching of air columns passing over the ridge and descending the lee slope.